Do I need need heat riser if replacing exhaust?
Thread Starter
Pro
Joined: Oct 2015
Posts: 651
Likes: 45
From: Raleigh area, NC
Do I need need heat riser if replacing exhaust?
Do I need need heat riser if replacing exhaust from the stock exhaust manifold back? Would it make more sense to get exhaust with headers so that everything fits?
Have a 1975 L-48 4-speed, previous owner removed cat converter, converted to true duals. Right side is tight, I have air pump, ac lines (compressor removed and saved). Left side more open, no power brakes or steering.
Have a shop or two who can do the work but I would need to order the exhaust and parts.
As always thanks for any help.
Have a 1975 L-48 4-speed, previous owner removed cat converter, converted to true duals. Right side is tight, I have air pump, ac lines (compressor removed and saved). Left side more open, no power brakes or steering.
Have a shop or two who can do the work but I would need to order the exhaust and parts.
As always thanks for any help.
Intermediate
Joined: May 2019
Posts: 26
Likes: 1
I just put dual exhaust on my 77 L82 4 speed. I was able to leave the heat riser off. The pipe with the donut gasket sealed tight to the stock manifold. You just need to spend more time with the ratchet because the studs are much longer to accommodate the heat riser. In my case, the threads were rusted/burned off the studs where the heat riser was, so I put some spacers in, then tightened the nuts against them. It worked great.
Le Mans Master
Joined: Apr 2011
Posts: 6,284
Likes: 1,171
From: Hermosa
You don’t need the heat riser. It’s job is to route exhaust under the intake for cold starts and running.
as long as you’re putting in new exhaust you may as well go with headers for the additional performance.
as long as you’re putting in new exhaust you may as well go with headers for the additional performance.
Race Director
Joined: Jan 2000
Posts: 12,399
Likes: 247
From: San Jose CA
You can't go wrong with Hedman or Hooker headers.
I'm running American Racing headers and they're works of art, undoubtedly flow better than the ones above but come with a premium price.
Traditional sound is subjective. Some people equate raspy drone-y flowmasters with "traditional sound". I really like Magnaflow style mufflers - straight pipes with baffled cans (absorptive). They have a tendency to follow the load of the engine as far as noise goes. The more power you're putting out and/or applying, the better they sound. Once you make a decent power level, though, they can get drone-y as well.
I'm running Borla ProXS on mine right now - 1 3/4" ARH headers, dual 2.5" exhaust to dual mufflers.
I'm running American Racing headers and they're works of art, undoubtedly flow better than the ones above but come with a premium price.
Traditional sound is subjective. Some people equate raspy drone-y flowmasters with "traditional sound". I really like Magnaflow style mufflers - straight pipes with baffled cans (absorptive). They have a tendency to follow the load of the engine as far as noise goes. The more power you're putting out and/or applying, the better they sound. Once you make a decent power level, though, they can get drone-y as well.
I'm running Borla ProXS on mine right now - 1 3/4" ARH headers, dual 2.5" exhaust to dual mufflers.
Drifting
Joined: Dec 2017
Posts: 1,306
Likes: 226
From: PA
As others said, you don't need it. If you don't go to headers, you can leave the valve in, just don't run vacuum to it. It's default, i.e. no vacuum, position is open. See this thread https://www.corvetteforum.com/forums...ooths-out.html, post #15
Last edited by vince vette 2; Jul 2, 2019 at 02:07 PM.
Intermediate
Joined: May 2019
Posts: 26
Likes: 1
As others said, you don't need it. If you don't go to headers, you can leave the valve in, just don't run vacuum to it. It's default, i.e. no vacuum, position is open. See this thread https://www.corvetteforum.com/forums...ooths-out.html, post #15
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Le Mans Master
Joined: Apr 2011
Posts: 6,284
Likes: 1,171
From: Hermosa
I can't make a recommend for an exhaust system since I have side pipes. But for headers Long tube headers would net you more power gain vs block huggers or short headers. 1 5/8" primaries unless you got something that is better than stock for flow. Long tube headers can be problematic for ground clearance however. Especially on cheaper ones that don't have quite the right bend to them.
Sound is going to be dependent on the mufflers you use, and a "good' sound is so subjective that it can be really hard to make a recommendation. One thing I think most people do not like is drone. Using an "H" pipe is supposed to reduce or eliminate the possibility of drone, but still muffler dependent. So the muffler is still the big influence. I prefer the independent firing pulses out each pipe and and H pipe tends to mix those pulses for a somewhat different sound.
My suggestion is to do some searches on mufflers and see what has worked well for others in the past. Listen to you tube videos etc. That should help you make a decision.
Sound is going to be dependent on the mufflers you use, and a "good' sound is so subjective that it can be really hard to make a recommendation. One thing I think most people do not like is drone. Using an "H" pipe is supposed to reduce or eliminate the possibility of drone, but still muffler dependent. So the muffler is still the big influence. I prefer the independent firing pulses out each pipe and and H pipe tends to mix those pulses for a somewhat different sound.
My suggestion is to do some searches on mufflers and see what has worked well for others in the past. Listen to you tube videos etc. That should help you make a decision.
Drifting
Joined: Dec 2017
Posts: 1,306
Likes: 226
From: PA
Since the L48 stock had peak horse power under 5,000 RPM, my recommendation would be to look to a tri-y header which can optimize torque in the lower RPM range. Also, as only 2 pipes come down to the collector, you can buy some ground clearance.
Race Director
Joined: Jan 2000
Posts: 12,399
Likes: 247
From: San Jose CA
FWIW, I went to 1 5/8" long tube headers with no stepping or tri-Y and significantly improved power everywhere on my car. This was when I had the stock GW350 engine in the car, which uses 462624 heads, low compression (7.8-8.5:1 depending on who you ask and likely how it was built) and the L-48 cam.