408 compression ratio

bluevenom867 said:

p.s. if you dont got heads yet,get heads with a larger CC volume,much rather have more CC volume than a thicker head gasket.

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Rick 91GT said:

Well your block height is 9.48" (or should be, have you had it checked) so with that 4" stroke crank, 6.2" rod your going to need a piston with a CH of 1.28".

JE makes a shelf piston with a -30cc inverted dome, they use a .927" pin so as long as your rods are .927 you should fine....only thing I could find in my catalogs.

Here is what I come up with..

Bore Size: 4.030
Gasket Bore: 4.100
Piston Top Land Dia: 3.995
Stroke: 4.000
Connecting Rod Length 6.200
Compression Height: 1.280
Deck Height: 9.480
Ring to Top of Piston 0.250
Gasket Thickness: 0.040
Valve Notches Volume: 30.00
Dome Volume: 0.00
Volume Head: 58.00
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:COMPRESSION RATIO: 9.570
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calculation variables:

Piston to Deck: 0.000
Crank Throw: 2.000
Vol. Above Top Ring: 0.90 cc
Piston to Dec Vol.: 0.00 cc
Gasket Volume: 8.65 cc
Volume Clearance: 97.56 cc
Cylinder Volume: 836.10 cc
CID: 408.018

Switching to a .050" headgasket will get you 9.38:1, if you want less then that then you'll need to go Custom as far as I know. I can't find a larger shelf stock dish to lower the compression. By using a .050 you still have suffucient quench area.

What blower model will you be adding, you'll need atleast a T -trim preferrably a YS-trim (if you want to stay Vortech) to feed that large cubic inch motor, a S-trim just won't cut it.

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vristang said:

I asked myself the same question when I built my 408, as I plan on boost in the future as well.

I went about as low as I could get away with N/A. The motor is pretty healthy now, without boost. Lower compression ratios mean you can run more boost later.

CR is in my sig.

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