I'm in the process of assembling a 393 stroker for my 64 falcon fx style car. I need some insight regarding deck height and valve clearance. I have a 1969 9.48 deck height block that has never been decked. My machine work is done and I'm assembling it now. My rotating assembly consists of a scat 3.85" stroke crank, probe 5.956" rods and probe pistons with a compression height of 1.600" This computes to: crank throw( half of stroke) 1.925 Rod length. 5.956 Compression height. 1.600 ------- 9.481 With a 9.48 deck height this puts me .001 out of the bore. I am running flat top pistons with a -4cc valve relief , procomp heads with a 60cc combustion chamber .540 lift cam and a head gasket with .039 compressed thickness. I'm figuring I should be around 12:1 cr Is this gonna work? Please advise or share your experience... After all of this figuring my brain is pretty rung out. Btw this will be a street/ strip car Thanks in advance RS59
Hmmm can't say I have ever calculated the stack up, but the .001 you are calculating is from nominal. There is still a certain amount of tolerance involved in what is actually manufactured and that you receive. I would not be worried about .001 calculated. If you sourced these components for that purpose I would say you are good to go.
This is the first stroker and first aluminum head engine I've built. It's more involved for sure thanks for your insight
I just put #1 piston in and put the head on with the gasket (Used if you have one) And adjust the valves with very soft springs in # 1. Then I turn it over while pushing the valve with my thumb to actually check for clearance. Usually the exhaust valve is going to touch if anything does. Take it easy. Use a dial indicator to check for exact clearance. Make sure the plunger on the indicator is parallel to the valve stem for correct reading
A street car that runs on race gas,doubt that. Whats that like $9/gallon? That extra HP from compression that high isnt worth it. I know plenty of fellas that never drive their cars because gas costs way too much.
I have a 302 based stroker in a Mexican block that was decked .030. With my rotating assembly I was .030 out of the hole. Im running a cometic .070 gasket to be where I need to be. Your combo "MAY" work, but it is important to check piston to valve clearance. Laugh all you want, but I have used Kraft singles cheese to do it. It may sound cheesy, but it works.
I run a 418W stroker,zero decked,flat top piston is dead even with the top of the block,.036 compressed head gasket,aluminum heads,no issues running 105 octane,leaded race gas.The aluminum heads are a little more forgiving than an iron head will be with high compression.If you are street driving it,it will get expensive on race gas,you can get head gaskets up to at least .070 compressed thickness.You also need to figure in your head cc volume to come up with your final compression. ROY.
Assemble it and check all the holes. Tolerance stack can bite you. The '69 blocks are unique with their lower deck heights... Way back in the mid-80s, long before the Mustang 'revolution' and off-the-shelf stroker kits for 351W, I built a stroker 351W on a '69 block and used Chrysler 318 rods (heavily machined) and 340 pistons (heavily fly-cut) and needed a pretty big relief with DO0E heads to get the compression down to reasonable...
Too many unknowns... You mention nothing about head gasket thickness, cam degree, head metal, etc. It's all about clearance. Just be sure you have more than 0.020" or your pistons will close/bend your valves and possibly break sintered metal valve guides. I love the Kraft cheese idea and am going to use it. It beats plumber's putty and play dough. I would even leave the plastic on the top so the cheese sticks to the piston but not the valve. I have a sneakin' suspicion that you will do more valve relief. - Dave
I learned a lot of things when I was building my 347 stroker... one being that your decks are almost certainly not going to be parallel with your crankshaft centerline. Mine was off by something like .005-0.010 from the front of the block to the back, which results in a measurable discrepancy in compression ratios across the board. I went around with a depth micrometer and found this out. This was BEFORE I got it decked, so my machinist was able to fix it relatively well, but he claimed that if you wanted it to be absolutely precise, that there was really no better way to do it than to mill each individual piston until they all came out even. This is due to differences in the actual lengths of the connecting rods, piston height, and the crankshaft itself. Unfortunately, nothing's ever gonna be perfect. But what you need to do is, if you can get access to a good depth micrometer and a dial indicator, go around to each hole and actually SEE where the piston is at by measuring it at the top of its stroke. You will see how incredibly difficult it is to get an accurate, repeatable reading down to the thousandths when that piston is in there, rocking a little bit back and forth, one side a little high, one side a little low... and you might start to gain an appreciation for how thoroughly trivial a lot of these calculations we do are when you slap the thing together and the real-world results end up being so remarkably different. A lot of us are perfectionists, I know I was and still am, but in the end you generally have to live with a lot of imperfections here and there.
What is the correct formula for compression ratio? Shineyside your right about not really a street car but its gotta be fun. I already got a sled for cruising. I like krackers cheese idea. Kracker n cheese ha
Thanks for the info. I lucked out , i got a nostalgia t/f guy comin over to sort it all out. Hes a genious. Put the tune on the top fuel dragster that won at bakersfield. With what i learned here and his guidance im in good hands. Thanks guys!!RS59
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