looking to ProCharge a 350 ZZ4


Asked by Sep 08, 2012 at 05:09 PM

Question type: Car Customization

so i have a crate 350 zz4 in my 84 trans am, i understand about getting a new tranny and rear end and all of that goodness....just wondering about what engine prep i would have to do with it being 10:1 comp.....Procharger says they have put it on a zz4 and i can run up to 11 lbs of boost with there intercooler safely...but i would like to lower it closer to 9:1 for a bit more reliability and less engine stress, i was hoping somewhere around 9:3:1 would be possible with a fatter head gasket....suggestions???

8 Answers


48 people viewed your question. They don't know and neither do I. Make friends with a good mechanic in your area. That way you can pimp your ride like you want, have help, and enjoy doing it. Offer to buy the pizza and beer.


I do not recommend using a fatter head gasket on a booted engine. Recipe for disaster. 10:1 is good for 11 or 12 lbs of boost safely on 93 octane. I am assuming you are most likely wanting to lower to 9:1 for the octane level requirement.


well yes, but wont putting a thicker gasket give it a lower compression....or does that just give it a bigger area to blow out


really what im trying to do is lower the compression without having to get new heads....my buddy took off his heads and smoothed out the inside near the intake and exhaust , nothing major, just kinda made it look shiny with sand paper and got 9:5:1 from 10:1


That trick will work to lower compression in naturally aspirated engines, but is not recommended for boosted engines. Too much boost will blow out the gasket. It would be safer to port and polish the heads as your buddy did. Not anything I would recommend a novice doing though. May be worth spending a few bucks to have a local machine shop do it.

Best Answer Mark helpful

thanks, i know a decent amount about tuning and engines, but im just starting to get into boost.....so what ur saying over all is that i dont have to lower my compression or anything as long as i dont go over 11 psi of boost, i shouldnt have any problems.....lowering the compression would only really accomplish lower octane requirement?


Yeah.. 10:1 is really about as high as you want to go for a boosted street reliable vehicle. After redoing the math, I would not go more than 4 lbs of boost and you would have to use 93 octane. 10lbs of boost would require race gas (110 octane). At 9.5:1, you could run 8-10 lbs of boost at 93 octane. My math was off on my first quote.


And correct. Lowering the compression ratio lowers the octane requirement.

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