Compression ratio for street

[2cudas2go]

I was wondering if someone could help me out on this.

I have a 440 short block with this cam: Chrysler purple shaft 484 lift

The pistons are:  TRW L2295F forged pistons 0.30 over (They are fairly high compression pistons)

The crank and rods are stock.

I am looking for heads to use with this combination and was wondering if I could use the Indy 440 ez-1 open chamber heads (80cc) and still use pump gas. This engine is for street use not race.

I plan to use a 6 pak intake with this setup.

Thanks,
2cudas2go

[The Cuda Guy]

Chryco is best suited to answer this but with alum heads the max is 10:5-10:6.

Cuda Guy

[nivvy]

10 to 1 with irons and 11 to 1 max with aluminums... as a rule of thumb... cam plays alot there...

how far are the pistons in the hole... how thick of a compressed gasket are you gonna use...

I am 10.92 to 1 with no ill problems... and with aluminum heads.......

http://www.csgnetwork.com/compcalc.html

[bb71challenger]

Yup, the more compression you run the more the cam factors in. IMO for a true street motor without having to factor in the cam, Dons estimates mirror my own thoughts. But then again at my altitude we get a max of 90-91 octane as premium. 86-87 is our standard octane, 87-88 for plus and 90-91 for premium. Yeah, it sucks I know. With iron heads I will try to get away with something like 9.7 or 9.8:1 with my engine.

[moper]

What are you wanting out of this engine exactly? What is the rest of the car (trans, gearing, convertor, power brakes, curiser, racer)? Why  do you feel the need to use those pistons? You can't be that general.

[Chryco Psycho]

I do not have my book handy as I am not really living anywhere anymore , but I think the 2295 piston is the 11:1 dome top so even with 80 cc alum you will be too high
 let me get back to this when I have my books handy , probably tomorrow 

[Jacksboys]

Also when aiming for high compression a good quench can play a big role in the maximum

[2cudas2go]

What are you wanting out of this engine exactly? What is the rest of the car (trans, gearing, convertor, power brakes, curiser, racer)? Why  do you feel the need to use those pistons? You can't be that general.

First of all, thanks for all the info so far. I do appreciate it. And to answer you questions Moper. I just want a nice potent street car. Very little racing if any. The car is a 4 speed with a 3:55 rear and power brakes. And the short block comes as is. I am just trying to make it work for the street on pump gas. If I can't make it work, I won't keep it.

2cudas2go

[Chryco Psycho]

ok the L2295F piston is the dome top & will have approx 10.3 compression with 88 cc heads so with a 84 cc Alum you will have approx 10.7 depending how close to the deck the piston is & assuming a .038 thick head gasket so it should be pump gas friendly depending on cam & quench
 with an 84 cc Alum head , at 80 cc you will be over 11:1 unless you use a thicker head gasket , I would use Cometic with alum heads , watch you valve to piston clearance as the Eddy heads do have the valve in the stock location & will hit the piston

[moper]

If the pistons are where they should be in terms of decl height, you may have issues with closed chambers and angled plugs and those domes. They would not be any part of my build, nor would the MP cam. Those are cheap, oldschool, and there are far superior available now. If the flat section of the the piston is at 0 deck, meaning flush with the top of the block, you've got compression and fitment issues. If they are down in the block a little, you can work with that. If it were me, I would take the short apart and have the domes milled off the pistons. Then you can run anything for heads. While you're in there, replace the cam with something designed in the more recent past. For what you're doing, aim to keep it at or below 9.5:1 static. If you do run aluminum heads, that can go up to 10:1 with any cam. Your cam will determine teh detonation threshold on this build. You must have the small cam for brakes. So you must keep the static down. 

[dwbiggs]

I have cam (below) with AL heads and 10.5:1.

[2cudas2go]

thanks Chryco, Moper and dw.

I guess i am going to have to think this through a little further. I thought i was getting a pretty decent deal on this short block, but if I have to do a bunch of extra stuff to make it work, it may not be such a great deal.

Thanks again,

2cudas2go