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Quick Cat 89
04-27-2005, 08:51 AM
what exactly are you porting when you port the stock exhaust manifolds. im wanting to open them up bad to see what results i get but dont know exactly how much to take out and where exactly to do it. i know most people go with porting instead of buying headers and i know you guys know how...i thought it was the lip at the end of the manifold right where it bolts to the exhaust but where else?

ZRS90sc
04-27-2005, 09:53 AM
some people send em to Tbird88, but i just took a die grinder to the lip and gave it hell, took a good 1/2 inch off, didnt make a whole big difference but i'm sure it was worth it

fturner
04-27-2005, 10:32 AM
what exactly are you porting when you port the stock exhaust manifolds. im wanting to open them up bad to see what results i get but dont know exactly how much to take out and where exactly to do it. i know most people go with porting instead of buying headers and i know you guys know how...i thought it was the lip at the end of the manifold right where it bolts to the exhaust but where else?

From what I've been reading, the only area you want to open up is the exit on the manifolds... at least take the lip thats there out, but some people go further and open it up to 2", which is what tbird88 does.

As far as the rest of the manifold goes... leave it alone as you'll hurt performance. The exhaust ports on the heads are VERY poorly done and the only way to fix those is to fill them in on the floor section by welding and then reshape them. Don't touch the manifolds at the inlet sections.

Just my opinion from all the reading I've been doing here.

Frit

Aaron Pedroza
04-27-2005, 01:27 PM
When I did mine, the only thing I really grinded on was the collector, if that can be called one. I also went through the whole manifold and knocked off any casting burrs and flaws but it was a lot of work and it may have given me 5 hp at most. The primaries would yield the best results but there isn't much room to bore those out much, you can break through the side pretty easy but smooth it out at least if you are looking to get the most out of it. One thing I was going to do was just take it to a place to get it sandblasted and then coat it with a ceramic coating, inside and out, to smooth it out and keep the heat out of the engine compartment.





what exactly are you porting when you port the stock exhaust manifolds. im wanting to open them up bad to see what results i get but dont know exactly how much to take out and where exactly to do it. i know most people go with porting instead of buying headers and i know you guys know how...i thought it was the lip at the end of the manifold right where it bolts to the exhaust but where else?

Quick Cat 89
04-28-2005, 09:04 AM
From what I've been reading, the only area you want to open up is the exit on the manifolds... at least take the lip thats there out, but some people go further and open it up to 2", which is what tbird88 does.

As far as the rest of the manifold goes... leave it alone as you'll hurt performance. The exhaust ports on the heads are VERY poorly done and the only way to fix those is to fill them in on the floor section by welding and then reshape them. Don't touch the manifolds at the inlet sections.

Just my opinion from all the reading I've been doing here.

Frit

so if i take out the lip and smooth everything a little bit up in the manifold i wont tell much of a difference at all? that sucks!! was the pickup worth the trouble of doing it? i know its a bit** to mess with anything on these cars.

fturner
04-28-2005, 12:23 PM
You will feel a difference when you remove that lip AND then install say 2-1/4" or 2-1/2" down tubes to high flow cats. Where the hurting comes in is when folks gasket match the exhaust ports on the head and exhaust manifold.

Frit

Aaron Pedroza
04-28-2005, 12:27 PM
If you went the sand blasting route, you may get 10 hp, you would notice that. It would probably lengthen the life of your wires too.