What is the perfect Main bearing clearance?

and what is the perfect Rod bearing clearance?

for a FI LT1 stroker motor.

also what weight oil would be the best choice for that motor?

thanks

 

I use 10w-30 regular oil

.0030 on both, the rear main cap was like .004

I did all the rods .0030

 

The above sounds good, though that rear main is a little on the big side? With a high -po motor and a relatively flexible crank (relatively small journal diameters on a small block) most people like clearances on the large side. Running it loose may need a HV pump to keep up but DO NOT use an HV pump with a stock capacity pan. Do a search if you want to know why.

Rich

 

I forgot to add I have a hi vol pump and big pan.....

The rear mains always seem to be on the high side.....that was the only one I installed without doing anything to it.

 

What pan do you have?

 

some circle track BS type of thing. Its a 8 1/4" pan w/kickouts etc. but I have a tube k-member, I had to smash the pan a little in the front to clear the rack.

Get the canton one.....or moroso has one.

I just did it the cheap way....My budget is low

 

.002" rod/.0025" main(1-4)/.0027" main #5

Those are the numbers to shoot for.

 

sweet thanks for that info. mashinstOne what weight oil would you recommend for those clearances?

 

For street use 10w-30

 

you don't think that .0025 is too tight?

I never heard of one being that tight unless it was stock

 

For a power adder car I would like to see them a little looser on the mains. But you know about opinions and how everyone has one.

Rich

 

For a street car even with a shot .0025" is fine, for high rpm endurance applications we only loosen them up a few tenths if that and everything comes out looking great at re-fresh time.

Like Rich said, every builder does things a little different, the common denominator is that it must work otherwise they wouldn't do it that way.

 

Do you do small blocks and big blocks differently? I have heard the theory advanced that a SB may need a bit more clearance due to more crank deflection. Of course, this depends on the power level and the crank used, the rigidity of the bottom end, etc. But as a general idea it kind of makes sense. A stroker SB crank has very little material in the "cheek" (the journals hardly overlap) when you really look at it that way,

Thoughts?

Rich

 

I have heard similar.

But most brgs out of the box are like .0027 and alot of them have a taper to it also.


Machinist what about the rear cap on a big block with a dry sump...does anything need to be done differently? Alot of the rear caps are always wayyy bigger It seems to be with all different bearings too

 

To be honest I personally don't have much experience with the BBC bottom ends. Our other machinist would be the guy to ask as he has been at it for over 30 years and is the guy I learn from.

Are you using "H" bearings? I rarely see much taper on them at all. You can mix the STD and over/under bearings to get your clearance spec, rarely can you stick to one box and get the numbers where you want them.