Contour Enthusiasts Group Archives Forums Modifications Forced Induction Gutted Cats + S/C

Anyone done this?

Just curious.

PM kinger i think that this is what he has done. i think that this is a better route to go because of the scavenging effect the gutted cats creates where as the headers wouldnt. i am no expert though.

Definitely NOT better than headers.

The stock manifolds have very small ports, mingle the exhaust gases, and "kind of" let them flow out on their own.

Making small expansion chambers in the manifolds is definitely better than running with the pre-cats, but it does not provote better scavaging & you still are stuck with all the stock manifold's drawbacks..

The reason Kinger went with the gutted precats was because he had the non-Vortech spec MSDS headers on the car that would not fit, now that he has the 3L with the Vortech on there. The old headers were sold off and his original manifolds were traded in for BNM gutted cats. He can always get the MSDS Vortech spec ones later if his wife lets him touch the car ever again after this project from hell...

Demon,

Yeah i was surprised how freakin small they were when we took mine off.


Brad,

to remove the front exhaust manifold with the S/C does the jackshaft have to come off?

Yes the jackshaft should come off to pull the manifolds on the front.

The difference between gutted cats and headers is going to be negiligible in my mind, maybe 5-10 hp but with 300+FWHP who gives a rip.

Warmonger provided a good analysis between gutted pre-cats vs headers in force fed cars and he belives gutted pre cats are better.

Is it on his webpage??

thanks for the info guys.

Originally posted by kinger:

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The difference between gutted cats and headers is going to be negiligible in my mind, maybe 5-10 hp but with 300+FWHP who gives a rip.

Warmonger provided a good analysis between gutted pre-cats vs headers in force fed cars and he belives gutted pre cats are better.

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Here is the summary, the post is in dyno and drag under "headers prive to be very helpful"

In reply to:

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Simon,

Aren't your running a vortech? With forced induction there is no need to run headers (normally) because the headers work on a scavenging principle and wave mechanics. They help create a suction on the cylinder that actually helps draw more air in the intake charge due to the intake and exhaust valve overlap. With the blower you are forcing the charge in which also forces the exhaust out when the valves are open in the overlap period.
The gutted manifolds will get rid of the restrictive cats in the stock manifolds and should work very well with the blower. As far as down low torque, that is a problem with a centrifugal force blower, perhaps you can change pulleys so the boost comes on quicker and then bypass the excess boost that you are developing.
Better yet, change the pulleys, up the boost, then get one of those water to air intercoolers from the streetflight turbo kit and stick it in there.
The other option that I highly reccomend is to use a small nitrous shot for the cooling effect that it has. With a nice kit, you could tailor it so that it gives a larger shot of nitrous at low boost (for added low-end torque) and then reduces it as the boost climbs. Combine that with the aquamist or the water/air intercooler to control detonation and you are in business.

warmonger

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Bnoon also optimized my manifolds and opened them up a little and smoothed out all the old flacking. They looked great and there is no way I would spend $700 for vortec spec headers over these modified manifolds. I do however have the MSDS Y-pipe

I've got a set of gutted and optimized manifolds siting on the shelf at home. Just working up the motivation to do it. It'll be a PITA since i will have to remove the jackshaft. One of these days I will get around to it. I still think headers will be better than the gutted manifold due to the non turbulent nature of them. But due to the fact that the vortech spec headers dont fit the SVT oil cooler this is the only option right now without messing with the oil cooler. Its cheaper too I think the gutted manifolds will still be significantley better that the stock ones.