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Compression

December 4 2017 at 4:00 AM

Ross  (Login Bad427stang)
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Response to Head gasket

In the end, any of your possible gasket combos are over .080 quench when you add the gasket, so at this point, you just want as much compression as you can without going too far with the cam you have. Anything over about .055 quench distance is the same

.030 352 with those pistons, assuming a 60 cc chamber and a .041 gasket, and guessing deck height at 10.160, would be about 9.1:1. That is .060 below deck and .101 quench (I know you said .070 below but the math doesn't work that it would be that much, you may be seeing piston rock)

The same combo with a .020 gasket would be 9.57-ish with .080 quench distance

Keep in mind that I used 60 cc, because most of the other heads I have seen come in a little big, and you cut them, but if it is at 58 cc it will be 9.30 with the .041 and 9.78 with the shim.

In either case, that is a lot of room above the piston and you are giving up the benefits of quench, so although it is a good compression ratio, you are losing the benefit of the quench.

Luckily, your cam is big enough that it should be fine on pump gas. Assuming the motor is together and you don't want to spend money on custom pistons, and the fact that you have two fresh sealing surfaces on the heads and block, for a little more performance I'd run the steel shim and you'd be between 9.57 and 9.78, then lash the cam tight (to make it act a little bigger for a little insurance) or if you want to be more conservative run a .041 gasket for compression between 9.1 and 9.3.

Either combo should be fine on pump gas.

However, 2 comments, not that I think you could get to 10:1 with your combo, but you mentioned it. It would not likely be happy with the cam choice you have. That's OK because more cam wouldn't match the car, so the 9s are a good number.

The second comment is, I wouldn't do this, but the Felpro blue gasket would get you to 9:1. You just don't need it and will be giving up power. However, it's likely the cheapest way out and if power wasn't your primary concern, it'd run on anything happy.gif





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- 70 Fastback Mustang, 489 cid FE, Victor, SEFI, TKO-600 5 speed, 4.11 9 inch.
- 71 F100 shortbed 4x4, 445 cid FE, headers, RPM intake, 1000 HP series Holley, 4 speed


    
This message has been edited by Bad427stang on Dec 4, 2017 4:01 AM


 
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  • Head gasket - Joe overholser on Dec 5, 2017, 8:50 PM
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