Oil clearance

[flexnuts02]

I am blueprinting my machined parts and have encountered a problem with the cranks main and rod bearing oil clearance.
I am coming up with .0801 for the mains and around .0500 for the rods.
This is the same crank from my old motor was polished for this time around.

ACL Main bearings thickness = .0782
ACL Rod bearings thickness = .0583

As far as I know both of these bearing sets are standard. Do my clearances suggest that I need an additional crank grinding, or are there bearing choices to properly compensate for the lost material?

Engine will see 35psi using 15w50 oil with a .0040 PTW new Wiseco's, stock crank, manley rods

 

[BogusSVO]

WOW!! Either you measured wrong, or your crank is way ground undersized.

.0801 is about 2mm

.5mm = .020

Now did you mean .008 ? if so then you have a ton of wear on the crank and it needs to be ground.

Go measure the the crank mains, and the rod throws.

Double check that what you are using to measure is accurate and "zeros" out.
Are you measuring in SAE or metric?

If the crank is truly measuring .080 under on the mains, and .050 on the rods, I do not think bearings are available, and you will need a new crank.

 

[flexnuts02]

If my measurements are dead on dont you think it is the machinists responsibility to see this before working my crank?

I measure in SAE with new blue point mic's from 0-4" they all zero on the standards and if they dont then I take note of the offset to add into the measure.

Ill double check a crank mic along with the bearings ball mic to see if I screwed up a decimal or something. I did the block mains I.D.s just yesterday and I know there is no need to re check them. That gauge was DEAD on accurate as B&B dial bore can get!

Its 95 here in our shop right now so hopefully I messed up some math in calibration, but while I work and later get to my own work again here are my measures for the TIGHTEST example of my clearances.

Crank mains O.D. = 2.2430
Block mains I.D. = 2.4009
Main bearings thickness = .0782

Crank rod throw O.D. = 1.7706
Rods I.D. = 1.8901 (Manley I THINK)
Rod bearings thickness = .0583

 

[BogusSVO]

Ok cool

Specs That I have.

Rod Housing bore= 1.8891-1.8905 so your measured spec fits.

Main Housing bore = 2.4016-2.4024 Looks like your main bore is a bit tight by .0007 - .0015

Std main journal 2.2435-2.2441 looks to be .0005 - .0015 under sized, but you still should be good.
(if you did a BSE the extra oil pressure will help here, but you maybe a few tenths of a thoundsand over OE max spec)

STD Rod journal = 1.7710-1.7717 you are a tad loose here also, .0004 - .0011
here again you may be a tad over OE max spec, But you are not building a OE spec engine

 

[flexnuts02]

Anymore input? At first you responded "Holy cow!"

Where should I go from here? Are my oil clearances acceptable for this 600hp daily driven engine, with the thick engine oil?

I do things right the first time!

Wow and it just now hit me.. When I figured my oil clearance I only added ONE bearing measurement when there should be two!

 

[BogusSVO]

First thing is take the block and double check the main housing bores, If your neasurements are correct, then bores are too smal and will lock up the crank at install.

Sounds like the block was lined honed, if it was, they got it wrong ( Or the specs I have are wrong, doubful tho, I took them from the Clevite bearing catalog)

Since you only figured with one half a bearing shell, go redo your math.

Next, install the bearings, then measure the ID of the installed bearing, then subtract your crankshaft dia. and that will be your true oil clearance.

 

[flexnuts02]

With the measurements ive taken previously, arranging them to find both the TIGHT clearance and the LARGE clearance of EACH individual bearing.


Mains clearance:
Tight .0018 .0013 .0015 .0012 .0010
Large .0024 .0019 .0026 .0019 .0025
Rods clearance:
Tight .0031 .0032 .0025 .0029
Large .0034 .0034 .0032 .0029


Measurements were taken at both axis on each journal.

 

[BogusSVO]

Just guessing but the tight clearances were right around the parting line on both the rods and mains.

The loose clearances were inline with the rod and block (or 90* from the parting line.

Nost bearings are a few tenths thicker at the parting line.

 

[flexnuts02]

With bearings plugged in it was pretty sloppy for readings, alot of un eveness.

The tightest clearance averaged out to .0023 and the big numbers average out to .0043


So through this discussion am I okay for crank and rod clearances?


35-40psi and thick oil.

 

[BogusSVO]

Start with about a 10-30 and check your oil pressures.

Cold idle
Warm idle
3000 RPM
WOT

That will help decide what is the best weight oil for your build.

Line bore needs checked again!!!

It is tight in the housing bore.

See post #4

 

[flexnuts02]

Well I guess Ill be re torquing the main caps back down again then for the 5th time .

Can I ask you, how could they be tight? Do they shave down the cap surfaces on the block mains as well as the main caps mating surfaces? I always thought they would have to leave the block mains alone and just shave off the caps mating surfaces to re bore the line.

 

[BogusSVO]

You should be able to look where they machined the caps and or block. The mating surface will be shiny, not dark and oil stained.

But most shops just cut the main caps for a align hone.

 

[flexnuts02]

So to verify, you think my Mains clearance of an average .0023" is too tight? Because Haines OE spec states .0008 to .0020" which means Im slightly larger giving me the room to run synthetic 15-50 oil

Do you still think it is tight? If so please explain why, and what I should be aiming for

 

[flexnuts02]

Im going to have to plasti-gauge them.

If I plug in the bearings and measure the inner bore with bearings installed I get a looser reading.

If I measure the inner bore with no bearings and use math to find the clearances then my mains show tight. Mkaes no sense to me.

So ill plasti-gauge them and then re-measure with the other methods just to quadruple check this.

 

[flexnuts02]

So I plasti-gauged the mains.

The mains are .0015 to .0020

The rods are large, I measured them in every way possible except plasti-gauge because the clearance is too large and it's hard to keep the rods from moving around while torquing the plasti-gauge

The rods are .0030 to .0035


To me thats large, the max OE spec is .002 and by the time my engine warms up these clearances will be large even with 15w50 oil

 

[flexnuts02]

Its been awhile for my update since I had to special order a set of +.0010 ACL rod bearings from across country,

**Rod oil clearances are now .002 .002 .0019 .0015.

I plan to split the bearings on the tight one, a standard and a +.001 to losen that gap back to around .002. Proper technique, says my machinist.

Since my machinist taught me its easier and more accurate to mic the crank journal, and then set your bore dial to the mic giving you less factors for error, I have re specced my crank clearances just to be sure.

**Crank clearances are now .0021 .0021 .0029 .0020 .0023

Machinist says its close enough and acceptable

One thing to keep in mind for the loose thrust clearance is that the crank journal is worn from the last motor, tapered but in spec too. So this makes me think I cant get it any better with this crank anyway since the block was lined back to OE.

BUT could I, should I call ACL to see if they make a +.001 main bearing? Because if they do and I bet they do, I could get that gap tighter for sure but is it worth it??