Lower Heat Riser Mounting

by 73 ss wgn Wed May 22, 2024 4:58 pm

Ready to replace the lower heat riser on the passenger side exhaust manifold on my 73 350. The old one rusted off. On the manifold there's a rusty nub where the new riser slot seems to want to mount. I don't know what that was when it was new. How was this originally mounted and what have folks done in my situation in the past? Thank you.

by 76Chevelle2Tone Wed May 22, 2024 5:54 pm

I got rid of mine. You can get a riser spacer.

by Mcarlo77 Wed May 22, 2024 6:29 pm

Are you talking about the heat stove tube bracket that mounts to the manifold like this one? It's held in place with a round-headed rivet from the factory.

by 76 Malibu Wed May 22, 2024 9:29 pm

I also eliminated mine. The exhaust shop welded the riser valve open. Otherwise, the heat stove on my car looks the same as MCarlo77's.

by 73 ss wgn Thu May 23, 2024 8:00 am

Mcarlo77 wrote:Are you talking about the heat stove tube bracket that mounts to the manifold like this one? It's held in place with a round-headed rivet from the factory.

Yes, that's what I'm talking about.
I might have used the wrong terminology. I can also see the lower shield it is supposed to tuck into. Gotta see if that is there as well.

by 76Chevelle2Tone Thu May 23, 2024 12:43 pm

73 ss wgn wrote:
Mcarlo77 wrote:Are you talking about the heat stove tube bracket that mounts to the manifold like this one? It's held in place with a round-headed rivet from the factory.

Yes, that's what I'm talking about.
I might have used the wrong terminology. I can also see the lower shield it is supposed to tuck into. Gotta see if that is there as well.

Just for clarity: Here is a picture of an exhaust heat riser. It is a valve attached to the exhaust manifold and when closed at cold start routes the exhaust air to the intake manifold.. It often rusts and if stuck closed can damage the engine from overheating.

The heat stove pictured by mcarlo above routes warm air coming off the exhaust manifold exterior to the air cleaner via soft flexible tubing which is often lost. The heat stove mechanism is safer which is why I keep mine functional but removed the riser.

Lower Heat Riser Mounting Oer-3887023_wp_xl

Lower Heat Riser Mounting Oer-3887023_wp_xl

by 73 ss wgn Thu May 23, 2024 2:28 pm

My 70 Corvette had that riser in it and I swapped that for a spacer to avoid the tragedy you noted.

My 73 is also missing the lower heat shield on that manifold and it looks like I'd have to take the manifold off to fix it back to factory. No way I want to try unbolting those 50 year old manifold bolts. I'm wondering if there is a spot welding solution here.

I've had this car since 1985. I seem to remember a silver flexible tube on that side, but I also seem to remember a solid metal tube there, and I see repros for sale that claim to be for a 73 350. But I can't find that tube in my box of random parts and there have been so many cars over the years I could be mistaken.

by 76Chevelle2Tone Thu May 23, 2024 3:34 pm

73 ss wagon,

You could try to just attach the spout section of the manifold heat stove.

As for the stove tubing here is a link.

https://www.ebay.com/itm/154306792511?fits=Year%3A1977%7CModel%3AMalibu&itmmeta=01HYKWKSVTPCSTA8WYCH7350N5&itmprp=enc%3AAQAJAAAA4KKCCnNVrPcr3Zcd7m9PanwT8XMEzSo2hwsuOCKClFKWcsoAVahUIqdHsU3drpDfh0t9IqvoR3%2BC46S3JATJ%2BajexkBVSmD1o4fnirDbT2HQ%2FCsnw%2FA7v2DEabASW4ZeGNdEg%2BSS84%2FdNDyXtAQtvRh%2FD7kDQdLbG53KS0DMF2pEWYcYEc8oZjA%2BFNUFnJ7J4KnafMH4BJuWgOprJnLq1E4W%2Bj87APmkno9nT2G7udmSRkuMNP0XB9ffl5g9DETTeUOBdsYxenBBK7zsMFEe9kC7b5uksClBGZ0NTOkh6d%2F4%7Ctkp%3ABk9SR_qdz_z0Yw

by 73 ss wgn Tue May 28, 2024 6:55 am

76Chevelle2Tone wrote:73 ss wagon,

You could try to just attach the spout section of the manifold heat stove.

As for the stove tubing here is a link.

https://www.ebay.com/itm/154306792511?fits=Year%3A1977%7CModel%3AMalibu&itmmeta=01HYKWKSVTPCSTA8WYCH7350N5&itmprp=enc%3AAQAJAAAA4KKCCnNVrPcr3Zcd7m9PanwT8XMEzSo2hwsuOCKClFKWcsoAVahUIqdHsU3drpDfh0t9IqvoR3%2BC46S3JATJ%2BajexkBVSmD1o4fnirDbT2HQ%2FCsnw%2FA7v2DEabASW4ZeGNdEg%2BSS84%2FdNDyXtAQtvRh%2FD7kDQdLbG53KS0DMF2pEWYcYEc8oZjA%2BFNUFnJ7J4KnafMH4BJuWgOprJnLq1E4W%2Bj87APmkno9nT2G7udmSRkuMNP0XB9ffl5g9DETTeUOBdsYxenBBK7zsMFEe9kC7b5uksClBGZ0NTOkh6d%2F4%7Ctkp%3ABk9SR_qdz_z0Yw

Got it! Thanks. Now to figure out attaching the base to the manifold.

by Mcarlo77 Tue May 28, 2024 9:07 pm

Looking at mine, I don't see any easy solution without removing the manifold from the engine. On the bench, a guy could grind off the rivet head and drill/tap the hole for a short fastener.

by 73 ss wgn Wed May 29, 2024 2:26 pm

Mcarlo77 wrote:Looking at mine, I don't see any easy solution without removing the manifold from the engine. On the bench, a guy could grind off the rivet head and drill/tap the hole for a short fastener.

Prospects look grim for an easy fix.

by Mcarlo77 Wed May 29, 2024 3:31 pm

Found an old Team Chevelle thread discussing how to remove the rivets. Method recommended was to heat the manifold and patiently drive the rivet out with a cold chisel. Of course, nobody mentioned whether it could be done while manifold was still on the car. New rivets are available if you Google GM pt# 3959544.

by 73 ss wgn Wed May 29, 2024 6:44 pm

Mcarlo77 wrote:Found an old Team Chevelle thread discussing how to remove the rivets. Method recommended was to heat the manifold and patiently drive the rivet out with a cold chisel. Of course, nobody mentioned whether it could be done while manifold was still on the car. New rivets are available if you Google GM pt# 3959544.

The two on the bottom are intact. The one on the top is a nub of rust, so that's probably a lost cause.

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