CJ love

[turbohunter]

Done

[turbohunter]

Got some time to work on the short block.
Loaded the first two slugs in, then degreed the cam. Everything was right on and events were within half of a degree. I’m calling that good.
Put in four more pistons. Had to leave something to do tomorrow 
I’ve ended up using all standards so far and all rod clearances are dead on at .003 or .0029. I’m going to go thank my machine shop. It’s turning over very smoothly.
Since I’ll be building more of my own stuff I’ve been investing in nice tools and loving it.
Reeeeeeeally enjoying learning this stuff.

[67xr7cat]

If the rods were wrong you need to check the difference in weight.  If is more than 10 grams I would get the crank rebalanced.  Keep in kind you have to use a fixture to determine the big and small end weights.  I'd assume they will weigh less being a shorter rod and some will say just make sure they weigh all the same and don't worry and likely will get away with it, but the correct way is to rebalance if it is off.

[turbohunter]

Thought to ask them that.
Did the weights and math while I was down at Scat. Bob weights came out exactly the same. They gave me the thumbs up.

[67xr7cat]

Well that is interesting. 

[turbohunter]

Anyway here’s my numbers. With standard CB743HN’s I have .003 clearance. Shooting for .0025.
And thank you Brent for answering my ignorant questions.

If you’re following along you may wonder why my target has changed from .0025 to .003. Simple, Brent.
My inexperienced train of thought was to pick a number in the middle of what I thought to be the two ends of the clearance spectrum (.002 and .003). Figuring that would be a sweet spot. Wrong. That doesn’t take into consideration the materials used in the bearing construction. The way I understand it is since I’m using uncoated bearings I need to allow a bit more oil cushion. Also the coated bearing is harder than non coated so tolerances can be tighter.
Again I’m just putting this out to help myself learn and maybe another couple guys that want to try this. Feel free at any time to add or tell me I’m full of crap.

[turbohunter]

Well that is interesting. 

I thought so too. But I was thinking simply just figuring weight. It actually has to do with reciprocating and rotating weight as you suggest.

[blykins]

Anyway here’s my numbers. With standard CB743HN’s I have .003 clearance. Shooting for .0025.
And thank you Brent for answering my ignorant questions.

If you’re following along you may wonder why my target has changed from .0025 to .003. Simple, Brent.
My inexperienced train of thought was to pick a number in the middle of what I thought to be the two ends of the clearance spectrum (.002 and .003). Figuring that would be a sweet spot. Wrong. That doesn’t take into consideration the materials used in the bearing construction. The way I understand it is since I’m using uncoated bearings I need to allow a bit more oil cushion. Also the coated bearing is harder than non coated so tolerances can be tighter.
Again I’m just putting this out to help myself learn and maybe another couple guys that want to try this. Feel free at any time to add or tell me I’m full of crap.

Brent said aim for around .003" on the mains. 

Rods can be a lot tighter since they're smaller.  Remember the .001"/inch rule.  You're working with a 2.200" rod journal.  You can run a .0022-.0025" clearance there for a street engine.

[blykins]

Anyway here’s my numbers. With standard CB743HN’s I have .003 clearance. Shooting for .0025. CB743HN1’s are back ordered.

Here's where I thought you were and that's why I had bearings sent to you this past week.

[turbohunter]

It’s all good.
I’m learning and it’s costing a little money but I’ll have them for the future.

[blykins]

It’s all good.
I’m learning and it’s costing a little money but I’ll have them for the future.

FWIW, I wouldn't run .003" rod bearing clearance on a BBC journal street engine.  Your .0025" number was solid.

[turbohunter]

Even with uncoated?

[blykins]

Even with uncoated?

Yep.

[turbohunter]

Even with uncoated?

Yep.

Wort 

Get it? Worts and all.

[blykins]

Even with uncoated?

Yep.

Wort 

Get it? Worts and all.

If it were a stock FE rod journal, then I’d be somewhere around that .003” point.  The factory rod journal is much larger in diameter than a BBC, and also much narrower, so it does need a little more cushion for the pushin’.  I think that’s what we were discussing in the other thread on the main forum, when one of the members was discussing using a factory crank.