Lower Heat Riser Mounting
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G3GM :: G3 Tech :: Engine & Driveline
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Lower Heat Riser Mounting
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.
73 ss wgn- G3GM Member
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Re: Lower Heat Riser Mounting
I got rid of mine. You can get a riser spacer.
76Chevelle2Tone- G3GM Member
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Re: Lower Heat Riser Mounting
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.
76 Malibu- G3GM Member
- Street Cred : 2
Re: Lower Heat Riser Mounting
Yes, that's what I'm talking about.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.
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.
73 ss wgn- G3GM Member
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Re: Lower Heat Riser Mounting
73 ss wgn wrote:Yes, that's what I'm talking about.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.
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.
76Chevelle2Tone- G3GM Member
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Re: Lower Heat Riser Mounting
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.
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.
73 ss wgn- G3GM Member
- Street Cred : 0
Re: Lower Heat Riser Mounting
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
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
76Chevelle2Tone- G3GM Member
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73 ss wgn likes this post
Re: Lower Heat Riser Mounting
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.
73 ss wgn- G3GM Member
- Street Cred : 0
Re: Lower Heat Riser Mounting
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.
Mcarlo77- Donating Member
- Street Cred : 78
Re: Lower Heat Riser Mounting
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.
73 ss wgn- G3GM Member
- Street Cred : 0
Re: Lower Heat Riser Mounting
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.
Mcarlo77- Donating Member
- Street Cred : 78
Re: Lower Heat Riser Mounting
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.
73 ss wgn- G3GM Member
- Street Cred : 0
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