High compression
Pro
Joined: Jan 2003
Posts: 706
Likes: 47
From: Denver Colorado
The answer is very much "it depends". The Cross-Fire has flat top pistons unlike the later L98 motors with dished pistons so that gives a boost in compression over the dished ones in later C4s. The cam you are running also matters as the amount of valve overlap impacts dynamic compression also, the altitude you are at matters as does the quality gasoline that you can get normally. Aluminum heads will allow more compression than your stock iron ones: they cool better. I ran a L83 Cross-Fire short block with early aluminum L98 heads, MLS (multi-layer-steel) gaskets and the stock L83 cam on 91 octane with my base timing at 8 degrees before top dead center. The static compression was about 10.5 to 1. I got away with it partially because I'm at 6,000 ft. altitude so the cylinder pressures generated were reduced. If you are at lower altitude, it may not work. If you can get better octane gasoline, that may allow more compression.
Thread Starter
Intermediate
Joined: Oct 2014
Posts: 33
Likes: 0
The highest octane pump gas around me is 93. Am I right to think my compresion with a 58 to 60 cc head give me 11 to 1 compresion? Is more valve overlap better or less sorry for all the questions I got the car cheep and really want to run it at the local 1/8 mile strip as well as driving it on weekends just not sure the best way to go
Pro
Joined: Jan 2003
Posts: 706
Likes: 47
From: Denver Colorado
The highest octane pump gas around me is 93. Am I right to think my compresion with a 58 to 60 cc head give me 11 to 1 compresion? Is more valve overlap better or less sorry for all the questions I got the car cheep and really want to run it at the local 1/8 mile strip as well as driving it on weekends just not sure the best way to go
