sobo

iTrader: (15)

Hello all,

Still plugging away at my engine build. I am currently at the point of blueprinting my new parts to insure my clearances are correct.

Before I begin any measurement work, I set a reference point. I always use the reference measurments that come with my micrometer set.

So, I start with the rod bearings. Every single rod journal measured 1.7710" with my micrometer. Thats good.

Then, I proceed to assemble my ACL "STD SIZE" rod bearings into my Crower I-Beam rods. Using a bore-gauge, I begin to measure the bearings both at 10* and 100* (Due to the tangs and whatnot). I did double check my bore-gauge to my reference.

I'm getting sizes of 1.7750 and 1.7737. (2 out of 4 rods I have done so far, both are the same)

Putting me at clearances of .004 and .0027.

Double checking with my caliper's puts me at approximately 1.774 for both the 10 and 110*, however I wouldn't trust these for anything more than a quick check up.

So, what gives? Why are my clearances so large on "STD" bearings? I was figuring that the clearances would have been on the tight side. Also, I'm not entirely sure why the bearings are so out of round. I had expected a small difference but not as much as what I have.

Any help is greatly appreciated. I'm sure I'm just doing something wrong here... Or maybe I have to turn my crank to get my desired clearances.

sobo

iTrader: (15)

Anyone?

sobo

iTrader: (15)

Well, incase anyone ever reads this and is having the same issue, do NOT follow Blueprint 103 on youtube. His measurements are okay for what he is doing, however using a dial bore gauge is much more precise.

Measuring both 10* and 100* will yield inaccurate results as the bearing is designed to taper where the halves meet.

Measuring straight down the rod will yield a more accurate result (Or so I've been told). After playing around with my dial gauge and my calipers I also realized my math was off.

My new rod bearing clearance is .0025 as it sits.

BogusSVO

iTrader: (1)

Glad you got it figured out.

You are correct, about the way bearings are made, they are not the same thickness at all points.

sobo

iTrader: (15)

I still cannot believe how large these bearings came in. I keep fiddling around with them and I'm between .0025 and .0027 on all of them. My crank is 1.7710 across the board, and has not even been micropolished yet. Do ACL "Race" bearings normally come in this large?

I decided to re-think my tooling here. I originally bought pretty much brand-name china stuff (Summit, jegs, etc...) and now I've decided to ditch all those tools and buy quality Mitutoyo measuring equipment. I was having a hard time getting repeatable results. This is a learning experience for sure, but I'm determined to do this right the first time.

Now I'm just wondering if I'm going to have to cut the crank and run oversize bearings to get the correct clearance I was looking for.

-Alex

BogusSVO

iTrader: (1)

What clearances are you looking for? Race bearings tend to give a bit more clearance any way. Ant hard particles have to be flushed out with the oil. The race bearings have a harder surface, so the embedablity is low.

Also if you do a BSE, the oil pressure of the engine is going up so a slight increase in oil clearance will be ok.

Since I do not have some of the details of your build, There is little I can say.

sobo

iTrader: (15)

Basically I'm aiming for .0025 clearance on the rods and mains. I'm looking to make quite a bit of power on the engine, around 700-800whp. 20w-50 Brad penn will be the oil.

The motor has a balance shaft delete and will be using a kiggly HLA.

I'm just not interested in running the rods at anything more then .0025, and I feel once the journals are polished the gaps are only going to become bigger.

BogusSVO

iTrader: (1)

Yes after the polish the oil clearance can and will open anywhere from .005 to .0015 depending on what shape the crank is in.

With the 20-50 and BSE, cold start oil pressures up around 90 psi or higher would not suprise me, unless you port the OFH and/or cut the oil pressure by pass spring.

Warm oil at 4000 rpm, would not suprize me to see 60 psi

You will have enough oil flow and pressure to go as high as .003