measuring for bearing clearnce

now that i have my block back from shop i tried measuring bearing clearance with a bore gauge. not sure i'm using this correctly, but i'm getting .0035" on the mains. would this be excessive? 360 block using a girdle and block has been line honed. i called my machinest to get the measure off the crank which he tells me he turned it.010", but he's giving me a measure of 2.7995". i zero my bore gauge to 2.7995 and get .0035" when i measure mains. so we are using two different mic's here as well.

I'd wait until I had the crankshaft in hand to check the clearances. IMO .0035" is loose, my 340 mained 434 is .0027-.0028".

thats what i figured. the last build had .002" on mains and rods, but i did use a snap gauge to measure.

You need to measure the O.D. of the crankshaft and set the dial bore gauge up with the same outside micrometer so you can see the actual differences between the two I have several dial bore gauges and inside and outside mikes, I use one outside mike to do all the measuring on the crankshaft and bearing I.D. on each motor That helps eliminate the chance for eyeball error and not every one has the same touch,feel, on using micrometers :shruggy :My .0027 might be your .0022 I like looser bearing clearances than tighter, shoot for .0010+ for each inch of diameter. I would and do run .003+ on SB cranks, mains and rods on both 318/340 and 360. Our motors are not the same as Chevys and Furds

Was the machine shop climate controlled? Not sure if that's an issue in MI, but down here in Florida, the good machine shops are climate controlled. They bring the blocks/heads inside for a minimum 6 hours to climatize before machining. You'd be surprised how much 25 degrees makes when the machine, block, or both are above the temps the manufacturers advertise the tolerance of the machines at. I am sure you know this, but have your tools at the same room temperature as what you are measuring. And then the question is what is the quality of tools you are using? As stated above, .001 per inch is pretty much the standard, but depending on what oil viscosity you'll use, what your power level is, and whether or not your using a power adder, will dictate the ideal clearance. I do disagree about Mopar engines requiring some different clearance than a Chevy or Ford. The crank and bearing doesn't care what brand it is, the clearance will be dictated by journal size, oil viscosity, power level, and whether or not a power adder is used.

while you have the dial bore gauge it would be a good idea to measure the main bores in the block to make sure they're not too big.

Tools and block are both same temp. Journal in 2.7995. I use amsoil 15/50 and engine should make about 650+HP and be spun 7000-7500rpm

Also I have been looking at what other engine builds are do with bearing
clearançe and I was surprised to see quite a few builders setting clearance at .0035+. Rods too.

I do as Cab mentioned, set the dial bore gauge up off the mic I used to measure the crank. I had to have the damper hub honed when I built my 408, so I measured it with my mic, locked it down and took it along with the damper to the machine shop. They then set up using my mic and honed the hub.

.0035 would be perfect. I'd rather have .004 than .002

For sure check it off the crank. Lock your micrometer when you measure the journal, and zero your bore gauge in the mic.

I will get those checked as well.

Check a few with plasti-gage ( not very accurate, but - just to see what you get. If your readings are correct, you can buy oversize bearings if needed.

Words to live by; If you have extra clearance you will know. If you don't have enough everyone will know.
Doug

I agree with Doug, was going to type the exact same thing as I was reading your thread.

Don't trust plasti gauge, I did and number 4 rod was bad (egg shaped) and the plasti gauge read good on all rod bearings. Well number 4 spun rod bearing in my driveway at idle, never saw more than 30 minutes total run time and oil pressure was perfect whole time. I even paid machine shop to check every thing, they had the whole rotating assembly when the bored and notched the replacement block. I even told them number 4 pumped water through it on the last pass down the track and if was even close to funny replace it. Well lessen learned, never again will I not check every thing myself with bore gauges and micrometers.

last build with this block had .002" on mains and rods using ACL bearings. now have federal mogul. will there be a noticeable difference in oil pressure going to .0035 vs .002?

I am running almost exactly the same thing you are. '91 360 block, filled with a girdle. Mine has ~.0035 on the mains, and ~.003" on the rods.

Oil pressure isn't the greatest... I have a Melling 72 pump. With the new mopar performance hydraulic roller lifters, and crane gold rockers (shaft oil)... the oil pressure isn't exactly stellar. Only has around 45~50psi hot oil through the traps at 6200~6300. I plan on shimming the pressure control valve while it's apart right now to help with that.

I just took the motor apart yesterday because I had broken a piston in it. All of the mains look great, so I can't say that the lower pressure or large bearing tolerances are hurting anything.

The only exception is the #4 main which coincidentally is right where the #4 main isn't tied to the #5 main on the girdle (because the oil pump is in the way on a small block). It has some strange wear on that cap side of the bearing where the only explanation is the crank and/or block is flexing. It has warn through to the copper, only on the front 1/3 of the bearing, only directly opposite of the #6 piston around 4 o'clock.

That being said... the last time I took this motor apart, it had the same strange bearing wear on ALL of the front 4 caps...I'm making a good 100hp more now then I was last time... so I attribute how much better it looks this time to the girdle doing it's job.

But this is at low RPM (MEGA torque) and probably 150hp+ more then your plans.

i have a 71LA block, but yes both are 360's. are you using full groove main bearing? i'm concerned with the low oil pressure. good to hear bearings look good but one. i know the girdle requires a .005 crush. maybe i dont have the girdle shimmed properly?

Plasti-gauge has no place on a performance motor.

.0035 is not too loose. Excessive side clearance or upper end oiling will usually show more oil pressure issues than a little loose on the mains.

Skip the high volume pump. Just use a standard pump and shim the relief if you need more pressure

I have a 3/4 groove bearing in mine. The shimminf is pretty straight forward, just take your time, measure carefully, and make sure you keep the right shims with the right stud when you're done!

ok, thanks Monte. i wont let .0035" bother me than.

when you were shimming the girdle did you apply any pressure on the girgle while checking for the .004-.006 clearance between the cap and the girdle? thanks

measured main bores without bearings. i get 3.0025 on front and rear main and 3.003 on 2,3 and 4 main. anyone know what the max and min. are?