Type 4 main bearing to case fit questions

[scottf1887]

I'm putting together a type 4 bottom end and I have run into an issue with my rear (flywheel) end main bearing during mock up. The case is a nice std main and the bearing is a mahle. The bearing does not want to seat into the journal of the case. It comes very close, almost to the point of meeting the top of the dowel. I'm afraid to force it in because I don't want to distort it. Is this common, or am I good to do some light tapping to force it in place? It just seems strange because the rest for in very well. Thank you for the help and I can post pics if it would help.

[raygreenwood]

[esde]

It's not unheard of to find a bearing in a "set" that is not the same size. Check it's part # or measure it. Maybe they get mixed up at some point of their lives, or a set gets returned with a wrong main bearing.
But as Ray said, it sound like you have a main for a case that has been align bored, that is a larger diameter than your standard case bore
_________________
modok wrote:
Bent cranks are silent but gather no moss. I mean, ah, something like that.

[scottf1887]

Thanks for the help guys. I took measurements and it looks like I got screwed with an oversized bearing in the box...correct my math here please though. The main bores is 70.06mm, the old bearing measured 70.02 and the new bearing measured 70.55. my math tells me that new bearing is for a first cut oversize case correct? Thanks again for the help.

[scottf1887]

I guess while I'm on it...does anyone have a single bearing they can sell me? Type 4 sets aren't cheap and I got this set at a swap meet last year so there's no refund in sight. Thanks!

[modok]

I don't have any spares. I'd try to turn the OD down to standard size, and probably have a 50% chance of success .

[scottf1887]

Yeah I considered that...I just hate to do it with all I'm putting into this motor. If anyone has one I'd really appreciate it! It's the last thing I need before sealing up the case

[modok]

If you had two sets of bearings, you could mix and match to use the ones that fit best.
Silverline bearings are VERY good, even though they are low price.

I have a LOT of old bearings and I find many of them measure on the small end of spec or below.....they shrunk? Isn't that odd....but I guess they must have. We know that the tin/aluminum alloy is does creep and so forth, it's not a highly stable material.
So....I'm not real excited about using ANCIENT NOS bearings.

[esde]

I'd call FAT performance and aircooled.net about finding a loose #1 bearing.
_________________
modok wrote:
Bent cranks are silent but gather no moss. I mean, ah, something like that.