[PAUL K]

Originally Posted by Douglas Willinger

Anyone have any information on experience with the MOLNAR 4.375" and or 4.65" stroke 3" main journal crankshafts? For instance the cylinder wall wear?

We've been building 4.375 stroke Pontiac engines for decades (not with Molnar crankshaft) and it makes great combination . No issues whatsoever. Not much experience with the 4.65 stroke.

[Douglas Willinger]

Originally Posted by PAUL K

We've been building 4.375 stroke Pontiac engines for decades (not with Molnar crankshaft) and it makes great combination . No issues whatsoever. Not much experience with the 4.65 stroke.

Is that with or without any amount of filling in any of the water jacket area?

I read somewhere that such was required with the 4.5" stroke to avoid cylinder wall scuffing.

Would very much like to see some stories of the 4.375" builds.

[PAUL K]

Originally Posted by Douglas Willinger

Is that with or without any amount of filling in any of the water jacket area?

I read somewhere that such was required with the 4.5" stroke to avoid cylinder wall scuffing.

Would very much like to see some stories of the 4.375" builds.

All the builds were performance deals so the the blocks were filled atleast to the water pump holes.

[Douglas Willinger]

Originally Posted by PAUL K

All the builds were performance deals so the the blocks were filled atleast to the water pump holes.

So as to avoid the cylinder wall scuffing, is such a partial water jacket filling required for a 4.375" stroke. Or for a 4.25" or even 4.0"?

[PAUL K]

Originally Posted by Douglas Willinger

So as to avoid the cylinder wall scuffing, is such a partial water jacket filling required for a 4.375" stroke. Or for a 4.25" or even 4.0"?

Filling the block seems to help everything, from what we've seen in our experience. However the Boss Bird guys have had success without ever using block fill. I can't say it's a necessity but almost every serious effort stock block build we've done has been filled.

[krisr]

Originally Posted by PAUL K

Filling the block seems to help everything, from what we've seen in our experience. However the Boss Bird guys have had success without ever using block fill. I can't say it's a necessity but almost every serious effort stock block build we've done has been filled.

Half fill? Just to help keep the mains a bit more rigid or are you talking more full fill and run alky?

[hojs69]

GTO JONES's
Senior Member

How many are running a 4.75 crank?



GTO Jones.......You are one of the few it appears.

[PAUL K]

Originally Posted by krisr

Half fill? Just to help keep the mains a bit more rigid or are you talking more full fill and run alky?

Filled to the bottom of the water pump holes.... seems to work best for us. We've went lower, approximately to the bottom of the middle freeze plug but that didn't help as much keeping the bottom of the bores round.

[ponjohn]

Originally Posted by PAUL K

We've been building 4.375 stroke Pontiac engines for decades (not with Molnar crankshaft) and it makes great combination . No issues whatsoever. Not much experience with the 4.65 stroke.

Stock block?

[PAUL K]

Originally Posted by ponjohn

Stock block?

Both but more stock block builds than aftermarket.