Triumphrat

loxx101

Sorry for bringing up main bearings again, it's not an uncommon topic, I know!

I'm trying to work out exactly what's going on as I think I might have it mixed up. I have read loads about it but it's not making sense. I have an idea in my head but I'm almost certain it's wrong judging by what I've read/seen.

Standard, what does a T140 have?

Mine had roller bearings on both the TS and DS. Is it normally a roller on the DS with a ball on the TS? The TS is the one you upgrade to a roller?

Cheers!

loxx101

Sorry, may not have phrased that very well.

SHOULD I go for rollers on both? I am going to be running the standard T140 inlet with a late 650 exhaust for more power and a couple more things will come to bump the power up a little. I'd like it to be as strong as possible.

If you have two rollers, how is float dealt with? I assume standard if it has a ball then it locates on that. Is one of the rollers a taper roller or not?

1963wak

late t140s have 2 rollers it was a mod to make them stronger,the timing side one is 3 piece and locates the crank.why not try a different timing on the cams? the standard set up aint too hot, 100' lobe centres work well.

Mr.Pete

Up to '75,you should have a drive-side roller with CN (normal) internal clearance.That was changed to C2 (tighter) clearance for '76 onward.
Originally you would have a timing side ball bearing,C3 internal clearance.You can use a double-lipped roller,CN internal clearance.

End float is very easy to check and get right with the 3-piece double-lipped roller on the timing side.

loxx101

Okay, awesome. Cheers! The machine shop I'm using said to not bother with the roller on the TS I think which conflicts with what pretty much everyone else has said!

Yeah, I am doing the cam timing different to standard Hoping for everything to be smoother and better than factory

So it's best to go for the later standard spec then I guess is what you're saying for bearings?

Mr.Pete

Use CN clearance for both roller bearings.
You can check end float before you tighten the crank pinion against the outer bearing lip on the timing-side roller.

If you have the "A" mark on the intake camwheel,use the keyway nearest to the "A" mark and time it on the "A" mark.Still check the timing,but chances are it will look good.

loxx101

Is it not better to go with C2 on the DS if the later ones use that?

Yeah, I'll be setting it with a degree wheel anyway but I'll start there Cheers!

Mr.Pete

The later cases had a little less interference fit on the outer race.It crushes the bearing less,so you can use a bearing with less internal clearance.

If you use the C2 bearing in early cases,there's almost 50% chance it will work OK.Not all cases are equal,and neither are all bearings.If it's not OK,there will be no internal clearance when the bearing is fitted in the cases and the inner race is fitted on the crank.The bearing will not turn easily without internal clearance,and it will fail.

If you try a tighter bearing (C2) and it doesn't turn freely,then you need a CN bearing.