351 crank in a 302 block?

FoxChasis said:

..... The main journals can be cut down but that weakens the crank ....

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I've always question the logic behind this "theory". All cranks are machined some degree. If the crank starts with a 3.00" main journal and is machined down to 2.50", how does this weakin it? The crank doesn't know it's got a smaller journal. 302 and 351 cranks are made from the same material. Maybe I'm missing something.

Maybe it's weaker compared to annother 351 crank, but it should have just as much strength as the 302 crank.

I agree that if it can be done, it is not worth it. There is very little in this world that cant be done. Cant be done practically and cheaply are other things.

2nd if you were to put a 351 crank in a 302 it would make it 351 cubic inches unless you offset grind the rod journals to reduce the stroke.

To explain:The 302 and 351 share the same bore size, so if the stroke is equal (by use of a 351 crank) then it would equal the same cubic inches.

Welcome back Justin!

tjm73 said:

I've always question the logic behind this "theory". All cranks are machined some degree. If the crank starts with a 3.00" main journal and is machined down to 2.50", how does this weakin it? The crank doesn't know it's got a smaller journal. 302 and 351 cranks are made from the same material. Maybe I'm missing something.

Maybe it's weaker compared to annother 351 crank, but it should have just as much strength as the 302 crank.

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I believe that it would have something to do with the crank being cast. Not sure how much material is good all the way to the center of the crank. There are imperfections in every casting. IF the crank was forged, then I believe it would be damn nearly as strong (within reason) with either set of journal diameters.

I bet that would be an interesting rod angle.

hllon4whls said:

I believe that it would have something to do with the crank being cast. Not sure how much material is good all the way to the center of the crank. There are imperfections in every casting. IF the crank was forged, then I believe it would be damn nearly as strong (within reason) with either set of journal diameters.

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Hmmm...good point. I never thought about the casting quality through out the crank.

hllon4whls said:

2nd if you were to put a 351 crank in a 302 it would make it 351 cubic inches unless you offset grind the rod journals to reduce the stroke.

To explain:The 302 and 351 share the same bore size, so if the stroke is equal (by use of a 351 crank) then it would equal the same cubic inches.

Welcome back Justin!

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not true, the 351 uses a longer rod and has a taller deck than the 302

simply puting a 351 crank in a 302(not that it would fit anyway) would lengthen the stroke but it would still not be equal to a 351

Kid wita 5oh said:

not true, the 351 uses a longer rod and has a taller deck than the 302

simply puting a 351 crank in a 302(not that it would fit anyway) would lengthen the stroke but it would still not be equal to a 351

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The rod has very little to do with the swept area of the piston in the cylinder. You would need a shorter deck piston height to work in the 302. The crank is going to still pull the piston up and down the same amount in the cylidner weather it has a 4.7 inch rod or a 6.7 inch rod.

The whole point is that it will not work. You dont see any 351 stroker kits (based on a 302 block) out there for a reason. Even a 347 is based on an overbore. Lunati sold one that was 350 cubes, but that was with a 60 overbore. A stock 351 has no overbore compared to the 302.

hllon4whls said:

The rod has very little to do with the swept area of the piston in the cylinder. You would need a shorter deck piston height to work in the 302. The crank is going to still pull the piston up and down the same amount in the cylidner weather it has a 4.7 inch rod or a 6.7 inch rod.

The whole point is that it will not work. You dont see any 351 stroker kits (based on a 302 block) out there for a reason. Even a 347 is based on an overbore. Lunati sold one that was 350 cubes, but that was with a 60 overbore. A stock 351 has no overbore compared to the 302.

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Agreed. All the rod length has to do with it is to help acheive a larger stroke if it applies in the sense that the piston doesn't travel too far down into the block or vice versa: too far above the block and into the cylinder head. This is the only reasoning for connecting rod length. If from centerline to journal distance is 1.5" on the crank, then your total stroke will be 3" overall - regardless of connecting rod length.

OK guys, just for the record the stock 302 main journals are 2.25, not 2.49. The 351C is 2.75 and the 351W is 3.5.

It is possible, but would be far cheaper to just by a stroker crank from Eagle or Scat or even better, the whole kit. Either 351 crank is basically a raw casting when used in a 302. Just about every surface of the crank needs to be worked. The counterweights need to be reduced, rod and main journals turned to 2.1/2.25", crank snout modified, rear main seal mods, etc.
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I own a 357 inch 302 stroker. It has a worked 351C crank, FPS did the crank work. They modded the crank to fit the 302 main saddle, ground the rod journals to 2.1,the rods are Eagle 5.4 H-beam rods and a custom piston for TFS High Ports. The engine is on a stand and is waiting for a car and was bought used from a local racer. He did supply the build sheet, quote for the job and all reciepts for work that was done. Ford Performance Solutions verified the engine and FPS build number on the block.

FWIW...The 2.1 rod journals are a Chevy spec, but most performance combos based on the 302 block use these.