I've scoured quite a few threads here and at another Vette site, and I've read through the SuperChevy articles on Corvette Headers and Exhaust Manifolds, but I'm still missing some important information, I think.


First I'll start with the things that I think I "know" so that anything that I got wrong can be corrected:

• If you go too big with headers / exhaust you will hurt low-end torque but help high-end HP; you may actually hurt the "scavenging" effect
• "Tri-Y" designs help to maximize torque and are great for HP, too but are EXPENSIVE and often have fitment issues
• Ceramic coating may or may not help with performance / scavenging (seems controversial), but will help with longevity, keeping heat down and looks pretty bling (I'm going with Ceramic coated)
• Focus on fitament or you'll regret your decision later
• "Full Length" / "Long-Tube" headers are the same thing (This confused me for a while)
• 5/8th is generally viewed as good for "mild street 350s" -but what the heck is the definition of mild?!? (not a useful term without a definition)
• You don't want a super short primary length, but teh secondary pipe is actually more important to power and torque
• 1 1/2" primaries for 170 CFM or less; 1 5/8" primaries for 180-200 CFM; 1 3/4 primaries for 210-240 CFM, 1 7/8" for 250-275 CFM (SBCs need never worry about more)
• Head Compability: check compatibility with straight vs. angled spark plugs; I'm actually incredibly confused about exhaust port shape compatibility-do you really need D port shaped headers for D port heads? -Obviously beware raised port heads
• Advanced collector types (beyond the Tri-Y) can help with torque and power- merge collectors that use venturi shaped merge areas and scavenger spike or merge spike designs smooth the airflow and help, too --both are more expensive than standard parallel merge collectors
• Engine assembly lube will screw up your header's ceramic coating- break in a new engine with manifolds on and then reinstall headers after break-in period

Common C3 Corvette Brands:

• Hooker (comps and super comps) -Competition are 1 5/8", Super Comp are 1 3/4, longer and thicker gauge metal
• Sanderson -known for tight fit and being gasket-free
• Patriot- have shorty and tight tuck variants; very reasonable prices
• Stans -the Tri-Y guys; have supported Chevy racing and hot rod types for a long time, fantastic quality at fantastic prices; no idea on fitment
• Summit -a cheaper "clone" of either the Hooker Comps or the Hedmans (some people said hooker some said hedmans... confused...) very reasonably priced
• Hedman- I don't know much about these other than they're very popular and there are some complaints about the passenger side angling down too far
• OBX Racing -another racing focused brand, start at 1 7/8" size? -can be ordered with O2 fittings pre-installed
• Pacesetter- I know very little about these- can come with O2 bungs pre-installed, though
• Melrose- the corvette T-top people; I think they also start with very large headers sizes

What I'd REAALLY like to understand is which of these are viewed as having fitament issues- either with Borgeson Box conversions, Steeroids Rack and Pinion Conversions, sticking down too far and scraping the ground with lowered Vettes, or with pipes that angle down too far.

-I'm not looking to cover side-pipes at all and I realize almost all of them have fitament issues with things like Rack and Pinion conversions.


I've pulled the listed Corvette Header compatibility information from Speed Direct's site for the Steeroids kit, and I've pulled information from the various Borgeson threads, for SBCs anyway (not looking to cover BBC fitment as I realize there are way bigger challenges there).

Here's what I have so far:

• Hooker: Borgeson- FIT (no mods), Steeroids- FIT (no mods) -this is for both Comp and SuperComp versions with SBCs
• Summit? -It will depend upon whether they're a Hooker or Hedman clone -if a Hedman clone, it seems there could be minor fitment issues
• Patriot Tight Tuck- Borgeson- FIT (no mods), Steeroids- FIT (no mods)
• Patriot "regular": Borgeson- ???, Steeroids- ???
• Sanderson Block Huggers- Borgeson -FIT (no mods), Steeroids -???
• Hedman long tube: Borgeson- FIT (no mods), Steeroids (MAJOR ISSUES) -Steeroids claims that MAJOR dimples are required; I'd say go with something else if a Steeroids conversion is in your possible future
• Generic "SBC Headers" (not corvette specific): Lots of fitment issues and Borgeson incompatibility- avoid
• "Schoenfeld" - never heard of these except from Mr Vette but supposedly they clear rack and pinion conversions very well
• Flowtech: Borgeson- FIT (with no mods), Steeroids- ???

Big questions I have:
From a performance perspective, is there anything that I should really avoid, assuming that I've decided to go with full length headers? (Are tight tuck long-tube headers going to cause a significant reduction in performance?)

How do I calculate my exhaust flow? -Use the exhaust #'s from my head's list / CFM sheet? They're ATK modified Profiles and @ 0.500 lift they flow 187 CFM and at 0.600 lift 196 CFM. Soo still in the 180-200 CFM range at the max and I'm looking to maximize torque in my build so I'm guessing 1 5/8" is right for me. -I'm assuming that going with a dual profile CAM that has a longer exhaust duration can help if your head flow numbers are a little bit higher than your exhaust flow numbers. (Note: Yes, I realize that any restrictions further down in the exhaust, mufflers, or cats would reduce the exhaust flow and that's not a minor consideration.)


Are the Summit headers a clone of the Hedmans or the Hooker Comps?

Are there any great-fitting, full-length headers that are also a great value? -The Hooker Comps seem to be just the best fit over-all, but they're honestly out of my price range for headers and I can't find a used coated set to save my life (why would anyone ever get rid of them if they work well and fit with everything?)...



Adam

 

I ran across this thread, and I thought I should chime in. At this time we do not make headers for anything older than a 1997 Corvette. I noticed you listed us for C3 headers, currently we do not offer a header for this generation.

Thanks for looking at us though!!

 

Thanks; I'll update the list.


Adam

 

[quote]If you go too big with headers / exhaust you will hurt low-end torque but help high-end HP; you may actually hurt the "scavenging" effect[\quote]
Mostly theoretical but irrelevant for a smallblock Chevy since the very largest tube that will bolt to the head exhaust flange is 1 7/8”

[quote]"Tri-Y" designs help to maximize torque and are great for HP, too but are EXPENSIVE and often have fitment issues[\quote]
Depends upon how they are made. Some Tri-Y headers designed for a very specific application perform contrary to the common knowledge, but it’s not like there are a lot of companies making Tri-Ys for C3 Corvettes. Back when they were more common…like 50 years ago, Tri-Ys were the lower-cost option. They had small primary tube size and were easier to fit.

[quote]Ceramic coating may or may not help with performance / scavenging (seems controversial), but will help with longevity, keeping heat down and looks pretty bling (I'm going with Ceramic coated) [\quote]
This is just a lot of marketing hype. Again, a theoretical advantage. The most common reason to have a header coated is to inhibit corrosion.

[quote]Focus on fitament or you'll regret your decision later[\quote]
Words to live by.

[quote]"Full Length" / "Long-Tube" headers are the same thing (This confused me for a while) [\quote]
Probably so.

[quote]1 5/8th is generally viewed as good for "mild street 350s" -but what the heck is the definition of mild?!? (not a useful term without a definition) [\quote]
There is no precise definition, but you can make a general assumption that the engine is stock or nearly so, making under 350 horsepower. Not to say that a small primary tube can’t work well on higher horsepower, but a bigger tube flows more gas, so that’s the prevailing thought on this one. But the reality is that if you spend most of your time just cruising around, you’d never know the difference.

[quote]You don't want a super short primary length, but teh secondary pipe is actually more important to power and torque[\quote]
The biggest issue with “shorty” headers is they have no real collector to speak of. Your headers can be a compromise in primary pipe size and length, but if it doesn’t have a good collector, like on Hooker Super Comps, then the design is just slightly better than iron manifolds. There is no shorty header that I am aware of that has a proper collector.

[quote]1 1/2" primaries for 170 CFM or less; 1 5/8" primaries for 180-200 CFM; 1 3/4 primaries for 210-240 CFM, 1 7/8" for 250-275 CFM (SBCs need never worry about more) [\quote]
Again, mostly theory in this context, Nearly every SBC header is 1 5/8 or 1 ¾, so that’s your primary pipe range unless you are looking at the 1 7/8 Hooker sidepipe. You would be able to tell the difference in a very high performance application, but less so in a street car.

[quote]Head Compability: check compatibility with straight vs. angled spark plugs; I'm actually incredibly confused about exhaust port shape compatibility-do you really need D port shaped headers for D port heads? -Obviously beware raised port heads[\quote]
In a magical, ideal world, everything would blend from one transition to another without nary a flea in the way. But the reality is it makes very little difference. As long as the header flange doesn’t overhang anywhere in the port, you are doing just fine. A standard round or rectangular header flange will work just fine on a d-port head.

[quote]Advanced collector types (beyond the Tri-Y) can help with torque and power- merge collectors that use venturi shaped merge areas and scavenger spike or merge spike designs smooth the airflow and help, too --both are more expensive than standard parallel merge collectors[\quote]
Yeah, this is true. But it would have to be a design consideration of the whole engine. Think racing application on this one.

[quote]Engine assembly lube will screw up your header's ceramic coating- break in a new engine with manifolds on and then reinstall headers after break-in period[\quote]
I don’t think you mean assembly lube. And if you do, why would anyone put assembly lube on a header? If you mean anti seize, then I have never heard of that outcome. I also don’t know why you need to use iron manifold to break in an engine. I’ve never done it that way. I guess if your initial fire tune up is way off (lean fuel, late ignition timing) and you do nothing about it, you might roast your headers, but my way of thinking is to set up the tune so that doesn’t happen.

The rest of your question, I have no knowledge or experience and therefor can't comment.

 

I just bought Flowtech Ceramic coated because plans call for engine swap with Angle plug heads. Here they are being connected to my exhaust pipes . They tuck up pretty well