Small Block & Big Block Chevy Specific Mouse & Rat Motor Discussion & Conversions

How much compression on pump gas with iron heads?

Thread Tools
 
Search this Thread
 
Old 03-02-2013, 03:35 PM
  #1  
TECH Enthusiast
Thread Starter
 
Felix C's Avatar
 
Join Date: Dec 2004
Location: Miami, FL
Posts: 627
Received 2 Likes on 2 Posts

Default How much compression on pump gas with iron heads?

Thinking of an old school build with either an iron head BB or SB.

What type of compression on 93 octane? 9.5:1 is the most possible?

Considering Comp 268H camshaft.
Old 03-02-2013, 03:43 PM
  #2  
TECH Veteran
iTrader: (11)
 
87silverbullet's Avatar
 
Join Date: Mar 2007
Location: Slidell,LA
Posts: 4,873
Likes: 0
Received 8 Likes on 7 Posts

Default

I've had 10:1 on a sbc on 93 octane with that same cam and iron heads
Old 03-03-2013, 05:13 PM
  #3  
Staging Lane
 
bigdog7373's Avatar
 
Join Date: Oct 2012
Location: south florida
Posts: 54
Likes: 0
Received 0 Likes on 0 Posts
Default

I run 9.5:1 on 87 without problem in my 350. I'd say you can run 10:1 easy on 93 without worry
Old 03-03-2013, 05:45 PM
  #4  
TECH Regular
iTrader: (9)
 
ironmanLS1's Avatar
 
Join Date: Jul 2012
Location: Export, PA
Posts: 422
Likes: 0
Received 12 Likes on 9 Posts
Default

I have a 350 with 11.4:1 with steel heads and a 400 at 11.7:1 with aluminum heads. Both run on 93. I usually keep the timing 36 or less. Had them both apart for inspection and no sign of detonation. But there are more variables than only looking at static compression.
Old 03-03-2013, 05:54 PM
  #5  
Staging Lane
 
bigdog7373's Avatar
 
Join Date: Oct 2012
Location: south florida
Posts: 54
Likes: 0
Received 0 Likes on 0 Posts
Default

Originally Posted by ironmanLS1
I have a 350 with 11.4:1 with steel heads and a 400 at 11.7:1 with aluminum heads. Both run on 93. I usually keep the timing 36 or less. Had them both apart for inspection and no sign of detonation. But there are more variables than only looking at static compression.
Wow 11.7:1 is the highest i've heard of on pump gas. That's a well tunes motor.
Also remember location plays a role is what you can run because of temperature and elevation.
Old 03-03-2013, 08:52 PM
  #6  
TECH Regular
iTrader: (9)
 
ironmanLS1's Avatar
 
Join Date: Jul 2012
Location: Export, PA
Posts: 422
Likes: 0
Received 12 Likes on 9 Posts
Default

It is about 7 years of constant tinkering with. I started racing these combinations years back and a 50/50 mix of VP110 and 94 (back then). I slowly worked away from the race gas and it continues to work well. The aluminum heads are a little more forgiving, but I got this 350 with steel heads that just keeps giving.
Old 03-03-2013, 10:39 PM
  #7  
TECH Veteran
iTrader: (11)
 
87silverbullet's Avatar
 
Join Date: Mar 2007
Location: Slidell,LA
Posts: 4,873
Likes: 0
Received 8 Likes on 7 Posts

Default

Originally Posted by ironmanLS1
I have a 350 with 11.4:1 with steel heads and a 400 at 11.7:1 with aluminum heads. Both run on 93. I usually keep the timing 36 or less. Had them both apart for inspection and no sign of detonation. But there are more variables than only looking at static compression.
Originally Posted by ironmanLS1
It is about 7 years of constant tinkering with. I started racing these combinations years back and a 50/50 mix of VP110 and 94 (back then). I slowly worked away from the race gas and it continues to work well. The aluminum heads are a little more forgiving, but I got this 350 with steel heads that just keeps giving.
Steel heads LOL! You can tell an old school racer.
Old 03-04-2013, 05:02 PM
  #8  
Launching!
 
supermouse4's Avatar
 
Join Date: Nov 2009
Location: Illinois
Posts: 245
Likes: 0
Received 1 Like on 1 Post
Default

9.5 sounds about right, I'd heard about having a CR above 10.0 for iron heads, but never knew that anyone had run it without problems or issues.
Old 03-06-2013, 06:40 PM
  #9  
TECH Enthusiast
Thread Starter
 
Felix C's Avatar
 
Join Date: Dec 2004
Location: Miami, FL
Posts: 627
Received 2 Likes on 2 Posts

Default

If any of you are old enough to recall the 1980s we did high compression iron heads on BBC and SBC and other big blocks and used 10:1, 10.5:1 etc and used pump gas. Do not know what octane it was but do not recall so much concern with detonation as now.

Have octane ratings declined since that era? Pontiac forums I have scouting insist on no more than 9.5:1 with iron heads. Reads strange to me as I had a 10.5:1 Pontiac then without issues.

Pardon have been away from big blocks for a long time.
Old 03-07-2013, 12:23 AM
  #10  
Teching In
iTrader: (4)
 
TheOneHodgepodge's Avatar
 
Join Date: Feb 2013
Location: Norwalk
Posts: 26
Likes: 0
Received 1 Like on 1 Post
Default

My static compression on my iron head 327 was 10.35 on pump gas. The cam was a little more aggressive. I've seen a 10.0 build with that cam before and its still running today in a 80 malibu.
Old 03-08-2013, 11:17 AM
  #11  
TECH Veteran
iTrader: (11)
 
87silverbullet's Avatar
 
Join Date: Mar 2007
Location: Slidell,LA
Posts: 4,873
Likes: 0
Received 8 Likes on 7 Posts

Default

Originally Posted by bigdog7373
Wow 11.7:1 is the highest i've heard of on pump gas. That's a well tunes motor.
Also remember location plays a role is what you can run because of temperature and elevation.
I have run 12.1:1 on pump with AFR heads and I am down south in the heat and humidity like you
Old 03-13-2013, 04:11 AM
  #12  
12 Second Club
iTrader: (49)
 
bww3588's Avatar
 
Join Date: Sep 2005
Location: Chillicothe/Lima, Ohio
Posts: 8,139
Received 8 Likes on 8 Posts

Default

Originally Posted by 87silverbullet
I've had 10:1 on a sbc on 93 octane with that same cam and iron heads
As do I. Except I have vortec heads which requires less timing so it's a win-win for me. I'm sitting at 10.3 right now with the 268h as well.



Quick Reply: How much compression on pump gas with iron heads?



All times are GMT -5. The time now is 12:28 PM.