Trying to get the motor started... how low is low compression?

[matt]

I think my bottom end may be shot... 70ish in most cylinders. There's always the chance it may be washout. Oil helped, but still didn't get them all above 100.

So what's the lowest compression you've seen with a motor that still starts? Any tips for getting her running?

[Brew]

Timing off?

[matt]

Cam timing was fine.

[trent]

naw man...70 is low...

[matt]

Oh, the other thing is that there was a ton of smoke/vapor coming out of the crankcase vent. Pretty clear sign that the car needs rings.

[trent]

Oh, the other thing is that there was a ton of smoke/vapor coming out of the crankcase vent. Pretty clear sign that the car needs rings.

whats the leak numbers?

[matt]

Leakdown tester is on loan across town... I'm going to pick it up Wednesday after work and go back up to the shop give that a shot.

[matt]

Hmmm.... thinking about this now...

http://www.zionsvilleautosport.com/store/shop.mv?Screen=PROD&Store_Code=6134&Product_Code=3.03.2SK&Category_Code=CKE

[325Projectz]

Damn, yeah, dude... You're getting a 2.8 stoker kit.

For that cheap I'd def go that direction since you're pulling your bottom end apart anyway.

[FredK]

That sucks dude.

I saw an M42 (not mine) with 120, 70, 110, 70 start and run smoothly. Had over 200k on it. The M42's stock numbers are closer to 180. You sure you cracked the throttle body open when you did the test? Cold, the car is going to have lower comp numbers anyway; maybe not THAT low, but it should start. Are you using a fresh battery? Fresh gas? Fuel lines in correct supply/return arrangement?

You probably picked up the M50 pretty inexpensively. I'd just get a complete engine and just reuse the M50 wiring, accessories, and DME. A 2.8 stroker kit sounds like a great deal, but there are a lot of hidden costs that you will come to appreciate only after you attempt an engine build.

You need a lot of new parts to make it work:
Rod bolts $35
Crank cap bolts $10
Main bearings $70
Rod bearings $40
Rings $120
Bottom end gasket set $50
Machine shop: Hone cylinders $60
New piston circlips $5
Headgasket set $150
You can borrow all the tools from the dealer, fortunately.

That takes you up to $540 plus the cost of the stroker kit, which is around $500. So in the end, you'll have a fresh 2.8L bottom end with a most likely mile-y M50 top end.

You could just put that money towards a compression tested M52 that you can inspect under power. This costs around $900 - 1100.

After your leakdown test, you should know more. If the head has a few burnt valves or something like that, just dump it and pick up another M50 or M52, depending on your budget. If the bottom end is shot, consider picking up a known good bottom end.

[matt]

Actually the head was just rebuilt... 12 new exhaust valves, M3 cams, etc...

I could just get a whole 2.8 bottom end and swap it in.

[trent]

Actually the head was just rebuilt... 12 new exhaust valves, M3 cams, etc...

I could just get a whole 2.8 bottom end and swap it in.

This is what I did. the square 2.8 bottom ends are generally bullet proof. Just don't get one from a 528 that had 100K + of 15K oil changes. :)

[FredK]

Ah, ok. Yeah getting a whole bottom end makes a lot of sense, especially since you have a rebuilt head.

[matt]

This is what I did. the square 2.8 bottom ends are generally bullet proof. Just don't get one from a 528 that had 100K + of 15K oil changes. :)

Whole used one? No new rings or bearings or anything?

The head seems solid... the motor wants to fire but it seems like its blowing all its combustion out the crankcase breather through the rings.

[trent]

Whole used one? No new rings or bearings or anything?

naw..waste of time, these motors were generally very strong, which is why yours with no rings is interesting.