99MediumBlueBird

New here, in fact I don't even own a truck lol. I'm building a 5.3 for my firebird. It will be my DD and it'll be NA. I want to keep the engine running on 91 octane. I will be running milled 241 heads. I can make this engine 11:1 compression ratio, I have a feeling it's too much. Any thoughts? I'm trying to reach about 375-400rwhp ball park range. What CR should I bring it to? I figured I'd come here since many of you guys have 5.3's vortecs. It is an lm7 by the way.

oakley6575

iTrader: (5)

11:1 is perfect imo. A lot of guys run high 11's with 91 octane. It depends on your cam choice too

AGearHead4Life

iTrader: (5)

11:1 sounds perfect to me for what you're doing. But I also haven't tried to tune an engine with that ratio...

jmgak47

iTrader: (3)

I would keep the dynamic compression around 8.2:1 and don't go above 11.5 on your static compression.

thegarrettgoines

11:1 if you can choose.
*thanks whoever for the 93 we have in Tx

ltr450ryder

iTrader: (13)

I had 11.5cr on 93 but your cam plays a big role in there too. I had a motor Spec'd with 12.5cr and with the cam Spec'd for it I could of ran 93 octane with It

hog

There are many factors that determine the best c/r. You could have 7.5:1 and have a knocking beast of an engine if its not built right.

peace
Hog