max Compression on 93 Octane
04-22-2010, 07:25 PM
#1
Melting Slicks
Thread Starter
max Compression on 93 Octane
While I have my LT4 out I am considering milling the heads to increase the CR slightly. Yes, I will mill the intake too.
How high can I go on 93 octane?
How high can I go on 93 octane?
04-22-2010, 07:30 PM
#2
Le Mans Master
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St. Jude Donor '03-'04-'05-'06-'07-'08-'09-'10-'11-'12-'13-'14-'15-'16-'17-'18-'19-'20-'21-'22
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There's not enough info here, it's all about quench and your dynamic CR; not static CR 
04-22-2010, 08:13 PM
#3
Team Owner
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St. Jude Donor '05
503 cam?
04-22-2010, 11:09 PM
#5
Burning Brakes
If it were me, I wouldn't bother. If you're still running the factory bottom end you're at 10.8:1. Lets say some time down the road you end up decking the block and need to mill the heads, then you would really be pusing it for streetability and would be forced to change heads.
Bottom line is you do have room to increase compression and still run on pump gas without any issues. You could bump it around 11.25 without worrying most likely, but you're not going to gain a whole lot.
04-22-2010, 11:33 PM
#6
Race Director
The top guys running for 1/4 mile times are willing to go into the lower 11's (static),,,possibly higher. For the ones I ran the DCR for, they were usually in the 8.2-8.5 range -- which is consider fine. (Escecially if you keep your running temps in the 180-210 range).
I'm thinking you'll only gain about 1-1.5hp/cc.
BTW: Mass engine builders don't recommend going over 10.25:1"ish" -- unless you have a great build and good reason -- because they don't want to assume the extra risk.
Last edited by GREGGPENN; 04-22-2010 at 11:36 PM.
04-23-2010, 12:52 AM
#8
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The Dynamic Compression is what the "Actual" compression is. If you think about it, the piston starts to move up in the compression stroke before the intake valve is all the way closed. Technically you are not building compression until it closes all the way. This form of compression takes into account the valve timing on the camshaft and that is why a cam is used to calculate compression. This number is the one that matters when worrying about knock. Typically one does not want to go above 8.75 MAX DCR.
Hope this helps!
