Carb heat shield?

[PWB]

Stupid question?

 

My '67 has been running rough and stalled on me out of the blue. I tore down the carb. to troubleshoot.

 

Does the heat shield (or heat conductor - I forget) get a gasket on both sides? If not, which side gets the gasket?

 

 

 

Thanks much.

 

 

 

Edited July 10, 2020 by PWB (see edit history)

[telriv]

Metal plate under carb. Gasket to manifold.

[KongaMan]

While (almost) everyone agrees that there's only one gasket used, I've heard folks advocate for putting the plate next to the manifold with the gasket between the plate and the carb.  The theory is that the plate will heat more quickly that way, as there is more of it in contact with the manifold.  They say it also keeps the slot in the gasket from getting plugged with carbon, which inhibits heat transfer to the carb (which is the point of the thing).

 

YMMV.  

[telriv]

From the factory is installed as stated.

[RivNut]

The plate against the carburetor is what conducts heat to the base of the carburetor. If Buick did not want heat atvthe base of the carburetor, they would have designed the heads and intake manifold differently. The nailhead intake in today's market would be described as an "air gap" manifold. On most intakes the manifold comes into contact with the block and has coolant circulating through it.  Therefore they have no need for the exhaust passages and the heating channel under the carb.  As Tom says - do it the way the factory designed it. They are the engineers; you're not.

[KongaMan]

 

47 minutes ago, telriv said:

From the factory is installed as stated.

Not saying who's right or wrong; just saying that different people have different opinions.  As a practical matter; it probably doesn't make a damn bit of difference.  The problems come when you don't use the plate -- not from how you install it.

[KongaMan]

2 hours ago, RivNut said:

The plate against the carburetor is what conducts heat to the base of the carburetor.

Not necessarily; the 4GC doesn't use the plate.  Perhaps the plate is there not to conduct heat, but to prevent damage to the AL body of the AFB from the exhaust gasses?

 

BTW, here's a NOS plate: https://www.ebay.com/itm/1957-1966-Buick-Skylark-Lesabre-Electra-NOS-GM-V8-4V-Carb-Base-Plate-1353377-/153513526705.  Anyone know how thick these are?

 

2 hours ago, RivNut said:

They are the engineers; you're not.

OTOH, there are binders full of service bulletins which testify to the engineers' fallibility.

[RivNut]

5 hours ago, KongaMan said:

Not necessarily; the 4GC doesn't use the plate.  Perhaps the plate is there not to conduct heat, but to prevent damage to the AL body of the AFB from the exhaust gasses?

Guess for all the nit pickers out there, it should be noted that the shield is for use only on the AFB carburetors. 

So: The heat shield is used in conjunction with the Carter AFB (Aluminum Four Barrel) carburetor to provide heat to the base of the carburetor AND provide protection to the aluminum from the corrosive qualities of the exhaust gasses.

[TheOldMan]

Ha, I just went through this and did this.   Gasket just for square hole carb on manifold, ( no cutout for the crossover ),  shield next, then gasket for the carb.

 

I figure ( probably wrong ) if the heat will dissipate better before getting to the shield then disparate even more before the carb.

 

IMHO.

 

Dennis.

[KongaMan]

The more one thinks about it, the more it seems that the plate is strictly for protective purposes.  If it helped to transfer heat, it would be used on every carb.  Along those lines, heat is transferred more efficiently without the plate; the carb base will heat more quickly from direct contact with the hot gasses than from the indirect heat transfer of gas to plate to air to base.  Moreover, it's not thick enough to retain any effective amount of heat itself.

[XframeFX]

I see James at BestOfferCounts  lists a Best Gasket heat shield. He scoped-out the best one out there for our Nailheads?

 

John B.

[telriv]

   Having the plate on the manifold does NO GOOD for heat transfer. Think about it & it will come as a logical conclusion. The exhaust hits the plate & has to transfer the heat to the base of the carb. through the smiley face of the gasket.  It WILL NOT dissipate heat as evenly the other way around, plate against carb, as the plate will have more of a tendency to transfer the heat. Trying to get what I'm tryin, to say???

    The way we use our cars today I don't know WHY anyone would want to use the plate anyway.  Block the blankity, blank holes in the manifold under the carb.  NOW YOU HAVE NO USE FOR THE PLATE!!!! as exhaust will NOT be in contact with the aluminum carb. base.  Even gut or wire open the hear riser valve.  I doubt if anyone will notice a difference & IF YOU DO it will more than likely be gone in 2-4 minutes. 

   With the alcohol in today's fuel  it will have more of a tendency to vapor lock as well as make the fuel boil in the bowl.  Could be the reason for hard starting after you turn it off warm, go into the store, & come out 15 minutes later & the car cranks & cranks to start. IT would help IF you put the pedal to the floor as the carbs. fuel has probably boiled in the bowl & dripped out the primary venturi's. The 4GC Rochester don't require one because the base is cast iron, BUT they come with there own set of problems.  IF you have a Rochester & it runs fine leave it alone!!!!   IF you think you want more power then the AFB is the way to go BECAUSE it flows more CFM's of air.

     When these cars were NEW they had to operate under ALL weather conditions WITHOUT any major problems. The reason why the plate was used for aluminum carbs.  TODAY I would think that 99% of our baby's are NOT takin' out on purpose in rain, snow, sleet, hail or any other weather conditions except IF maybe your caught in the rain..  Then you'll most likely stop & sit it out (under cover IF possible) which I have been known to do on those occasions that may arise, BUT I drove the car EVERY DAY.  In ALL weather conditions when it was new. I just bought a new Riviera that NO ELSE had at `18 in my town. Who had Chevelle's, GTO's, 442's, 'Vettes, etc. Boy were they SURPRISED when I put a woppin' on them with my Big Barge Luxury cruiser while they were in the rear smokin' their tires.

    Anyway everyone have a nice week-end.

 

Tom T.

[PWB]

Thats EXACTLY whats happening to my car in this Florida heat.

 

The channels were made for colder climates cold starts, right?

 

So ditch the shield and install the gasket without the holes - should do well here?

 

Edited July 11, 2020 by PWB (see edit history)

[KongaMan]

What you need to block off is the "frown" cutout at the top.  The point is to keep the exhaust gasses away from the aluminum carb base.  One way or another, you need to do that.  As a practical matter (as Tom mentions), you probably don't need to worry about heating the carb, anyway, because you're likely not driving in cold weather.

[telriv]

Paul,

 

    I don't think you will find a gasket WITHOUT the holes/smiley face as I haven't come across any, BUT then again I have never really looked.  BUT after awhile even the good gasket with the metal in it will erode over a period of time because of the exhaust.

Sorry,  don't mean to be yelling, JUST BLOCK THE HOLES LIKE I'VE BEEN TALKING ABOUT FOR AT LEAST 30 YEARS.

 

Tom T.

[KongaMan]

2 hours ago, PWB said:

Thats EXACTLY whats happening to my car in this Florida heat.

Reroute your AC lines through the manifold.  That should keep your carb base nice and cool, and eliminate any consequence of boil over or vaporization.

[telriv]

Note,

 

    The "Nails" have an air gap intake manifold with a pretty open area underneath.  It may be new technology for some, BUT Buick has had this since 1953.

   You would be amazed at how well it works.  Get the engine up to temp. & point your heat gun at the front of the manifold at idle.  It will more than likely be at coolant temp.  Now run it at about 2k RPM's for a few minutes & point the heat gun to the same area. I would guarantee the temp. will be lower.

   Why is this???   As the fuel/air mixture is traveling through the manifold at a pretty high rate of speed & with all the velocity the "Nail" needs to feed each intake port the fuel/air mixture actually has a cooling effect.  I would expect if everything is as it should be & running properly it will get down to about 120-130* with the hood open.  With the hood closed it will run hotter because there is no other way of getting cooler outside air, just under hood hot air.

    Why do most race cars have some kind of hood scopes or a way to get cooler outside air into the engine.

It creates HORSEPOWER for free. It's not just for Ram Air as you need to be doing about 100MPH for it to make a difference.

 

Tom T.

[RivNut]

How many of you guys are old enough to remember running your coiled up fuel lines through a "cool can" which you filled with ice before you pulled into the staging area?  Cool fuel = denser charge = more power. 😎

[telriv]

Yep, been there done that so many times I couldn't keep track.

[KongaMan]

BTW, the gasket in the OP is a bit different from the old gasket I've got hanging here.  Look at how much longer the heater opening is.

 

[steelman]

Wait, PWB has a 67, which means 430 big block. does it have the same heat riser through the intake manifold that a nailhead does? Also, it would not have an AFB, but a Q-jet? Most of these responses apply to the nailhead. Do they apply to the 430 as well? Gasket in the first post is for a Q-jet.

[PWB]

Thanks all.

 

The cat-pee ethanol has a LBP than gasoline. And it is hot as hell here.

 

My base fiber gasket was blown. You have to put a special hi-temp base gasket. Fel-Pro 60043

I took a piece of my old gasket, put a lite on it and it burned up. So did the new one in the carb re-build kit.

What junk.

 

Time to ditch my ratty, tuned down A.I.R. carb anyway. 

 

The corvette guys also have it figured out by completely insulating and sealing:

 

https://www.corvetteforum.com/forums/c1-and-c2-corvettes/1978466-q-jet-carb-base-gasket-tech-info-the-hot-slot-manifold-problem.html

 

 

 

 

I'll set the A.I.R. aside and put this gem in:

 

 

Edited July 13, 2020 by PWB (see edit history)

[carbking]

On 7/11/2020 at 3:00 PM, PWB said:

Thats EXACTLY whats happening to my car in this Florida heat.

 

The channels were made for colder climates cold starts, right?

 

So ditch the shield and install the gasket without the holes - should do well here?

 

 

NOT cold starts? There is no heat when the engine is cold  Not going to help starting.

 

The ports are there for driveability in cold weather or cool humid weather.

 

And as far as plugging the holes in the intake are concerned:

 

I KNOW we are talking about Buicks on a Buick forum, but folks get here by using "search" as well as just reading the forum. Lots of folks think of blocking the entire crossover, not just the holes. Some gasket manufacturers actually supply intake manifold gasket to block the entire crossover. So just wanting to nail this down to a specific point. Block the holes under the carburetor, but don't even consider the possibility of thinking about blocking the crossover UNLESS you have a trailered racecar (good for about 1 1/2 percent increase in power at WOT).

 

Since I rebuilt my first carburetor on my own car in 1959, I have made two MAJOR mistakes on my own automobiles: the first was thinking I was smart enough to get some decent HP out of a Pontiac 301 by using a turbo, the second was listening to the internet, and blocking the crossover on a Pontiac 350. At my age, even with a manual transmission, the car simply was not driveable for the first 20 minutes or so after starting around town (my "heel and toe" skills have deteriorated  ). I finally solved the problem with a carburetor with manual choke.  Oh, and the Pontiac 301? Turns out it wasn't low power. The power and torque are good from 2800 RPM to 2900 RPM. What is needed is a 28 speed transmission to keep the engine in its torque curve!

 

Know this post was verbose; but I felt it necessary to emphasize to block the holes under the carb, but not the crossover.

 

Jon

[KongaMan]

That Vette solution seems to make more sense.  If you'll notice, the OEM plate is open in the middle.  IOW, there's no way to avoid leakage between the barrels.  Similarly, if you don't need a gasket between the plate and the base, why would you need one between the pate and the manifold?  Put it all together, and it seems that the optimal solution is a plate sandwich (plate between two gaskets), with all three pieces cut to seal between the barrels.

[RivNut]

Go to V8Buick.com and search for "Doc's dual plane modifications" for a nailhead manifold.

 

 

[XframeFX]

Paul's application (PWB) is for a '67 and, not a squarebore carburetor. More gasket choices for the Quadra-Jet than for our squarebore nailheads?

 

John B.

Edited July 15, 2020 by XframeFX (see edit history)

[carbking]

Additional information by the OP would have been useful, but since not present, will "scattergun" this post:

 

Four different "original" Rochester quadrajet (Q-Jet) carburetors might be found today on a 1967 430 Buick:

 

7027240 (early production - Federal cars)

7027241 (California cars) (all you folks that believe the "odd last number = standard transmission" - take note of this number)

7027248 (late production - Federal cars)

 

7041305 (service replacement carburetor produced first in 1971)

 

ALL of these carbs were specified to use flange gasket 1378509.

 

1378509 was a thin metal plate with asbestos fibers affixed to the plate. The heat channel looks like the gasket pictured by KongaMan, but the interior of the gasket is completely open, there is no division between the various ports. Because of the asbestos, new gaskets will NOT be of the same construction. One might find a new old stock gasket, or maybe not.

 

I mention the various carburetor numbers one would EXPECT to find because of customers (or potential customers) calling us for rebuilding kits, AN AVERAGE OF 65 PERCENT HAVE A NON-ORIGINAL CARBURETOR! As an aside, this is the major reason we do NOT sell rebuilding kits by application only.

 

If a non-original carburetor is present, then the gasket to the carburetor SHOULD be the exact gasket specified by the manufactured for THAT carburetor. 

 

Rochester did not specify the part number for the heat baffle, and I don't have a Buick parts book, so cannot post that number.

 

There are a very few heat baffles being reproduced. One needs to KNOW what the original looks like when purchasing these, as they are often over-sold by unscrupulous vendors. Carter did specify part numbers for these, and there are almost 200 DIFFERENT for Carter carburetors.

 

And without totally beating the dead horse, research would be much easier if more information were presented.

 

Jon

Edited July 15, 2020 by carbking (see edit history)

[PWB]

My blown base gasket had 

provided a mighty wind.

 

🤴
 

 

 

.

Edited July 15, 2020 by PWB (see edit history)

[carbking]

Additional information:

 

The gasket posted by KongaMan is for a square-bore, but the heat channel in this gasket is the same heat channel used by Buick on the 1967 430. Note the difference in the heat channel in this gasket versus the pictured Corvette gasket.

 

The gasket itself, obviously, is different.

 

Jon.

[PWB]

 

Thar she blows....