Main bearing clearance


robthedoc

robthedoc

civic disobedience
Joined
Feb 14, 2013
Messages
1,533
hi guys I'm using acl flexigauge to measure the clearance of the mains. It's too tight. Minimum clearance is 0.024 mm I'm reading less than that.

Crank hasn't been ground and measures in spec. Bearings are std size acl race bearings.

Anyone come across this before? Going to measure the bearing thickness but had kinda hoped I wouldn't have problems like this.
 
You still using the arp studs?
 
No that was with the standard bolts torqued to standard settings.
 
.o24mm= .00094"
Just to make sure, you are reading it in mm and not inches?
 
I am mate, using green acl flexigauge. The mm scale starts at 0.025 and I am definitely tighter than that. Spoke to JEM engines this morning and Erik there is saying to bring the block, crank, bearings, bolts and arp studs. He will torque the caps down with the studs with the crank out and line hone to correct the crush from the studs. He seems confident that the clearance should be spot on when the mains are honed. Heres hoping anyway.
 
I got them and fitted them but when I realised the torque difference between them and the standard bolts and reading all the info on the box about line boring/honing, was thinking about sacking them and just using the bolts. It was with the bolts that I was finding the clearance was too tight.
 
Ok so I've dropped the block and crank etc off and I now need to find out the main journal size for b18c4. Anyone any ideas? I have most of the data for the engine but can't find this anywhere?
 
Sorry heads up my arse today... its the main bore size I need
 
B16b,b18c,b18c4 cranks have the same size journals. Therefore the main bores in the blocks will be the same size.
Not sure where I find that info tbh, may be a case of adding bearing thickness, clearance and the journal size together.
 
That's kind of what I was thinking but when I said it to him he said I was thinking like a motor mechanic and not an engineer... Near enough isn't good enough apparently lol.

He said that acl'a catalog will have the standard bearing housing size specs. Will need to have a look tonight. Fml this is hard going like. Here's hoping this doesn't lead to oil pump problems like you mentioned man.
 
robthedoc said:
That's kind of what I was thinking but when I said it to him he said I was thinking like a motor mechanic and not an engineer... Near enough isn't good enough apparently lol.

He said that acl'a catalog will have the standard bearing housing size specs. Will need to have a look tonight. Fml this is hard going like. Here's hoping this doesn't lead to oil pump problems like you mentioned man.
Click to expand...

Sounds like your in good hands mate so you should be alright.
Not sure where to find that kind of technical info from a reliable source tbh.
 
Anyone? Main bearing housing bore size?? I will buy pints for anyone who can find this...
 
Hi Rob,

The sizes we have for this engine and the 5M1959H set is 59.000 - 59.020mm for the tunnel.

RegardsMark Shadbolt | Product Engineer (Bearings)
ACL Bearing Company (Australia) Pty Ltd,mark_shadbolt@acl.com.au
 
So 20microns is the tolerance is it? So you could have 59.000 on main 1 and 59.020 on main 5 for example and that's within spec?
 
I might be wrong (I often/usually am) but I think that they are all the same but they will be between 59 dead and 59.020, as in one engine 59.010 to another at 59.020 this is why there are different options for standard size bearings?
 
it's common to need different size bearings on the same crankshaft. Perhaps this is why along with the tolerance on the crank journal? I don't know either so it's all guess work until your engineer can clear it up lol
 
I got schooled when I suggested adding journal size to bearing thickness plus clearance to work out bore size. Was like being an apprentice again... standing there thinking how stupid am I? But I will ask when I go to pick it up lol.
 
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