Exhaust Manifold
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Joined: Sep 2023
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Exhaust Manifold
I’ve got a 73 with a L48 my left side manifold is cracked I’d like to find a good used set of #3989036 manifolds . I’ve found RH ones but no LH does anyone know a good scours for used parts. Sec question is there a good quality set of short headers that will work without modifying stock exhaust
Team Owner
Joined: Mar 2002
Posts: 44,639
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From: Huntsville AL
First, there is no such thing as a LH 3989036 manifold, this manifold is interchangeable for both RH and LH sides and is marked 3989036 RH.
The correct 1973 Corvette w/ 350 engine manifold is 3932461 RH and is installed on both the RH & LH side of the engine. I just verified this on my original 1973 w/ L82 engine.
Also interesting is the 1985 GM parts manual doesn't list this PN in any of the 57-82 manifolds, it shows the 372243 for 66-68 RH & LH, 68-71 RH, 72-80 RH & LH. I'm assuming this is a replacement PN manifold.
The correct 1973 Corvette w/ 350 engine manifold is 3932461 RH and is installed on both the RH & LH side of the engine. I just verified this on my original 1973 w/ L82 engine.
Also interesting is the 1985 GM parts manual doesn't list this PN in any of the 57-82 manifolds, it shows the 372243 for 66-68 RH & LH, 68-71 RH, 72-80 RH & LH. I'm assuming this is a replacement PN manifold.
Burning Brakes
Joined: Oct 2013
Posts: 1,114
Likes: 520
From: McClellandtown, Pa.
I’ve got a 73 with a L48 my left side manifold is cracked I’d like to find a good used set of #3989036 manifolds . I’ve found RH ones but no LH does anyone know a good scours for used parts. Sec question is there a good quality set of short headers that will work without modifying stock exhaust
Just making sure, I see you have 1974 as part of your forum ID. You mention you have a 73 L48 and are looking for exhaust manifolds with part#3989036. That is the part number for ‘a 74 L48 w/o AIR (smog). That means these manifolds won’t be tapped for the smog tubes. If indeed you have a ‘73 you’ll need manifolds with part number#3932461. These of course will be tapped for the smog tubes, because ALL ‘73’s have AIR.
Check (google)Bairs Corvettes in Linesville, Pa.
Hope this helps,
Tooch
Race Director
Joined: May 2006
Posts: 18,692
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Hi Cmh1974,
Just making sure, I see you have 1974 as part of your forum ID. You mention you have a 73 L48 and are looking for exhaust manifolds with part#3989036. That is the part number for ‘a 74 L48 w/o AIR (smog). That means these manifolds won’t be tapped for the smog tubes. If indeed you have a ‘73 you’ll need manifolds with part number#3932461. These of course will be tapped for the smog tubes, because ALL ‘73’s have AIR.
Check (google)Bairs Corvettes in Linesville, Pa.
Hope this helps,
Tooch
Just making sure, I see you have 1974 as part of your forum ID. You mention you have a 73 L48 and are looking for exhaust manifolds with part#3989036. That is the part number for ‘a 74 L48 w/o AIR (smog). That means these manifolds won’t be tapped for the smog tubes. If indeed you have a ‘73 you’ll need manifolds with part number#3932461. These of course will be tapped for the smog tubes, because ALL ‘73’s have AIR.
Check (google)Bairs Corvettes in Linesville, Pa.
Hope this helps,
Tooch
Melting Slicks
Joined: Feb 2018
Posts: 2,321
Likes: 720
From: Marietta GA
I found a used set with the correct P/ N RH on eBay. If the studs are still on the manifolds you will need to remove them before installing them on your 73 engine. I am a pretty old guy and it took me about 10 seconds to break the first stud off using a 3/8 inch socket. Use a torch with map gas to heat up the stud before Turing it just a little, a guy on YouTube kept adding candle wax, so I did the same. After f- cking up the first stud, I took it really slow. Look for the YouTube video so you don’t brake any of the studs. I had mine power coated and they look extremely good.
Thread Starter
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Joined: Sep 2023
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First, there is no such thing as a LH 3989036 manifold, this manifold is interchangeable for both RH and LH sides and is marked 3989036 RH.
The correct 1973 Corvette w/ 350 engine manifold is 3932461 RH and is installed on both the RH & LH side of the engine. I just verified this on my original 1973 w/ L82 engine.
Also interesting is the 1985 GM parts manual doesn't list this PN in any of the 57-82 manifolds, it shows the 372243 for 66-68 RH & LH, 68-71 RH, 72-80 RH & LH. I'm assuming this is a replacement PN manifold.
The correct 1973 Corvette w/ 350 engine manifold is 3932461 RH and is installed on both the RH & LH side of the engine. I just verified this on my original 1973 w/ L82 engine.
Also interesting is the 1985 GM parts manual doesn't list this PN in any of the 57-82 manifolds, it shows the 372243 for 66-68 RH & LH, 68-71 RH, 72-80 RH & LH. I'm assuming this is a replacement PN manifold.
thank you
Race Director
Joined: Nov 2006
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From: Sunshine Coast, Queensland, Australia
2025 C3 of the Year Finalist - Modified
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Cruise-In VIII Veteran
All the small blocks in the late 60"s and through the 70's are 2 inch outlets. To get 2 1/2 inch manifolds you need to look at aftermarket replacements or , if my memory is correct, 63-64 high performance small block vette.
I went with ceramic coated aftermarket manifolds that I then port matched and mildly ported.
I went with ceramic coated aftermarket manifolds that I then port matched and mildly ported.
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Team Owner
Joined: Mar 2002
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From: Huntsville AL
The GM 3932461 RH exhaust manifold is 2" outlet
GM 3846563 (LH) and 3797902 (RH) are examples of 2 1/2" exhaust manifolds. 65-67 C2's that were equipped with RPO N14 (side mount exhaust) all had 2 1/2" exhaust manifolds (someone correct me if I'm wrong).
GM 3846563 (LH) and 3797902 (RH) are examples of 2 1/2" exhaust manifolds. 65-67 C2's that were equipped with RPO N14 (side mount exhaust) all had 2 1/2" exhaust manifolds (someone correct me if I'm wrong).
Last edited by Mr D.; Sep 7, 2023 at 08:16 AM.
Team Owner
Joined: Mar 2002
Posts: 44,639
Likes: 1,827
From: Huntsville AL
Team Owner
Joined: Mar 2002
Posts: 44,639
Likes: 1,827
From: Huntsville AL
For what it's worth if you find a used set of 2 1/2" Ram Horns be prepared to open the wallet for them. Reproduction 2 1/2" Ram Horns are $400 EA which IMO is outrageous. I sold a set that came off my 65 N14 car for $300 a few months ago, they had been setting on a shelf for 12 years.
Race Director
Joined: Mar 2017
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From: Virginia
Or you could by repros with 2 1/2 outlets. If the part number is wrong anyway, it should only matter that it works.
One possible example (call to confirm 2 1/2 outlet, and consider ceramic coating, even though it doesn't look stock).
https://www.jegs.com/i/JEGS/555/30110/10002/-1
One possible example (call to confirm 2 1/2 outlet, and consider ceramic coating, even though it doesn't look stock).
https://www.jegs.com/i/JEGS/555/30110/10002/-1
Dr. Detroit
Joined: Mar 2012
Posts: 10,095
Likes: 4,026
From: New Braunfels Texas
I’ve got a 73 with a L48 my left side manifold is cracked I’d like to find a good used set of #3989036 manifolds . I’ve found RH ones but no LH does anyone know a good scours for used parts. Sec question is there a good quality set of short headers that will work without modifying stock exhaust
Jebby