does 1/8" make a difference with headers?
 

why are SLP's long-tube headers 1-3/4", while ARH, Dynatech and StainlessWorks are 1-7/8"? are the factory headers 1-7/8"? trying to decide what to go with, thanks

yes

go with 1 7/8

/thread

http://www.camaro5.com/forums/showthread.php?t=63640

SLP headers are way over-priced. If you go 1-3/4" just get BBK.

Yes, 1/8 inch does make a difference. With each progressive size up in diameter you will make a little more power (the more power a car is already making the more this is true) and the peak power numbers move further up the RPM range. For these cars, I like going with 1 7/8 headers for naturally aspirated street applications. For race or forced induction applications then I like 2 inch. Here is a good article that explains this and several other factors in selecting headers.

It seems like the SLP header cars alway make less hp/tq than the cars fitted with ARH 17/8's on my dyno.

Maybe power robbing factory manifolds are 1 3/4" but they aren't long tubes into 3" collectors. I bought a complete SLP system for its unique sound which makes this driver happy. A couple of horsepower is the difference at high RPM in 1 3/4 vs 1 7/8.
Also the right CAI selection will show some difference on the dyno.

Its all about how a header scavenges the gasses away. Conventional headers it is best to go to the size you need to scavenge the gasses you create. Most semi stock or mild power adder equiped cars are fine with 1 7/8...High HP 700 RWHP up can benefit from 2 inch exhaust. However, in my case I actually went with 1 3/4 Doug Thorley Tri Y headers. The way they scavenge is unique in that they clear the gases out of opposing firing cylinders thus clearing the tube for the next one that fires. The net result is a collector that is not constricted to 3in but is equivilent to a 4 1/2 inch collector. Just food for thought.
Stock is fine with 1 3/4
mild is fine with 1 7/8
wild is fine with 2

On a typical bolt on street car application you will pick up about 5-10 horsepower and 5 lb.-ft between 1 3/4 and 1 7/8.

The SLP System and a CAI gave me enough pull till I get a cam. I won't do a cam till my main warranty is over. I don't race mine, so it suites me.

1 3/4 - na
1 7/8 mild FI
2 inch if you are going bigger then stock and a big blower etc

You will notice if you actually get one car and swap all these out where you gain and lose power. Unless you drag race it only, power in the midrange and torque is more important then the 10 hp at 7000 rpm

I went with 2" primaries. My car with full exhaust and cai and 2" primaries sw headers dyno'd 434 rwhp. Engine pulled 429 before tuning. Mine's an ls3 and everything else is stock.

It's been shown that each size bigger gave bigger gains while not compromising any lowend.

wow is that SAE numbers? this is probably the highest exhaust/CAI/tune car ive ever seen!:thumbsup:

Doug Thorley Long Tube Headers vs 1 7/8"...
 

I'd been a traditional "Bigger is Better" sorta guy when it comes to primary sizing...but there are exceptions to about every rule. This is the only 1 3/4" Header verses 1 7/8" header Dyno that I've seen where a 1 3/4"design (DT Try-Y) could come close to a 1 7/8"......and in this case it actually made more power. It's hard for us to reccommend a product to a customer that costs more and doesn't make as much power when it comes to these.

Food for thought.
Ivan @ Southwest Speed :D