Does anyone have any info about stroking the 351W using stock 302 rods and stock 302 pistons? Does anyone have the formula to determine the proper rod length and compression height? I seem to remember somebody talking about using stock 302 pistons and rods to make a 351 stroker (I think it was a 393).
393 Can only tell you that our 393 used a Scat crank and 351 rods with matching pistons. Much grinding on the block and such was done for clearance problems. Did know of a use of 289 rods in 302's for a "long rod engine" but to use the 302's in 351's I couldn't tell you, offset grinding of cranks and use of "Chevy" rods could be another setup? Maybe Mavman can help on the formula you ask about, had that info somewhere but time has dealt me some "Where did I put that" problems.
Don't think you can stroke the 351 with the 302 rods and pistons. I know you can do it with 300 rods and 400 pistons. My dad did this several several years ago when he was still drag racing. There is also a article on stroking that engine in "fast Fords and mustangs" I think the Dec edition. Tomm
Strokers I believe you have hit it right, but still have to use a stroked crankshaft, about 400.00 , to get 393.
old guy, that's what i was thinking. Get a stroker crank and find the stock pistons with 351 rods and there you are! of course it would need to be balanced and block clearanced. I'm still working on the equation. As I recall, it wasn't that difficult! Do you remember the compression height for a stock 302 piston? Try this site http://www.holley.com/HiOctn/TechServ/TechInfo/IECPTech4.html here is the equation Rod length=Block height-(.5 x stroke)-compression height for a stock 302 BH 8.206 - (.5 x 3.00) - 1.616 = 5.090 or for compression height BH 8.206 - (.5 x 3.00) - 5.090 = CH 1.616 For a ford 351W stroked to 393 BH 9.503 - (.5 x 3.85) - 1.616 = RL (5.962) stock 351W rods are 5.956 HMMMM So, if I deck the block .006 I'm back to where I need to be. What do you think?
compression height for a 302 piston is 1.600". Add this to the 5.956" stock-length 351w rods, and 1/2 stroke (3.850" stroke /2) this adds up to 9.481. Most 351w blocks before '74 are 9.480" deck height or '74-later ones are 9.500". Very little grinding was done on the block--mostly near the hump at the oil pump, had to clearance part of the front counterweight (hit the oil pump--DO NOT GRIND THE RIB ON THE OIL PUMP--IT WILL BREAK!), and a lot of grinding on the rods to clear the camshaft. An added note, if you plan to spin it as high as I did, might consider some aftermarket rods! Stock 351w rods were not designed for this much stress (yes, I can tell you this from experience). I broke one, only thing salvageable was the heads (luckily), water pump, timing cover, and intake manifold. Good luck
also forgot to mention that most 302 pistons hit the counterweights when nearing bottom-dead-center, so be careful that you choose some decent pistons. I used SRP # 138734 flat tops to arrive @ 10.7:1 compression with the piston .015" in the hole. It loved to rev! http://www.geocities.com/mavman687
mavman, the 302 pistons hitting the counter weight is something I would not have thought of! I know different aftermarket pistons have slightly different compression heights. I assume the SRPs you are talking about have a short skirt? Do you happen to know the length from the top of the piston to the bottom of the skirt. I have a set of 302 clevor pistons that could work with the stock 351W rods and stroker crank but I question the skirt clearance! I would not rev an engine like this all that often so a good set of stock rods with new rod bolts and a decent crank would be fine. Sounds like you have done this! BTW, what size combustion chamber were you using and was the piston a true flat top without reliefs or a dish?
The arrow shows where I had to remove material from the TRW pistons I originally planned to use. After I got them clearanced, I found that they valve reliefs were WAY too small, and they could not be cut deep enough without breaking through the piston. I scrapped the TRW idea and went with the SRP's. Much nicer piston, and I did not have to remove any material to make them work! They were 200 grams lighter too--and you can ask Old Guy, lighter internals make the engine rev MUCH faster!
the circle shows where I had to grind the rod to gain clearance between the rod big end and the camshaft. Some people do not have to do this, but my cam is just under .700" lift and 266 duration @ .050 solid roller.
so, if I'm around 500 lift I may not need to clearance the rods? Nice pictures! Did you have the whole assembly balanced using SFI balancers and flexplate/flywheel?
See the little bump on the rod where the big end transitions into the beam? That is the weak point in ALL 351w rods. This is exactly where I've seen at least 3 of them break. I guess you're using Cleveland heads? Man, that thing should scream! Use some 4v heads and you'll have more motor than the car can take! Also, you might or might not have to have the pistons flycut deeper as the piston's rate of acceleration is different in a 393 than a factory 351--meaning that the piston is closer to the head at any given valve timing event with the 393. This is another reason I went with SRP's--the piston has MUCH deeper/wider reliefs. I had .100" intake .080" exhaust valve-to-piston clearance, even with the cam I used. The SRP's have a flat top with 2 valve reliefs (5cc reliefs I believe) and I used a 60cc chamber Victor Jr. heads. Ran some 6.60's in the 1/8 mile at just over 103 mph in a 2800 lb car. With the lighter pistons, it would rev so fast that I dont think I would have been able to shift it soon enough in first gear with a c4 transmission. Good thing I went with a powerglide!
yes it was all balanced. You must balance the entire assembly if you go with a stroker crank, as the cranks are just machined, and balancing is left up to the final installer. Used an SFI flexplate from JW Performance, and a stock 28oz damper (which slipped the outer ring when the engine let go, so it's junk now)
you might or might not have to grind the rods as I did with your cam. There's only one way to find out! Put the short block together "dry" and check all clearances between the rods and block, rods and cam, check everything! There must be a minimum of .060" clearance. A good stroker's life will depend on attention to detail!
