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Old 06-22-2010, 04:03 PM
ThirdDegree ThirdDegree is offline
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Help with cylinder head ID and porting

I have an 85 Z28, with TPI. I have a good knowledge of these cars it just when they switched to TPI that seems to keep everybody guessing. Anyway, being that it has a flat tappet cam I would think that it has the L69 416's and not the roller 081's. After going back and fourth between 350 or LT1 or 305 my wife sealed my fate with a limit on car money to do some stuff to the house. So unfortunately I am going to have to use what I got. I have never ported a set of heads and I am very weary about doing this. It seems to me I would be better of paying someone else to do it or get some practice parts before doing so.
From the articles I have read on porting, you should do these things.
-Remove the ridge from the intake and exhaust ports
-Only remove material from 1/2 of the valve seat (into the throat)
-Scribe a line where the bore would be with a head gasket as a guide and unshroud the valves a little then smooth out the combustion chamber without removing more that 2cc's of material.
-Pocket Porting ONLY - this includes a gasket match intake and exhaust with some deep pocket action in the 1/2" before the guides.
-Last get coarse emery rolls to sand out the casting flash on the ports.
Now here's where information get a little conflicting! This article says to cut the guides down to a cone shape
http://www.popularhotrodding.com/eng...ads/index.html
This article says to leave a minimum of 0.125" of material around the guide bosses.
http://www.chevyhiperformance.com/te...ing/index.html
So which method is correct? Who has done porting? Is there anything I am missing besides a good valve job? I posted this question on thridgen.og, but it seems to me every post on that board has an argument, so.... yeah. Thanks.
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