What Is A Reasonable Approx. Cost For An M20 Rebuild?

[Low Level E30]

Hey guys,

Just like the title says --- if I drop my stock M20B25 off at a shop and have a basic refresher rebuild done, what should I expect to spend, reasonably?

I know prices can vary - I'm just looking for ballpark figures.

Thanks,

[PeaveyBassist]

Couple grand probably.

Will

[Low Level E30]

Couple grand probably.

Will

Really?

I know shops that will rebuild American pushrod V8s for a couple hundred bucks --- now I realize BMW motor tolerances are much tighter, and so on --- but surely it shouldn't cost a couple grand to rebuild a bottom end....????!!!

[Super Eurobeat]

Hot tanking or jet blasting, boring out the cylinders, align honing and boring, resurfacing, balancing everything, making sure all parts are the exact same weight, disassembling and reassembly, plastiguaging to see if everything is the same, shot peening etc...and the list goes on
A average motor rebuild for us it at least 3000. We make sure everrything is blueprinted cause you get an extra 7-8 horsepower from that.
But we do most of the work seeing as how we have a couple of machine shops at our disposal. I do all the head work myself and pay my buddy to do the bottom end.
All piston, connecting rods, pins, valves, springs, etc... are all the same weight going into the motor, none of that tolerance between grams.
That way there is less vibration in the engine and it lasts generally 20 percent longer, bearing wear is damn near perfect wear evenly, and the engine produces less heat.
I wouldnt bother rebuilding if its not gonna be blueprinted.

[PiercedE30]

+1 definitely doing this when building my other motor

[StereoInstaller1]

Really?

I know shops that will rebuild American pushrod V8s for a couple hundred bucks --- now I realize BMW motor tolerances are much tighter, and so on --- but surely it shouldn't cost a couple grand to rebuild a bottom end....????!!!

I personally have been involved in more than 30 V8 350 Chevy builds. Ranging from bone stock to mildly modded new engines to 11.5 to 1 big-cammed aluminum headed 450HP beasts.

Never have I seen the machine work only cost "a couple hundred", not at a reputable shop anyway.

Parts can be as cheap as a few hundred (like PAW kits, all Chinese, but OK)

Machine work is typically more like $600 on the cheap end, just for the bottom. That is why I recommend a crate motor for most installs.


As far as your M20 goes, why not just buy a decent used motor? These things are so tough even when brutally abused, I just can't see doing anything else.

You should hear the racket coming from my top end. The PO NEVER did a valve adjstment in more than 60,000 miles. The car still sees redline (or near it) several times a day, runs fine (kind of a rough idle) and I have put over 20,000 miles on the poor old fucker making racket like that the whole time!

(I am still debating the M30/M50 or stay M20 issue myself, so I have done my valve adjusts and keep on flogging her.)

Anyway, good luck on the whole debate.

Luke

[nando]

the machine work on my engine was only $250, but all they had to do was bore/hone, clean stuff up and I put it together myself. still, a couple grand sounds about right when you add in all the little things that you should replace while you're in there. my stroker was about $3500 inlcuding the $1200 pistons/rings.

[Mossman]

M20 in this 88 325 I picked up had compression under 70 on 5/6 cylinders, one was barely at 100...so I went ahead and tore it apart.

To be honest the head gasket had no visible problems, i inspected with the naked eye as best I could. Cylinder walls weren't scored. Rings looked okay. WTF I said....oh well, I honed the cylinders with a hand drill,did rings and rod bearings, left the mains alone. W/P seemed tight, did the timing belt and tensioner obviously while the head was off.

Took a straight edge to the head and it was perfectly flat. Now I wish i stilll sent it to the machine shop but to be honest it was pretty clean and it wasn't warped at all so I saved a couple hundred there.

Slapped it all together with a new headgasket and stock bolts, spent $500 on the car and like $350 on parts + my own labor in my spare time at work, and she runs like a champ. Gonna do my 1st oil change later on this week and check compression, but what I'm getting at is you could probably pay a shade tree mechanic to do it for you for probably a grand out the door, but yeah if you insist on having the bottom end apart and everything rebuilt from the ground up then yeah, 3k isn't too bad even.

[rs4pro3]

A.J. Talk to Kevinn C. He has a shop there in atlanta that can do a full rebuild for a very reasonable price.