I'm doing a head and cam swap to a 1998 Formula. It has stock pistons. Using a set of 59cc PRC Stage 2.5 5.3L cylinder heads(w/ recessed valves) and a stock MLS gasket, what compression am I looking at having here?

I've calculated approx 11.3:1 but I want some pro's expertise.

I'm double checking but I believe I'm going to need 7.4" pushrods. Any input on this?

 

Depending on your cams base circle and shaved heads with stock gaskets it may not be a 7.400.

How did you get 11.3:1?

(I am not a pro by any means) Just wanted to see your math.

 

I just used an online calculator but I did it without complete knowledge of the compressed thickness of the HG and other head gasket info needed for the calculator.

 

It wouldnt happen to be the one where you have to send paypal to use was it?

 

there is a formula to figure up the cr, but i dont remember what it is.

what is the stock heads combustion chamber size and stock cr?

 

61.15cc is stock on the 5.3 head IIRC.

 

i wouldnt think your cr would be that high but i could be wrong.

 

No it wasnt

 

11.46 according to Pipemax

.051 compressed thickness, 59cc chamber, 3.915 gasket bore diameter, 3.898 cylinder bore, piston out of the hole .007

 

Hmm thats weird. I came up with this after using one of the compression ratio calculators out there in google land. I just would like an approximate CR number.

Bore Size: 3.9"
Stroke: 3.662
Combustion Chamber: 59cc's
Compressed HG: .048"
Dome/Dish: 0
Deck: .007
HG Bore Dia: 3.915"

I did this into a calculator and came up with 11.26:1

 

has this stock block been bored a tad?