Crank pulley...WTF

LT1Caddy · Poncho Master!

Crank pulley...WTF

4SPEED427 · A Poncho Legend!

Both are three bolt. The pulley actually will interchange except that center opening has the little lip in the back to center it in the balancer and of course the size of that hole is different between big and small block.

Mike Ward MB · Addicted!

Crank Pulleys have three mounting holes as Carl has described.

Water Pump Pulleys have four mounting holes with the smaller centre hole that slides onto the water pump shaft.

LT1Caddy · Poncho Master!

Hi... Thx Mike and Carl. Well I'm trying to find a crankshaft pulley (ASAP). Mike thinks he has one... But I googled and started looking and Summit/Jegs show them with 4 holes, but description says Crank not WP.
Checked a couple of other sites, Musclecars, Corvettes, Chicago Vettes, some 3 hole, some 4 hole. They have a part # for these, I have no part # as usually stamped on the part by GM.

Little confusing, thought there might be an ironclad "rule"...

THX Guys

4SPEED427 · A Poncho Legend!

I've parted many big block cars over a few decades and certainly have never encountered any 396/427/454 with a 4 bolt crankshaft pulley. I've never parted any solid lifter engines. Maybe they have a 4 bolt flange? Although I be surprised if that is so, they do have the deep groove pulleys to keep the belts from coming off at high RPM.

4SPEED427 · A Poncho Legend!

I just googled "big block chevy crankshaft pulley", clicked images and couldn't find one 4 bolt crank pulley. I'm betting Summit and Jegs have pictures that are not accurate for the part number.

73SC · A Poncho Legend!

I have pictures that should help. This is a long neck water pump

1. This is the best one I can find that shows the three bolt holes for the crank.

2. This one shows my pulleys, 4 bolt water pump two groove and I did use the engine's 3 groove crank pulley. The reason for this is because the 454 did have AIR and that third groove was for that. If you have a three groove it should work with your two groove water pump pulley. Mine does.

3. A comparison of the size of the Rat and Mouse, remarkable that there is so much interchange of parts and fitment, the genius of General Motors.

-- Edited by 73SC on Wednesday 28th of April 2021 01:56:25 AM

SD 396 · Poncho Master!

As the previous comments state, the BB Chev have 3 holes to bolt on the crank pulley.
In your other post you are looking for a two groove pulley, the one without the provision for AC. There stamped steel is a two year part and was replaced for simplicity with the 3 groove on everything whether it had AC or not.

Not sure if you're going for original looking or functionality.

It may help if you take a picture of your balancer for reference.

Good luck with your search.