I don't remember the exact year , but they are around '79 to '83 stock 351w heads that were listed at 69cc. I ground the chambers smooth and polished them, which I figure might have added another cc. That's why I said I can't accurately calculate untill I measure the actual volumes. The heads I'm using are about as far away from performance as they made, but with all the port and polish work and replacing the valves, I think they'll work pretty well for what I want, though.

 

Wreckit87- I got curious and and punched some numbers for the fun of it and came up with 11.20:1 just by changing the heads to 60cc's on my set-up. What kind of piston head volume figure are you using for your pistons? I'm gonna double-check my figures, but I don't see how you can be at 10.8:1.

 

Ya know, you are very right on that one. I apologize. I just took the guy's word that I got the stroker kit from. He claimed 10.5:1 with a 64cc and 10.8:1 with a 60cc so I just went with that. I was using an 8cc piston head volume btw and I just ran it and my calculations came to 11.275:1 so he is pretty wrong. Sorry about that.

 

No problem, you helped verify for me the number I was using to calculate with my pistons. A quick trip to E-bay found an ad for a 393 stroker kit advertising 10.5:1 CR with 64cc heads,( GoFastStuff), using the same pistons. This is what I based my 399 stroker on. I don't know how they can figure that CR unless you use 4 head gaskets! I don't come up with exactly the same figure as you, so we must be figuring something a little different. I came up with 11.204776:1 for the 399, and just for grins, 11.061592:1 for the 393. What year block are you using?

 

Yeah that's the same kit I bought. $659 I didnt think I could go wrong ya know? I figured everything with a .060 and I suppose he came up with 10.8 using a .030 but he was still wrong.... IDK! Whatever i guess RUN IT! lol. Mine is going in a '72 block. And yours?

 

Something just caught my attention. I need to do some recalculations, and I'll get back to you.

 

I ran a few figures and you can indeed achieve 10.5:1 (or lower), in a 393 stroker with those pistons and the right head gaskets using 64cc heads. I suspect I may have made a mistake when I ran the 60cc figures with the 393 set-up. I have a '79 block and I was calculating off that deck height.Everything you have is going towards increasing compression, where I am going the other direction, excepting the overbore. My pistons are down in the bore .017, yours stick up out of the block .006. You know that the seller claims no responsibility for fitment. The pistons list a requirement of a minimum of .015 deck clearance, and most motors have clearances greater than that. I would be concerned about clearance issues with your set-up, and all the probs associated with high compression motors. Is this motor bound for the street or trailered to the strip?

 

Just so you know I checked the cc of those H273 pistons back when I was building my 302 and they were 10cc (I had them .010 out of the hole)... I had to rap the pistons with tape... I used shipping tape and kept it flush with the top, that way I had a seal where the valve relief falls into the edge of the piston. I did it like three time just to get an average and they all came out to 10cc. I can't remember what they say they are... do you?

 

Here's that piston .010 out the hole...

 

They list them at 8cc, glad to hear they're 10, that brings my CR down a touch.

 

What exactly do you mean when you say our blocks are different? If I'm not mistaken we both have the 9.503 deck height if thats what you were implying. Only the 69-70 blocks have the 9.48 deck. It's going to be a 99% street car maybe the strip once or twice but it's not gonna see a trailer thats for sure.

 

I don't know, but my research shows all 351w blocks have a 9.48 deck height before 1974. I have to go by what I read, I don't have personal knowledge in this area. As a street machine I think you should definately consider a piston swap. You're almost at 12:1. No way will that motor run on pump gas without a double-expresso shot of high dollar octane boost and a lot of other mods. While I'm headed for the street with mine, it's not intended as a daily driver and I'm prepared for the consequences of even 10:1 in a streeter. I plan on installing 2 inline transmission coolers, an oil cooler, a racing radiator, and a high flow water pump just to deal with overheating issues. I wouldn't think of bolting up a stock starter. I think it would be in your best interests to start at the beginning of this thread and read through them. While I don't agree with HemiEaters reccommendation of 9:1, I think 9.5:1 is an ideal MAX for daily streeters, and 10:1 is MAX hot streeters. Numerous verbal and written opinions tout 10:1 as ideal, but I think that's a little stout. At any rate, 12:1 is over the top. Despite outward appearances by some replies I may submit, my motivation at this forum is to assist those that I can, and learn from all who I can, what I can, and not to showcase my vast knowledge or intelligence, of which there is little.I am joined by a group of honest, (more knowledgeable than myself), people who share that mission, for the most part. Anyway, it's my opinion that you should search for some "turbo" 302 pistons, and check that deck height before you commit to too many decisions that hinge on your present set-up.

 

Ford lists in their performance parts catalog that only the 1969/70 351W blocks had the 9.480" deck height and 71-95 were 9.503".

 

Based on what ya'll have typed I got

4" bore (has it been bored out any??) (.030 would add roughly .1 to the ratio)

3.85 stroke

H273CP pistons (book shows 8 cc's in valve reliefs)

.018 deck clearance.

Adding in a felpro 1011-2 gasket (.039 compress thickness x 4.1 bore) I get the following


60 cc heads - 10.8923

64 cc heads - 10.422

68 cc heads - 9.9945

72 cc heads - 9.604


Refigured with Felpro gasket # 1134 - (.041 compressed thickness, 4.18 bore) I got it to drop slightly a little bit

60 cc heads - 10.796

64 cc heads - 10.335

68 cc heads - 9.915

72 cc heads - 9.531




Refigured again with Felpro gasket # 1137 (.053 compresed thickness x 4.21 bore)

60 cc heads - 10.46

64 cc heads - 10.030

68 cc heads - 9.636

72 cc heads - 9.276

Hope this helps some.

 

51 Dueller, Thanks for the info, my print disagrees, I hope you are correct, and probably are.I have 3 books that list '74 as the 1st year the 351w was 9.503, but they are all written by the same person. Still, you wouldn't think he'd get it wrong 3 times. Redtires 019, you should have read a few more replies, we are talking .060 overbores here, which play hell with the comp. figures. If you come up with something different using .060 bores, let us know. Thanks for the effort ,though. If you don't agree that Wreckit 87 is overboard on the CR, now would be the time to voice your opinion. And if you come up with something different calculating the CR's we are talking about, that too, because if you would go to the start of this thread, you would see that this was me asking for help in calculating the CR for my motor.