Technical Performance Question about Headers
Thread Starter
Pro
Joined: Jun 2004
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From: Scottsdale, AZ
Technical Performance Question about Headers
I've scanned through all the threads I've saved, tried to recall all the people I have spoken with, and still am conflicted. I am sure the technical experts on the forum know the answer to this question.
I have a 63 roadster and we are putting in a 383 stroker (480 flywheel hp, 465 lbs torque). I am planning on installing custom side pipes. My question is this:
Assuming the same diameter pipe from collector to end of pipe (probably 4"), and same collector size (3") on each header, which is better performing: a shorty header (Sanderson) with bigger primaries (1-7/8") but shorter length from port to collector, OR a header with longer and/or equal length tubes (Hedman or Hooker), but with smaller diameter primaries (1-5/8")?
Thanks in advance,
I have a 63 roadster and we are putting in a 383 stroker (480 flywheel hp, 465 lbs torque). I am planning on installing custom side pipes. My question is this:
Assuming the same diameter pipe from collector to end of pipe (probably 4"), and same collector size (3") on each header, which is better performing: a shorty header (Sanderson) with bigger primaries (1-7/8") but shorter length from port to collector, OR a header with longer and/or equal length tubes (Hedman or Hooker), but with smaller diameter primaries (1-5/8")?
Thanks in advance,
Team Owner
Joined: Oct 2000
Posts: 38,897
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From: Washington Michigan
Smaller diameter/longer primaries enhance low-end torque (which is what a 383 is all about); larger primaries enhance top-end power, but will cost some low- and mid-range torque. Easy answer - where do you spend 99% of your driving time - at redline, or below 4500 rpm? 
Race Director
Joined: Nov 2000
Posts: 10,340
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From: Beverly Hills (Pine Ridge) Florida
From my experience (and I am sure other's will have conflicting ones). Shorty headers will never give the same overall output than a set of long tube/ eqaul length headers will. Shorty's are designed for one thing: To fit easier. Also, larger diameter tubes will help the top end (more flow), but will hurt the low and mid range typically. Now the big question is by how much will one be more effective than the other. Sometimes a Shorty header is the only thing that will fit properly.
But my first question is: Was the engine actually dyno'd and what was the exhaust setup on the dyno?
Plasticman
But my first question is: Was the engine actually dyno'd and what was the exhaust setup on the dyno?
Plasticman
Team Owner
Joined: Mar 2003
Posts: 26,118
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From: Greenville, Indiana
Originally Posted by JohnZ
Smaller diameter/longer primaries enhance low-end torque (which is what a 383 is all about); larger primaries enhance top-end power, but will cost some low- and mid-range torque. Easy answer - where do you spend 99% of your driving time - at redline, or below 4500 rpm?
John makes a vailid point that is often the point of the discussion. I am of the opinion that if you have a 383 and it has a halfway sane cam for the street, you will have more low end than you possibly need regardless of tube size and length. You can get your exhaust oversized to the point that it will affect your throttle response at the low end. If you short change yourself on tube size, you can lose power on the top end and not be able to fix it. Without knowing what flow your heads have, I'd say you should go with the 1 5/8's primary size. The length of the pipes and the collector determine at what point you "come up on the pipe".
Your header manufacturer should be able to answer your specfic questions.
I wouldn't put headers on a car unless I wanted to make sure I could "go for it". In that case, I would want what was tuned into my chassis and engine. Again, your header manuf. can suggest what is best unless he is working out of a blacksmith shop.
Safety Car
Joined: Feb 1999
Posts: 3,631
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From: Fountain Hills AZ
Originally Posted by Plasticman
Also, larger diameter tubes will help the top end (more flow), but will hurt the low and mid range typically. Now the big question is by how much will one be more effective than the other.
Plasticman
Plasticman
It can be a real crap shoot unless you have a comparison of very similar combinations. I've noticed that many of the magazine dyno comparisons have shown little or no loss of low end power from the larger tube headers. In every case though, the dyno reads start at 2k rpm or higher, which doesn't tell you anything about what is happening below that rpm. In street driving, what's happens from idle to 2k is a BIG deal.
As for tube sizing for a 383, I'd consider 1 3/4" the minimum. I have 1 5/8" long tubes on my 327 and noticed no loss of low end compared to the stock manifolds.
