Crank main bearing clearnace to tight

[Requiemk]

Assembling my engine and crank main bearings are far to tight, annihilates plastic gauge and crank clearance to tight with even just main caps nipped slightly with 3/8" bar.

I remeasured everything and tried different crank in engine, same result.

new bearings are standard size and so is all engine specs/rebuild.

I then tried these new bearings in another spare engine to same result.

bearings match part numbers and all stamped std, measure up to spec with micrometer.

I am out of ideas, it should work...?

[Unclejake]

I suspect a crook set of bearings. It happens rarely but evidently it does happen.

Have you calculated the journal to installed bearing clearance using measuring gear (rather than plastigauge) and are you certain it is all of the bearings, or could it just be one that is tight?

[Requiemk]

i have measured each journal on one engine and all came up to spec.

It runs a single piece crank girdle so all main caps are tightened as one, i have not tried eliminating specific bearing/bearings but there is no obvious difference in wear marks to any of the bearings compared to others.

i have really come to conclusion it has to be dud bearings but thickness measures sweet so am still baffled.

[Unclejake]

I have never worked with a one piece crank girdle. Is this a motorcycle engine?

Aidan had an issue a few months ago with a Pre65 Cortina motor rebuild. One of the main bearings was a different size to the others (.010" under I think).

I would install the bearings and girdle with no crank and measure it up with an inside micrometer, or a bore gauge

[Hemi]

I have never worked with a one piece crank girdle. Is this a motorcycle engine?

Aidan had an issue a few months ago with a Pre65 Cortina motor rebuild. One of the main bearings was a different size to the others (.010" under I think).

this . when i refershed the ca i had one bearing that decided it was too virgin to run ..

in short check each cap by itself .

if not how tight? have only once run across a bearing begin too tight and it was because out of the set one was oversize

[eke_zetec_RWD]

if above all measures sweet, crank bent?

[Unclejake]

Oooo. Good point ^

[Requiemk]

Engine is a rb30, 6 cylinder

i disassembled a second engine a while back and put these bearings in last night as a test and still gives same results as first good block.

This would in my eyes eliminate the engines themselves and just put it down to bearings or installer.

I think i will need to check each bearing individually just quite time consuming with girdle.

Its far to tight, instead of being in range of 0.025 to 0.030 it was down below 0.010 and i think that was just because its all the squash i could get out of the plastic gauge.

thrust is also noted, within spec and not dragging.

[Requiemk]

I have never worked with a one piece crank girdle. Is this a motorcycle engine?

Aidan had an issue a few months ago with a Pre65 Cortina motor rebuild. One of the main bearings was a different size to the others (.010" under I think).

this . when i refershed the ca i had one bearing that decided it was too virgin to run ..

in short check each cap by itself .

if not how tight? have only once run across a bearing begin too tight and it was because out of the set one was oversize

i haven't measured each individual bearing but each have std size markings on them, i was under the assumption after a few spins of the crank the tight bearing would soon be apparent when removed and checking for wear marks.

[Unclejake]

I think you would see witness marks on a single tight bearing too, but if you can turn the crank by hand it can't be that tight!. You are looking at it and I am not so I expect you are absolutely correct though. A bent crank will grab at a certain point in my VERY limited experience.

I have had an RB30 but never pulled it down. I never knew they had a once piece girdle.

[Requiemk]

This is turning it with a breaker bar

2 seperate engines, 2 seperate cranks.

hmm i wonder how interested they are in giving me another set....

cheers for the help, second opinions are always choice to hear

[Escorto.]

also check that youve got the caps in the right places.

had this problem with my xflow. caps were in the wrong order.

[Testament]

get a 0-1"/0-25mm mic and measure the thickness of all the bearing shells? although unlikely two bent cranks is possible too.

The only installer caused issue I can think of would be are you using the right tightening sequence, this could be a bit more critical with a girdle v.s separate bearing caps. still pretty unlikely though.

have you got some old bearing shells you can put in as a test?

[Requiemk]

I'm going to shotover to work later today and put some old bearings back in and recheck. I can confirm one engine span fine with old bearings just a few months ago, im not sure of the other.

Tightening sequence followed and torqued to specs.

all bearing main caps and apart of a solid one piece girdle so cant have them in the wrong order.

I measured about 6 of the bearing shells with such device and all were on spec.

[Unclejake]

You aren't putting anything like Molly grease between the shell and the block/main caps are you? Stupid question I know.

[fuel]

perhaps there is something stuck to the underside of the bearing preventing it from seating properly. With the bearing in question, is it the same as the other main bearings? Are you able to swap them over between journals, and if so is it just the one journal giving troubles or the one bearing in other journals giving the same results?

[Requiemk]

using plan oil 15w/40.

everything was thoroughly cleaned prior to fitment, nothing underneath bearings, double checked this.

Ill attempt to try eliminate which bearing/journal is giving me problems this arvo.

[Unclejake]

Good luck. A tube of engine assembly paste is a good investment IMHO. Repco stocks it

[Testament]

Or Moreys works good too.

[Requiemk]

engine assembly paste and moreys were on hand and used just 15w40 was closest to me at the time

oh well solved

Turns out girdle was switched from other block, i don't no how everything was in separate areas/labelling so i will just be happy now its all together