Hey guys,

What is thecompression ratio that you should run on a pure street 347 stroker? I bought the Ford Racing 347 Short block, forged pistons andforged crankversion, AFR Aluminum Heads with 185cc intake (61cc Combustion chamber) , and the Ford Racing M-6250-E303 hydraullic roller camshaft with 498/498 lift and 220/220 adv duration. The pistons in my short block are Forged Aluminum Pistons with 4cc Valve Reliefs...I was told that the compression ratio will be 10.5:1. Anything I need to be concerned about, considering I have aluminum heads and the cam I mentioned? Intake is a Performer RPM, 600cfm Holley carb...thanks!

 

Just run good fuel, mine is 10:1 and I run midgrade with no issues. 10.5:1 is not bad, the duration on your cam is fairly light so it should be smooth with lots of vacuum.I would think between 10 and 10.5:1 is good, more than that and you are pushing it.

T

 

yup, i always heard 10:1 with premium pump, but with aluminum heads they dissapate heat quicker and you can play around with 10.5 or possibly even 11:1 with 93 pump gas

 

10:1 with midgrade wow your braver than me

 

That compression is plenty safe.

 

with todays gas which sucks for our old engines compared to what they had when our cars were new i use premium anything 9:1 and over...

 

hell, you can try the cheap stuff, just dont fill it in case you need to blend it out with premium. not to mention if it pings you can always back a degree or two out of your timing

 

My computer comes up at 10.7 to 1 with a .040 head gasket (compressed).

Most pistons do not come all of the way to the top of the deck, this will lower C/R a bit as well.

 

its hard to get figures from a computer, because you have to know EXACTLY how many cc's your heads are, the + or - volume of your pistons, how far below deck they are, true crush thickness of headgasket, diameter of head gasket, low well your rings are sealing..... so many variable.

 

The difference in price for a tank of 93 octane as opposed to 89 octane mid grade is about 2 bucks. I would certainly pay the difference if it was my engine.