1 For the forged/engine builders, what should the Main & Rod bearing Oil clearances b

turbostar

turbostar

Member +
Hello guys after some searching i still cant find a diffinetive anwser to the above,
im am finally going to put my engine back togeather, its a forged build with wiseco pistons, pec conrods, and acl bearings (mains/rod & thrust) etc
(my crank is standard size so im useing standard size acl's)

what i need to know is what oil clearances am i looking for as im going to use red plastigauge to check the main & rod oil clearances, what should they be???

secondly im useing ARP rod bolts and 4AGE ARP main cap bolts that are torqued higher than standard specification does this have a difference on the oil clearances?
 
Rob H

Rob H

Member +
The stock spec for the n/a is 0.016-0.048mm with a max of 0.08mm. The turbo runs the same spec as far as I know but it also depends on the oil you are going to use and other stuff too but there is a formula for working it out if you want to calculate the other stuff into it.
 
S

Skalabala

Member +
You do not want more than 0.05mm on the big ends. Any bigger with those tiny bearings + boost = problems in the future.
You use 20w50 full synthetic if the gap is 50
15w40 full synthetic if the gap is 30-40
You MUST use full synthetic.
Bigger than 50 then you want to use 25w60, not good for the turbo.
ACL tend to have a bigger gap as it is supposed to make space for extra thermal expansion in race engines.
 
turbostar

turbostar

Member +
Skalabala said:
You do not want more than 0.05mm on the big ends. Any bigger with those tiny bearings + boost = problems in the future.
You use 20w50 full synthetic if the gap is 50
15w40 full synthetic if the gap is 30-40
You MUST use full synthetic.
Bigger than 50 then you want to use 25w60, not good for the turbo.
ACL tend to have a bigger gap as it is supposed to make space for extra thermal expansion in race engines.
Click to expand...

Forgive me if this is a silly question :-/

Ok when you say
You use 20w50 full synthetic if the gap is 50
15w40 full synthetic if the gap is 30-40

What mesurment is 50 & 30-40 is the 0.05mm the 50 ur talking about?
If you see what i mean??

Thanks Dan.
 
S

Skalabala

Member +
Mains you are looking at 70 microns max. Specs say 60 is good but out of experience I know 70 is good. Limit is 80
The limit on the specs on the big ends are 80 but trust me it will not last at that clearance! Not even 70
Anything above 50 on the big ends then you should start to stress if you want long bearing life.
You are forging so you probably will want to run some nice boost and the 4e bearings are only 15mm wide(poor hydro planing threshold)
So you want less than 50 for your build :)
 
turbostar

turbostar

Member +
I checked the mains with plastigauge today and
ther all between 0.039mm - 0.046mm
So this is ok?

Just got to do the big ends when im next in the work shop.
 
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