Porting heads and gaskets and headers?

[Guest JAMIE T]

I need some help from the technical masters. I posted this question in the LT1 forum on camaroz28.com, but it seems those guys are all about "which cat-bck should I get?".

I am porting the heads of my LT1. I have Hooker 1 3/4" primary long tube headers.

I bought two differant header gaskets to compare and port my heads to. One is Felpro# 1406, D-port gasket(it is very popular with the LT1 guys). I also picked up the 1470 gasket(LT1/LT4 specific). The 1406 is a bit larger than my headers openings, and the 1470 is very close in size as my headers ports.

Obviously, since I am going through all this trouble, I want to port these heads for maximum power. I am following along with this DIY head porting page,http://members.cox.net/gmarengo/ he used the 1406 gasket to open his exhaust side to. I need to know if I open up my exhaust ports to the larger gasket, will my efforts be wasted when I bolt up the headers?

[Mike C]

IMO, yes. You'll make more power with the smaller port since gas flow doesn't have to deal with the step caused by the too small header compared to the port. Also, most flow gains come in the bowl area and from a multi-angle valve job more than increasing port size. Spend your money cleaning up the bowl and chamber and pay for a good 5 angle valve job, or at minimum a 3. Chevy's have such short exhaust ports, most restriction is in the intake.

[Guest JAMIE T]

Thanks Mike, I ended up using the smaller of the two gaskets as my guide. I have ported plenty of heads before, but mostly small block Fords. They have TERRIBLE exhaust ports, stock, you can cover it with your thumb. So, even when ported they still are not as big as the headers. My Victor Jr's(SBF) on the other hand have raised exhaust ports and flow plenty.

Honestly, these LT1 castings are pretty good. I have about 3 hours in each intake port. That time was mostly spent flattening the roof and opening up the bowl, and off course teardropping the valve guides. I also spent some time, smoothing out the combustion chambers. There was a lip(@1/16" on the exhuast side) from where the factory had cut the seats. Hard to explain, I may try to get some pics.