dual exhaust ? cut frame ?
Thread Starter
Racer
Joined: Jul 2002
Posts: 255
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From: bklyn ny
dual exhaust ? cut frame ?
a friend of mine recently purchased a 1981 corvette . the cars engine was a clean crate motor and there were headers on it . i noticed that when i took the car for a test drive that there was a ratteling on the drivers floor pan. at first i thought it was the heat shield then i looked underneath the car ....dun de dun dun... someone actually took the time to cut the frame and box it so that the exhaust pipe on the drivers side could be straight , the ratteling i felt was the exhaust pipe hitting the innermost corner of the floor pan. my question is : is this common practice ? it looks to be a professional weld but is it as strong ? also how would you remedy the exhaust from hitting the floor pan ? thanks in advance.
Le Mans Master
Joined: Apr 2002
Posts: 7,281
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From: Boston
Re: dual exhaust ? cut frame ? (kingdavidrules)
It might have professional craftsmanship but that is a "bubba" work and actually really stupid. Who would cut the frame in order to have strait exaust 
........bubba of course. It would be wise to modify the frame for better performance due to less flexibility, but just to pass pipes :rolleyes:
It might be stronger now but I doubt it.
Paul :cheers:
[Modified by inferno-vette, 1:08 AM 8/2/2002]
........bubba of course. It would be wise to modify the frame for better performance due to less flexibility, but just to pass pipes :rolleyes: It might be stronger now but I doubt it.
Paul :cheers:
[Modified by inferno-vette, 1:08 AM 8/2/2002]
Racer
Joined: Apr 2000
Posts: 499
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From: Kristiansand
Re: dual exhaust ? cut frame ? (kingdavidrules)
I wont consider it bubba work if its done properly, you have to modify the crossmember to install duals on later C3's.
I made a new crossmember with cutouts (see 700r4/exhaust articles at my page) and it works quite well. But I used rubber mounts to keep the pipes in place.
Miker might jump in here also..:-)
The crossmember is only supporting the engine/trans and it's not really a part of the frame.
But it is important if you get hit from the side. That's why I made a straight crossmember instead of something like the Bowtie version.
I made a new crossmember with cutouts (see 700r4/exhaust articles at my page) and it works quite well. But I used rubber mounts to keep the pipes in place.
Miker might jump in here also..:-)
The crossmember is only supporting the engine/trans and it's not really a part of the frame.
But it is important if you get hit from the side. That's why I made a straight crossmember instead of something like the Bowtie version.
Burning Brakes
Joined: Dec 2000
Posts: 795
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From: Madison MS
Re: dual exhaust ? cut frame ? (Ingar, Norway)
Yeah, that's my question. Did they actually cut the frame or cut and modify the cross member? In order to put duals on a later C3, you need to cut and modify the cross member. 74 was the last year for true duals which run through the cross member. In 75 they started with the cats and single to dual exhaust. Some modification to the cross member has to be done or the exhaust hangs too low. So to answer the question, yes it is common practice to modify for duals. But if they did in fact chop on the frame, then no, there is no need for that to fit duals.
As for the rattle, you may just have to dent the pipe at that point unless you want to drop the exhaust and put a bend in it to bypass the point.
Hope this helps.
dl
As for the rattle, you may just have to dent the pipe at that point unless you want to drop the exhaust and put a bend in it to bypass the point.
Hope this helps.
dl
Drifting
Joined: Jun 2001
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Re: dual exhaust ? cut frame ? (dladd74roadster)
Here is a picture of the factory cross member for dual exhaust. Not a great photo but there are actually two holes in the cross member for the exhaust. The picture looks like the pipes are welded in the holes but they aren't.
This is a 1976 vet, it orginally came with the single exhaust but I changed it. It still had the cross member for dual exhaust, don't know what year they changed cross member but it must of been later than 76.
[Modified by Tominator, 3:33 PM 8/2/2002]
This is a 1976 vet, it orginally came with the single exhaust but I changed it. It still had the cross member for dual exhaust, don't know what year they changed cross member but it must of been later than 76.
[Modified by Tominator, 3:33 PM 8/2/2002]
Pro
Joined: Apr 2002
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From: WInnipeg Mb
Re: dual exhaust ? cut frame ? (Tominator)
My car originally came with 2-1-2 exhaust with only one pipe comming through the crossmember. I still have the two holes for dual exhaust in mine. When i got my exhaust done a few days ago they just put pipes through both the holes. So i'm guessing it was later then 79 that they used a diff. crossmember
Race Director
Joined: Apr 1999
Posts: 15,147
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From: NM
Re: dual exhaust ? cut frame ? (kingdavidrules)
The 68-79 crossmember had holes for dual exhausts. This changed for 80-82. I don't know for sure but would think that the earlier crossmember would be a basic bolt in operation. Anyone done this?
tom...
tom...
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Melting Slicks
Joined: Oct 1999
Posts: 2,581
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From: Tolar Texas
Re: dual exhaust ? cut frame ? (kingdavidrules)
Take the car to an exhaust shop. They will be able to make the necessary adjustments to eliminate the vibration. This should cost very little $.
My cross-member was notched by the installer to provide room for the dual exhaust. The trans mount was also relocated to fit the 700R4. I don't think that any actual difference in cross-member "strength" is significant.
Inferno-Vette, when they installed the ZR1 LT5 engine and 6 speed transmission into your '82, what mods were performed on the cross member to facilitate the dual exhaust and 6 speed? When are you going to post pics of your car for us to see? Why did you remove your '82 Vette w/ZR1 LT5" signature? :rolleyes:
My cross-member was notched by the installer to provide room for the dual exhaust. The trans mount was also relocated to fit the 700R4. I don't think that any actual difference in cross-member "strength" is significant.
Inferno-Vette, when they installed the ZR1 LT5 engine and 6 speed transmission into your '82, what mods were performed on the cross member to facilitate the dual exhaust and 6 speed? When are you going to post pics of your car for us to see? Why did you remove your '82 Vette w/ZR1 LT5" signature? :rolleyes:
Burning Brakes
Joined: Aug 1999
Posts: 774
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From: Palatine IL
Re: dual exhaust ? cut frame ? (Tom73)
Yep. I bolted a '76 trans cross member to my '80. I had to file the mounting holes a little bigger on one side but it was easy. Make sure the thing is straight. It looks like this:
Melting Slicks
Joined: Feb 2000
Posts: 3,050
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From: Fairport NY
Re: dual exhaust ? cut frame ? (kingdavidrules)
You may want to check with BowTie Overdrives. When I converted to a 700R4 I purchased their crossmember. You could run any exhaust configuration you would want with their crossmember. Rod
[Modified by Red73, 9:54 PM 8/2/2002]
[Modified by Red73, 9:54 PM 8/2/2002]
Thread Starter
Racer
Joined: Jul 2002
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From: bklyn ny
Re: dual exhaust ? cut frame ? (vettesite)
i like what you did with the exhaust , especially the "H" pipe. do you know where the best place to put the "H" pipe is ? i recall reading an artical on it but do not recall where it was best placed.
