'65 Heat Riser Operation Question

[48Super]

I have feed up a stuck heat riser valve on my '65 and I am trying to determine if it is now working properly. When the thermostatic spring is installed, there is about 1/2 turn "windup" in the closing direction so that there is tension between the slot in the valve shaft and the pin that the outer end of the spring in in contact with. As the thermostatic spring gets heated up, it expands relieving the tension and the outer end of the spring will no longer be in contact with the stop pin. To me, the way it looks is that the spring does not actually force the valve to the open position. I believe the exhaust gas acting on the valve plate is supposed to push the valve open once the spring tension is relieved. My problem is that even when the engine is warmed up and I rev it up, the the valve is still in the closed position but I can easily rotate open. Should be so simple, what am I missing? I'd like to get it working properly and not just give up and wire it open permanently. Any information will be appreciated.

[cobravii]

Most people (myself included) remove the flap from inside the heat riser. I pulled out everything and welded up the holes where the rod goes through. I don't drive in the winter or in cold weather so it didn't matter to me that it wasn't there. no more rattling either.

[Guest Steeleco]

I removed mine also. I think the valve has a flywheel on one side with a counter balance weight on it that keeps it closed until the spring heats up and rotates it a 1/4 turn to open it.

[60FlatTop]

Just speculating; those heat risers shift exhaust flow through the intake manifold to warm the fuel charge from the carb during the first 3 to 7 minutes on a cold start. It keeps the car from stumbling or stalling when you put it in gear and pull out of the garage by aiding vaporization of the fuel.

Now that cars are generally fuel injected the fuel can be made less volatile since there is a high pressure atomization right into the cylinder on most.

As FI gets more advanced those of us with old vacuum pump engines might find cold starting a real PIA. A working heat riser will help.

To the flapper restricting exhaust flow, the factory designed it to handle 5,000 RPM's worth of gas flow. My boats might see 4,000 RPM once a month.... maybe.

They aren't hard to keep working and do more good than bad. Better to keep them maintained if you can. When numbers of owners learn to live with the stumble or stall there is a perception that "Oh, all those '60's cars do that." It detracts from an otherwise nice car and the future may make it worst.

Bernie

[JZRIV]

Mike,

This is a very good question and I'm not sure I have what is an accurate answer but will comment anyway to maybe spur addition points of view. Someone can correct me if I'm wrong but I always thought there should be enough wind-up in the spring to fully open it at the proper temperature without the end of spring coming off the post. Once the engine is hot enough and the valve is open, the engine and exhaust system temp will continue to climb until it reaches reaches max operating temp. During this time the spring may continue to unwind and eventually come off the post but prior to that happening, the valve should be open. The counter weight is an assist and holds it open once there but think the spring should be the primary mover.

Not sure if it will help but here is a pic of my 66 valve after freeing it up.

I did note the shaft is off center in the opening which would tend to make one think the exhaust flow would also assist opening but it doesn't seem like there would be much force generated from that; especially since its designed to allow some to leak around the flapper. Its been a couple years but am pretty sure I bench tested mine repeatedly with a heat source and it opened w/o exhaust.

Did you remove the thermostatic spring during the process of freeing it up?

Edited May 11, 2013 by JZRIV (see edit history)

[RivNut]

I posted this sometime earlier but it will be quicker to post it again rather than search for it.

It's the page from my '64 chassis manual that explains the heat riser operation. I didn't read Jason's post and compare it to this; I'll let you do that.

It's in a PDF format, hopefully you can open it.

Heat riser operatioin.PDF

Ed

[JZRIV]

I posted this sometime earlier but it will be quicker to post it again rather than search for it.

It's the page from my '64 chassis manual that explains the heat riser operation. I didn't read Jason's post and compare it to this; I'll let you do that.

Ed

Ed, Thats a much better explanation than the 66 manual has where its barely mentioned. I haven't had any caffeine yet this morning but if there is a 1/2 turn wind-up and a 1/4 turn movement it might make one think the valve should be open before coming off the post but if there is any resistance at all to movement of shaft, that won't happen. The valve has to be really free and have a loose flopping around feel when handling it off the car. Testing it cold is one thing but when it heats up it could bind up again so be aware of that. I know you said you can move it with your hand but it might be a bit too snug yet or perhaps have a tight spot in the closed position and once it starts moving (breaks loose) its OK. I have a feeling that might be all it is.

Try working with it some more and bench test it holding in vice at the same angle it is on the car. I slowly heated the housing and flapper plate with a propane torch keeping it away from T-spring to simulate being heated by exhaust.

Edited May 12, 2013 by JZRIV (see edit history)

[48Super]

Thanks for the excellent information everyone. I will remove the heat riser and perform a bench test as you recommend. When I initially removed the valve, I took off the thermostatic spring and glass beaded the entire part. I used some PB Blaster and carefully worked the counter weight back and forth until it was totally free. The flapper seems to move with no problems and the spring seems OK. Unfortunately, I did not get a picture of the valve before I took it apart so I'm not certain I have the thermostatic spring installed exactly as it was originally. The stop spring (located on the shaft between the thermostatic spring and the valve body)which limits the travel of the flapper was rusted away but I found a NOS replacement on Ebay. Jason, where did you get the anti-rattle springs shown in the picture of your valve? They look brand new, did you make your own replacements? Hopefully, I can get this thing figured out and maintain the original function.

[48Super]

I was successful in getting the valve to open under spring tension only. Jason, you were absolutely correct about the problem. When the valve was cold, the flapper was free, when heated up, is had a slight bind. I noticed that the shaft bent ever so slightly. A little tap with a hammer got everything operating properly. I must have tested it about 6 times just because it was so neat to see it finally working correctly. I've included a few pictures showing the valve in the open position. Compare these to the picture of Jason's valve and you'll notice that the stop pin for the spring is on the opposite side of the shaft (toward the bottom of the valve when installed on the car). This had me confused because the manual shows it the way Jason's valve looks. The counter weight is also a different shape. I suspect the previous owner replaced the valve with a similar one. Thanks for the assistance!

[Guest Rob J]

Does anyone know of any type of high temp lube or grease that could be used on the riser to help smooth it's operation?

[48Super]

Rob,

I lubed my heat riser with a high-temp lube I've had around forever. It is basically powdered graphite mixed with some type of solvent. The solvent burns off and leaves the graphite to to the job. GM make a product they recommend for this purpose, see the following info:

AC Delco

Part 10-6000

88900415

Rust Penetrant and Inhibitor

•Contains a special blend of solvents and lubricants

•Dissolves rust and corrosion to loosen nuts, bolts and other fasteners

•Lubricates heat valves and removes manifold deposits to ensure correct heat valve operation

ACDelco Car Care Products - Car Care Tips - Car Shop - Auto Shop

Hope this helps.