C3 3" Exhaust Question?
Thread Starter
Drifting
Joined: Jun 2002
Posts: 1,620
Likes: 7
From: Orlando Florida
C3 3" Exhaust Question?
Does anyone have any information on installing 3" exhaust on your C3? Im getting ready to give it a shot on my 75. I tried to purchase a cross member from Bowtie Overdrives, but all they had available was there member for the 700R conversion, not for t-400. Has anyone ever modified one of those to use with a t-400? It appeared it would allow additonal clearance for the 3" pipes to go straight back from the headers. Im not sure if the local exhaust shop can bend the pipes to fit through the stock cross member holes. He should be able to, but I'm concerned about having the pipes so close to the tranny because of the heat concerns. Has anyone succesfully installed 3" with the stock cross member? Any pics would also be much appreciated. :chevy
Melting Slicks
Joined: Aug 2000
Posts: 2,310
Likes: 1
Re: C3 3" Exhaust Question? (tiresmokin75-427)
Here's a 3" pipe going through the '77 cross member, but it's just the one side http://users.erols.com/jerryp58/corvette/exhaust2.jpg.
I think it's the digital camera that makes it look like the hole has been modified. The muffler guy & I had discussed whether or not a 3" pipe could fit trough and he tought it could. He never said anything about modification.
The other side would have been a really tight fit with the trans linkage, but then again, my trans linkage might have been designed knowing there'd be no pipe on that side.
I think it's the digital camera that makes it look like the hole has been modified. The muffler guy & I had discussed whether or not a 3" pipe could fit trough and he tought it could. He never said anything about modification.
The other side would have been a really tight fit with the trans linkage, but then again, my trans linkage might have been designed knowing there'd be no pipe on that side.
Thread Starter
Drifting
Joined: Jun 2002
Posts: 1,620
Likes: 7
From: Orlando Florida
Re: C3 3" Exhaust Question? (jerryp58)
Jerry, Thanks for the pic, hopefully someone else will have some pics showing the pipes comming off of the headers thru the holes. Im alos concerned about ground clearance in the rear. Im only running a 15X8.5 w/26" tall tire.
Melting Slicks
Joined: Mar 2000
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From: WANTED: '68 rear valance with b/u light assemblies IM, e-mail, or PM me here. Thanks!
Re: C3 3" Exhaust Question? (tiresmokin75-427)
This is an easy fix for any quality high performance shop. Find one in your area and have them modify your x-member.
Melting Slicks
Joined: Aug 2000
Posts: 2,310
Likes: 1
Re: C3 3" Exhaust Question? (tiresmokin75-427)
FWIW, here's a pic of my '77s rear http://users.erols.com/jerryp58/corvette/temp/rear.jpg .
Those are 2-1/2" pipes. The car is on the ground. 15x8 wheels with 245-60 tires. So, if I calculated the sidewall height correctly, the tire height should be between 26" & 27".
Those are 2-1/2" pipes. The car is on the ground. 15x8 wheels with 245-60 tires. So, if I calculated the sidewall height correctly, the tire height should be between 26" & 27".
Team Owner
Joined: Apr 1999
Posts: 21,953
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From: Reno Nevada
2024 C3 of the Year Finalist- Modified
Re: C3 3" Exhaust Question? (tiresmokin75-427)
I have a custom (home made) modified cross member. I cut two half moons out of the crossmember straight back from the headers. I then went to a Semi truck repair place and bought two 5 inch lengths of 4 inch exhaust pipe. So I welded these pipes into the two half moons that I cut out. so I was able to run three inch pipes through it. It's worked great for 12- 14 years now. My only change would be to not pass the exhaust through a cross member because it's more difficult to work on.
I would get heavier walled pipe 5 inches long and cut it in half and weld it in place so the exhaust passes under the crossmember. I'll try to get a picture later
I would get heavier walled pipe 5 inches long and cut it in half and weld it in place so the exhaust passes under the crossmember. I'll try to get a picture later
Thread Starter
Drifting
Joined: Jun 2002
Posts: 1,620
Likes: 7
From: Orlando Florida
Re: C3 3" Exhaust Question? (gkull)
Gkull-Much thanks, Since its been so long, you wanta make another cross member? :D I really want to get as much input as I can before doing this. Do you have any clearance problems in the rear? JerryP's pics look like he has good rear end clearance, but he's running 21/2 vs. 3". Anyway, thanks for the information.
later,
Joe
later,
Joe
Team Owner
Joined: Apr 1999
Posts: 21,953
Likes: 1,444
From: Reno Nevada
2024 C3 of the Year Finalist- Modified
Re: C3 3" Exhaust Question? (tiresmokin75-427)
Here's my crossmember. My underneath still has the oil all over from the bad power steering pump that i replaced.
You can see that i have a pretty good straight shot back. The existing factory 2 holes would have placed the pipes right next to the 700R4's bigger tranny pan.
[Modified by gkull, 7:21 PM 8/25/2002]
You can see that i have a pretty good straight shot back. The existing factory 2 holes would have placed the pipes right next to the 700R4's bigger tranny pan.
[Modified by gkull, 7:21 PM 8/25/2002]
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Thread Starter
Drifting
Joined: Jun 2002
Posts: 1,620
Likes: 7
From: Orlando Florida
Re: C3 3" Exhaust Question? (gkull)
Yea that looks good. It's much nicer to see the pipes coming straight back, or close to straight right off the collectors. I will have to show this to my exhaust guy and see if he can modify mine. I don't feel that secure with my cutting torch. It's a one shot deal. Thanks again,
Joe
Joe
Pro
Joined: Jun 2001
Posts: 683
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From: Calgary
Re: C3 3" Exhaust Question? (tiresmokin75-427)
I installed a three inch mandrel bent exhaust system on mine. I went through the stock crossmember, but had to modify the factory transmission exhaust hanger to hold the pipes higher, so they wouldn't touch the crossmember. The lowest part of the exhaust is right in front of the differential, and I sometimes rub there. I have an X pipe under the differential.
If I was to do it again, I would buy oval pipe from http://www.drgas.com and use it from the crossmember to the differential, to gain clearance back. Oh, I would also buy some quieter mufflers as well! :lol:
If I was to do it again, I would buy oval pipe from http://www.drgas.com and use it from the crossmember to the differential, to gain clearance back. Oh, I would also buy some quieter mufflers as well! :lol:
Race Director
Joined: Nov 2000
Posts: 11,872
Likes: 12
From: Waterloo ontario Canada
Re: C3 3" Exhaust Question? (tiresmokin75-427)
I have a 3 inch exhuast on my 75 but I didn't even consider going through the stock holes. They are too close to the transmission. I cut knotches out of the bottom of the stock crossmember then beefed the area up with 1/4 inch plate. I also drill the rest of the crossmember full of holes to lighten it them powder coated it.
Race Director
Joined: Nov 2000
Posts: 11,872
Likes: 12
From: Waterloo ontario Canada
Re: C3 3" Exhaust Question? (ZD75blue)
I haven't a clue about the cross member but the front vacuum tube lost 19 pounds after the acid dip and holes. I powdercoated the piece of swish cheese. All brakets are also done.
My son runs a powder coat division at work so I can get anything done.
My son runs a powder coat division at work so I can get anything done.
Thread Starter
Drifting
Joined: Jun 2002
Posts: 1,620
Likes: 7
From: Orlando Florida
Re: C3 3" Exhaust Question? (ZD75blue)
74vette: Thats great info. Your exhaust guy must have some high dollar equipment in the shop to do those bends. My guy is good and has done many f-bodies ect., but does not have the newer benders ect. So I will most likley have to modify the crossmember. I wish I could just buy one somewhere!!
Thanks for the info.
Norval: You system is state of the art in my book. My capabilities are not at your level. Your exhaust and crossmember look freakin awesome. Thanks for the pics.
ZD75: I dont know if they mfg. 3" cats. Im sure you can find them on the forum, most questions get answered here. Later,
:cool:
Thanks for the info.
Norval: You system is state of the art in my book. My capabilities are not at your level. Your exhaust and crossmember look freakin awesome. Thanks for the pics.
ZD75: I dont know if they mfg. 3" cats. Im sure you can find them on the forum, most questions get answered here. Later,
:cool:
