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View Full Version : What octane 9.5:1 comp?



miike
04-29-2013, 03:53 PM
Iron heads, forged internals 502.

Thanks

BUIZILLA
04-29-2013, 03:55 PM
minimum of 93...

JayZ
04-29-2013, 04:57 PM
Carb motor? Premium 93 or whatever you can get. Programable efi? You can probably run less octane.

miike
04-29-2013, 05:05 PM
Carb, no anti knock sensors

joseph m. hahnl
04-29-2013, 08:13 PM
Depends when the intake valve closes.


http://classicinlines.com/CompressionRatio.asp






Not recommended




Regular 87-89



Supreme 89-91



Premium 91-93



Race Only





below 7.0



7.0-7.7



7.7.0-8.4



8.4-9.1



above 9.1




The ideal DCR range for a performance motor on pump gas is 7.5 to 8.5

roadtrip se
04-29-2013, 11:19 PM
Running 93 with 10 to 1 on a MEFI3 system. Might be worth looking into aftermarket EFI...

pipnit
04-30-2013, 02:28 PM
with those heads I would guess 93 or higher as people mention. Spend some $$$ on some aluminum heads and you can go a lot lower. I'm at 9.5:1 and run 87 octane with AFR heads and no problems what so ever. 87 is all I can find at the docks around me. At least it's not ethanol gas...

tmdog
05-01-2013, 11:08 AM
9.7:1 with AFR alum. heads, 93 octane only.

miike
05-01-2013, 11:39 AM
Sounds like I want 93 then...

Don't want aluminum heads, I run salt with no FWC