High Compression & Pump Gas??
04-07-2008, 07:43 PM
#31
Senior Member
RACING JUNKIE
Join Date: Sep 2007
Location: Montvale, VA
Posts: 1,431
My 496 is 11.5:1.Canfields and I race with 93 octane :shock: No problems yet.Plugs look good and have seen a speckle.Motor never goes over 145 degrees water temp though.But my GMPP Fastburn (aluminum headed ZZ4,basically)in my Impala is only 9.5:1 and will not run on 91 octane without rattling,gotta use 93 in it.But it is also 4200 lbs with a 4-speed and 2.73 rear gears.Talk about a load taking off on a hill!!Especailly if my woman's with me :shock: Don't tell her I said that 
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04-07-2008, 10:56 PM
#32
Member
JUNIOR BUILDER
Join Date: Nov 2003
Location: Phoenix, AZ
Posts: 70
Re: High Compression & Pump Gas??
Originally Posted by NightStalker496
I've been told many times that a high compression engine (12-13:1) can be driven on pump gas as long as it does not have a heavy load on it, i.e. it's just driven normally down the street. I'm planning a 13:1 BBC project with aluminum heads and now I'm wondering if there is any truth to this? Also, if this is true what would be the max dynamic compression ratio or cranking psi, I should aim for so if I had to drive it on pump gas for a few miles it would be ok. Thanks
Hey just a note before you start that BBC project- We have a 604 BBC pump gas motor 900 hp ready to rock with all brand new parts- interested? Let me know, Ill post it back on Racing Junk
www.worldsfastestorganization.com
04-18-2008, 04:11 AM
#33
Junior Member
SHOW GUEST
Join Date: Jul 2005
Posts: 7
I see people saying that build lower compression engines and spray to get the HP you want. Well just what does Nitrous do? It raises cylinder pressure ......what is the difference?????? What is the first thing that must be done to use Nitrous? You HAVE to RETARD the timing. In my opinion timing is the single largest contributor to detonation. You can detonate an engine just as bad with an 11-1 motor as you can an 13-1 and use the same gas due to timing. You cannot run the same timing at 11-1 that you can at 13-1. On the same motor. Matter of fact you WILL slow down by switching to racing gas if you have your 11-1 tuned properly. I hear people saying that their 10-1 engines will not run on pump gas. Well give me your 10-1 engine and I will save 4.00 a gallon and probably run faster.
Good answer,plus the guys at NOS always tell you to up the octane when you spray,anyways :?
06-04-2008, 04:47 AM
#35
Junior Member
SHOW GUEST
Join Date: Aug 2007
Posts: 2
I run 11.5 compression on the street with 93 octane but I have a digital rpm switch with a timming retard adjustment on the dash. This is my setup in case I want to use the spray. Must have the octane if you want to spray.
06-05-2008, 03:02 PM
#36
Senior Member
RACING JUNKIE
Join Date: Mar 2006
Location: EUGENE,OR.
Posts: 3,391
I run 12.5 pistons in a 427 BBC all roller & Lunatti (healthy cam). I am certainly no expert, but here is what I DO know... With extensive port & polish, my comp is about 10.2 now. I run 50/50 93 & 110 leaded... occasionally straght up 93 & ZERO problems at low & high RPM's. It has 488's & 3500 stall. No pings, hestitaions, etc... again, I am not an expert. I will say I have over 100 hours on this motor w/ fuel above. It's a hell of a topic that everyone has thier opinions on though!! Good luck.
