Type 4 center main or not...

[ecksrash]

I have a dilemma... I have an opportunity to buy a crank at an amazingly good price. It has been cleaned up from prior use and it came from the best crank builder of all time. I have a large stroke crank in my engine now and it has the type 4 center main. The crank I'm considering has a longer stroke, but all type 1 mains. I understand the concept of having a type 4 center main. I see that CB offers their cranks in all type 1 journals. What are your thoughts??

[farmer]

Long stroke, high rpm, high hp. - Definitely type 4 centermain.

When I build bus engines for T2 bay campers with more than 78 mm stroke I also use type 4 center mains to avoid crank flex.

T

[Piledriver]

On T1s, do T4 mains require a new case or is there a solution for align bored cases?

[farmer]

Yes it requires a new case, - or at least std mains. i have not heard of any oversize bearing solutions.

[Piledriver]

My one remaining functional neuron had a firing delay...
Half baked idea, but perhaps a T1 block could be machined to take actual T4 main bearings?
"Just" align bore to T4 std size.(assumes all T4 mains and an otherwise non-roached T1 block)

Yes, the bearings oil holes probably wont line up with the T1 block, but that's relatively trivial to correct.

#1 would be ~no worse than fitting a flanged crank?
Might even be able to switch to the better late WBX thrust setup?
(separate steel thrust rings, no thrust faces on the #1 bearing itself)

Would certainly open up used block availability, there has surely(?) been more than one T1 block scrapped due to only the mains being pounded out past available T1 oversizes.

Another thought--- are the T4 main bearings (aluminum/copper/lead alloy) sturdy enough to align bore to take the Chrysler or BMW main bearing shells? Would allow the trimetal bearings to be used.

[Marc]

...perhaps a T1 block could be machined to take actual T4 main bearings?
"Just" align bore to T4 std size...

One way of fitting a wasserboxer crank into a Type I case is to bore for a Type IV #1 main, so I don't see why it wouldn't be just as feasible to bore the center hole that large instead. I've seen "linebore" Type I bearings up to 67.5mm O.D., dunno why you couldn't go another 2½mm (obviously the dowel pin holes would need to be deepened and the alignment of the oil passages checked/corrected).

Standard Type IV is 70mm O.D. and 60mm I.D., while for Type I it's 65/55 so there'd be plenty of meat to align-bore the Type IV bearing out to accept Type I shells...sounds pretty sketchy to stack bearings within bearings but people have been doing it for years to graft a 350 crank into a Chev 400 block, and it seems to hold up OK, even in racing service. The Chev uses kerfs to position the bearings; on the VW you might be able to use longer dowel pins that pass through the Type IV shells into the Type Is - that'd be one way of ensuring the oil passages stayed in alignment....interesting thought, anyway - someone must've tried it by now.

http://www.competitionproducts.com/King ... info/5620/

[Piledriver]

Was thinking the steel shell trimetal Dodge or BMW main bearings as are typically used on the "all T4 main" T1 setups.
Requires a std T1 block though, this may provide an option for a cut block.

Might even be a bearing upgrade for a T4... The steel shells are usually tanged like rod bearings for alignment, but its the crush that keeps them in place once assembled anyway.

I regret not buying that Portalign setup for $500 back in the day.