Another M42 engine build

[mabeer]

Well I guess I might as well document this refresh or build or whatever it turns out to be.  Long before the young man in the picture was even a thought in our minds my wife and I bought this car for her birthday in the fall of 1990.  I remember test driving Jettas and Miatas but when we drove this that was it.    It's his car now and we're having a great time working on it.  Next step is to pull the head and take the head and block to the machine shop to get things checked out.  What direction we go, either simple refresh or bore and stroke will depend on what we find.  More to come.

[keflaman]

COOL! I was stationed overseas and missed out on that part of my son's lives. I look forward to reading your documentation of the journey.

[unevolved]

Awesome!  Bore/stroke while you've got it out, and boost later!

[mabeer]

Ugh, can't believe it's been over a month since we pulled that thing.  Well a week in awesome Colorado Springs where Bryce visited the Air Force Academy and a mad rush to finish clients taxes and now back to matters at hand.  One thing about the trip to Colorado, once Bryce is a junior he can take out his car.  This fits nicely with unevolved's suggestion to bore and stroke while it's out and boost later.  I think boost may be mandatory at 7,000 feet. 

Anyway on to the progress (or lack thereof):

I was expecting to see quite a bit of corrosion on the block because the profile gasket was pooched out and I had a slight coolant leak I could never track down, but I think it looks great



Some of the old but surprisingly good bits.



The crank seems in great shape.  All the mains measure 1.769 across both axis, the end play was somewhere between .005-.006 inch, let's call it .0055.  Here's a picture of journal 3 where the notorious 180 deg. thrust bearing resided.  I've never done this before but it looks pretty good for a 220k mile engine.  What do you experts think?



So that's it for now.  I'm going to run the block and head to the machine shop to double check my measurements.  They both appear flat using the straight edge feeler gauge technique but I want that verified of course.  Cylinder one seems a bit wonky, 2-4 seem cylindrical, but I was just using a telescoping gauge and a micrometer for the cylinder bore rough check sine I don't have a dial bore gauge.

The endless research continues and I am having trouble deciding what direction to take this thing.  Good problems to have in my opinion.

[keflaman]

That's the number 4 journal and it looks fabulous! Make sure you use the full thrust bearing upon assembly. I pulled my engine almost a year ago and you've already outpaced me. Nice work!

[mabeer]

Thanks keflamen, yep 4th journal.  I had to go out to the garage and figure out why I counted wrong.

[mabeer]

Definitely plan on 360 thrust bearing as well.

[wazzu70]

Crank looks great. The ones that have issues are obvious! The look all gouged up.

All new bearing kits for M42 come with a 360deg thrust bearing. Well thats what I have been told, but im sure someone somewhere will get a kit with a 180deg and prove me wrong

Consider getting the coated bearings. They arent much more and seem to really help if your engine loses oil pressure unexpectedly.

[mabeer]

Which way would you go?

1) given the crank looks good-simply go up one size on pistons, keep stock m42 crank and put money into head and cams? What cam specs don't know.

2) M47 crank, keep stock rods, custom JE pistons, re grind cams probably to Warsteiner's 250/250.  I think I'd sacrifice a bit of displacement and only go 85 and preserve some meat for a later day.

I'm leaning towards #2 for a couple of reasons.  Take care of the bottom end now while its out and apart, head can be reworked later if results aren't satisfactory.  It would be a reverse build from what i8ur911 is doing (I think he's doing more #1).

Am I being penny wise and pound foolish for keeping stock rods?

I look forward to your thoughts.

[wazzu70]

What is the intended use for the car? As a mixed street/track car, stroking makes a ton of sense if you can afford it. Most people bypass stroking due to increased cost.

For a strictly track car the shorter stroke/bigger bore can be desireable, especially if you are shooting for the higher revs.

For 93.42% percent of the people, a stroker crank makes the car much more enjoyable

[mabeer]

Ok, good to know.  It's a street car.  Just ordered M47 from dealer  .   Part's guy said sometimes the European only stuff gets bounced back sometimes the order goes through fine so we'll see.  Should have it in 7-10 days.

What about keeping stock rods and using JE pistons?  Any downside?

[wazzu70]

On a street motor you are probably fine with stock rods. On the other hand, the rods are a weak link if you want to really add some power (turbo 300+whp).

Rods really arent that expensive overall, so its nice insurance. If you wanted to keep factory rods, one smart option is to upgrade the rod bolts to ARP hardware.

Im sure you know, but the crank snout needs to be modified to work. The keyway for the woodruff key needs to be lengthened.

Check out the Metric Mechanic brochure for M42/M44 engines if you havent already as it has lots of great info.

[Warsteiner]

You also need a new crank bolt and custom spacer.

~R

[mabeer]

Thanks wazzu70 & Warsteiner.  I did know about turning the snout down and the required keyway, but not the bolt or spacer.  Do you have any specs?

[mabeer]

Crank order looks like it went through so I went ahead and got the pistons ordered.  I ordered pistons and rods from Steve at top end racing, nice guy .  Went with JE 85.0mm with 28.15 CH shooting for CR of 10.8/1.  I went 85mm bore to preserve future upgrade/maintenece options, I know the restraint was amazing .  I went ahead and ordered new rods too, wazzu70's words seemed wise so upgraded those to Pauter 140mm. 

The head pressure tested okay and was only out .0015 inches from flat.  I think I'm going to have the head freshened up at the local machine shop although Korman is working up a quote for me too.  Steve  at top end suggested running with stock cams and see how we like it.  I'm not opposed to dropping new cams or leaving the old.  I just don't want to lose the bottom end the M47 will theoretically give us.  The goal here is just a fun extremely streetable ride not maxing out the dyno or a screaming track rat, but at the same time I don't want to leave fun usable power on the table given everything else we're doing.  Does that make sense?  Anyway, I'm very intersested in your opinions on this.

Now while we're waiting for parts attention shifts to getting the rest of her tidied up.  Rear sub frame bushings, trailing arm bushings, sway bar bushings and end links.  We picked up some ST springs a while back for $70 so we'll get those on along with some new Bilstein sports.   I did the front bushings years ago and they may be do for some attention again.  New seals for tranny as well as all new shift linkages etc. 

Also planning on redoing power steering hoses cause they leak like crazy. 

Last summer I just replaced rear wheel bearings, some remanned?? (questionable) half-shafts, front hubs, drive shaft, center bearing and guibo and so basically she's going to be new from front to back till we are done.

Let tme know what you think about the head.