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73-87 Chevy _ GMC Trucks => Engine/Drivetrain => Topic started by: shortchevy84 on June 15, 2006, 01:40:00 am

Title: how high of compression?
Post by: shortchevy84 on June 15, 2006, 01:40:00 am
looking at new engine for my truck. how high of compression can i go and still use 87 octane fuel? the 4.6L northstar crate engine available from this website

www.crateenginedepot.com/...827C2.aspx

looks like an excellent choice. it says it can take 87 octane, but i was led to believe that a 10.0:1 CR would be to high for only 87 octane. is this true, or is that just for older style engines? if 10:1 is allowed with newer engines on 87 octane, what other good options do i have to acheive 25+mpg hwy and still have 300+hp. truck will not be used for towing, only as a dailer driver, and i have a 700r4 tranny with approx 3.08 gears. thanks alot for any replies!

Title: Re: how high of compression?
Post by: roundedline on June 15, 2006, 01:17:00 pm
Aluminum block and heads allow higher compression with lower octane since they don't retain as much heat.

Keep in mind that motor doesn't come as pictured. None of the accessories are included nor is the wiring harne$$

Chris Lucas
www.73-87chevytrucks.com
www.captkaoscustoms.com
Project Su
Jimmy 2WD Project

Title: Re: how high of compression?
Post by: DnStClr on June 16, 2006, 05:42:00 pm
I think the Northstar engines from 1999-2002 could run on 87 octane, but not sure about the newer ones. They include a knock sensor, you know, to send a signal to the pcm when the engine starts knocking, to retard the timing. The power is reduced and fuel mileage suffers too, so many people mix 91 and 87 octane in em. In order for the engine to get 320 hp, the higher octane is required. You'd think a 283 cubic inch engine could be run on low octane huh?

Don St.Clair
Culleoka Tn

Edited by: roundedline at: 6/19/06 2:29 pm
Title: Re: how high of compression?
Post by: roundedline on June 16, 2006, 07:10:00 pm
The northstar he posted is the one from the XLR, it sits logitudinally in front of a 4L60E.

Chris Lucas
www.73-87chevytrucks.com
www.captkaoscustoms.com
Project Su
Jimmy 2WD Project

Title: Re: how high of compression?
Post by: DnStClr on June 16, 2006, 09:36:00 pm
Well if I'd only read more than two lines down :lol  Quick, delete that part of my post so I look smart.

Don St.Clair
Culleoka Tn

Title: Re: how high of compression?
Post by: roundedline on June 19, 2006, 02:30:00 pm
ok, I did... :D  

Chris Lucas
www.73-87chevytrucks.com
www.captkaoscustoms.com
Project Su
Jimmy 2WD Project