The Stovebolt Site Forums The Shop Area Engine Shop Exhaust Heat Valve

I forgot........on the 235 for '55 which way is off on this? When the weight is horizontal or vertical? Thanks,Scott

Viewing from front:

Horizontal(approx. parallel to ground)= heat on.
45 degree counterclockwise rotation(spring tension should provide resistance when cold)= heat off.

Any idea on how to fix one on a 63 w/integral head. My stays in the vertical position, so truck stays cold in nature until reaches norm operating temp.

You are far more fortunate than most who have them stick in the heat on position and constantly cook their carburetors. I intentionally stuck mine in the counter clockwise heat off position and use the choke.

Thats what I've been doing. Trucks a lil cold natured until she reaches norm operating temp, then she does fine.

Is there any good reason to disable the valve so that they are always allowing heat to flow? The PO of my truck must have removed the flap from the butterfly.

Thanks,
Steve

No valid reason I know of unless he enjoyed cooking his carb and having hot start issues.

Thanks, but since the valve is gone, all the heat would escape through the exhaust so overheating shouldn't result. I guess the downside would just be no preheating in cold weather.

Steve

Not exactly. With the flapper missing exhaust will be allowed to go up and over the intake runners and down the other side possibly resulting in a permanent too hot condition. This was discussed recently on the HAMB and the suggestion over there of using a pc. of sheet steel shaped like the gasket and placed between the manifolds may keep heat down and improve performance.

Good catch Curt. I didn't see that. He'll most likely experience percolation/hard hot start issues without fixing the problem.

Guys,

Wow- I think I'm having a brain meltdown. Doesn't a closed flapper force the hot exhaust up to warm the carb and intake manifold (by not allowing it to go through the exhaust pipe) whereas an open (or missing) flapper would allow the exhaust to escape through the exhaust pipe normally and therefore not heat up the intake manifold and carb? Sorry if I'm just being numb!

Steve

This pic is from Denny Grahams web site.

...Dennys pic...

...Dennys pic...

Here's a section view from the shop manual:

http://chevy.oldcarmanualproject.com/shop/1948_51truck/51ctsm0604.htm

With the flapper completly removed exhaust can go up into the heat box unrestricted. IMO a properly functioning setup is worth obtaining for the cold start driveability it provides.

Curt,

Thanks. Now I get it, my heat riser valve is in between the exhaust manifold and the exhaust pipe (1958 Apache with 283) whereas you're referencing an earlier set-up that's higher up in the exhaust manifold.

Sorry for the confusion!

Steve

The initial post was about a 235. Since you didn't say it was for a later V8 we all assumed you were referring to the same engine. See how giving complete information can eliminate confusion.

Yes, my bad.
Steve

Hi guys, my flapper is stuck in what I believe is the partially open position. I've hit the weight with a hammer and some PB Blaster to free up the rust but no luck so far. Is this something that I NEED to fix or will it be fine? I've yet to start the motor, but I'm in the process of prepping the motor now. I'd like to keep the exhaust manifold on the motor if possible.Thanks

Keep working at it. Some heat from a torch can help. Tap it back and forth over and over and over. It'll eventually loosen up. Don't put much twisting force on the weight unless you want to replace the tiny pin that holds it on. You might end up having to split the manifolds and access it that way too.

I just put fentons on my truck mostly so the exhaust shop would know where to put the pipes in preparation for my new engine. I am running with no intake heat at all (hey its only temporary) AND its getting cold out around here. and it runs better that it has for a long time. go figure...

Tiny,
I took your advice and it worked! My heat valve is working great now! After removing it from the block, it took about a week of PB Blaster and hammering and some time with a mini torch. Now it moves really easily. I can't believe how locked up it was. Thanks again.

I'm happy it worked for you.