Originally Posted By Hot 340
Originally Posted By Dragula
Originally Posted By Hot 340
Originally Posted By 72Swinger
What pump gas? Non ethanol? 91 or 93? 11.1 with aluminum heads is about the max in the REAL world IMO.
whats your combination? Are you seeing detonation at 11?


I ran 11.6:1 in my 484 with no issues for years. I have a 605 hemi now, and I am right around 11.0-11.1:1 with no issues. The Hemi's are very resistant to having issues with detonation. I would be very comfortable running 12:1 on 93 and watching my timing and tune up. What we use around here is E10, so until they get rid of it, that's what I am running mine on.

I would not run any lower than 11:1 on pump gas with a hemi. If your building it, build it for 12:1 with .027 head gaskets, and switch to thicker ones if you have to.
any trouble with 12:1 on a hot day? That would be my concern.


Never had an issue at 11.6 and I drove it a bunch in 90 temps.....You have to remember anything with aluminum heads that heats up loses compression as it gets to temp...The Hemi has a huge combustion chamber....And drops compression a little at temp. Its not really 12:1 at 185 degress anymore.

'70 Cuda,...605 EFI Hemi Street Car (6.20 best pass, 1.33 60ft)
https://www.youtube.com/watch?v=WYw6RA-k5Bk (6.25 at 108.75mph from inside car)
https://www.youtube.com/watch?v=3zQEb9uxFng (6.25 at 108mph from outside car)
https://www.youtube.com/watch?v=JCvfzsC4NgM (9.9)

'66 Barracuda AWB Stretched nose Blown 440 Car in build stage

'71 Duster Drag Car 400 Low Deck 512 best 6.002 at 115.44mph
https://www.youtube.com/watch?v=Znuo3jMUXTk