Good compression for alluminum heads and pump gas???

[Paul-ish]

This is a 400 getting stroked to a 451...It's getting Eddy performer heads and i'm shooting for around 500 hp.
With a couple choices in KB pistons and a couple choices in cc head size im not sure where exactally I want this to end up.
I can go anywhere between 9.4 to 11.3.   I'm thinking mid to high 9's but have never done a motor with alluminum heads and could use an informed opinion.

This will be a street perfomance car...not a race car. I'm looking for good street manners and it to run on pump gas.

[68X426]

I'm looking for good street manners and it to run on pump gas.

My stroked Hemi with alum heads does what you want with 9.5. My pump gas is only 91.

I think your cam choice will have the greatest influence on manners and performance. The experts will need to weigh in, I'm just saying that at 9.5 my motor is a very happy warrior in the real world of streets and 91 octane.

[Paul-ish]

That's about where i was thinking...mid 9's. It's not gonna be a radical cam profile.
I have been told by friends to keep it low 10's or under...

[Challenger340]

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[Paul-ish]

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[1Bad70Charger]

Compression makes power and you can get A LOT higher than mid 9s on a big block Mopar engine using pump gas and I suggest 10:5 to 1 is a no BRAINER, and perfect mix for the street, pump gas, and reaching your power goals.

The Eddy Heads alum heads allows you to run more compression also and 10:5 with the right cam selection and quench is what you really need to focus on and I have had MANY, MANY 10:5 to 1 pump gas engines running 10:5 and even 11 to 1 is no problem (as long as your engine builder figures our the proper quench and cam selection but 10:5 is a very nice happy medium and this one is a no brainer as long as your not planning forced induction.

I am into all American Muscle Cars and was running 9:57 compression on a forged LS6 engine in a 2002 corvette Z06 I recently sold running 16 lbs of boost no problemo ALL on 93 octane pump gas and making over 800 crank horsepower! 

10:5 is the way to go and at a MINIUMUM if you really want to play things CONSERVATIVE do yourself a favor and do at least 10:0 to 1 compression. 

[Troy]

An old car with a carb and 2 valves per cylinder is a whole lot different than a new car with EFI, multiple cams, and lots of valves (and especially variable valve timing). Many modern 4 cylinder engines run 11-13:1 compression without knocking because they have a brain and near infinite tunability. The engines will pull back the timing and/or change the fuel mixture to compensate for any irregularities. An "old" engine just can't do that. The higher your compression the more exact your tune needs to be (and alternatively, the quality of your fuel). For a street engine your biggest unknown is the fuel so I'm always leery of pushing the limits. I can live with a bit less power if it means my engine will run better on a more consistent basis - and won't blow up! You can get away with about a point more compression by using aluminum heads but I don't know of too many true "street" engines pushing more than 10.5:1. Most are probably closer to 10:1 - especially if the best you can come up with is 91 octane.

People with more knowledge than me will know how to spec a cam out to compensate for more/less compression.

Troy

[YGBSM]

I am running true 10.7:1 compression on an aluminum headed 496 with 93 octane.

[1Bad70Charger]

I am running true 10.7:1 compression on an aluminum headed 496 with 93 octane.

I agree that with the right cam and proper quench this is close to perfect (10:5 probably being ideal) for running 93 pump gas with no issues and making max power on a street car! 

[Paul-ish]

Thanks for all the input guys...I figure from what ive picked up here and other sites 10 to 1---> 10 to 3 is where ill end up
I should also mention we have 94 octane gas here and thats what shell run.

[1Bad70Charger]

Thanks for all the input guys...I figure from what ive picked up here and other sites 10 to 1---> 10 to 3 is where ill end up
I should also mention we have 94 octane gas here and thats what shell run.

Perfect, enjoy it in good health!    Shit, with 94 octane 11 to 1 would be a no brainer! 

[Troy]

Unless you travel.

I have 94 octane at 1 station just up the road from my garage. Most other local stations may have 93 but sometimes when I travel the best is 91. Out on the country back roads there's no telling what you'll be able to get.

Troy