How much compression on pump gas with iron heads?
03-02-2013, 03:35 PM
#1
TECH Enthusiast
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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.
What type of compression on 93 octane? 9.5:1 is the most possible?
Considering Comp 268H camshaft.
03-03-2013, 05:45 PM
#4
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.
03-03-2013, 05:54 PM
#5
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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.
Also remember location plays a role is what you can run because of temperature and elevation.
03-03-2013, 08:52 PM
#6
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.
03-03-2013, 10:39 PM
#7
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.
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.
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03-06-2013, 06:40 PM
#9
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Thread Starter
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.
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.
