Engine Failure Diagnosis (pictures)

[peerless]

The discoloration on the chamfer of the crank journal is from the flash. The original machine shop chamfered the holes and the second machine shop rechamfered them to clean them up.

I also seen all the scratches on the bearings. That block was fully hand washed when I got it back from the machine shop. The hone seemed pretty heavy/rough so I think the grit may have been from the rings wiping cylinder walls during break in as they are smooth now.

Also regarding the pistons again, I put 20 miles on this engine and the pistons never quieted down. They ratted loudly no matter the engine temperature. And when I would get on it, it would smoke pure blue out the tail pipe. The head was gone though with new valve guides and seals.

I want to be able to reuse this block for another engine I am building. Its going out to 86mm (.080") Someone had commented that it appeared the line hone was off by looking at the bearings. I think its from having a tight main set-up.

Can anyone comment on the wear patterns of the main bearings?

[tommurphy73]

Did you measure the ring end gap at different points in the bore. This may explain the scuffing on the rings. What did the top of the pistons and spark plugs look like after the drive. If it was detonation it might be possible to see something there.

[Tuner]

Can anyone comment on the wear patterns of the main bearings?

The crank wasn't polished well enough and the whole thing wasn't clean enough when it was assembled.

[redvictor]

I also seen all the scratches on the bearings. That block was fully hand washed when I got it back from the machine shop. The hone seemed pretty heavy/rough so I think the grit may have been from the rings wiping cylinder walls during break in as they are smooth now.

Looks to me like the engine was full of grit.Bearings and rings are scratched to bits.You say you hand washed the engine.Hand washing will never bring the grit out of the cylinder walls.Did you wipe the cylinders with trans fluid until the paper was spotless?
Did you also brush the oil galleries in the block and crank out?
To me also scotchbriting the bearings for clearance is not the way to build engines....

[xenginebuilder]

I recently suffered a engine failure of a new engine. The machining was done by a few different shops and it turned into a disaster. I was hoping to be able to openly discuss the subject without being ridiculed for a meat ball rebuild. To be honest I invested alot of money into the short block and to have it fail really hurts the pocket book and a little pride off the top.

Unfortunately, the painful lessons are the ones we remember the best.

I offer in no particular order some observations and opinions regarding your problems and pictures-

Heavy visible crosshatch is stock rebuilder technology for cast rings in non-round bores. If you plan to rebuild similar engines for performance use, buy a BMW torque plate and find someone who can hone the block properly with more than one stone grit.

As PFC1 noted, the rings look wrong. I know you said they are different widths so they only go in the grooves a certain way, but it looks like a taper face top ring with a barrel face 2nd, usually the barrel is the top ring, at least in the engines I used to build. You might want to research your ring package a little further to see if the right rings were specified and that the piston manufacturer put them in the right order.

Venolia is a good old piston manufacturer, but just looking at that skirt design is straight out of the 60's, probably round and straight. Modern pistons have tapered and barrel shaped skirts so you can run high strength forgings and still have reasonable cold clearances. Quite frankly a straight wall piston with that kind of clearance will never quiet down until you really get your foot on the gas. If you set it up at .003" or so like modern pistons, it would turn black and seize the first time you got it hot.

The rods have unusual wear because the caps are not indexed to the rod properly. The big ends need to be resized and honed together to fix that. All of your wear is next to the parting line, and diagonally across in the rod end, wear if any should be oriented more towards the 12 and 6 o'clock positions.

A lot of those scratches look like coating deterioration, the coating is balling up and leaving a track as it is flushed out.

I sent the bearings to HPC coatings and had the rod and main bearings coated. This was another $125. They where all black and bitchen looking when I got them back. But on closer examination the coating appeared to be awfully thick and appeared uneven in a few spots.

I've never had HPC do coated bearings, so I can't comment too critically, but backyard coatings are like having your car painted in someones back yard, most coating problems are related to poor prep and application rather than the coating itself. I would ditch the coated mains and just use the plain bearings since it is on the tight side anyhow.

Now mind you I am a home builder so my ability to properly check the machine work is limited. So I am at the mercy of the machinist and have to trust the work is done correctly.

Buy the 2 or 3 10ths reading micrometers for the different sizes you need, a dial bore gage, and a cheap 12" digital caliper. For less than $500. you can check someone else's work before you screw it together and have a problem.

I am hoping to be able to reuse the bearings and possibly the rings. If I had the money I wouldn't hesitate to replace it all. But....

I'm sorry, but both should be in the trash can. If you look at the top ring taper, it is already worn flat on either side of the gap due to the coarse hone, you will likely not have success with those rings sealing in another block, according to you they were not sealed in the present block. As far as the bearings go, there have been positive posts here about Swain and others, I personally only used coatings applied by H.M.Elliot http://www.hmelliott.com/. I would talk to some of the coating guys first about your coating failures.

[robert1]

I'll add one thing to what Xbuilder said. Those Deves rings are just cast rings IMO you need to get a quality moly ring set from Sealed Power.

[David Redszus]

During the last 30 years of building high performance BMW engines, I have never found any aftermarket component to match the quality of the stock BMW parts. The same goes for all dimensions and tolerances.

For a street machine, get a factory shop manual and build the engine exactly to the factory numbers. You won't do any better. It may cost more the first time. But you won't have a second and third time to pay for.

[peerless]

Thanks guys for all the responses.

Some interesting things I have heard so far is that the main bearings show that it needs a line hone, yet I had it line bored and honed. xenginebuilder noted that my rod bearings where worn because of the caps not being indexed yet those rods where rebushed and resized? The entire rotating assembly down to the clutch cover was even balanced.

The pistons do have a slight taper to them. They are 3.342 at the skirt and 3.341 even with the pin. I didn't measure under the rings or the crown. Can do that tomorrow.

I also don't think I will be doing anymore coating unless they are applied by the bearing manufacture such as the Clevite 77 Tri-Armour series.

I have already decided to get new rings and bearings. I really like the design of the deves rings. The second ring has a expander, so its a 2 piece second ring. They also have a 4pc oil control ring set up. The 2 pc second ring is another reason why you can't get the rings mixed up.

I don't like the factory style oil control ring as its a cast 1pc design and every single M20 engine I have pulled apart they are all 90-100% plugged and also stuck into the ring lands.

Thanks so much for the comments. It helps get me back in the right direction.

[williamsmotowerx]

.001" of taper is nothing. they're not tapered pistons.

is there a piston direction for these? offset pins?

[bobqzzi]

Your best bet is to either find a stock BMW /Mahle piston that fits, or call somplace that makes a decent piston like Wiseco, JE, or CP. No need to do anything special with the rings- whatever one of those manufacaturers offer will be fine. There is nothing superior or special about Deves rings that will make them last longer or work better. Your current pistons are scary and a huge step down in quality from the stock ones.

The factory oil ring is an extrememly effective design.

I can't help but agree with David R- put it together like the factory did and you'll get 200K of excellent service

[peerless]

.001" of taper is nothing. they're not tapered pistons.

is there a piston direction for these? offset pins?

As I mentioned I didn't get a chance to measure the pistons completely.

The crown of the pistons is 3.305. Just under the ring pack, 3.336, even with the wrist pin, 3.341, at the skit 3.342.
So maybe I am mistaken, but I would call that a tapered piston.

bobqzzi,

Your best bet is to either find a stock BMW /Mahle piston that fits, or call somplace that makes a decent piston like Wiseco, JE, or CP. ........... Your current pistons are scary and a huge step down in quality from the stock ones.

So I am expected to throw out a set of forged pistons that cost me $700 of hard earned cash after only 20 miles of use. All of this because a machinist made a error in cylinder bore size.

I think now I have heard enough comments. The reason this engine failed was the bore was over machined and the pistons rattled and whether it was superior factory pistons or cheap quality Venolia pistons the result would have been the same.

I myself made the mistake of not properly checking the machine work and deserved the failure I got handed. It has been an expensive lesson learned. I am purchasing a full set of micrometers and a inside bore gauge to make sure my future engines dont' take a shit on my.

Also so you guys might understand, this engine was not my first engine ever assembled, but it was my first engine to fail due to poor machine work.

Here is another engine I am currently building for a customer. M20 engine, S50 rods, Wiseco pistons ($1,200). I promise you I will be checking every clearance and making sure things are a cleaner during assembly.

[redvictor]

.001" of taper is nothing. they're not tapered pistons.

is there a piston direction for these? offset pins?

As I mentioned I didn't get a chance to measure the pistons completely.

The crown of the pistons is 3.305. Just under the ring pack, 3.336, even with the wrist pin, 3.341, at the skit 3.342.
So maybe I am mistaken, but I would call that a tapered piston.

bobqzzi,

Your best bet is to either find a stock BMW /Mahle piston that fits, or call somplace that makes a decent piston like Wiseco, JE, or CP. ........... Your current pistons are scary and a huge step down in quality from the stock ones.

So I am expected to throw out a set of forged pistons that cost me $700 of hard earned cash after only 20 miles of use. All of this because a machinist made a error in cylinder bore size.

I think now I have heard enough comments. The reason this engine failed was the bore was over machined and the pistons rattled and whether it was superior factory pistons or cheap quality Venolia pistons the result would have been the same.

I myself made the mistake of not properly checking the machine work and deserved the failure I got handed. It has been an expensive lesson learned. I am purchasing a full set of micrometers and a inside bore gauge to make sure my future engines dont' take a shit on my.

Also so you guys might understand, this engine was not my first engine ever assembled, but it was my first engine to fail due to poor machine work.

Here is another engine I am currently building for a customer. M20 engine, S50 rods, Wiseco pistons ($1,200). I promise you I will be checking every clearance and making sure things are a cleaner during assembly.

you've been very lucky then.Building engines is all about checking clearances,not leaving measuring for others to do for you.That's a recipe for disaster as you've realised...
When you get the tools and use them you'll realise that good machinists are hard to come by....

[garart]

Your new pistons is 86mm (original is 84mm) . What head gasket you use? Original head gasket bore is 85 mm. Look how much pistons edge is higher than block. It can touch gasket and emit sounds. Those engines assamble very good- i made them more than 10 years and have no problems.

[robert1]

Your new pistons is 86mm (original is 84mm) . What head gasket you use? Original head gasket bore is 85 mm. Look how much pistons edge is higher than block. It can touch gasket and emit sounds. Those engines assamble very good- i made them more than 10 years and have no problems.

You may have assembled good engines for 10 years, but their transmissions are JUUUUUUUUUNNNNNNK!!!! Google BMW transmission problem. And yes I've already replaced the one in my wifes car.

[af2]

You are saying the Getarag trans sucks? You are correct!