75 passenger side (right) exhaust manifold

[brusso]

Does anyone know if there is a concave surface between the heat riser valve and manifold. I would like to replace the 2-1-2 exhaust with true duals and eliminate the heat riser. I assume that I could replace the studs with the shorter (driver side) type and have the custom exhaust dude do his thing. louscustomexhaust.com.

 

[AKRAY4PLAY]

both sides should be concave, mine were on the '77. you can take the riser out, but need a spacer if you stay with the y-pipe. cheapest thing would be to pull the riser out and knock the flapper out then re-install. the flapper on mine rusted the pins in half and it fell across the pipe causing overheating and poor performance. Brian

 

[KenSny]

both sides should be concave, mine were on the '77. you can take the riser out, but need a spacer if you stay with the y-pipe. cheapest thing would be to pull the riser out and knock the flapper out then re-install. the flapper on mine rusted the pins in half and it fell across the pipe causing overheating and poor performance. Brian

I gutted the heat-riser valve and welded the shaft holes closed and used it as a spacer. If you don't want to ruin the valve then buy a spacer. I have seen spacers for sale at one of the parts houses. Try Eckler's, Corvette Central, etc. I don't remember which one had them.

BTW: I still needed the spacer when I installed '74 true duals on my car.

 

[brusso]

KenSny, I have seen the spacer that you mentioned on Mid-America's web site.

I'm torn between going to the custom exhaust guy, that I have used in the past, and an Off Road exhaust system from my local Corvette parts guy. (corvettesclassics.com) If the passenger side manifold has a concave surface, for a donut, then I will probably go with the custom exhaust. Also, I would like to have an H pipe arrangement. I've heard that with an H pipe you get more low end tourqe but lose some hp on the top end? I also want loud flowmasters. The upside to the Off Road system is that the pipes are oval in shape, even under the rear spring, to allow better road clearance. Anyone know the pros and cons for an H pipe. That may help me decide. Tanx.

 

[KenSny]

I bought the "off road" '74 dual setup for my '75 from Mid-America 3-4 years ago. They are 2-1/2" ROUND and fit like a dream, I only had to cut the long straight pipe to length and bolt it all together. The only reason they call them "off road" is because of the exhaust-legal-tangles....... for the '75s and up cars and they are doing a CYA by saying that you should only install the setup on a car used only off-road..... yeah right!

I can't remember now on which side of the spacer I installed the donut.

 

[resto75]

Yeah something tells me off roading in a vette isn't reallly recommended.

I can just see a vette with monster mudders on it, and don't forget the "off road" exhaust. You could just get headers and go back from there depending on your state regs.

 

[brusso]

OK I guess that in the future I will not make certain assumtions. I assumed that everyone, in this forum, knew what an "Off Road" exhaust was. I thought that my post was wordy enough without that explanation. So my question still stands. Is there a concave (kon-kave 1.Curved like the inner surface of a sphere. Middle English, from Latin concavus. concavely adv. concaveness n.) surface between the heat riser and the passenger side exhaust manifold. Thank you for the input thus far, but I still need some help.

 

[KenSny]

OK I guess that in the future I will not make certain assumtions. I assumed that everyone, in this forum, knew what an "Off Road" exhaust was. I thought that my post was wordy enough without that explanation. So my question still stands. Is there a concave (kon-kave 1.Curved like the inner surface of a sphere. Middle English, from Latin concavus. concavely adv. concaveness n.) surface between the heat riser and the passenger side exhaust manifold. Thank you for the input thus far, but I still need some help.

Geeeeeez - if you feel that way about, take it apart and find out for yourself. Would be less hassle - right?

 

[mvftw]

I took out the hear riser and had true duals 2 1/4" with H-pipe put right to the manifold. Also put in stainless steel studs.

 

[brusso]

Thanks mvftw, That's what I was looking for. Sorry for everyone else if I displayed a little tude. Thanks again for everyones input.

 

[mvftw]

I just want add that ask the exhaust pros on what size pipe to get. I asked 3 pros and all said a stock 350 works best with 2 1/4". I know people will say they use 2 1/2", but that should be used for over 325hp. Also the X-pipe is better, but not with C3's because is has to go to far back. X-pipe needs to be as far forward as possible to work right. C3's have the x-member in the way. But find out for yourself!