4AGZE main bearing clearance

[Vertigo]

ive got myself some ACL race series bearings, and about to measure the clearances. looking online for some numbers, and all i can come up with is 0.015-0.033mm, which is quite a bit tighter than the smallest plastigauge i can find. whats the deal here?

also, while were talking mains, these bearings seem to have a top and bottom half, one kind which was wrapped in yellow plastic (the ones without the grooves). the ACL website doesnt really give any indication what this means, just that there are top and bottom shell halves. que?

[evil_si]

the top shell has an oil feed hole, the bottom half generally doesnt.

what colour flexi gauge do you have? orange, green? other option is to use ball guage and micrometer if you have access to

[Vertigo]

right, figured as much, just wanted to double check.

i have the green plastigauge, which is what my mate used on his 3SGTE (admittedly, not an indicator of similarity in clearance).

[Vertigo]

so i went ahead and measured with the green stuff, came out with 0.050mm on all 5 journals. this is on the looser side of acceptable, but thats ok as ACL race series are meant to be a little looser.

[Grrrrrrr!]

so i went ahead and measured with the green stuff, came out with 0.050mm on all 5 journals. this is on the looser side of acceptable, but thats ok as ACL race series are meant to be a little looser.

Depends if you specify the looser ones or not. ACL race bearings with the H code are standard clearances, ACL race bearings with the HX code are extra clearance (0.001" I think).

Can anybody explain why you want looser clearances anyway? More clearance = more oil flow = lower oil pressure. Is it extra cooling of the journals/bearings from the extra flow that people are after?

[Flannelman]

Looser berrings tolerate detonation where tighter wont.

The main advantage of reduced clearance is the ablitly to run lighter grade oil, however the valvetrain must be able to run the oil as well or excessive oil consumption through the valveguides will result.

[Grrrrrrr!]

So the bearings survive until...



??


Wouldn't it just be better to avoid det?

[Flannelman]

of course it would.

by the way, was the sparkplug inline with where that hole in the piston is?

[Grrrrrrr!]

No idea, that's out of a mates drag car, he thinks he just set the mixture a bit too lean.

[matt dunn]

Normally lean detonation will burn the centre of the piston,
where over advanced detonation will burn the thrust side,

But that one just looks wierd..........

[sergei]

looks like a bolt went through there..

[allencr]

...bearings seem to have a top and bottom half, ...what this means, que?

Yeah, 180 does work & 360degree grooves have also been used successfully in many engines, 190-270 degree grooves from the factory, or hand made, some with extra holes at the ends of the groove, are used in many performance engines

http://www.circletrack.com/tipstricks/4636_crankshaft_rod_bearing_installation_tips/index.html[/b]

[matt dunn]

FWIW,

My car runs genuine toyota bearings and clearances,
and has done 4 years of racing with about 550hp at one stage.

When the engine was stripped down the engine builder looked at the bearings and siad they look like they will do another 4 years fine.
We put Big Ends in it as a precaution but the mains are still in there and perfect.
And there has been a lot of det in the engine lately too,
will post some piston pic's later.

Dont follow the advise of someone that builds V8 engines,
as the bearing tricks with them dont work.

I know of a few guys who has 2JZ's built and rebuilt by supposedly good V8 engine builders, only to have bearing problems straight away,
the clearance tricks with the american /aussie V8's do not apply to the Jap stuff.

[Vertigo]

Thanks for that, Matt. Your proven experience with the A series is invaluable. What V8 clearance tricks do you mean, and what do you recommend in our case?