Looking for compression ratio

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Oct 15, 2001 | 08:46 PM

MattD

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Looking for compression ratio

I have a 302 that I rebuilt. I went with Hypereutectic pistons.
I then put on a set of FORD Motorsports GT 40 "P" cast iron heads (60 cc chamber nominal). I was wondering what my compression ratio is? Is there anyone out there who knows?
Thanks for the help. Matt

1978 F100 Custom
320 horsepower 302
C6, 9 inch
Ford Motorsports E303 cam
GT 40 P heads
Crane roller rockers
Weiand Stealth Intake
Edelbrock 600 cfm carb
full length headers
More mods to come!

Oct 16, 2001 | 09:53 AM

jrocco

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Joined: Oct 2001

Posts: 300

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From: Crosby TX

Looking for compression ratio

I can run the cals for you, but need the following information:

How much is the block overbored?

Are the pistons flat top, dished or domed?

If dished or domed, how many cc's for the dish or dome?

What is the distence from the top of the piston at TDC to the top of the block?

If you can supply this info, I can give you a fairly good idea of the compression ratio.

Jerry Tomasello
Crosby, TX
jrocco@hal-pc.org

Oct 16, 2001 | 10:00 AM

jrocco

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Joined: Oct 2001

Posts: 300

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From: Crosby TX

Looking for compression ratio

By the way. What did you do for headers. I have the GT-P heads on a 351W that I'm building up for my 1980 F100 and I can't seem to find headers that will fit.

Thanks
Jerry Tomasello

Oct 18, 2001 | 09:31 PM

MattD

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Looking for compression ratio

Jerry,
For headers I went to AutoZone and got the Flowtec Headers.
1 5/8 primaries , 3" collectors. They bolt up fine but the only draw back is that you have to unbolt the drivers side every time you want to change the #1 spark plug. Ford motorsports makes "P" headers for Mustangs, but they are not full length headers.If you want to get them anyway the part # is M-9430-P50 . Only Ford Motorsports Dealerships can order them. There are 12 dealers in TX. Anyway Ill get back to you with the specs.
Thanks, Matt

1978 F100 Custom
320 horsepower 302
C6, 9 inch
Ford Motorsports E303 cam
GT 40 P heads
Crane roller rockers
Weiand Stealth Intake
Edelbrock 600 cfm carb
full length headers
More mods to come!

Oct 18, 2001 | 09:43 PM

MattD

Thread Starter

Freshman User

Joined: Sep 2001

Posts: 39

Likes: 0

Looking for compression ratio

Jerry,
The block is brand new (4" bore)
The pistons are flat top
As for the piston top to deck height, I dont Know! I didnt measure it, I just made sure the pistons didnt come put of the top of the block! I would guess it would be stock height.
Thanks for trying even if you cant help.
By the way I can give you the dealer nearest you if you tell me the major city clocest to you.

1978 F100 Custom
320 horsepower 302
C6, 9 inch
Ford Motorsports E303 cam
GT 40 P heads
Crane roller rockers
Weiand Stealth Intake
Edelbrock 600 cfm carb
full length headers
More mods to come!

Oct 18, 2001 | 10:02 PM

jrocco

Senior User

Joined: Oct 2001

Posts: 300

Likes: 0

From: Crosby TX

Looking for compression ratio

I assumed the following for the compression ratio calcs:

Stock Bore - 4.00"
Stock Stroke - 3.00"
Head Gasket Thickness - 0.043"
Head Gasket Bore - 4.1"
Flat Top Pistons with no valve reliefs
Top of Deck to Top of Piston - 0.047"
Ford FT40-P Heads with 59cc Combustion Chambers

Total Combustion Volume = 77.98 cc
Swept Cylinder Volume = 617.78cc

Compression Ratio = 8.92

If you have any valve reliefs this would reduce the compression ratio slightly.

Hope this helps.

I decided to order the Ford Motor Sports Headers from Central Coast Mustang. They seemed to have the most experience in applying them.