High Compression & Pump Gas??

Old 02-03-2008, 09:07 PM
  #1  
NightStalker496
Junior Member
SHOW GUEST
Thread Starter
 
Join Date: Nov 2007
Posts: 2
Default High Compression & Pump Gas??

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
NightStalker496 is offline  
Old 02-04-2008, 05:50 AM
  #2  
bjuice
Administrator
RACING JUNKIE
 
bjuice's Avatar
 
Join Date: Apr 2003
Location: Greenville s.c.
Posts: 3,239
Default

NOT TRUE......
12:13 to 1 you better have race gas,,,or you will detonate and kill it.
__________________
Bjuice..

"I'M YOUR HUCKLEBERRY ! "
bjuice is offline  
Old 02-04-2008, 10:07 AM
  #3  
sc4405
Member
JUNIOR BUILDER
 
Join Date: May 2005
Location: Dexter, New Mexico
Posts: 69
Default

bjuice is right - that thing's gonna hammer even under the lightest acceleration. And of course pump gas ain't what it used to be..... 8) JB
sc4405 is offline  
Old 02-04-2008, 10:14 AM
  #4  
v8Fiero
Senior Member
MASTER BUILDER
 
Join Date: Nov 2007
Location: Wisconsin cheesehead!!
Posts: 213
Default

I agree with everyting said above. why do you want high compression if your not going to use it?

if you just want that little extra at the track, you can use pump gas compression (9 or 10-1 comp) and throw some nitrous at it to bring it up to the race track performance that you want.
v8Fiero is offline  
Old 02-04-2008, 10:16 AM
  #5  
edvancedengines
Senior Member
DYNO OPERATOR
 
Join Date: Feb 2006
Location: VA Hospital, Dallas, Tx (214 302 1924) cell-972-464-7400
Posts: 540
Default

The problem is not if it can do full throttle acceleration. The problem is when trying to do small part throttle acceleration at lower rpms like as in normal driving.

I am a big compression on the street freak, but this is beyond me with current available pump gasolines. I would be scared to build it knowing this.

If this is what you are determined to do, I strongly suggest to use E-85 Fuel which is available in some places at the pump.

Also follow Big Joe's advice about killing it in gear with foot on the brake.

Ed
edvancedengines is offline  
Old 02-04-2008, 07:16 PM
  #6  
a13badazztoys
Junior Member
APPRENTICE
 
Join Date: Sep 2007
Posts: 24
Default pump gas !!

If your max DCR is over 8.75.. I sure would not try and run any
pump gas!! :cry:
a13badazztoys is offline  
Old 02-04-2008, 09:16 PM
  #7  
NightStalker496
Junior Member
SHOW GUEST
Thread Starter
 
Join Date: Nov 2007
Posts: 2
Default

Thanks everyone, I was planning to run race fuel all the time but it's a streetcar and I was worried that I might want to drive it futher than my fuel cell would allow. I think I'm going to lower the compression to 11 - 11.5:1 and run a good head so I can have the best of both worlds. The combo is gonna be a BBC 496 (4.31x4.25), 11 - 11.5:1, 280/[email protected] .722"/.722" cam. I think that cam will put me around 175psi cranking with 11.5:1 static. What heads would you reccomend for best performance and will this be ok for pumpgas?
NightStalker496 is offline  
Old 02-05-2008, 04:16 PM
  #8  
bjuice
Administrator
RACING JUNKIE
 
bjuice's Avatar
 
Join Date: Apr 2003
Location: Greenville s.c.
Posts: 3,239
Default

your still too border line for pump gas in my book at 11;5;1 ...10:1 max is where i would want to come in...plus you cannot guarantee the quality of fuel you are gettting from the pump ( someone might have mentioned earlier)...

as far as the heads are concerned..there are many more qualified people to answer this..but what i will say is stay away from any heavy port work with the heads or intake for street use..a good bowl blend is about it..

Brian
__________________
Bjuice..

"I'M YOUR HUCKLEBERRY ! "
bjuice is offline  
Old 02-05-2008, 05:10 PM
  #9  
hammertime
Senior Member
RACING JUNKIE
 
Join Date: May 2003
Location: Coldwater, MI
Posts: 2,998
Default

Originally Posted by bjuice
your still too border line for pump gas in my book at 11;5;1 ...10:1 max is where i would want to come in...plus you cannot guarantee the quality of fuel you are gettting from the pump ( someone might have mentioned earlier)..

Brian
I agree with Brian for sure 11.5 in my book is to high also. I'd go with a Brodix BB2 head if it were mine.
hammertime is offline  
Old 02-06-2008, 06:41 PM
  #10  
nofear57
Senior Member
EXPERT BUILDER
 
Join Date: Jun 2005
Location: potash country
Posts: 262
Default

Ya 10:1 maybe 10.5:1 Forged pistons max but check the plugs. Brodix or AFR alum. heads and I would have a real good bottom end so NOS can be added for that "Ka-Pow" factor :wink:
nofear57 is offline  

Contact Us Archive Advertising Cookie Policy Privacy Statement Terms of Service