engine and drivetrain Engine Builders With Knowledge: Crankshaft End Play

[TobyB]

You're having fun!

 

One of the things I've absorbed about knurling is that it retains oil well, and thus provides more

of a flotation bearing for the piston on 3 of the 4 strokes.

 

.011 isn't a lot of end play...

 

hmmm....

 

t

[PatAllen]

i went over and over and over in my head, i quadripple measurend the crank shaft bearings to make sure it wasnt one con rod making this noise. impossible. above 1000rpm cant be heard at all.

 

axial play...11-12 thou....well beyond the prescribed 6 thou, but certainly not the source of such loud knock...modified the bearing to have like 2 thou...will see

 

oil pump chain...certainly a bit slack, on new sprokets, new pump and new chain, previously adjusted relatively tight, once seated went ±1/4 side to side...not that bad altough i will shim it a bit ...will see

 

next the con ronds small end bush...there is a noticeable play, but ive never seen any failed and all the 02 motors i took apart felt the same...snug tight, maybe 1-3 thou of axial movement when forced by hand....

 

next the pistons skirts...they feel on the loose side. they are new mahle NOS 8:1. no scuff at all on the skirts but as i said they feel loose, maybe 4-6 thou. ive seen worse in my life like double of that and the motor was running fine. could it be the source of the knock ?? that the most close guess i am making.

I decided to ditch the almost new 8:1 and use one set of used u.s Tii pistons i was keeping for another build, but with a light knurl. This will wake-up the Automatic a bit

They fits just snug tight on the knurl edges, the knurl will wear and loosen after few miles (from my understanding of the concept and all the pages i read about the subject).

 

this will make a nice and purposefull test  motor....to be continued...

[gracer]

I use a stethoscope to locate engine noise source.  Yours sounds like chain slap to me.  G

[kbmb02]

next the pistons skirts...they feel on the loose side. they are new mahle NOS 8:1. no scuff at all on the skirts but as i said they feel loose, maybe 4-6 thou. ive seen worse in my life like double of that and the motor was running fine. could it be the source of the knock ?? that the most close guess i am making.

 

You seem to be enjoying this; I like your sense of adventure. Stating what you already know, 4-6 thousandths of piston-to-wall clearance is a lot for OE cast pistons. I believe spec is 0.0018", at 0.0035" and beyond it's common (but not always) to hear 'em rocking and knocking. Have you checked the taper of the cylinders? -KB

[PatAllen]

what bugs me is that this block was mint, 1.8 late e21....i compared the bores with another very stout 2.0....the 1.8 idefenitively loose, could it be that the 1.8 where loose on the tolerances ??

all the 320i (1.8 e21) i heard in my life had all kind of weird engine rattles....might not just be a coincidence....from my collection of block and pictures in the faq, the 1.8 block are lighter and has less webbing....humm....

[PatAllen]

just finished with my debatable idea of knurling the pistons...of course they where too wide "as is", once filed down and sanded a bit, and by using the bore itself as a file to smooth them down, i get near zero friction and no play so they must be like 0.5-1thou of gap...lol...it doesnt take much of honing to break them loose....5 seconds of honing and its too late already. Lesson learned about honing too much...

gona be tight in there...

[PatAllen]

today i finished to reassemble this mess. at 3pm it was idling in my garage. the noise is gone...but assurely i changed too much parameters to pinpoint the source.

-new timing chain

-shimed oil pump (on new chain and sporkets 2 years ago)

-Tii pistons with knurl to get them very tight in the block

-balanced set of rods with matched pin

-welded thrust bearing to get near 2 thou of axial play on the crank

 

There is still a slight groan that i associate with the 1.8 block. i remember so well my (2) 320 and my 318....

 

Thoses Tii pistons got balanced to infinite stupideness 2 or 3 years ago during the winter, along with the rods. this realy makes a very smooth motor at 4krpm, much more than the previous set of NOS mahle with "as is" rods from another motor.

 

The Tii pistons brought their sets of problems, they dont very like the "automatic" distributor with a vacuum retard and too much advance curve...so i had to toss it in the neighbour pool and slap in a Tii distributor. Pinging gone.

 

There is a noticeable amount of new "hump" in that motor, going from 8:1 to 9-9.3:1 realy makes a difference, when considering everything elses remained exaclty the same (same carb, same exhaust, same intake, same head).

 

So for now, it runs, and very well....time will tell how stupid it was to knurl pistons myself !!

Edited August 10, 2014 by PatAllen

[PatAllen]

its been a while since i did that, this engine realy runs great. totaly worth it to knurl pistons. i have done some mileage with that motor, it pulls very strong and is STILL very quiet.

 

hth

[BeMyWay]

Thanks for the follow up on this build.  

[oh2fly]

The engine clearances are just about identical between all m10 engines. e21s don't make any more noise than a 2002.

[PatAllen]

The engine clearances are just about identical between all m10 engines. e21s don't make any more noise than a 2002.

this is truly debatable.

how many 02 and e21 did you onwed and heard over the past 20 years ?

 

all E21 1.8 i heard in my life make more noise, different block casting, different crankshaft. i mean ALL of them. i have 5 1.8 block in my home basement and maybe 15-20 2.0 block. all 1.8 i have are loose on the bore clearances. all of them.

[Hans]

Wasn't there an issue with E21 motors in the day - poor quality control or some such thing?

[TobyB]

...now I wanna go knurl some pistons...

 

The 1.8i piston is pretty odd- the pin is so low in the pot.  It goes against all the modern (like, from 1960 onward) 'high performance'

thinking of shorter, lighter, get the pin as high as you can to reduce side loading pistons.  Why BMW didn't at least

lengthen the rod is quite strange...  as if it's almost a conscious non- performance 'downgrade' And if I was building some

sort of odd 1.8 performance motor, the first thing to do would be to raise the pin that way...

 

Plus there's that semi- counterbalanced crank...

 

So if there was an M10 that was going to behave differently, I could sure see it being the 1.8i version.

And yes, that block is a lot lighter than an early 2002 block.

 

What I've observed,  I haven't measured the stock blocks' bores carefully, because, well, we bore 'em to .040 as a matter of course.

 

t

[Preyupy]

The noise from the 1.8L engine is normal.  It is 6.5lbs lighter than the early M10 blocks.  They changed the casting molds and some of the non structural parts of the block are quite a bit thinner. 

[PatAllen]

never said it wasnt normal, i said they where making more noise than 2.0L. on paper the tolerances seems identical but once aged i am sure they get more piston slap due to the lower pin position. i have two 1.8L who spun a bearing, and one who lost a valve head into the combustion chamber.

 

i never got th idea too of the pin height. Even ford with their escort simply made the deck height different when they went from 1.6L to 1.9L...hence all the errors made by unaware backyard mechanics who didnt noticed the indexing of the cam sproket that was different...

hey did you knew i had a US Escort GT Turbo "sve", was 1.6L turbo with a IHI. never ever saw another. what a crap car it was lol...