1973 STEP A SIDE

iTrader: (4)

Trying to help my son build his first stroker .

I talk with Texas Speed and they said to run a -3cc piston with a 67cc head and .051 gasket for a 11.45 compression ratio.

So I ordered up the rotating assembly from them and a set of Trick flow heads from Total Engine Airflow @ 67cc .

I have been trying to use a online calculator to see what differences a .040 head gasket would make to tighten up the quench . The C/R numbers keep coming up over 12/1 ratio .

.040 = 12.75/1
.051 = 12.38/1

What am I doing wrong ? TIA !!

G Atsma

You might be figuring the piston reliefs the wrong way, calculating them as "domes" rather than recesses. A -3cc piston has reliefs (as per TSP's spec), and a 3cc piston has a "dome", raising your compression beyond what TSP spec'd to you.

1973 STEP A SIDE

iTrader: (4)

Bore: (diameter) 4.070

Stroke: 4

Cylinder Head Volume: 67


Effective Dome Volume:
Use (-) for Dome and (+) for Dish. -3

Deck Clearance: 0


Compressed Gasket Thickness: .051

Number of Cylinders: 8

CALCULATE

Compression Ratio : 12.38 : 1

Total Displacement (in.3) : 416.32

G Atsma

Oops had it bass-ackwards! But I still think you figured it backwards from what you wanted.
You calculated for a dome instead of the relief TSP figured for.

1973 STEP A SIDE

iTrader: (4)

This is the piston

WISECO K464X7 CHEVY LS SERIES -3CC DOME 4.070 INCH BORE PISTON SHELF STOCK KIT

I would think it is less 3cc in the chamber

1973 STEP A SIDE

iTrader: (4)

I found this

Wiseco Chevy LS Series -3cc Dome 4.070 inch Bore Piston Shelf Stock Kit - K464X7Comp Ratio @ 65CC: 11.8:1Comp Ratio @ 70CC: 11.2:1Comp Ratio @ 68CC: 11.4:1Comp Ratio @ 67CC: 11.6:1

Rod: 6.098 / 6.125 ??? I have 6.125 rods .

1989GTA

What octane gasoline will you be using?

1973 STEP A SIDE

iTrader: (4)

91 when at home and 93 when we drop into the big city .

JimsNovaLS

Like G said, use a positive 3 for your valve reliefs and you should get something around the 11.4 spec. Don't worry about the .040 gasket raising the compression, the tighter quench will make the 11.7ish compression less detonation prone than the 11.4 with a bigger quench. You'll be fine on 93, mine is with 11.8, no timing retard. 91 might have the PCM pulling some timing at times. You do have knock sensors don't you? I used Felpro .041 MLS gaskets on my build, .036 quench cold with aluminum block. Iron block, you'll want more like .040.

KW Baraka

iTrader: (7)

I agree with Jim....use the thinner head gasket for a tighter, more optimal quench.

KW

1973 STEP A SIDE

iTrader: (4)

The builder called me late last night and told me he is coming up with 11.41/1 We also live at 7000' elevation . I don't know how that plays into all this . He told me that we could bleed off some of the compression with the cam over lap . He also was telling me I don't want to be that close to the edge of octane as you never know what is coming out of the pump .

As far as knock sensors yes we will be running them .

Builder wants me to run the MSD Atomic efi #2950 not sure about knock sensors and that system .

1973 STEP A SIDE

iTrader: (4)

Thanks !! We will be setting down with the builder this week and see what are best plan of attack is .

Smo's04Gto

iTrader: (8)

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

NA keep your quench tight it helps to control detonation. Last engine on 91 pump gas we ran .037 quench will 11.6 compression shifted at 7K never had any issues. Tuner will play a big roll.

1973 STEP A SIDE

iTrader: (4)

Thanks ! That is what we are going to do ,

gagliano7

For dome volume put in 3 instead of -3 and i come up with 11.55.

1973 STEP A SIDE

iTrader: (4)

Yes but the piston has a 3cc dome on it . That would take 3cc away from the chamber size .

JimsNovaLS

No, the piston has a slight domes to help offset the deep valve reliefs. If they hadn't put those slight domes on the piston it would probably be listed as a -6cc. It's listed as a -3cc piston because that's the NET negative volume, valve relief volume minus the smaller dome volume. You must use the +3 in your calculation. It's confusing because the piston has reliefs and slight "domes" to offset the deep reliefs. It's a net 3cc "hole" in your piston. I used the Wiseco -3cc pistons in my 427 and was surprised to see the little "domes" on a -3cc piston.