Heat Valve on Exhaust On 1961 Cadillac - Gaskets Keep Blowing

[Jack Miller CLC# 24441]

This is my 3rd pair of upper and lower gaskets on my heat valve on the left front side of the exhaust in 18 months. Every time I change it I lube the valve spring and make sure that the door opens and closes with no catching and it is as it should be.
Does anyone here have any idea what I can do, so I can stop this from happening?
I really do not like exhaust work and this should last a long time.
I even asked my local supply house for a heavy duty gasket and they said that there is only one type.

Thanks
Jack

[The Tassie Devil(le)]

Hi Jack,

You need to ensure the surfaces are completely distortion-free, and than construct Gaskets out of an Exhaust Gasket material that has an internal reinforcing membrane.

I would say that what is happening is that there is some excess flexibility in the Exhaust system that is causing excess movement in the area of the Diverter Valve.

Plus, make sure that the threads are not binding when the nuts are tightened, as if it cannot be securely tightened, no gasket will stay in place.

There is a fair amount of Heat and Pressure when the Valve is shut, so the Gaskets, especially the upper one, gets the most heat.

Bruce.

[TJ Hopland]

What vintage motor is this?   I assume they all have some sort of crossover passage in the intake? Is it possible that its blocked not allowing any cross flow so when the valve is shut there is just no where to go?  That would sure make things run hot till it opened.  If this was on a later engine where the valve was vacuum controlled it would not open till coolant temp came up which could be a fairly long period of time.  If its a earlier model where its a locally mounted coil I would think it would open fairly quickly but still could be abusing the gaskets.

[Jack Miller CLC# 24441]

Hi Bruce,

How are ya? Nice to hear from you.
This is my 61 Cadillac, I sold the 75 just too much rust to repair for an old man like me. I got a 77 Corvette for the Eldorado.
I have changed the gaskets and I had a huge 10 bay busy muffler shop (Meineke) change them last. I had bottomed out and they repaired the exhaust and for some reason the gasket blew out and they replaced it. All of the pre-made gaskets that I have used, have a reinforcement in the center of the gasket but they still blow out. I have to do this tomorrow. I even had the surfaces of the heat valve honed flat on a machine that does heads and other surfaces.
I wanted to take the car on a nice fall drive but I don't want this to keep on happening.

Thanks
Jack

[Jack Miller CLC# 24441]

What vintage motor is this?   I assume they all have some sort of crossover passage in the intake? Is it possible that its blocked not allowing any cross flow so when the valve is shut there is just no where to go?  That would sure make things run hot till it opened.  If this was on a later engine where the valve was vacuum controlled it would not open till coolant temp came up which could be a fairly long period of time.  If its a earlier model where its a locally mounted coil I would think it would open fairly quickly but still could be abusing the gaskets.

Hey TJ,

I rushed the question and I forgot to enter the year, sorry. It is a 1961 series 62 convertible 390 motor Y pipe to single. There is a coil on the side and it is not hung up. It closes and opens freely if pushed with your finger. Please read my last post to Bruce.

Thanks
Jack Miller
1961 Series 62 Convertible

[Dave and Deb]

Hi Jack,

Try Remflex gaskets.  We've had similar problems with our '60 and installing these graphite Remflex gaskets solved the problem.

www.remflex.com

Dave & Deb

[Misfit]

I have a 61 engine in my 59 and when I had new exhaust put on, the heat riser was removed. There were no gaskets in between the manifold and riser, or the riser and pipe. The riser has machines surfaces on both sides of it.

MisFit

[Fatz n Finz]

Hi Jack,

Bruce has hit the nail on the head with the flexing issue ,for me any way. The same thing has happened to me just last week for the second time like you blowing from the same place. When taken apart the exhaust flanged end was weak and able to move it around with little or no pressure, plus little chunks were out of it all round the sealing edge. I cut the whole thing off squarely about 3" down the pipe matched up a new flange at my exhaust centre, bought the pipe cut this 3" down as well knocked this flange flatter to suit, welded this onto the old exhaust at the correct angle ( you may need to make up a jig / template for this before you cut anything ) and job done.

[Jack Miller CLC# 24441]

So you are telling me that I do not need the heat Valve?
Why was it on the pipe in the first place? To warm up the motor quicker?

Thanks
Jack

[Otto Skorzeny]

The idea for the valve is to close off the exhaust pipe when the engine is cold  in order to facilitate a quick warm-up for the carb.

Unless you live in Alaska (and even there these cars seem to start and run pretty well without the thing) your car will work just fine without it.

Many people wire them open, remove the butterfly valve inside or remove the entire thig all together.

My '56 hasn't had one on since I bought it. I didn't know it was supposed to have one until I saw it in the manual

[Misfit]

It sends hot exhaust gasses through the intake manifold, which in turn heats the choke thermal spring and also helps prevent carburetor icing in the cold climates.

MisFit

[The Tassie Devil(le)]

G'day Jack,

The Heat Valve is there only to allow the engine to warm up faster in colder climates by warming up the incoming fuel/air mixture to enable better combustion, and for the Automatic Choke to turn off sooner.  

It is there to enable the driver to simply start the car, and drive away, and not have a care in the world about it stalling etc.

Once it starts to play up, stick and the like, then it is not doing its' intended job, and will start to be a nuisance, even though the average motorist won't realise it is playing up.

Most times, when it seizes, it will be in the fully open position, and not cause a problem, apart from the choke taking longer to go off, and then the engine will start using more fuel as it runs richer for longer.

Me, I remove them when replacing the exhaust and if necessary, remove the guts and seal up the pivot holes in the sides and leave the block in place.

But, if they seize up in the closed position, or partially closed, then there is a real problem as the gasses from that side are being directed across under the Carby, and putting too much heat in the wrong place.

Me personally, I like to keep the incoming air/fuel mixture as cold as possible, and therefore increasing power.

Bruce.

[John Morris #23947]

What about a restricted exhaust, like a clogged muffler? Causing excessive back pressure?

[Jack Miller CLC# 24441]

What about a restricted exhaust, like a clogged muffler? Causing excessive back pressure?

Johnny Boy,

Stick a potato in the rear of your exhaust pipe and find out!

Have Fun
Jack

[John Morris #23947]

Hey Jack! Nothing a little laxative or Drano cocktail won't fix!!

[Jack Miller CLC# 24441]

I have to get a kit so I can now re thread and put a Heli coil in on the exhaust pipe end, as between the Heat valve (or the mechanic stripped the inner side) and Y pipe is loud.
The torture never stops.

Jack