stevieturbo

Do the exact same rules apply ?

Most info relates to n/a or nitrous assisted engines. Primary header diams are sized to reflect n/a usage, often with big cams and a lot of overlap, with scavenging in mind.

But do the same rules apply, to a high powered supercharged motor, that may use a mild cam, with relatively low amounts of overlap ?

There is talk of how cams and overlap can effect cylinder fill and subsequent emptying, or how the overlap may assist blowing out the exhaust cycle on overlap, should you use a lot of overlap.

But say you are more reliant on the piston pumping out all the waste, with little or no help from incoming charge, with only minimal overlap...

Will the small headers help extract, or will they be too small, to get rid of the huge amounts of power boost can make ?

Obviously Im querying for my own dilemna.

I currently have 1 3/4" LT's that I cut n shut to fit my car but want some decent stainless ones. I can either buy and adapt a set of 1 7/8" LT's ( probably Kooks looks like closest fit ) or get a set of 2" made here in the UK.

Nobody here can bend 1 7/8" tubing.

382, Edelbrock 215cc heads, Vortech V7 YSi, 8.7:1 CR, dual 3" with X-pipe system, currently on modified 1 3/4" LT's
224/230 on 115+4 0.581/0.591 lift ( although soon be increasing that with 1.75 rockers )
Guess at 800+rwhp.

Will 2" headers into a 3" merge collector as the UK source will make me really lose me anything at lower rpms ?
And will they have a positive effect at higher rpm's ?

Or should I try and adapt a set of 1 7/8" Kooks from the US. Space on my right side is very limited due to my steering linkage, and I have to buy, to try....which isnt easy being 4000 miles away ( which is why I opted for cheapy Pacesetters first time around )
But the Kooks do look pretty good. Left side will fit no probs. Right may require 1 or 2 tubes modified at worst.

Steve Bryant

iTrader: (1)

Stevieturbo,
Since your car is RHD, a conversion and turbocharged . . . fitment of long tube headers made in the US for any car might be an issue. Holden (GM division in Australia) makes a number of RHD LSx powered vehicles. I'd be tempted to do some web surfing on the Aussie sites. Also, regarding the primary tube diameter (1 3/4" versus 1 7/8"), I think that it depends on the amount of boost and RPM range that you are running. For a given header design and primary tube length, I personally don't think that it will make much difference.

All my best,

Steve

stevieturbo

Hi Steve, Im supercharged, Vortech V7 YSi, not turbocharged.

I currently have 1 3/4" Pacesetters intended for an F-Body. I had to cut and re shape the front 2 tubes on the right hand side. Other than that, they fitted pretty well.
The left side fitted almost perfectly without any alterations.

I did modify the collectors on both though, but I didnt strictly speaking have to. It just simplified fitting to the car.

A friend has a Monaro CV8, and no way would any LT headers intended for it, fit my car. The steering linkage just sits totally different to mine.

I have studied as many pics as I can, and the F-Body headers are pretty good. Ive seen some C5 stuff that looks good too, but as I say, when you have to buy these expensive items, just to get an actual look....its impossible.
The C5 headers do look like a very snug fit, close to the block all the way down, which is what I need. I would have to sort my own collectors though, but thats no big deal if the tubes were ok.

Before I got the Pacesetters, I had already bought a used set of tubular OE Holden manifolds, a set of Mac Mid-lengths for an F-Body, then finally the Pacesetters.

At the minute, I hang onto 4th til 7000rpm over the 1/4, and it makes about 19psi at that point. Normal shift is around 6500rpm though. I see about 16psi at 6000rpm.

So my query at the minute...is do I stay at 1 3/4", or go for the locally made 2" primaries ?

I am tending to think just go for the 2"....it surely cant hurt that much at lower rpm's, and if it does free up some power at the top.....it will all be good

SStrokerAce

iTrader: (2)

From what I have found exhaust tube diameter is relative to power levels, so if you VE% is much higher than normal levels it's something you should consider.

Bret