Bearing rattle in new engine. - don't think is is the crank now.
Turbo Mini Forums

I got the new engine up and running the other day, and all seemed well for 20 miles at least.

When first building oil pressure on the crank over I thought I may have heard a slight bearing knock when I shut off the starter, I thought I was hearing things.

I got it fired up and put 20 miles on it at which point I abondened the test run when bliping the throttle at 1200 - 1500 rpm I heard slight bearing rattle.

I thought mabie a big end nut was slightly loose and didn't want to take chances by writing off the head, rockers and rebuild gearbox etc.

I have torn it apart now and can find nothing major with it, When I did the dry build I plastiguaged everthing and all was mid tolerance.

The only possible issue I can think of causing a problem is that I slightly marked a 2 of the crank journals when knocking the pistons through the block.

I removed the high spots from the crank with a little 1200 grit wet and dry paper, one of the bearings has a slight score, I mean insignificant can hardly be felt with a finger and covers no more then 5% of the bearing surface area.

Could the wet and drying have just opened tolerances up enough to cause rattle, it was definately only on one bearing I heard it from, or could it be something else and I've pulled my engine apert for no reason?

sorry for the long winded post.

the bad bearing, some bits may be shiny but they are completely smooth.

Edited by minimole23 on 5th Aug, 2008.

What oil pressure did you have, both before and after your test run?.Are you quite sure that this is the bearing that is giving concern -a photo of the other bearings might help.There are many people on this forum better qualified than I to give an opinion on this, but I do wonder of there was some oil contamination in the feed to this bearing.I dont think anything that you did to the journal when assembling the rods was a significant factor.

Are you sure it was a bearing knock? And not a rattle from the clutch release bearing or maybe a little pinking. A bearing needs to be quite worn to actually give you a knock that you can hear. Normaly you would notice a significant drop in oil pressure before you get a knock.

As above, it could be a bit of det. Especially since you say it happened once when you shut it off, that happened to me when I was running rich, it ran on a bit and rattled for a second ot two (as in det not bearing rattle). Do you have an oil pressure gauge or a light?

Edited by Jay#2 on 31st Jul, 2008.

That bearing does not look healthy, with out wanting to sound patronising did you use any assembly lube?

Any pics of the crank where you rubbed it with the wet and dry?

in my book the bearing is a tad galzed scored in the grove ...but this will not cause the problem you have described.

possible debris left in on the on the build

you may have detonation ... timing firstley !!

you did not mention any! oil pressure figures................ ? all throughout

I've pulled my engine apart for no reason?

possible! .... please give us more info
Anyway!
i use P400 on the crank, more than up to the job

the nicks in the crank wont render this problem if you have no high spots

get the timing and mixture right first even under low boost .. say 4 psi when you have sorted things


have you had the whole rotaing assembley balanced ..??

Edited by BENROSS on 1st Aug, 2008.

oil pressure was 65 psi when cold at idle.

I think oil pressure dropped slightly when hot at about 1000 rpm to 40psi but when revved shot straight back up again. I wish I got an audio of the noise now.

It would seem unlikely to be detonation as when initially cranking I had the dizzy a whole load retarded by accident. and the slight knock still occured when letting the starter off.

when assembling I used a generous coat of engine oil, and span the engine over with the plugs out for initial oil pressure build.

i'll get the crank miced up to double check everything, by the way, the main journals are unmarked.

The whole rotating assembly was indeed balanced.

Edited by minimole23 on 1st Aug, 2008.

From my experience that shell in the photo shows high spot contact (which I would expect after what you had to do to the crank journal) but it certainly isn't worn to the extent that it would "rattle" and if you heard it when you first started the engine (maybe) it wouldn't have had time to wear anyway.

More interestingly, you've said twice that you heard the noise as the starter let go.

Are you sure there is nothing loose on the flywheel/clutch ???

Clutch release bearing has already been mentioned but what about the clutch cover bolts, the strap to pressure plate bolts (if it's pre-verto) or even the flywheel retaining bolt (did it come undone too easily when you stripped it back down, keyplate in backwards?).
Or even a problem with the starter allowing its pinion to touch the ring gear.

Edited by Rod S on 1st Aug, 2008.

Schrödinger's cat - so which one am I ???

Pic of all main bearing shells and big end if possable
Regards
Paul

what spec do you have

Paul here is the picture.



and the spec is

1275cc std turbo pistons
Benross head
276 cam - though I'm gonna rip it out and throw a 286 in.
minispares ultralight flywheel
balanced rotating assembly
1.5:1 roller tip rockers
10.5:1 comp ratio
weber 45 and megajolt when run in.

It is an N/A engine (for the moment)

Edited by minimole23 on 1st Aug, 2008.

what do the bearings shells in the block look like ,
and also when you installed the crank how easy or hard whas it to spin befour you put the rods on could you just turn it by the crank webs or was it easy to spin by the nose?

I have to say, looking at them all now, unless the top halves are seriously different, that is what I would expect for an engine run a few miles on a used (but good) crank with new bearing shells.
The marks are just the high spots from the previous wear on the crank and the polishing you did.

I can't see there would be any bearing "rattle" from those.

I've had shells right down to the lead bronze backing (the bit that looks copper coloured instead of grey) with little noise unless the oil pressure was really low at tickover.

There must be something else, flywheel, clutch, starter etc..

What do the thrust washers look like ???

Schrödinger's cat - so which one am I ???

The thrusts look just as when I put them in, I was getting 4 thou endfloat, which is about right.

The bearing shells in the block look just like the lower shells.

What I shall do is just get the crank double checked for size and put another set of completely undamaged big end shells on it.

Paul H. When I installed the crank it span easily, getting slightly tighter when each cap was torqued down, but still span easily just off the crank tail.

could the noise really be the clutch release bearing at 1200-1500 rpm be then when the throttle is blipped? It sounded just like bearing rattle.

if a faulty bearing was a culprate what would oil pressure drop to?

I should add that I have not adjusted the clutch proporly before I went for a drive, made sure it worked then got on and tried to put some miles on it. It is has new arm, plunger and bearing on with an orange diaphram.

here is a pic of the damage to the crank journal.



Thanks

Edited by minimole23 on 3rd Aug, 2008.

Big ands and main bearings do not 'rattle' they rumble.

I wouldnt be concerned with those bearings, putting another set in there will only do the same thing.

Did you remove the protective coating on the bearings before you installed them?

And no jokes about PJ and Duncan's one hit wonder

the damage to the crank isnt enough to cause the engine to rattle imo, but does need a bit of a fetttle to stop it knackering the bearings.

have you got straight cut drops?

no longer a series, but still 1.3 turbo.

I haven't got straight cut drops.

The crank was measured for size today and it was spot on as expected, No 2 journal was a tad smaller then the others but still well within tolerance.

hmm, must have been something else. Oh well at least I have peace of mind now.

Thanks for everyones input.

make sure the flywheel is on tight!

"Turbo's make torque, and torque makes fun"

"did you know you can toast potato waffles?"

what is the end float on the drop gears?

if they are baggy the can flap frm side to side due to the helix of the gear and make a right racket.

Edited by minimole23 on 5th Aug, 2008.

should be ok then.

hmmmm.

I'm gonna beat out the timing chain cover as the chain did foul that a touch at first, but I thought I solved it.