Help with '64 Heat Riser

[Ed S.]

Removed the heat riser from my 64 L76, 2 1/2 inch exhaust (replacing the exhaust system). Cleaned the heat riser. Need help in identifying it - determining if it is original, service replacement or after market. Car was "restored" - including engine removal and rebuild by previous owner.

AIM says the PN for this "exhaust valve" is 3767651. I cannot find any references for that number, including a search of old threads in this forum. Most references state the PN is 3887034, which is applicable to a number of SB & BB engines.

The counter weight on my heat riser has a number, 90019 cast into it on the side.

At least two somewhat obscure vendors (not the usual suspects) list this heat riser, with 90019 to be correct for a 64.

I have attached 2 pics - copied from a website but my heat riser is identical to this one - especially the butter fly which has an impression that runs vertical to the cross shaft - no others that I have seen on any vendor sites have this impression.

One last thing, when my heat riser is on the manifold, the counter weight hits the starter / solenoid heat shield when it is full open. The heat shield does not interfere with the operation of the counter weight - they just touch when fully open.

All that said, can anyone shed light on whether my heat riser is an original, if not what is the correct PN for an original and, can you recommend a source for a good repro.

BTW - I am sure I am installing the heat riser correctly; passenger side, counterweight towards the back, closer to the fire wall, with the beveled edge for the donut on the bottom - it really can only go on one way.

Thanks to all

[Joe L.]

Re: Help with '64 Heat Riser

Removed the heat riser from my 64 L76, 2 1/2 inch exhaust (replacing the exhaust system). Cleaned the heat riser. Need help in identifying it - determining if it is original, service replacement or after market. Car was "restored" - including engine removal and rebuild by previous owner.

AIM says the PN for this "exhaust valve" is 3767651. I cannot find any references for that number, including a search of old threads in this forum. Most references state the PN is 3887034, which is applicable to a number of SB & BB engines.

The counter weight on my heat riser has a number, 90019 cast into it on the side.

At least two somewhat obscure vendors (not the usual suspects) list this heat riser, with 90019 to be correct for a 64.

I have attached 2 pics - copied from a website but my heat riser is identical to this one - especially the butter fly which has an impression that runs vertical to the cross shaft - no others that I have seen on any vendor sites have this impression.

One last thing, when my heat riser is on the manifold, the counter weight hits the starter / solenoid heat shield when it is full open. The heat shield does not interfere with the operation of the counter weight - they just touch when fully open.

All that said, can anyone shed light on whether my heat riser is an original, if not what is the correct PN for an original and, can you recommend a source for a good repro.

BTW - I am sure I am installing the heat riser correctly; passenger side, counterweight towards the back, closer to the fire wall, with the beveled edge for the donut on the bottom - it really can only go on one way.

Thanks to all

Ed------


I doubt that this is an original heat riser valve but I would not rule out the possibility. First of all, the number seen on the counterweight of a heat riser valve is NEVER the part number for the valve ASSEMBLY. Any number on a counterweight may be a GM casting number for the counterweight alone, a derivative of that number, some other number, or no number, at all.

The original heat riser valve assembly for your application could not have been GM #3887034. That part number did not even exist in 1964. It came along in later 1966 for PRODUCTION and SERVICE.

The original valve for your application was GM #3767651. That valve was discontinued in January, 1966 and replaced by GM #3886071. The latter was discontinued in August, 1966 and replaced by GM #3887034 which is still available today at about 75 bucks, GM list. However, the current day valve may differ in very minor ways from the original.

Usually, GM heat riser valves have no part number on the body of the valve although I've seen a few that did. Some valves, especially in "days-of-old" did have a casting number on the counterweight. I believe original 3767651 valves may have had casting number 3746844 on the counterweight. The same number was on the 3886071 and at least earlier manufactured versions of the 3887034. I believe the number has disappeared from the counterweight in later years since I think the manufacturing source has changed.

It would likely be extremely difficult to locate an NOS 3767651 and I would not even consider a used valve. Actually, original valves and the current GM valves are configured VERY close to the same. I would not sweat the nuance differences, including casting number on the counterweight.

[Richard G.]

Re: Help with '64 Heat Riser


Here is a really old one I have that I believe is a GM product.
It could date from the 60's.
I have no proof but its another example from a 2-1/2 exhaust system.

[Joe L.]

Re: Help with '64 Heat Riser

Here is a really old one I have that I believe is a GM product.
It could date from the 60's.
I have no proof but its another example from a 2-1/2 exhaust system.

Richard------


Are there any embossments on the counterweight or elsewhere on the valve?

[Ed S.]

Re: Help with '64 Heat Riser

I am going with the one I have,the one with the 90019 cast into the side of the counterweight --- better than buying a new service replacement or a repro I think. As a discussion point, notice that on the pic that I attached the butterfly has a hump that runs perpendicular to the cross shaft. Mine has that same butterfly. I haven't seen any others like it on vendor websites, but there are a few on E bay that have that same feature and the sellers claim they are old, original small block Chevy parts. As for my counter weight making contact with my solenoid heat shield, I removed the 2 part shield and evenly ground off about 1/8 of an inch of material off of one side of the offending piece; repainted and reinstalled it, clearance is good. Heat shield is a repro from a vendor - probably not correct dimensions. I am good to go but.... If anyone has more info on an old 90019 heat riser I would be interested to ready your comments.

[Richard G.]

Re: Help with '64 Heat Riser

At Joe's provocation I took a closer look at the heat riser.
I did find some more numbers embossed on the counter weight.
Looks like it is indeed a GM part. It was on my 340hp 63.
However I have no clue if it is an "as delivered" part or not.
This is the only markings I could find.
Pictured below;

[Joe L.]

Re: Help with '64 Heat Riser

At Joe's provocation I took a closer look at the heat riser.
I did find some more numbers embossed on the counter weight.
Looks like it is indeed a GM part. It was on my 340hp 63.
However I have no clue if it is an "as delivered" part or not.
This is the only markings I could find.
Pictured below;

Richard------


This has a derivative of the casting number used on the counterweight of the original GM #3767651 valve. Of course, as I also mentioned, it was used on some later valves, too. However, I highly suspect this is an original 3767651 valve assembly.

I believe there would be virtually no visible difference between this valve and the later 3886071 and 3887034 valves, at least the ones manufactured in the 60's and 70's.

So, what's the difference between the 3767651 and the 3887034? I believe the 3767651 had the shaft riding in simple holes bored into the body of the valve. The 3887034 used replaceable bushings in the body of the valve for the shaft to ride in.