Maximum Compression Ratio

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In my opinion 10:1 to 10.5:1 is a safe range for aluminum heads and pump gas with a conservative timing curve. I run 17 initial/35 total all in at 3500.

In regards to cams. They don't "bleed" off compression. IF you care looking for less cranking compression increase the lobe separation angle. THe duration at .050 isn't the magic bullet for detonation resistance, LSA is.
 
Though normally with duration increases, overlap increases. This bleeding down some compression.
Hence why it is normally said.
True but not totally accurate.
 
Longer duration resulting in greater overlap occurs during intake valve opening and bleeds exhaust gasses into the intake charge at lower rpms, deceasing idle quality. Decreased dynamic compression comes from the later closing of the intake valve during the compression stroke. Greater duration camshafts close the intake valve later like increasing the lobe separation does (/roccodart440).
 
IQ52 said:
Longer duration resulting in greater overlap occurs during intake valve opening and bleeds exhaust gasses into the intake charge at lower rpms, deceasing idle quality. Decreased dynamic compression comes from the later closing of the intake valve during the compression stroke. Greater duration camshafts close the intake valve later like increasing the lobe separation does (/roccodart440).
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I get that, but the guys reading it may not. They may say "let me buy this larger duration [email protected] cam and that will give me the detonation resistance I need" That cam also has a 104LSA. See where I was going with my comment? Really we need to look at both specifications.
 
Agreed! Though cams are a bit of a mystery for most.
 
With all of the above posts, You have been given good counsel, play it safe unless you have the time & $$$ to blow it up and learn the hard way. Even just saying iron vs
aluminum doesn't cut it because of different chambers/spark plug positions/depths etc. etc. etc.. You have to consider if it's not a racing for the money project, You want
it to live long enough to enjoy, even if it does eventually give up(which can happen even if You do everything right), and with longevity comes carbon buildup in the chambers
etc. the older an engine gets, the more octane needy/sensitive it gets....keep that in mind.
 
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