Maximum/target Dynamic CR for Aluminum Heads?

[John Chesher]

I've seen a lot of conflicting advise about what should be the target or maximum DYNAMIC compression ratio to avoid detonation on 92/93 octane pump gas. I've seen anywhere from 8 - 8.5, but almost all references are vague as to whether the heads are iron or aluminum or specifically state the range is for iron. Can any of the awesome engine experts on this site suggest to me what my target should be to get maximum power while avoiding detonation? I'm running aluminum vortec-style heads and also a 180 degree thermostat, with an aluminum radiator that keeps the coolant at 180 degrees.

Appreciate the help!

[Wayne K.]

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[Wayne K.]

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[Ted S.]

Re: Maximum/target Dynamic CR for Aluminum Heads?

8.0 max iron heads; 8.5 max aluminum heads

[Ted S.]

Re: Maximum/target Dynamic CR for Aluminum Heads?

8.0 max iron heads; 8.5 max aluminum heads

[Duke W.]

Re: Maximum/target Dynamic CR for Aluminum Heads?

DCR is not some magic go/no-go number. Plus, there is no single accepted method for computing it, and rarely can you get the camshaft data you need to compute it accurately. It's just a guideline, and a vague one as that as you have found out.

The 30-30 cam installed at OE indexing in a 327 at 12:1 SCR has a DCR of just 7.47:1 as computed by the engine Analyzer simulation 3.0 program, but they are vague on how it's computed.

Do you think this configuration will run detonation free on unleaded premium?

I seriously doubt it!

Duke

[Duke W.]

Re: Maximum/target Dynamic CR for Aluminum Heads?

DCR is not some magic go/no-go number. Plus, there is no single accepted method for computing it, and rarely can you get the camshaft data you need to compute it accurately. It's just a guideline, and a vague one as that as you have found out.

The 30-30 cam installed at OE indexing in a 327 at 12:1 SCR has a DCR of just 7.47:1 as computed by the engine Analyzer simulation 3.0 program, but they are vague on how it's computed.

Do you think this configuration will run detonation free on unleaded premium?

I seriously doubt it!

Duke

[John Chesher]

Re: Maximum/target Dynamic CR for Aluminum Heads?

Thanks for the responses. Sounds like my best bet may be to call Holley tech support (the cam manufacturer), as I'm currently running the Lunati 60102 cam.

[John Chesher]

Re: Maximum/target Dynamic CR for Aluminum Heads?

Thanks for the responses. Sounds like my best bet may be to call Holley tech support (the cam manufacturer), as I'm currently running the Lunati 60102 cam.