37 Pontiac Heat-Riser issue and Valve Job discussion

[Guest bofusmosby]

I spoke to my mechanic again today, and he has sent off my carb to have rebuilt. In the meantime, I was talking to him about the heat-riser/intake manifold assembly, and I asked him if there was any kind of hole in the tube inside the intake manifold that runs directly below the carb, which is there to heat up the air and gas mixture as it enters the engine. Well, to my surprise, he said that there is no tube there inside running right below where the carb mounts on.

Others here have mentioned that there should be a metal tube that passes hot exhaust gasses, which is how the intake air is warmed. Is it possible that this car does not have one? My mechanic said he looked inside with a small mirror, and could not find any sign of what I was describing, or what others have said. Any ideas or opinions on this? I'm a bit confused right now. I am wondering if this tube is completely rotted away, or if maybe someone could have removed this 'tube'. If the tube has rotted away, then this would explain why the engine is running so bad, but is it possible that this tube could have been removed in some way that would still enable the car to run OK.

I would really appreciate any and all feed-back on this, and thank you!

[Guest]

Jim, I know you have a service manual for your Pontiac. I'm pretty sure it will describe the choke and how it's heated and the exhaust manifolds heat riser/exhaust diverter to heat the bottom of the intake manifold when cold. It sound like your mechanic is delving in uncharted waters, that's ok if he's a good mechanic...but he needs a road map to help you out. Always consult the manual before setting off on a adventure.

D.

[Guest bofusmosby]

helfen

I left both the actual service manual as well as the Motor's manual with him, and I had looked for this before, but there was no mention (or photos) of any tube located inside the intake maniford directly below the carb. I was only going by what others here on this site had told me before. I was told that there is a tube that runs below the carb that contains heated exhaust gasses, which heats up the air/gas mixture when the car is cold. One of our members went as far as to say that 50 years ago, his 37 Pontiac was running the same way, and after pulling the carb, he found a pencil eraser sized hole in this tube. Replacing this tube corrected this problem he was having.

Here is a link to the actual thread that was made a year ago, and please read posts #'s 17, 18, 38 and 40.

http://forums.aaca.org/f120/37-pontiac-engine-not-running-right-295369.html

Please let me know what you think.

[Guest]

Jim, I've been looking at some pictures of stock 37 Pontiac's ( hard to find ). First let's talk about a missing tube. There is a tube that goes into the exhaust manifold on one end and the other end goes to the choke. This is called a divorced choke type. The heat from the manifold travels up the tube and acts against a bimetal spring in the choke housing to open/close the choke.

You also have a heat riser which when the engine is cold directs exhaust gasses around a chamber surrounding the intake manifold to heat the bottom of the manifold when cold to aid in warm up. Here are a few pictures of a Chevy straight six exhaust manifold showing the heat riser chamber. These are not exactly the same as yours, but are similar and operate under the same principals;

http://67-72chevytrucks.com/vboard/attachment.php?attachmentid=401252&stc=1&d=1226011637

http://67-72chevytrucks.com/vboard/attachment.php?attachmentid=401231&stc=1&d=1226004060

You can see in the pictures the weight and the bi metal spring. Inside the exhaust manifold is the shaft holding the diverter valve. In the first picture you can see the shaft and the diverter butterfly valve. Here is another picture in which the valve is straight up in the manifold directing hot exhaust gasses at the bottom of the intake manifold.

http://67-72chevytrucks.com/vboard/attachment.php?attachmentid=402732&stc=1&d=1226533077

In the link you referred me to someone speaks about a vacuum leak personally I have never seen the exhaust passage burn into the intake manifold. If the valve sticks in the closed position you will have a harder time warming the engine up. If the valve is stuck open you will have driveability problems when the car is warm. I can remember always using graphite penetrating oil to free a stuck shaft. My 59 Pontiac needed this to be done every service. I guess they gave so much problems that on my 69 Pontiac they eliminated the valve altogether.... the boss is there on the manifold for one, but it's not machined for the valve.

In regards to your other topic about acceptable engine compression and how to perform it. some people had no problem saying that even 90 PSI was acceptable when I think the manual said 140 PSI. On the link you refered me to for the heat riser you mention;

#19

bofusmosby

The History Guy

Join Date: Mar 2010

Location: Tampa Florida

Posts: 956

Re: '37 Pontiac Engine not running right. HELP!

One thing I forgot to mention. On the passenger side of the engine, there is an "engine breather tube" that mounts to the side of the engine. The opening is below the engine. This car (the engine had been rebuilt about 2-3,000 miles ago) Does not blow any smoke from the exhaust, however, I noticed the last time I ran the engine, that there was some sort of white smoke exiting the engine breather tube. Maybe this is normal because of the engine missing, but just in case, I figured I'd mention this in case it meant something.

__________________

Jim

This description is incorrect. On the left side of the engine there is a oil fill/breather tube with a breather cap with wire mesh in it. Air enters this cap and down the tube and circulates down into the crankcase and exits through the rear side valve cover via a tube called a road draft tube. That white smoke is crankcase vapors, and when it gets excessive it indicates worn piston rings and cylinder walls. A very small amount of blowby is normal even in a fresh engine, as the engine wears it gets progressively worse. When you pull up at a stop light and these gasses come out from under the engine compartment and around your car you know for sure you need a rebuild.

D.

[Guest bofusmosby]

Thank you helfen for your response. Unfortunately, none of the links worked for me. When I drove my car to the garage, when I arrived (about 15 miles) I had checked this breather tube, and there was no smoke coming out, so I am in hopes that this is not an issue.

Here is a photo I'd like you to see. This is of a 37 Pontiac that was restored, and in the process of being reassembled. Is this what you are speaking about?

[Guest Pete Woodruff]

Jim, this subject was covered in ETCetera, the Early Times Chapter newsletter about a year ago. There are 2 tubes used in the heat riser system for '37'-'39 Pontiac eight cylinder engines. Group No 3.264, part No. 500340 is the tube under the carburetor which connects the mounting flange with the actual intake manifold plenum. It is about 2 inches long and the diameter of the bore it sets in. The second tube is external and about 24 inches long. It directs air from the cooling fan to the thermostatic spring which controls the heat riser valve. It is Grp. No. 3.647, part No. 499890.

[Guest Pete Woodruff]

The following illustration is from '37 Pontiac sales literature, the tube under the carburetor is clearly visible.

[Guest Pete Woodruff]

Here is the link to the heat riser article on the Early Times website:

Manifold Heat Control Valve

[Guest bofusmosby]

Thank you Pete for your response. My car is a 6 cylinder, so are there any differences? Also, I know about the tube that goes from the heat riser to just behind the fan, but that one is missing on mine. Are there any photos avaliable showing this? Also, would this tube be visible if the carb were removed? According to my mechanic, he sees nothing like that looking down into the heat riser where the car was mounted. Is it possible that this could have been disabled, and there would be no way that this could effect the operation of the engine?

[Guest Pete Woodruff]

I checked my link to the heat valve article, and it worked; but to get to the second page of the article, I had to use the Manifold Heat Control Valve drop down boxat the top of the first page.

[Guest Pete Woodruff]

Jim, I checked my parts book, the under-carb tube for the six cylinder is part No. 500341. The external tube part No. is 499891. The parts book illustration is shown on page 2 of the heat valve article. Its possbile that the tube under the carb is nearly invisible if it is in good condition. What typically happens is corrosion from exhaust gases eat holes in it, which lets exhaust gases into the intake manifold...exactly what an EGR valve does on a late-model car. The engine will not run well, if at all, when this happens; especially when starting or idling. Pontiac used this system for many years, apparently beginning in 1937, the '37-'38 manifold is a different part number then the '35-'36 manifold. The sixes used this tube through 1952.

[Joseph P. Indusi]

I think the Pontiac set up is similar to the straight eight Buicks. I will describe the Buick system as I think the Pontiac is similar.

The choke needs warm air to relax the bi-metallic spring that holds the choke plate in the nearly closed position as the engine warms up. On the Buick exhaust manifold, there is a steel tube that runs through the inside of the manifold but does not have any openings in it. Air enters the bottom of the tube and as it passes through the tube the air is warmed. When it gets to the top of the tube there is a pipe that conducts this warm air to the bi-metallic spring mentioned above. The heat tube is just a hollow tube running through the exhaust mainfold, Nothing more.

To heat the base of the carburetor when the engine is cold to improve cold weather warm up performance, exhaust gasses are passed through a plenum in the intake manifold. There is steel flapper valve on the valve body that connects the intake to the exhaust manifold. The flapper valve also has a bi-metallic spring that allows some of the exhaust gasses to pass up through this plenum. As the engine warms, the exhaust manifold heats up and the bi-metallic spring relaxes and the counterweight on the valve shaft moves the valve to a position where the exhaust gasses all go out to the exhaust pipe; circulation of exhaust gasses in the intake manifold plenum under the carburetor is stopped.

It is important to know that this plenum in the intake manifold has no internal connection to the intake manifold itself; that is the pathway that conducts the air-fuel mixture from the carburetor to the intake valves porting. If the plenum did have such a connection, then the engine would be aspirating a mixture of fuel-air from the carburetor and exhaust gas. In another discussion Rick60 alluded to the possibility that the plenum wall could rust out and open an internal hole into the intake manifold. I have seen this on one Buick straight eight intake manifold. If this happens, and it is rare, then it will defy most attempts at diagnosis. It would be equivalent to driving a a more modern car with the EGR valve stuck in the open position. It is possible that this could be detected by a low vacuum reading on a good engine at idle (throttle plate essentially closed). The way I tested the intake manifold for this problem was to separate the intake manifold from the valve body and the exhaust manifold. I turned the manifold upside down on a level bench. I poured water into the plenum opening until it filled up. Then I watched the water level to see if it went down. Sure enough it went down and I noticed water coming out of the carburetor bores and one of the intake ports proving that the exhaust plenum had a hole allowing a connection to the intake porting.

I hope that this is not your problem but it is a possibility as it will mimic a faulty carburetor.

Joe, BCA 33493

[Guest bofusmosby]

You guys have no idea how much I appreciate this info! I know that my mechanic said that the vacuum is less than half that it should be, and while driving the car, it seems to run OK, but when idling, it is horrible! A very strong odor of gasoline was also present. The carb is being rebuilt right now, but I am thinking that this may actually be the problem. Let me ask you something. If there were to be a hole, allowing exhaust vapors to enter the carb, or the intake going into the engine, exactly where would this hole be? In your link, there are part numbers for the parts in the diagram, so what would be the actual part number of the part that could cause this? This way, I can look at the diagram in your link, and see for myself, and also, so I can show this to my mechanic, so he will know what he is looking at. The mechanic I has is a good one, but he is not versed on these old cars.

[Guest Pete Woodruff]

Jim, if you look at the manifold heat valve illustration in my post above you will see the heat riser tube. Note how the carburetor sits on a large, relatively square casting, this area is filled with exhaust gases when the heat riser valve is closed and partially blocking the exhaust. The tube connects between the carburetor mount and the intake manifold runners which exit from the bottom of the center section. Any hole in the tube will allow exhaust gases to contaminate the incoming mixture of fuel and air and cause poor performance. This will NOT be accompanied by a strong odor of gasoline, so it is likely that you are having carburetor trouble. Looking down into the manifold with a good light should be sufficient to tell if there are any holes in the tube.

The hot air "stove" for the automatic choke is not like that on the Buick engine. If you follow my link to the ETC newsletter and look at the parts illustration shown there, you will see a diamond shaped piece just above the exhaust manifold labeled "cover". There is an indented area cast into the exhaust manifold adjacent to the cylinder head, which is closed off by the "cover". The small heat tube that connects with the choke housing on the carburetor originates behind this cover, air is drawn in around the cover where it becomes heated and passed up the tube into the choke housing to warm the bimetallic spring. I have never seen a manifold crack in this area, but if it did, a small amount of exhaust would be drawn in too. It would not be enough to cause rough running, but it would soon corrode the choke mechanism to the point that it would cease to function.

The part number for the internal manifold heat tube for '37 & '38 six cylinder engines is 500341. Unfortunately, it only fits those 2 model years.

[Guest bofusmosby]

Thank you Pete! I appreciate the education on this. I'll be sure and post the results of the carb rebuild, and if it has any more problems. Now, I at least know what to tell the mechanic.

[Guest]

Here is the link to the heat riser article on the Early Times website:

Manifold Heat Control Valve

Pete, that is a great post you provided, is the tube extending into the intake part of the exhaust manifold casting?

D.

[Guest bofusmosby]

OK, I have a question. After studying the diagram, and remember ing what my car looks like, I now know that the counter-weight for the heat riser is missing. Knowing this, I also believe that the valve inside might also be removed, or stuck open. This is the valve located inside the bottom section where the exhaust pipe connects. I also see in the diagram that this lower section is where the exaust and intake manifolds have a common section. Now, if this valve inside is either removed, or forced (stuck) causing the exhaust to go straight to the exhaust pipe, then will I still be getting the heating directly below the carb? The reason why I ask this is that it is obvious that either the inside valve (in the bottom assembly) is missing, or stuck in one position or the other. The section that the carb mounts to get very hot very quickly and stays that way. Is this normal? Let me add that this car was in Montana car, where it gets (and stays) quite cold, located in or near the mountains. If the valve were to be removed, then this heating of the intake air would be constant. Maybe in a very cold climate, this would be OK, but down here in Florida maybe not. Also, if this valve were to be either stuck or missing, would this possibly cause a hole to form in the passage, allowing exhaust gasses to mix with the intake air/fuel mixture?

[D Yaros]

If the valve is missing/open you would NOT be getting heat to the carb or intake manifold. If it is there and stuck closed I would think you would have a restricted exhaust, which you certainly would notice.

[Guest Pete Woodruff]

helfin, I'm glad you liked the article. The tube is actually part of the intake manifold; that whole relatively sqaure casting contains the exhaust gases when the heat riser valve is closed, but it is part of the intake casting. The exhaust manifold passes down past this area of the intake, then has a flat mounting surface that the intake bolts down onto. If you look closely at the illustration above, you can see the heads of the bolts at the bottom corners that hold the intake and exhaust castings together. The heat riser valve deflects the exhaust flow up into the square area of the intake casting to preheat the incoming mixture, and the exhaust manifold casting has a little passage that bypasses the heat riser valve allowing the exhasut gases to flow down into the exhaust pipe.

[Steve_Mack_CT]

Been following this post with interest, as my '39 Packard had a very simillar set up. Won't confuse things further by explaining that as the factory documentation and comments you are getting here from some knowledgable folks seems to be helping. I just wanted to make a couple quick comments I hope help as well:

Follow factory lube recomendations on the parts calling for graphite or simillar. The balance is between these often troublesome parts getting stuck vs. overlubrication. I can see a less experienced mechanic assuming "they didn't have WD-40 then, it is better" - you don't want to do that.

These systems DO impact driveability and after one winter lay up my car had both the auto choke frozen (partial choke position - not good) AND the butterfly valve in the exhaust frozen shut. Yep, warm weather driveability issues..

If you learn enough about these you can check periodically and likely fix yourself in the future. This, along with a carb rebuild and at the least plugs and points should get you out of the woods from what you have described.

Bear in mind the biggest nemesis for this era is the higher ethanol gas, extended driving, and other conditions that will lead to a hot carb will cause this and the issue will present itself as a sensation of running out of gas. I suggest now is the right tome to have your guy do a couple simple preventive measures like re-routing fuel lines where possible away from the exhaust manifold, and as I mentioned before setting the float up a tad higher than spec (most of the kits will have this advice in them now) will help a lot.

Hopefully, even with some engine wear, this allows you to fully enjoy your car, Jim.

Edited April 5, 2012 by Steve_Mack_CT (see edit history)

[Guest Pete Woodruff]

Jim, you obviously need the counterweight to have the system work correctly. The heat riser valve typically sticks in the closed position, it is naturally closed when the engine is cold. You could easily see the valve if you remove the exhaust pipe and look up into the manifold. I believe your valve is there and stuck closed, otherwise the square area of the intake under the carb would not get very warm. Even if the valve is missing I would not expect much heat to rise up into this area, the high speed flow of the exhaust would want to follow the path of least resistance, which would be down and out. This would make sense if you have seen the manifold castings seperated, the heat riser valve literally redirects the flow of gases upward when it is in the closed position.

[Guest Pete Woodruff]

Dave, I would tend to agree with you that a closed heat riser valve provides restriction, but my '40 Deluxe Eight had the valve stuck closed when I drove the car home from New Hampshire to Ohio and it went down I-90 at 65 miles an hour with no problem! Based upon my experience with a Pontiac, Jim's car could perform pretty normally despite a stuck heat riser.

[Guest Pete Woodruff]

Steve, you make a good point about lubrication, which I forgot to mention. Heat riser lubricants are typically penetrant-type light oils with grahpite added; the graphite is essential. The oil will burn off/evaporate from the heat, but the graphite will remain to lube the valve shaft. My '40 Pontiac lubrication chart tells you to mix powdered graphite with alcohol and use this to lube the heat riser. GM used to make an aerosol heat riser lube that foamed upon application to allow the graphite time to soak into the shaft/bearing area. I always operate the heat riser valve with the counterweight when applying lube to be sure it works into the valve shaft.

[Guest bofusmosby]

Thank you guys! One thing I know for sure, is that the counter balance piece is missing and the tube that goes from behind the fan to the intake manifold is also missing. I also know that the entire heat riser asembly gets hot quick, and stays that way. This is why I am wondering if there is a valve inside, if it is stuck. If the valve is stuck closed, would this constant heat Possibly speed up the effects of the high heat going into the intake manifold, eating a hole in the wall which divides the exhaust and intake manifolds?

Right now I am trying to fugure out what might have happened if my mechanic tells me that the carb rebuild doesn't take car of this problem. One thing he said though, is that the vacuum was less than half of what it should be. As already mentioned before, this might be an indication of this problem occuring.

[Guest Pete Woodruff]

Jim, have you looked down into the intake yourself to see if there are any holes visible? I would expect them to be fairly obvious. My '40 ran quite well with a stuck heat riser, it certainly idled and carried slightly more then 18 inches of vacuum. Low vacuum is certainly cause for concern; I believe you said the engine has been rebuilt, the valve clearance is critical to having proper vacuum, as is proper camshaft and ignition timing. The easiest item to check is the ignition timing, valve clearance is more difficult, but far more important to the life of your engine. You would have to remove the timing cover to check and see if the camshaft timing marks are correct. Your mechanic needs to follow established diagnosis procedures for low vacuum, most all of these steps apply to old or new cars.

[Steve_Mack_CT]

Yeah, way back there Jim made mention of a vac issue - another very typical symptom of this era, makes me wonder if it is as simple as a loose hose. But best advice there is as Pete suggests following the diagnosis procedures methodically. Sounds to me like the engine has not had a lot of attention, you may see a night and day difference once all these issues are attended to...

[Guest]

helfin, I'm glad you liked the article. The tube is actually part of the intake manifold; that whole relatively sqaure casting contains the exhaust gases when the heat riser valve is closed, but it is part of the intake casting. The exhaust manifold passes down past this area of the intake, then has a flat mounting surface that the intake bolts down onto. If you look closely at the illustration above, you can see the heads of the bolts at the bottom corners that hold the intake and exhaust castings together. The heat riser valve deflects the exhaust flow up into the square area of the intake casting to preheat the incoming mixture, and the exhaust manifold casting has a little passage that bypasses the heat riser valve allowing the exhasut gases to flow down into the exhaust pipe.

Thanks for the explanation. This system is almost identical in operation to a straight Chevy six I have in my Oldsmobile (came that way from the factory) and Olds calls this square part of the casting the stove, not to be confused with the term stove bolt. I have owned/raced Pontiac's nearly all my life, and have yet to find a heat riser that I liked. As said before my 69 Pontiac didn't come with a heat riser valve from the factory, which means hot gasses in the V-8 passed back and forth in the intake all the time. The first thing most Pontiac enthusiast do is block off the heat riser at the cylinder head for better volumetric efficiency. We need a cold charge of A/F to the cylinder. The point I'm trying to make is my Pontiac has heat risers blocked off at the heads, I run a Factory aluminum RA4 intake with the cast iron tube heat riser removed so there is no heat source surrounding the intake, The Q jet choke is removed along with the fast idle cam. I run a factory high performance camshaft. The gist of all this is I never have a hard time starting this car even in seventeen degree weather. I start the engine just like owners of all old Porsches that never came with a choke. Crank the engine with the throttle closed until 60 psi oil pressure, then pump the throttle five times and crank the engine with the throttle closed using the throttle as the choke plate, when it fires modulate the throttle to bring the rpm up to 1,000 and don't drive the car until 115 degrees ( that is the temperature Pontiac calibrated for cars that had a (green) cold light from 1959-1964. 90% of the wear is in the first ten minutes of operation. The reason the choke and the fast idle are removed is 1. fast idle and immediate start up there is no oil pressure (some cars you can hear a momentary con rod knock before oil pressure. 2. With the choke removed, you won't be able to drive the car until it's warmed up a bit. I had to do this back in the past when these cars were daily drivers because the wife would just go and stick her foot in it..this prevents this from happening.

So Pete, if this heat riser butterfly valve were stuck in the open position on Jim's car, and Jim warmed up the car before driving off as said above would you conclude as I have that there would not be a driveability issue as long as the exhaust gasses from the exhaust side hasn't blown into the intake?

BTW the fresh air tube you posted in the picture that takes air from the fan and blows it to the bi-metal spring is something I can't recall seeing. I'm sure my dad's 50 had one, but I can't see it in pictures. I will have to pay close attention to the cars that will be coming to the Flathead Reunion West next month.

Thanks for your knowledge and help to us! Not much information / enthusiasm for these great cars of pre-1955-even with the Pontiac crowd. You don't see many at a POCI event, maybe that's why we have a chapter here a AACA called Oakland/Pontiac club which is possibly more dedicated to factory stock 1958 and earlier Pontiac's? What are your feelings on that?? Someday I hope I can have another one.

D.

Edited April 5, 2012 by helfen (see edit history)

[Guest bofusmosby]

helfen

The car has never had a problem when first started...except what I have now. I am thinking that the valve on mine is stuck closed, and somewhere there may be a hole in the 'Stove" area allowing hot gasses to mix with the intake air a fuel. It stands to reason that the more this valve is closed, then the better the chance of this happening. Remember, where the car came from, I doubt the previous owner would disable this heat riser, and leave it in the open position, since it gets so cold in Montana. One thing is for sure, someone removed the outside counter weight, which means that the heat riser can't be working as it should.

When the car is being driven, there is no hesitation, and the engine seems to have as much power as it ever did, except when it is idling. I am in hopes that the carb rebuild will eliminate these probelms, but if not, then I at least have an idea as to what to tell the mechanic.

Thank you all very much!

[Guest Pete Woodruff]

helfen, its possible that Jim's valve is stuck open, but unlikely as the at cold engine "at rest" position was closed. If the spring is removed from a working valve, it will be "at rest" in the open position due to the counterweight. I agree that once the engine is warmed up, it should run properly as the heat riser would be open if working correctly. The real issue is proper operation of the choke and getting it fully open as soon as possible. Not only does fuel economy suffer...at $4 per gallon...but engine wear and crankcase dilution are severe when the choke is even partially closed.

The external air tube was used from '35 to '38 on the sixes and through '39 on the eights. My '40 does not have one. Presumably Pontiac found that the system would work correctly without this tube; and I don't recall ever seeing a similar set-up on any other brand of car.

Edited April 5, 2012 by Pete Woodruff
missing word (see edit history)

[Guest]

[quote

Thanks for your knowledge and help to us! Not much information / enthusiasm for these great cars of pre-1955-even with the Pontiac crowd. You don't see many at a POCI event, maybe that's why we have a chapter here a AACA called Oakland/Pontiac club which is possibly more dedicated to factory stock 1958 and earlier Pontiac's? What are your feelings on that?? Someday I hope I can have another one.

D.

Pete, care to comment on this part?

[rick60]

This is the part that has been discussed in this thread. I don't think this particular part is applicable for a '37.

http://www.ebay.com/itm/1940-41-42-46-47-48-49-50-PONTIAC-HEAT-RISER-TUBE-NOS?item

[Guest bofusmosby]

OK, here's an update.

I got a call from the shop today, and they told me that the shop that rebuilt the carb said it was full of trash. Well, they got the carb back, installed it, and also installed an in-line fuel filter between the tank and the fuel pump. Well, after doing this.....there is no difference! The mechanic told me that he has an adapter that connects an air hose to the cylinders, and when applying 125 psi in air, they can hear the air coming out the exhaust pipe. He is going to attempt to adjust the valves to see if this will make a difference, but he won't know until he tries it. According to what he has been reading, as well as what he hears, he believe that this is a valve issue, and not the rings. Well, some consolation. Either way, if the car needs a valve job, he says the engine has to be pulled. I was also told that if it gets to that point, it would be a good time to do a complete rebuild. He put some oil in the cylinders, and the compression went up quite a bit.

The guy I bought the car from swears that the engine was rebuilt , and that it hasn't been driven much since then (maybe 2-3000 miles). BUT, this rebuild was done maybe 15-20 years ago. My mechanic doesn't believe that the engine was ever touched, so did the seller deceive me? I have always been one to take a person at their word. What an idiot I have been.

Here's a question I have for those who might know the answer. What would be the going rate to have my engine rebuilt? What kind of money am I looking at? Also, does anyone know someone in the Tampa Bay area that might be willing to do this job for a reasonable rate? Of course, a reasonable rate would depend on ones financial situation, but what would be considered a reasonable rate?

I hate the idea of even thinking about it, but I may end up having to sell this car. I know I won't get for it what I paid. As a matter of fact, it will be several months before the car is actually paid off. I am hoping that adjusting the valves will take car of this problem, but I have my doubts.

Any ideas?

[Ben Bruce aka First Born]

Jim, a long time since I worked on a flat head engine, but don't remember having to pull the engine for a valve job. Perhaps, but I think not. Don't want to burst your bubble, but valves generally get looser, not tighter. A loosely adjusted valve would prevent it from opening all the way. For adjustment to be the culprit, it would have to be tight enough to prevent it closing.

The head will, of course , need to be removed to do a valve job. A close inspection at this time should reveal if the engine has indeed been rebuilt. Since your pocket book is like so many of ours, perhaps just a valve grind, if needed. If the rings are badly worn, this MAY cause a little more oil to be burned, but just live with it until you can do more. Don't despair.!!

Ben

[Guest bofusmosby]

Thank you Ben, but remember, on the flat-head engines, the valves are in the block, not the head. I am only going what what was told to me. With your explanation of the valves, I was thinking the same thing. To adjust the valves would be to adjust the amount that the valves are opening, not closing. I personally don't see how the valves being adjusted could cause any difference in compression. If I am wrong, please, someone correct me on my way of thinking.

I am still curious as to the amount of money it would cost for a valve job, compared with a complete engine rebuild. This car has a 6 cylinder flat-head engine.

[Guest]

Thank you Ben, but remember, on the flat-head engines, the valves are in the block, not the head. I am only going what what was told to me. With your explanation of the valves, I was thinking the same thing. To adjust the valves would be to adjust the amount that the valves are opening, not closing. I personally don't see how the valves being adjusted could cause any difference in compression. If I am wrong, please, someone correct me on my way of thinking.

I am still curious as to the amount of money it would cost for a valve job, compared with a complete engine rebuild. This car has a 6 cylinder flat-head engine.

Jim, it is possible to do a valve job on these cars with the engine in the car providing you have the proper equipment. I have a tool to compress the valve springs and remove the keepers to take the valves out of the block with the engine is in the car. Also sometimes valves do stretch, and on some engines with repeated stretching leads to the head of the valve breaking off.

In your words- " To adjust the valves would be to adjust the amount that the valves are opening, not closing" Jim, the clearance is not there to adjust the amount of opening or closing. The camshaft profile does this. the valve lash or valve clearance is a certain amount of clearance determined by the manufacturer. This clearance is included to assure proper valve seating. If there were no clearance or lash, then dimension changes due to temperature changes will lengthen the valve stem and keep the valve from seating. This is why it is so important that valve lash adjustments be made in accordance to the maintenance schedule. Cars like air cooled Porsche's and VW's are supposed to have valves adjusted EVERY 3,000 miles!

Jim, please get your mechanic to perform a leak down test on every cylinder to see the condition ( % of leak down ) of valves and piston/ring/cylinder wall sealing. this will tell him/you what the % is and if there is a unacceptable amount of leaking and where the leak is coming from. If he does not have a leak down tester find a competent mechanic who has the tools to do a quality job for you.

D.

Edited April 17, 2012 by helfen (see edit history)

[Guest bofusmosby]

helfen, thank you for your insight. Let me ask you. Is there any possibility of 'adjusting' the valves causing more compression in the cylinders, or will this just be a waist of money? Also, if the car were to need a valve job, what is the typical expense associated with this? I know that different shops charge different amounts, but what do you believe would be the average on this? Also, if this were to be done, should the engine be rebuilt at the same time? If so, what is the typical charges for rebuilding one of these 6 cylinder engines?

Sorry to ask so many questions, but I am at the point of trying to decide if I will be getting rid of this car and taking a horrible loss, or sinking more money into it. This economy is making it very difficult to come up with the funds just to have the carb rebuilt, let alone having either a valve job, or an engine rebuilt! I'm getting kind of desperate right now.

[Guest]

helfen, thank you for your insight. Let me ask you. Is there any possibility of 'adjusting' the valves causing more compression in the cylinders, or will this just be a waist of money? Also, if the car were to need a valve job, what is the typical expense associated with this? I know that different shops charge different amounts, but what do you believe would be the average on this? Also, if this were to be done, should the engine be rebuilt at the same time? If so, what is the typical charges for rebuilding one of these 6 cylinder engines?

Sorry to ask so many questions, but I am at the point of trying to decide if I will be getting rid of this car and taking a horrible loss, or sinking more money into it. This economy is making it very difficult to come up with the funds just to have the carb rebuilt, let alone having either a valve job, or an engine rebuilt! I'm getting kind of desperate right now.

Jim, the answer to the first question is IF a valve was out of adjustment so that there was no lash and the valve was starting to leak and stay open and you caught it in time and adjusted the lash to spec.and it didn't leak anymore I think the compression would come back as long as the valve face and the valve seat didn't get carboned up while the valve was hanging open.

First determine what the engine needs. The compression test and the leak down will tell you what you need to know. You know the leak down will not only tell you about valves sealing, piston ring cylinder wall condition, but can also detect a blown head gasket.

To be honest with you I have no idea how much this type of thing cost these days as I do my own work myself and before I retired ( 6 years ago ) I was in automotive engineering 34 years and only before that was I working in the field as a mechanic. So I don't know labor cost anymore. Just try and stay cool and don't get discouraged. There are many among us here to try and help you out. I understand that you need to ask questions so don't worry.

BTW, The Early Times chapter of Pontiac Oakland Club International (POCI) is having their annual Flat head reunion convention (west coast) about 30 minutes from my house next month- May 2-3-4-5th. I would love to have one of these flathead cars so I will be attending their show and their tech seminars. I have lots of questions for these guys.

As Bruce Cabot once said in a very famous movie... "keep your chin up";)

Don

[Guest bofusmosby]

Don,

Another concern I have is the fact that by putting some oil in the cylinders, the compression went up. If I am understanding things correctly, then would this mean that this would be definite ring problems, and not the valves, or could adding this oil cause the valves to seat better as well? When he put 125 psi of air into the cylinders, he could hear it escaping from the tail pipe (exhaust valves) as well as the carb (intake valves), but could not hear it though the crank case. This would point to bad valves, and not bad rings. Maybe my thinking is wrong, but it would seem to me that these are conflicting answers/results. Of course, if the oil being added to the cylinders could help seal/seat the valves, then all this could still be the valves.

Opinions?

[Steve_Mack_CT]

Jim, it sounds like your mechanic is an honest guy trying to help you, but is really not experienced with a flathead. Is he charging you time to research? Fair enough but you need to ask if that is the route you want to take. Bear in mind valve jobs were "routine maintenance" when these cars were new. Your issue, I think could be valve seals not rings as you have described the test. As Helfen points out valve work can and was nearly always done with the engine in the car.

I suggest you put out some feelers for a local shop that has experience with these engines. you may want to opt for an "overhaul" vs. "complete rebuild" if you are on a bit of a budget. Nothing too fancy, but check bearings, check replace rings, hopefully get away with honing cylinders not boring even for clean up, and valves. Much less expensive than a "full rebuild". "Overhauls" were and are still done with the engine in place. Bear in mind this is different from a "make it like new" rebuild. BUT consider how you will be using the car, and if you need to go that far with it. Another plan, although risky, is finding a replacement engine. I like this less though, because when all is said and done you are not guaranteed a better engine is in there.

Are you active in any local clubs - especially an AACA region? there is always someone or some group who know their stuff and if they don't want the job, can point you to someone who does and is qualified. I cannot overstate the importance of local experienced hobbyists, this forum is great, but so is that kind of help. Been there, I am pretty mechanically inclined but not a pro. That said, you would be amazed at what can be learned in a few hours.

If I remember right you bought this car very reasonably, I am guessing you will still be in fine shape after attending to the engine, but if you have to sell it now, you can probably get your money back as it sits. I would rather buy a car in need of engine work than heavy duty bodywork, and I think most would agree there. Hopefully you are able to keep her though...

Edited April 17, 2012 by Steve_Mack_CT (see edit history)

[Guest bofusmosby]

Thank you Steve. Believe my, I am hoping to keep the car, but I was just quoted an estimate of $1,800 for a valve job, which is completely out of my budget. My mechanic seems to be a straight up guy. I believe that he is a very good mechanic, but I doubt that he would have the old equipment needed to do some of the repairs. He has already told me that if he were to do the valve job, he would have to remove the engine. I told him that if it comes down to it, I might look to find someone who has the old equipment to to the job with the engine still in the car. That should come with a pretty good savings, compared to removing the engine. He is going to try adjusting the valves on a couple of the cylinders first, to see if he can increase the compression. He said that if he can't increase the compression on the first 2 cylinders, there will be no point in continuing any further.