4age crank tolerances

**MRMOPARMAN** · 09-11-2006, 11:00 PM

gday guys, just pulled the 4age down, it spun the first 3 rod bearings.
next part is the mesuring and checking to see if anythings salvagable.

does anyone know of the minimum diameter the rod and main journals can be ground to? its an early bigport crank with 40mm rod journals.
ive tried searching all the tech referance articles, but unless im going blind i couldnt see those mentioned!

thanks, Cameron.

**legend** · 09-11-2006, 11:55 PM

u could find out by checking the main bearing sizes from toyota/acl etc
as u grind a crank u must use the next size bearings i think the bearings are available in
3 different sizes after std
also check with a good machine shop in your area they will be able to tell u

good luck

**slide86** · 10-11-2006, 12:42 AM

ok.
the main journal diameter should be between 47.985 - 48.000 mm (1.8892 - 1.8898 in.)
the crank pin diameter should be between 39.985 - 40.000 mm (1.5742 - 1.5748 in.)
max circle runout 0.06 mm (0.0024in.) of the centre journal

hope this helps. (from the 4age book)

**30psi 4agte** · 10-11-2006, 02:21 AM

Originally Posted by MRMOPARMAN

gday guys, just pulled the 4age down, it spun the first 3 rod bearings.
next part is the mesuring and checking to see if anythings salvagable.

does anyone know of the minimum diameter the rod and main journals can be ground to? its an early bigport crank with 40mm rod journals.
ive tried searching all the tech referance articles, but unless im going blind i couldnt see those mentioned!

thanks, Cameron.

3 !!!! WTF Hat trick !! lol.

Any particular reason why 3 went ?????

Slide is on the money with all his measurements (+ rep m8)

sounds like he has the same 4a bible i have

**MRMOPARMAN** · 11-11-2006, 10:30 AM

well im not sure.. 1 and 3 spun a little and didnt hurt the crank, number 2 chewed up the crank, and number 4 got hot but didnt spin!

i just assumed it was an oil starvation issue, my mate thinks i may have cooked the oil breifly, but i was talking to an engine builder who thinks all the oil may have been in the top end and couldnt get back quick enough.

so now im lookin at installing tubes from the rockers to the sump. didnt some red tops have these, or was it 3sges?

anyways thanks for the replies guys. i think those mesurements are pre machining, the engine builder reckons he can take up to .75mm off the crank and still get bearings. so its lookin good again. especially since theres no discolouration in the crank or rods

**30psi 4agte** · 11-11-2006, 09:25 PM

Yeah the 4a is prone to forcing oil up into the head. But you would have had to be constantly over 6000 rpm for extended peroids to totally drain the sump.

Me thinks the oil level may have been low to start with to pump the sump dry.??

**MRMOPARMAN** · 12-11-2006, 11:23 PM

nup, replaced the oil a couple of days beforehand, and overfilled the sump to the top of the F mark to make sure it wouldnt surge. it did spend a lot of its time at or above 6k rpm.

my mate now has yet another theory, in which my sump has been bashed in a fair bit by previous owners. i havent checked the pickup yet but he reckons its possible it might have restricted the pickup somewhat, which would be quite possible judging by the sump.

anyways i had all the bores and everything checked. and its going to need a major rebuild. atm its looking much cheaper to get another engine and do a re ring + bearings on it for the short term

**takai** · 13-11-2006, 12:31 AM

Yeah the pickup could have been clogged somewhat. I know my stock bottom end has survived about 100 competition km this year, and thats on an engine which i thrashed around in my SX for about a year in road trim before it came out.

It can sustain living above 6000rpm all the way around the kink at Mallala without having any issues.
I do know that the pickup is clean though.