Cutting down counterweight OD

[donclark]

Does anyone have experience with cutting down the outside diameter of crankshaft counterweights? There are a lot of new high-end cranks out there for 351 small block Fords but the counterweights will not fit the 302 architecture. Looks like about 0.325" will need to come off. BTW, the bob weights of these are typically around 1600 grams and my combination generally runs around 1320. Seems like it should work?
Thanks, Don

[racear2865]

Ive cut them down in a lathe, Ive cut them in a crankshaft grinder and Ive cut them on a 4 axis mill.
reed

[sanfordandson]

lathe works well.

[SupStk]

I've used a lathe and crankgrinder. Lathe is the easiest but the grinder if needing eccentric counter weights.

Kinda curious how much more stroke you trying to stuff in a 302?

[donclark]

I've used a lathe and crankgrinder. Lathe is the easiest but the grinder if needing eccentric counter weights.

Kinda curious how much more stroke you trying to stuff in a 302?

Not that much, 3.265 with a 4.160" bore. I like to keep a decent rod length/ stroke ratio. Old school, I know.

[SupStk]

I'v built 3.250 and 3.400 stroke SBF with cranks that didn't need the counterweights turned. I do when balancing at times to avoid the counterweights looking like swiss cheese.

[user-23911]

Like this?

https://www.youtube.com/watch?v=AKzd-VGAQuk

[Caprimaniac]

Think about doing this for 3.5. Or larger stroke for the 8.2.

Why do a 3.265 High end crank w/alot (?) of work when you can get a race- ready 3.25 high- end crank?
If you have the crank already or need to squeeze the last drop out, i can see your reasons.

[Geoff2]

Yup, no problem at all. I have cut down 440 Mopar crank c/weights to use 383 rods in a 383 block.

[swampbuggy]

Donclark, you mentioned your intentions above and said old school, if your cylinder heads will support that combo (IMO) you are going in the right direction. NASCAR engine builders know it"s the best way, oldschool or not. Mark.

[donclark]

Think about doing this for 3.5. Or larger stroke for the 8.2.

Why do a 3.265 High end crank w/alot (?) of work when you can get a race- ready 3.25 high- end crank?
If you have the crank already or need to squeeze the last drop out, i can see your reasons.

Pure economics, scored a NIB Bryant billet for about 20% of new cost. I have a good friend who will trade labor and even if we need to add mallory it will come in pretty inexpensive, relatively speaking.

[donclark]

Donclark, you mentioned your intentions above and said old school, if your cylinder heads will support that combo (IMO) you are going in the right direction. NASCAR engine builders know it"s the best way, oldschool or not. Mark.

Heads are Yates C-3's from a championship ARCA team, decent flow numbers, but as Jim Kuntz once told me "The C3"s tend to work better than the flow numbers would indicate."
Thanks,
Don

[swampbuggy]

Don-----i experienced the same thing with my last motor and it was a BBC, which generally makes on average less HP/CI than a Small block. But it made 2.35 HP per CFM----------856 with 364 which was a pleasant surprise. Mark

[dwilliams]

I've cut down 400 cranks to fit in 351Ws and 351C cranks to fit in 302s. Did them all with an angle grinder and coarse wheel. Took two-three hours, usually, depending on if I was just reducing the OD or if I was fitting the crank as close to the piston skirts as I could.

Some of the "351C" aftermarket cranks have 351W-sized counterweights. Because I'm a slow learner, I got caught by that twice, and had to rebalance after grinding the counterweights down when the crank went "thunk" when assembling what was supposed to be a drop-in rotating assembly...

[MadBill]

We did a 380" SBF with a 3.47" crank, 5.4" rods and 2 ring CP pistons and when we turned it over it went 'tic'. A few file strokes on some high spots on the CWs and no sign of contact on later tear down..