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1952 Flathead engine overhaul


craigger01
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Does anyone in this group have information on engine overhaul for the Flathead six?

I am working on a 1952 2 Door Chieftain. Engine runs backwards on shutdown.

I am going to do a compression test and leak down check to determine whether it has intake or exhaust valve leaks and piston blowby.

I am suspecting a carbon buildup at this point . Possible needs a valve job. I have never worked on a flathead before , so new at this.

 

Thanks

Craigger01

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You should by all means do the compression and leakdown tests. Post your results. How long has it been since the car was driven regularly? If it is a long time, Don't get too hung up on the test results unless they are really horrible.

 

Pontiac flatheads have a piece of sheetmetal tubing inside the intake manifold. The hole under the carburetor flange is the inside of the tubing, and there is exhaust on the outside. When that tubing rusts through, exhaust gets in the intake and it makes the engine run horrible. At some point you might want to take the carburetor off and look down the hole. There is also a heat riser on the manifold. You should fix it if it doesn't work. The weight falls toward the block when the engine gets hot. That is the "open" position. It really should work to make the car run right, but above all you do not want it stuck closed.

 

But do your compression and leakdown first. That is the best place to start.

 

 

Edited by Bloo (see edit history)
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So I did a compression check and got these results on the first one dry> 1- 90, 2- 82, 3- 0, 4- 95, 5- 0, 6- 82. I then squirted oil in the spark plug holes two strikes each cylinder.

Second compression test 1- 112, 2- 82, 3- 0, 4- 115, 5- 107, 6- 102.  I then sprayed deep creep penetrating oil in number 3 and 2 more squirts of engine oil in the spark plug hole and got 110 compression.

Then performed a leakdown. I have blow by , air coming from the oil fill spout, cap off on TDC of 1,2,5,and 6. The compression on 3 and 4 come up 90 degrees before TDC. I think i have a couple of stuck intakes valves. 

More investigation to come. Also the heat riser valve is stuck in the closed position. 

 

Craigger 01

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The zero compression was most likely sticking valves. It sounds like you have them all moving now. How long did it sit?

 

Start spraying your heat riser with penetrating oil at both ends of the shaft. Spray on a little more every day Above all, don't try to force it. Any hot/cold cycles from running the engine will help loosen it. after several days of oil, if still stuck, you could try tapping very lightly on the end of the shaft with a brass hammer. Not in the direction of rotation, but right on one end and then the other, taking advanatge of any endplay the shaft might have. Put more oil on. Try again in a day. Don't overdo the tapping and mushroom the shaft. You are just trying to send a little shock wave through the rust. Actual movement could come a day or 2 later.

 

Mopar (Chrysler) 4318039AC "Rust Penetrant" is real heat riser solvent just like the old days, and is about the most effective penetrating oil you can get. It works even better if what you are spraying it on gets hot/cold inbetween sprayings (like a heat riser does on a car that gets driven every day).

 

Now that you have compression in all cylinders, If you can get it running and drive it the blowby and compression numbers will probably improve over time. I would not give up on the engine yet. There is a good chance it will bounce back.

 

P.S. Bad gas will make your valves stick Is it running on nice fresh gas?

 

 

Edited by Bloo (see edit history)
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So having some good luck with everything so far. The leakdown was a bit dismal.

All numbers over 100 on the differential

1- 30, 5 - 26, 3 - 28, 6 - 24, 2 - 48, 4 - 24. at TDC .

I was able to free the heat riser with penetrant and the brass hammer with a tap to the side as suggested.

The carb butterfly was also seized from sitting and was able to free it as well with penetrant and sitting in solvent overnight.

The car is empty of gas according to the gauge and the fuel pump did not pump any product yet. I had turned it over quite a bit when i completed the compression checks.

I am uncertain how long it has sat. The son said he used the car as a wedding car and his oldest has finished high school. Could be as much as twenty years in the garage but i don't think so as the dust on it wasn't that thick.

The 1/4 inch tubing on to the carb choke control from the exhaust manifold was corroded so replaced it also.

I am going to put five gallons of premium in the tank after i check the lines.

Would you happen to know what the clearance is on the valve to lifter gap should be.

I had removed the intake/exhaust manifold and valve side covers to check that all valves were moving as advertised. Also to clean up and repair the heat riser.

I measured .013 on both the intake and exhaust valves on number one. I haven't looked at the rest yet but they appear to be about the same. There is just a bit of movement as I have turned each one when at TDC.

When i removed the manifold i could see there was a significant exhaust leak at number 4 cylinder. I have sourced a supplier locally that can provide gasket material. I plan on making my own (Old school) for the reassembly

 

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You really should get a manual! It has been a lifesaver for me.

 

My manual is too old to help with your 239. Going from memory, I think the spec is .013 cold, .011 hot. You will probably get more authoritative answers from others here. There are several owners of newer flatheads who have been doing engine work lately.

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Craigger01,

    I can't help you with the mechanics of the motor -- it looks like you are getting some valuable assistance....

    I have been a parts man for 50 years, and have mountains of engine parts -- N.O.S. -- U.S.A. made.....

     Camshafts, Valve Lifters, Pistons, Rings, Intake & Exhaust Valves, Push Rods,  Rocker Arms, etc., etc., Plus Water Pumps and Fuel Pumps & more...

    Call me if you need or want ---- Craig --- 516 - 485 - 1935... New York.....

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Hey Gary F,

    Thanks for the shout out !!! NO ONE on planet Earth had the 8 cylinder pistons for Gary F -- and they wanted twice as much to make them in Aluminum -- as I charged Gary F. For N.O.S. U.S.A. Steel !!!!!!!

    And Gary F. Was so prompt with his payment --- I gave him a $ 125.00 / set of matching piston rings for FREE !!!!!!

    So, when you are ready to dig in, Craigger, I am here for you !!!!!

            Yours, Craig....

Stay healthy, Gary F. And Craigger, we must survive !!!!!!!

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Had some more success today. Traced out some exhaust gasket material I bought from NAPA along with cork material for the valve side covers and intake/exhaust . everything went together fine. 

Bloo you were bang on with the valve stem to lifter clearance. I checked them all and they are within tolerance. Also when I was cleaning the oil and dirt off the side covers the front one has some embossed lettering on it. Surprise there was stamped Clearance .011 - .013. Good call Bloo. 

Got the engine firing on squirting a little gas in the carb. I had put some premium fuel in the tank and thought all was well. As it turns out the car had not run in 13 years. I drained all the gas or whatever was in there. Pulled the drain plug on the tank and blew air through the fuel line from the pump to the tank. Still no fuel to the carb so removed the fuel pump. Has one with a strainer bowl which was plugged solid. Cleaned it out and finally the car runs without spray. Had to keep it at high RPM seems the float may be stuck as it would not idle and seemed to be overfueling. I will take the carb apart tomorrow and clean it up. Also the choke does not work appears to be seized in the open position. 

Once I get it running/idling smooth I am planning on getting it up to temp and then rechecking compression and leak down. Hopefully it trends in the right direction.

 

Craigger01

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While looking in the trunk I found a copy of a manual for the car. The car is a Rochester installed . I could not find a model number. Does anyone know if the Rochester is the proper carb. When I phoned my local parts guy he said it should be a Carter. I need a carb kit as this was full of old gas and sediment.

 

Craigger01

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Craigger01,

   Sorry to say, your parts man is "incomplete".

   They did come through with Rochester AND Carter during those years, and both are correct.....

    I CAN supply you with a NEW Material (Ethanol Gas Compatible)

Carburetor Rebuilding Kit....

   Always best to simply call me --- Craig --- 516 - 485 - 1935.....

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  • 2 weeks later...

I received my Carb kit from MobileParts. Thanks Craig! I have the carb soaking in CRC product called Tyme. I was not able to get a gallon in Canada but was in the US last week and brought a gallon home.

I am going to leave the parts soaking overnight and plan on reassembling on Sunday. I will let you know how it goes.

 

 

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A Big Shoutout and Thanks to all that responded to my query.. I was able to get the engine starting a running very well. It starts easily and idles smooth. Acceleration is good. The carb kit i received from from Craig at Mobileparts was correct and the instruction that came with the kit spot on. Its a little muddy right now but when it dries up I am going to go out and run the car for a couple hours. I will then plan on completing another leak down and compression test to compare with my initial numbers. I will post once i do that.

 

Thanks again for all the support here at the Pontiac forum.

PS

I also have a 1960 Pontiac Parisienne convertible waiting for restore. Might be a couple years before i get to it though.

 

Cheers

 

Craigger01

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Ok.  so I have the engine running very well. It appears to be overfueling though but not affecting how it runs. I am thinking my float settings are wrong as fuel continues to come from the bowl gaskets. I am using 1 9/32 for the upper float setting and 1 3/4 for the lower float setting.

Any one know anything different. These numbers come from the carb kit.

 

Thanks

 

Craigger01

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Is it running rich for sure or just leaking? The Rochester B is famous for warping and leaking out the bowl gasket.

 

Are you using a stock mechanical fuel pump? Many aftermarket electric pumps are higher pressure, and may alter the effective float level, or just plain blow past the float valve.

 

If you are pretty sure it's too rich, you could try lowering the float 1/16" or so and see what happens.

 

A bad float could cause it. Next time you have it out, dunk it in hot almost boiling water and look for bubbles. If it leaks you need a new one (unless you are really good at soldering, and soldering floats is pretty fiddly and annoying even when you know how).

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thanks I will work through your suggestions. I usually use a chunk of tempered glass and level the mating surfaces with a bit of sandpaper but didn't do this on the rochester as it had the raised ibbing on the surface. I thought it would seal up very well. It just seems to be leaking from the bowl matting surface. Not running rich at all. I think the fuel pump has been changed as there were 4 more in the trunk of the car. i think will try lowering the float first.

Edited by craigger01 (see edit history)
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Bloo: Thanks for your suggestions. I took the carb off and apart this morning. Tested the float and it was fine, no holes. I then took both the bowl and mate and used a 120 grit automotive sandpaper to level the matting surfaces. I did this by putting the sticky sandpaper down on a piece of tempered glass. I then worked the surfaces until all were even. You were right both surfaces had heavy warping. I had never had to take so much material off. I then also opened the distance for the seat setting distance from the spec of 1 9/32 to 1 15/32. The bowl surfaces are sealed and no more fuel running down the carb. Mission accomplished. Car starts, cold and hot fine and idles nice. Acceleration static is good also. I haven't taken it out for a run yet. King pins are shot so tackling them next. Once the frontend is done I will get a mechanical inspection for insurance and be on the road in a week or two.

 

Thanks again for all the  here at Pontiac forum.

 

Craigger01

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Hey Craigger01,

   Here in the United States, your set is ONLY the reproduction -- both U.S.A. and Chineseum.....

    Before you call me for them, see if my friend Norm, Mid Canada Suspension has a set of N.O.S. U.S.A. King Pins... If you need his phone number, I have it, of course.  You are welcome to say that you are

   Craig, Mobile Parts' friend and namesake, of course.... Hey if it saves you

$ 5 - $ 10, something is something !!!!!

   Let me know if you need Norm's phone number or me....

       Glad to read that your Pontiac is running smoothly.... Yours, Craig...

     

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  • 2 months later...

One last update. The engine is running very smooth now. Ended up having the fuel tank acid washed and steam cleaned. Also had it coated internally.

Car rune even better as some old the sludge that had built up in the tank was restricting fuel flow.

Put on over one hundred miles and did another individual cylinder compression test.

1- 112

2- 108

3- 110

4- 112

5- 112

6- 108

Starts and idles smooth. 

Thanks again for the help on this site.

 

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On 3/27/2020 at 9:22 AM, Bloo said:

You should by all means do the compression and leakdown tests. Post your results. How long has it been since the car was driven regularly? If it is a long time, Don't get too hung up on the test results unless they are really horrible.

 

Pontiac flatheads have a piece of sheetmetal tubing inside the intake manifold. The hole under the carburetor flange is the inside of the tubing, and there is exhaust on the outside. When that tubing rusts through, exhaust gets in the intake and it makes the engine run horrible. At some point you might want to take the carburetor off and look down the hole. There is also a heat riser on the manifold. You should fix it if it doesn't work. The weight falls toward the block when the engine gets hot. That is the "open" position. It really should work to make the car run right, but above all you do not want it stuck closed.

 

But do your compression and leakdown first. That is the best place to start.

 

 

you really have me stratching my head over this sheetmetal tubing under the carburetor flange, having been around pontiac straight eights for 47 years, and i don't believe the six intake is different except for the number of cylinders. the intake and exhaust manifolds are all cast iron except for the choke stove and the heat riser flapper valve, so where is this sheetmetal tubing that's prone to rusting ???, now if you're thinking of the V8 intake manifold, it has a sheetmetal tube pressed into the exhaust crossover portion of the intake manifold, not so in the straight eight and six.

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It is directly under the carburetor. It is the round bore the air-fuel goes through. On some of them at least it is a piece of steel tubing, exhaust tubing more or less. It is not cast iron. There is exhaust from the heat riser on the outside of the tubing.

 

This probably doesn't apply to 2 barrels. I have not seen a bad 2 barrel one, and so cannot tell. Those may be the expected cast iron. The six did not get a 2 barrel until the last year of production. I do not recall when the eight went 2 barrel.

 

KlqwkhT.jpg

Edited by Bloo (see edit history)
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4 hours ago, Bloo said:

It is directly under the carburetor. It is the round bore the air-fuel goes through. On some of them at least it is a piece of steel tubing, exhaust tubing more or less. It is not cast iron. There is exhaust from the heat riser on the outside of the tubing.

 

This probably doesn't apply to 2 barrels. I have not seen a bad 2 barrel one, and so cannot tell. Those may be the expected cast iron. The six did not get a 2 barrel until the last year of production. I do not recall when the eight went 2 barrel.

 

KlqwkhT.jpg

well the pontiac 239 six engine started having a carter WCD 2010 two barrel carburetor in the start of 1952 production, and craig's pontiac is a 1952, so the part you're talking and showing doesn't apply to his pontiac. thanks boo.

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3 minutes ago, pontiac1953 said:

well the pontiac 239 six engine started having a carter WCD 2010 two barrel carburetor in the start of 1952 production, and craig's pontiac is a 1952, so the part you're talking and showing doesn't apply to his pontiac. thanks boo.

i believe the pontiac straight eight went to the carter WCD two barrel in 1949.

 

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Pontiac first used a two-barrel carb on the 8 in 1940 - Carter WD-0 569s.

 

The heat riser tube pictured by Bloo is an aftermarket piece, produced by the Standard Hygrade Company. The pictured tube, HT-28, is listed for Pontiac 6 only 1941-1942.

 

Hygrade lists an earlier tube, HT-23, for Pontiac 1933~1939. They do not differentiate as to 6 cylinder or 8 cylinder in the listing.

 

Jon.

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  • 1 month later...

The first Rochester single barrel carb was 1950 for Chevrolet. GM did suggest the use of the Rochester as a service replacement for older Carters, which was a bad idea for the car owners.

 

In 1949, Chevrolet used the Carter W1 number 684s.

 

Rochester did produce a two-barrel carburetor in 1949, the type AA 7001570 for the Oldsmobile 8.

 

Jon

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  • 3 weeks later...

Those are some pretty good contain figures but do watch out- if you're setting the valves with the engine cold and static allow a little extra (15 thou' or so) because the spec is 11 -13 hot and running. 

I set mine 13 cold, static and once up to temperature even that managed to close up to the point of the valves not sealing fully.

 

I bought a set of go-no-go feelers, with the car jacked up, the inter fender panel removed, wheel off, access to set the lash is pretty good though you'll curse at me a few times because you gonna burn between your thumbs and index fingers on the exhaust- that's just part of the procedure!

 

Proper valve lash on these is vital for smooth running. You'll get it smooth, then set the lash correctly and you'll be surprised just how more refined the engine gets. It doesn't have a huge CR to be l begin with, and with large valve overlap by standard you see a lot of losses with only a couple thou' too tight.

 

The difference becomes noticeable upon driving; in a high gear at low speed, moderately heavy acceleration is where that shows up most, I find.

 

Phil

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