Detonation

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[socalamcadmin]

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Do you agree with this statement to avoid detonation?

 Don't build a stock or mildly modified AMC engine with more than 9.25 to 1 compression and 10-degree advance at the crank with a quick curve in the distributor (all in at 3,000 rpm or less and 32 degrees overall) and run 91 to 93 octane pump gas. For a highly modified engine--you are on your own to believe who you want. But don't get too far from home on a hot and dry summer's day

And for the stock-to-mild type of AMC V-8, you can't beat the Sig Erson AMC TQ-20 cam and springs. For the same in an AMC I-6, the new Crane torquer cams

[Racing Zorba]

This is the philosophy I have gone with. I believe with lower compression you can save you amc engine

[Flywheel401]

In my 401  ran 12.75 compression for a little while,That will cause detonation
   if you dont run Aviation Fuel. or something close. Switched over to 9.5 comp. it run's strong no detonation worries , and will last long time,so will a higher comp. ratio, like 10.50 - 11.00 comp.
     I think that 10.50 comp would have been a better choice for me . Going down to 9.50 comp the
    Torque and power curve has drop 30%-40%  but that is just my opinion about detonation
                                                                                              Fly........

[iapexl8r]

Wow there is so much more to factor in on this discussion. one thing most people over look on these high comp motors (above 10 comp ) is the cam overlap. With agressive overlap you bleed some compression.
Then you have the heads.I have ran aluminum heads (Worked to remove any head/piston hotspots) with 12.5 comp and agressive valve overlap on california 91 octane of course proper timing and carb tuning also play into the mix .

my theroy is: the comp ratio, cam , heads, pistons,gear ratio, carb and exhaust all need to be engineered to match.
 forged pistons above 10 to 1 comp ratio is manditory. the exception would be with a turbo/supercharger or nitros

[amcramblermarlin]

I agree; greatly oversimplified to only consider mechanical comp. ratio; many other factors to consider, such as valve timing, ignition timing, jetting/fuel air ratio, fuel quality etc... removing sharp edges from the stock combustion chamber and piston will help to eliminate hot spots, helping to reduce detonation. From what I've read, every sharp edge in the chamber potentially is a hot spot. The old AMC Bible, "Performance American Style" contained a discussion on chamber mods, recommending to round off all comb. chamber edges... and told about how Wally Booth converted his heads from wedge type to open chamber type, using custom 'pop up' pistions... there is a quench issue also, and spark plug heat range. Of course operating engine temp/cooling factor. Hmm, paleface think mon need study bit more...  first thing; retard timing! (AMC Metropolitans have a thumbscrew on the distributor to regularly adjust ign. timing for exactly that, to accomodate varying factors such as altitude, fuel quality etc...) Certain new cars are able to have a higher comp ratio by having computer controlled fuel injection, detonation sensor, ignition timing etc...