Engine rebuild decisions-another advice requested...

[Dave M]

I've posted a couple of times recently, trying to decide how to best go about rejuvenating my 500,000km M50 bottom end. Winfred may recall.

I've all but decided on a 180,000km (110,00mile) block for $500 Canadian (@$350 U.S.) located in Toronto. Without being there, I run the risk of shipping a piece of crap 1000 miles north. Unless I pay the seller extra to disassemble the thing to measure the bore etc. I have no assurance that the block is within reasonable spec. (he's already pulling the head). Understanding my predicament, the seller offered to source the rings and bearings and quoted me an additional $500 Can. to replace the rings and bearings (Labour inc.). I checked BMA and rings and main/rod bearings would cost me @$350-400 Can depending on shipping ($120 U.S. for rings, $120 U.S. bearings) .

So, to me, its seems like a deal. For $1000 Can. ($700 U.S.) I’ll have a ‘good to go’ refreshed bottom end, mated to my recently rebuilt head @25,000 miles ago (various gaskets and a clutch kit in addition, of course). I called Bavarian and the ‘gentleman’ on the phone quoted me $500 U.S., IF he could find a decent one (can’t imagine what shipping to Canada would be). Other available complete engines in Canada are $1200 to 1500 Can. and the risk is greater.

I planned on doing the bottom end work myself (just buying the short block), but it just doesn’t seem as economical, and the risk of receiving a piece of $hit is eliminated (Mark D’Sylva has stated that they do good work).

Am I missing something large? Is there anything else I should have them do? Winfred mentioned tips on refreshing the bottom end, so if you’re reading, please advise. I’d like to make a decision next week so my big german paperweight can get strapped to a pallet and sit around here for 9 months pissing off my wife :)

Thanks for reading,

Dave M

Going for the million km mark (I wonder what the odometer does?),

[Kalevera]

Sounds like a plan, man. $700 seems like a good consumer price for a rebuilt bottom end, given the other options.

You could just find a junked M50 to mess around with if you're still jonesin' for the "learning experience" of rebuilding one per the last thread.

Best, whit

[winfred]

the bores will not be worn unless this thing was turboed or supercharged and raced, it WILL still have hone marks on the walls from when it was built, i did a m20 that had 311k miles on it and i couldn't find a ridge with a knife and it had hone marks. the only way id screw with the bimmer short block would be if it got dammaged by rust with the head being gone and walls being exposed to moisture without being oiled, or it was overheated and the pistons started to melt and or seize (nasty up/down scoring/blue marking and aluiminum deposited on the cylinder walls) a couple of the builds i've done (last one was a m52 in a 97 528) were due to a blown headgasket allowing water into the cylinder and it sitting too long and lightly pitting the walls

[winfred]

you can get crappy rebuild components and they screw up a otherwise good build, deves rings SUCK!!!!!!! besides being a pain in the dick to assemble the 4 piece oil ring they suck in terms of performance and every wrench i know agrees

[Derek A.]

Have you checked with BMW NA ? The price on a rebuilt short block might surprise you. There are so many of those motors floating around that you might find a deal on something new.

[Dave M]

Hmmm, good points. I must re-iterate, a large reason I'm entertaining rings and bearings is so I receive a solid bottom end. I have only the sellers word to go on here (and Mark D'Sylvas word that they are reputable). I haven't asked what brand of rings will be installed, and may look into BMW NA (although if it is coming from the U.S., shipping, duties etc. would be a major deterrent).

Winfred, if you are confident that the short block (assuming no supercharging/turbo) will be OK to install, I would be much more willing to forego the rebuild and install the block as is. What else might I need to do? Thanks again for your wisdom,

Flip-flopping,

Dave M

[winfred]

as long as the oil's been changed a few times (more then a couple) and the motor didn't die from overheating it's good to go, unless i had some other high performance type purpose i wouldn't think twice about dropping a 100k bimmer short block into my own car virtually untouched, id do gaskets and seals including the gasket on the oil pump pick up tube and the seal on the oil filter housing. if it had 200k miles on a dohc motor id freshen it up for my own car but wouldn't have a problem on a customers car. all of that said it is a mechanical device and failure is possible, but if as advertised a good 100k or so motor that got it's head sold i doubt seriously it'll be a problem

[George M]

Winfred is exactly right of course. A 100k Bimmer bottom end that had decent treatment has 200K miles left on it without touching any of the components. An example is I refreshed the cylinder head on my 148K M-30 that also had all the cylinder cross hatching and the new owner drove the car 1700 miles and it didn't use any measurable oil which I believe is astounding because many new cars would consume oil over that distance. If you have the short block handy, carefully inspect the cylinder bores. If they are pristine, you are good to go. If you drop it in, personally, I would pull the pan and change the oil pump...not necessary, but what I would do and regasket the whole motor which is what you will be doing anyway as most of the gaskets are up top...but put an oil pan gasket in it at least.
HTH,
George

[Dave M]

George, I do not have access to the engine, which is the root of my concern and the reason I considered having the rings and bearings done. Of course Winfred is right, thats why I spend so much time here.

I shall gather as much information as possible pertaining to its history and make a judgment as to whether it may be dropped in ‘as is’ (the cheaper and preferred option). However, I will have to take the word of the seller on the mileage and condition of the cylinder bores. Any tips, questions I should ask? Maybe pictures?

Having both yourself and Winfred’s opinions has made me think more than twice about the straight swap (avec gaskets/seals). Your input is much appreciated. I shall keep the board informed of any news or purchases and will document the swap and associated work along the way.

Aside: Although you’ve said goodbye, I see you’re still coming in handy around here. Hope its warmer than it is here so you can pack the miles in on your road bike. You’ll be racing the masters nationals before you know it (no presumption of age made here).

Thanks again guys,

Dave M

[Bellicose Right Winger]

I'm not sure if they're pulling the head because you're only buying block, or because you asked for an inspection. If head is included in price, I'd leave it alone and ask them to do a compression check instead. Provided the starter hasn't been sold, they should be able to hook up a battery and do this. Maybe you can get a photo of the head with valve cover removed to get an idea of oil change frequency.

Paul Shovestul



George, I do not have access to the engine, which is the root of my concern and the reason I considered having the rings and bearings done. Of course Winfred is right, thats why I spend so much time here.

I shall gather as much information as possible pertaining to its history and make a judgment as to whether it may be dropped in ‘as is’ (the cheaper and preferred option). However, I will have to take the word of the seller on the mileage and condition of the cylinder bores. Any tips, questions I should ask? Maybe pictures?

Having both yourself and Winfred’s opinions has made me think more than twice about the straight swap (avec gaskets/seals). Your input is much appreciated. I shall keep the board informed of any news or purchases and will document the swap and associated work along the way.

Aside: Although you’ve said goodbye, I see you’re still coming in handy around here. Hope its warmer than it is here so you can pack the miles in on your road bike. You’ll be racing the masters nationals before you know it (no presumption of age made here).

Thanks again guys,

Dave M

[winfred]

compression tests on motors that have sat for long periods of time usually look bad, and leak down tests look worse, adding oil makes nearly useless results, you can pump enough oil in there to make it say whatever you want

[Bellicose Right Winger]

Interesting. Even recognizing the risk, I think I'd still want to know. Certainly don't want to add oil. How long does engine have to sit for this to happen?

Paul Shovestul


compression tests on motors that have sat for long periods of time usually look bad, and leak down tests look worse, adding oil makes nearly useless results, you can pump enough oil in there to make it say whatever you want

[winfred]

it's best to do ether test warm, it depends on the motor on how long it takes to loose compression some take to sitting better then others, for example the 78k mile m30 i installed in my 535 had been on the shelf for almost 3 years and it was a bitch to turn over due to compression when i was regasketing and setting the valves before instalation, a m50 that sits for a few months usually turns over quickly on the starter, a year or more and it can take a while to get it started and will smoke on start up and usually suck a little oil for a couple hunderd miles till it cleans out and reseats the rings


Interesting. Even recognizing the risk, I think I'd still want to know. Certainly don't want to add oil. How long does engine have to sit for this to happen?

Paul Shovestul