The GMC V6?

[GMC-V6]

I was thinking about swapping the 3.86 crank from the 478 V6 into my 305 V6... Then you'd have a 4.25 bore by 3.86 stroke netting you 329 V6.. bump up the compression and shazzam you have the same power as the bigger V6s from a smaller higher compression unit probably saving a bit of front end tonnage too😎

I do love them all 305/351/379/401/432/478 plus the 637 V8, and 702 V12🤩

Always thinking of ways to do it differently
Mike

[The Rocknrod]

Can't wait.

[factorystock]

Originally Posted by GMC-V6

I was thinking about swapping the 3.86 crank from the 478 V6 into my 305 V6... Then you'd have a 4.25 bore by 3.86 stroke netting you 329 V6.. bump up the compression and shazzam you have the same power as the bigger V6s from a smaller higher compression unit probably saving a bit of front end tonnage too😎

I do love them all 305/351/379/401/432/478 plus the 637 V8, and 702 V12🤩

Always thinking of ways to do it differently
Mike

Not that simple. 401 and up use a gear driven crank, 305 and 351 use a chain. V6 engines are not about high rpm horsepower, there all about low rpm torque. They all have heavy internal parts that like to run slow .

[GMC-V6]

Yes I am well aware of the low end torque and that they are slow revers... Swapping cranks wouldn't make it a high revving engine it's probably in fact slow it's revs down..

They also have 4 ring diesel style pistons.

I am sure it's no a bolt in and run deal
Mike

[factorystock]

The best candidate for performance would be from a 351 out of a '66-'68 GMC pickup with a 500cfm Holley and dual exhaust.

[GMC-V6]

Don't the 351 have a chain timing? If so then the 379 was a 351 with the 3.86 stroke crank put into it... Just like the 432 is the 401 with the 3.86 crank.. So given that, I would guess the crank gear can be swapped to the crank sprocket??? Maybe one would have to source the 3.86 stroke crank from/for the 379 V6 to make it work out?

Mike

[factorystock]

Originally Posted by GMC-V6

Don't the 351 have a chain timing? If so then the 379 was a 351 with the 3.86 stroke crank put into it... Just like the 432 is the 401 with the 3.86 crank.. So given that, I would guess the crank gear can be swapped to the crank sprocket??? Maybe one would have to source the 3.86 stroke crank from/for the 379 V6 to make it work out?

Mike

Yes, you are correct about the 379, completely forgot GMC made one of those. Good news is the 351 and 379 both had chains. Your on to something now. It should work if the crank is out of 379. Not sure of how to calculate what the compression ratio would be. Too bad the 379 was a one year wonder, only available in '73, it is a very rare engine, GMC discontinued the V6 gas family that began in 1960 in '74. Just imagine if you could find a great running low mileage 379 out of a '73 GMC farm grain truck!

[350TacoZilla]

I always wanted to bore a 305 out to accept something like 502 pistons or some other common off the shelf option, tons of meat in the block from what I've seen and still no where near 478 bore. Maybe have custom rods and custom cam ground,do little port work to heads and intake for little more power bump.

[1967GMCC20]

My 305 had very low compression ratio...that's why you could lug it to 1200rpm. It was fun, but my 70 stock 315hp 402 from CST is night and day. 1) better fuel economy 7.5mpg to 12mpg. 2) Power..up hill no downshifting, more road speed as well. V6 went to a good home for a 67 4x4 resto. Still have 435G Trans 4spd....