[Skip Fix]

After we had this discussion I went and checked the block I had been racing with the RAIV heads, it saw 7000 many times. One of these 1976 557 blocks! So maybe I need to find a new block for them to have a home on!

[screamingchief]

Probably a good idea Skip,but I do believe a good many of the failures come along with the increase in the use of the 3" main 4.21"/4.25" stroker cranks.

My feeling is the added stress of the longer stroke cranks,coupled with their smaller main size and reduced crank-pin overlap is just not conducive towards long life with the thinner web blocks.

Just a case of "too much movement" in the bottom end for the thin webbing to hold together...

With virtually no means to really address it well,that is,without making things worse often.

I feel the 3.75" crank is a much safer bet in the thin web blocks,but I still would push it too far myself,especially not with primo vintage hardware at risk.

JMO/FWIW.
Bret.

[Half-Inch Stud]

Please figure that regardless of crankshaft material/Dimensions used, the quality of the Balancing of the Rotating assy is KEY to reducing ANY crank flex, to remove ANY Main journal deflections imparted to the CAP&WEBS.

Not Twist/Untwist...rather the wafting of the counter-weights at TDC & BDC.

[Tom Vaught]

Agree that few stock blocks will tolerate "orbiting" inside the main saddles due to a flexible crankshaft. Factory cranks are better than some of the off shore pieces but a good forging or a billet will in some cases allow a "weaker" block to survive.

A very good balance job will improve things greatly at high rpm.

You still need to find a very good balance machine to actually spin the crank though.

JMO

Tom V.

[myckee]

Sooo, now that we all know which years to look for, which webbing to look for, and, which casting numbers to avoid; how about letting the rest of us in on the your easy, identify at a glance, secret P Dude?

Please?

[455Dave]

Originally Posted by David Holmberg

Looks like I'm the only SOB here that can keep his word...

Mongo = Blabbermouth...

Wrong, there's one more SOB!

David and I our pushing our 455s way past what they were meant for sometimes side by side. Like David once said, that last 200 feet is definitely white knuckle time. You hope the "good" block and the bottom end work holds out for one more pass.

[myckee]

Whoops, it looks like the secret was posted a couple of pages back. I must have been half asleep when I read this thread last night. LOL

[baron_]

Holy thread revival! Or something.


additions

The dirty one on the left without any caps is a '77 400 block
the block on the right is a '70 455 block, supposedly high nickel

Would have been nicer to have an early 400 block for comparison, but didn't have one available at the moment

[gene simmons]

The only high nickel blocks i know of were built for Arnies blown motors. How about using a main support on a newer block with studs? that is something the pontiac community hasn't accepted.

I have heard for years the newer blocks will take 500hp with studs added.

Too often people think the lifter bore brace is going to keep blocks from cracking up the mains.

It may help support lifter bores, with roller cams, that have steep ramps.

Bill Foder had welded Bore Brace's back in the 70's on his Zepplin FB, using a 400.
He turned it 9000rpm.

[PONTIAC DUDE]

Originally Posted by gene simmons

The only high nickel blocks i know of were built for Arnies blown motors. How about using a main support on a newer block with studs? that is something the pontiac community hasn't accepted.

I have heard for years the newer blocks will take 500hp with studs added.

Too often people think the lifter bore brace is going to keep blocks from cracking up the mains.

It may help support lifter bores, with roller cams, that have steep ramps.

Bill Foder had welded Bore Brace's back in the 70's on his Zepplin FB, using a 400.
He turned it 9000rpm.

If you do a search. All this has been discussed to death over the last 7 years.

[screamingchief]

Holy thread revival! Or something.

Still,this is all good info and exactly what this place should be about,open exchange of said info.

I've been meaning to dig this thread up too,ran across an interesting block to add,the deep mystery that is the '77-'78 XX cast 400 block!

Found one in a friends garage up north while there visiting to go to the hot rod power tour among other things,just so happened to have the digicam and thought about this thread and snapped a few.

Was interesting,I think it was an SR block as it did'nt have a VIN or unit number stamped on it???

Just the block code stamped X7 which shows to be the '78 W-72 400.

Enjoy!

[screamingchief]

A few more of the same block.

Do note they went back to the '74 #481988 casting (I know it's kinda hard to make out,trust me I looked really close) instead of the #500557 or #568557 casting no.s.

And do check the date code as well,it's much clearer.

The bulkheads are pretty much the same as the earlier/thicker main web blocks.

BTW,if there were ever a thread that screamed "sticky" to me,this is it,JMO.

[Skip Fix]

Man even with pictures it's hard for me to see much difference without them being side by side. I have a X7 in the shop besides that new 557. might have to look side by side. Rumor was also the X7s and other 220 blocks used spring pins in place of dowels.

[screamingchief]

Rumor was also the X7s and other 220 blocks used spring pins in place of dowels.

This one has dowels,look at the pic full size,they're visible there.

Also the front cap was off before the pics were taken,solid dowels I assure.

Cant say they were all that way,just this one.

Lots of other details in the pics if you look close.

[Skip Fix]

I could tell that one had solid dowels but several W72 motor sources have said they had the roll pins. The questions continue!
Still looks like the webbing stops about the dowels like the 557 to me.

[gene simmons]

Originally Posted by PONTIAC DUDE

If you do a search. All this has been discussed to death over the last 7 years.

I havn't been here for 7 years.
So has the x7 blocks (w72) and the xx in the center of the x7 block for 76 -78, the change over from 481988 to the 500... blocks in mid 1975, old news.

[screamingchief]

Skip,your right about it being hard to compare the various pics,so I will post some old ones here again to show the difference between the thick and the thin.

First two pics were posted a few pages back (post #117 IIRC),first pic the "thin" #500557 casting,next pic is the '67 block (Jeff's block) I used to compare to that,next pic is my earlier #481988 400 block I posted on the second page,and the last will be a closer shot of the bulkhead area in question on the XX 400 #481988.

IMO the bulkhead on this XX block does'nt look that bad at all,IMO it actually looks a little "cleaner" than the earlier #481988 casting.

Visually the XX block is waaayyyy better than the #500557 casting with the lack of material on the underside of the bulkhead.

HTH.

[Skip Fix]

The closer I looked at the others after printing them out that is where it looked a little different ,your help alot.

[RUDOLFSSON]

I examined one 500557 block today and wanted to share some pictures to this thread…. Now this is some piece of junk! Look at how thin it is!
It had had some major carnage (sleeve and deep dents all over plus the crack), but what about the extra two holes on #2 main cap LOL (my guess, they put 4 bolt cap in there because they saw the crack.. ?)
It has 75 date code but it’s got a 76 vin code.

[chuckies76ta]

Wow, Great read on blocks. Should be Sticky..

Charles