I have a BMW M20 that need the rod bearings replaced. I have ordered a Bently service manual so I wont be doing this blind. I don’t want to pay a shop to do it if its something that a competent person can do. I have a decent selection of your everyday tools but I’m not sure if this is out of my league. I would much rather do it myself and learn, then pay someone to do it for me. I know I would need to use plastigage to check for clearances and but is this something best left to a machine shop. Who here has done this themselves? Is it hard to change these?
could be a bitch if you scored your crank when you spun the rod bearings. putting fresh bearings on a scratched crank = no good.
everything should be able to be done from under the engine without pulling it… but fawk, seems like your taking a shortcut, if ur replacing rod bearings chances are the crank is shit
It’s an M20, who gives a fuck, slap new bearings in and go.
And if that doesn’t work, a whole new (used) bottom end is CHEAP. Probably as cheap as new bearings and gaskets…
This is the other option that Im looking at. Right now I have a M20b27 so finding the 2.7l shortblock is kinda hard. Ive been looking on ebay but havent found anything lately. Theres one about an hour away from my house but I think someone else already has dibs on it. Im waiting to hear back from the seller to see what the status is. If that does gall through tho, I need to have another option lined up.
sometimes you people worry too much. My SHO was knocking like a bitch from rod knock. Everyone on SHoforum said exactly what you just said, but guess what? I installed new beraings and here I am 32,000 miles later breaking 1/4 mile reccords.
:rx3:
ah ok.
i should apologize, because clearly a sample of one (your SINGLE experience with your car) is enough to extrapolate over the entire world of cars.
translation - if it worked ONCE for you, it should work EVERY time. :bloated:
the fact still remains. ask any reputable engine builder. if you replace rod bearings in a motor with a scored crank, it will not have the same longevity if you had the crank machined.
:crap:
TRUE
Sorry to say but if you have to ask if this job is out of your league it probably is. I would recommend reading, then watching someone experienced who knows what they are doing do this before attempting it
he didn’t say why he is replacing the bearings, if he is just replacing them for maint then it is no big deal. my engine was knocking really bad but the bearings did not spin and damage to the crank was minimal. Its not like
he is building a race car here and if it will get him another couple years out of it then just do it.
i understand that. if it is for pure maintenance, then go for it. but i still wouldnt recommend taking it on solo.
also, my sarcastic comments weren’t directed towards the author of the thread, they were towards the guy saying “hey, i didnt have my crank machined, so nobody needs to have their cranks machined”.
I actually located a stock M20b27 which is 1.5 hrs from my house. The whole motor in running condition for $250. Includes Motor, harness, ECU, and a chip that Ive been wanting. This should make it much easier. If anything, Ill take the old motor appart and try my hand and refreshing the bottom end. Worst case is I waste $100 on parts and fuck it up. Otherwise Id say that its a pretty cheap learning experience.
:word: good idea
Remember to number all the caps, they must go back on in the same place they came off, and remember to torque every bolt to the required torque, get a tube of assembly lube, and inspect the crank and the rod journals carefully, any scoring or uneven wear and your new bearings will not last long.