ls1290

iTrader: (20)

If a NA 4xx cid motor wasrunning about 13.9:1 compression, what octance level fuel would it need? I am guessing about 100. TIA

<small>[ July 12, 2002, 05:09 PM: Message edited by: Pro Stock John ]</small>

Paul F

iTrader: (2)

I would think more then 100 octane would be needed. Good luck finding that in unleaded. <img border="0" title="" alt="[Sad]" src="gr_sad.gif" />

rich

In our race motors that are na we use 114 octane and with n2o and 14:1 we use 118. you will need to get ahold of Torco race fuels or vp race fuels. Sorry don't have there #'s but they are expensive about 5 bucks a gallon and up. that is for leaded probally more for unleaded

Pro Stock John

iTrader: (34)

I was thinking 114-116 octane gas.

Any more compression and you need alchohol. <img border="0" title="" alt="[Smile]" src="gr_stretch.gif" />

ls1290

iTrader: (20)

I have pretty good access to unleaded 104 and leaded 120( if I deciede that replacing the O2 every month is 'OK' with the leaded ). Would a compression level about 13.0:1 be OK will 100 unleaded.

Terry Burger

iTrader: (4)

I think you can run 14.0:1 with 100 octane. We do it all the time with blowers.

ChrisB

It will also depend on the rest of your setup - how restrictive your intake and exhaust path is, as well as your cam specs.

Chris

AlonzoVersion 1.0

If your going to run that high be sure to pull timing out.

Colonel

Properly setup, 104 will be fine (that is if we're talking about MOTOR octane, not pump or research octane.)

VipZ28

iTrader: (4)

ok 14:1 is obviously alot to ask <img border="0" title="" alt="[Smile]" src="gr_stretch.gif" /> How about 12.5:1? could that be done on pump gas<93> w/ conservative timing? i've seen it before on some old style motors, but haven't really looked at what comp. ratio LS1 guys are running...

XtraCajunSS

iTrader: (2)

I ran a mix of 5 gal 93 and 7.5 gal 104 with no issues at 12.75:1. This is with a conservative tune though. I will most likely run straight 104 once Geoff gets my tuning dialed in. Better safe than sorry...

Shane

ls1290

iTrader: (20)

Another thing to consider that I live up here in the clouds in Colorado, so there is not as much O2 in the air as lower states. Currently I have a 383 Stroker running about 12:1 and runs justfine on pump gas( 91 Octane ). I am looking to build a 4xx Stroker and would like to run at about 13:1.

<small>[ July 16, 2002, 09:09 AM: Message edited by: ls1290 ]</small>

rich

I was talking to an engine builder in Mississippi and he said the rule of thumb is 10.5:1 on pump gas. With aluminum heads you can go up 1 piont of compression because the aluminum head desperses heat that much faster.with the aluminum block another 1/2 point of compression. With a computerized ignition that is as adjustable as the ls1 he said you might be able to go up another point of compression on pump gas with 100 octane it would be ok. That puts us at 13:1 on pump gas with maybe a little kr 100 octane would solve that. With the n20 shot that big he said to go with at least 110 if not 114 octane and pull 10 degrees of timing out.

ls1290

iTrader: (20)

</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by rich:
<strong>I was talking to ....... pull 10 degrees of timing out.</strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">That is great info Rich, thanks <img border="0" title="" alt="[Smile]" src="gr_stretch.gif" />

rich

You are welcome.Glad to help.