Main and Rod bearing question
- Thread starter cmng
- Start date
Its a risk I'd have thought. I think you need to measure it and specify it correctly.
I think mine were all the next size up when my engine builder checked. I'm sure in the manual there is info on checking and specifying the bearings
I think mine were all the next size up when my engine builder checked. I'm sure in the manual there is info on checking and specifying the bearings
O
Odin
Guest
cmng said:
Well if they happen to be the right size then I don't think it would hurt lol, But this is the sort of thing that needs doing properly otherwise you new engine will be knocking after the first few miles lol lol lol.
You need to get everything messured and then buy the right sized bearings for the job ;-) .
Rob
If your just refreshing your engine then refitting the same bearings as already fitted should be fine, the actually size difference between the different grades are minute, so probably unlikely to make a difference what size you use especially on a crank with a few miles on it.
The different grade bearings,pistons etc basically allows you to blueprint the engine.
The different grade bearings,pistons etc basically allows you to blueprint the engine.
O
Odin
Guest
And we all know what happened to your billy bodge engine don't we :der: :lol: :lol: :lol: :lol: .GINGA said:
Rob
Nothing happened to the big ends and mains, it was just a small missing dowel problem that caused the piston problemsThunder God said:
Still it didn't cost me £35k to build it and I don't recall ever getting ovetaken by £100 Audi 80's, Nova's and corsa's :lol: still I'm sure if I'd wasted that amount of money doing 1/2 a job, I'd be scared of putting my foot down aswell :nerner:
Maybe just me, but I would use the correct grade for replacing the bearings whatever you do, the different grade bearings are colour coded with a mark on their edge, and you can work out the sizes from the series of numbers on the crank, block and rods.cmng said:
The grades are there for a reason after all, so it's allways worth working them out to be on the safe side. If you are blueprinting the engine or anything has been worn/repaired then you will need to measure up to verify sizing.
Call me a fussy bugger if you like :lol: .
The jist I'm getting from this thread is that the 'grading' of the bearings actually refers to their size/oversize and not the material they're made from ?!cmng said:
So, to answer the question you're asking, you need to get the crank and rods measured first, so you can see how much they've worn and therefore decide, what 'grade' (size) bearings you need to fit for the rebuild !
Hope that's right ?!
The grading of the bearings is to exactly match the bearings to the crank/conrod when using new parts, the actually size difference between the 3 grades is less than 1 thou (0.001") iirc its more like 0.0005"youngsyp said:
On a engine with even a few miles on it, will probably have worn the crank enough that you will not be able to match any of the std size bearing grades to the crank, which means the next overside bearings up and a crank regrind.
If your going to the trouble of removing and stripping your engine down, then you will be best getting everything spot on.
Second what Youngsyp and Ginga say.
They don't cost anymore, you just have to specify the right size
They don't cost anymore, you just have to specify the right size
The easiest way to do it will be to measure the crank to determine the amount of wear and how far out of round it is, then decide which oversize bearings you require iirc the 1st oversize is only 0.008" ish bigger so depending on wear you may need to move straight to the second oversize.
One you've determined how far you need to regrind the crank, buy the bearings then supply them to the machiner with the conrods so they can machine the crank to the correct size for the bearings, that way if theres any mistakes it down to them.
One you've determined how far you need to regrind the crank, buy the bearings then supply them to the machiner with the conrods so they can machine the crank to the correct size for the bearings, that way if theres any mistakes it down to them.