Author Topic: aluminum head compression ratio  (Read 811 times)

Offline mentally_challenger

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aluminum head compression ratio
« on: April 26, 2006 - 10:40:48 PM »
Has anyone ran 11.5 conpression on premuim pump gas with aluminum head? i understand you can boost a CR with alu. but it still seems kinda high. A local machine shop foreman told me this is his rule for aluminum, he also said it it will cost $350 for "stage 1" port job on my edelbrock. is that the standard rate?




Offline Chryco Psycho

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Re: aluminum head compression ratio
« Reply #1 on: April 27, 2006 - 12:15:36 AM »
I would say it is too high depending on th cam used  I have run 11;1 with alum heads & pump gas with just slight pinging
 porting is like a finger print everone is different , I port a lot of heads & I have no idea what a stage 1 port job is , to me there is a right way to do it , you can make the ports a lot larger which couldbe a stage 2 I guess 

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Offline Follicly Challenged

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Re: aluminum head compression ratio
« Reply #2 on: April 27, 2006 - 06:47:14 AM »
Ask your "FOREMAN" guy if the Stage 1 job is "cleaning & straightening all the way through the port", or just a "pocket port & gasket match".
Probably the "latter", if he's dis-assembling, porting, cleaning afterward, checking guide clearance, and re-assembling checking installed heights, seat contact, and spring pressures. Couple of hours involved there already, $350 is cheap.