M42 maintenance list

[5ickride]

Thanks, and I agree with searching, just get lazy sometimes...

Back to topic. I priced out most, if not all, of the parts I listed and it came out to almost $1k in parts. Sooooo, needless to say, I'm going to have to scale this back a bit. Being that the engine is relatively young (miles not years) i'll stick with the most common issues and do a tune up for now. My guess is the Timing Chain Tensioners should be close to the top of the list? I'm also experiencing some idle bouncing so hoses will also get replaced.

[Ryann]

There’s just one head gasket – can you clarify “full set”? (I can appreciate ‘full’ set meaning gasket + head bolts) (head bolts being a one-time use deal)

A head gasket set= everything you need to refurb and reinstall the head. It's got some other gaskets you'll need such as the intake and exhaust manifold gaskets, valve cover gaskets, upper timing cover gaskets, profile gasket, throttle body gasket, etc. etc.

Victor Reinz set pictured below.

[Simon S]

Ah - gotcha. Quite right.

And yeah - all the parts add up - and it sucks.
At least you're more-informed now - and can maybe plan/save for more action down the road.

Your guess is right - tensioner and hoses. Good.

[Simon S]

In an effort to make this a balls-out, informative m42 thread on preventative maintenance – it seemed prudent to share a summary by peerless. I would really like to keep this thread free from any forum politics – and just appreciate/share his input for what it is. Take it or leave it.

Here is my experience with rebuilding 2 M42's. One took 3 engines to make one good one.

We will start with the factory flaws and how they should be corrected.

1) Stamped steel chain guide. These fracture and break apart. Replace with upgraded dealer part, its a all nylon/plastic construction. You will need one new 45mm long bolt in conjunction with the new guide.

2) Steel oil pressure relief valve, aluminum front cover. The steel valve can seize causing a immediate loss of all oil pressure - good bye engine. Replace with updated dealer part, made of nylon/plastic. Make sure you get the spring and spacer as well. The spring is slightly longer so it all a matched assembly. You will most likely want to replace the oil pump rotors, front pump cover and bolts. All of this is about $45.

3) Front chain cover. These are known for leaking profile gaskets. The rail that holds this gasket gets corroded and leaks. Every one notices when it leaks outside the block, but no one notices when it seeps behind the block. This creates a rust cavity potentially damaging the front face of the block. Expect to at a minimum to replace the front cover. If the block is damaged, you can surface the front face to clean up any rust damage. .015" MAX.

4) Main thrust bearing. The factory in all their wisdom decided to only use half a thrust bearing shell. This is not capable of handling the high rpm loads created by the M42. You will find the bearing to be rounded and burnt black. The crankshaft thrust surface must be inspected carefully. On the 2 engines I built one crank was scrap and the other barely within spec. To correct this problem you will want to replace with a full 360* thrust bearing. I do not know if the standard replacement bearings come with 2 halves. I use the early eta M20 main bearing set and have the lower main caps custom machined so they fit. This not only gives me a full 360* thrust surface, it also gives me a full 360* oil groove for improved oiling to the rod bearings. As a note, I pulled the oil pan on a M42 with 80K miles, it already had thrust bearing material in the pan, along with 4 oil pan bolts.

5) Crank pulley. While the stock crank chain gear does not wear very much a new upgraded part is available from the dealer. It has 2 rubber rings molded into it. This helps keep harmonic vibrations in check. This may help prevent the oil pan bolts from backing out

6) Rod bearings, I use custom Clevite 77 NASCAR performance bearings. This is a upgrade, the stock pieces should work just fine as well.

7) lock-tite all your upper oil pan bolts to prevent them from backing out. This is a big problem on the front 6 bolts that surround the gasket for the oil pump pick area of the pan gasket. When these back out and fall into the pan the gasket can push out and you lose oil pressure. See number 5.

Regarding valve guides, they should be fine as they have very little side loading due to the valve train arrangement. I did not need a cam removal tool either. When loosening and tightening the cam tower bolts, take your time, do it slow and evenly. Remember the camshafts are hollow and can break easily.

If anyone tells you the stock M42 is a great engine, they are pulling your leg or don't know the M42 very well. The stock M42 is very self destructive.

I have pictures to back up every flaw I just described above. Everything I said above comes from direct experience with the M42 engine.

Expect to pay about $2,500+ in parts and machine work to properly rebuild the M42. If you need help/advice along the way just give me shout.

Again – I know the dude was banned. It’s the information and feedback of a guy who spent time working with these engines – and then took the time to share what he learned. That’s all. It's the value of the information - that inclines me to share it as well.

[ayemattyyy]

Amen Simon. Who cares what happened with the guy, but that is damn good information.
Matt

[5ickride]

That's great info there!

[Ryann]

I read about using a 360 deg. thrust bearing on Metric Mechanic's site.

[xwill112x]

i wouldnt call the m42 self destructive, ive beat on mine now for over 100k miles and it still wont die. Chain has had the 3k rpm death rattle for around 15k or so now, and at well over 200k on stock everything internal, it runs damn good. Maybe a few flawed designes, but definitly not self destructive. Bullet proof imo.

[trackjunkie21]

i wouldnt call the m42 self destructive, ive beat on mine now for over 100k miles and it still wont die. Chain has had the 3k rpm death rattle for around 15k or so now, and at well over 200k on stock everything internal, it runs damn good. Maybe a few flawed designes, but definitly not self destructive. Bullet proof imo.

Just because yours hasn't, doesn't mean you can generalize and say it's a very reliable engine. that's like defending the old Chevy 350 diesel motor, or the vega motor.

[Ryann]

that's like defending the old Chevy 350 diesel motor

No offense man. But it's NOTHING like defending the good-for-50k 350 diesel.

I have to admit that as much as I like it, it really does have more semi-serious flaws than it should.

[aworthybrother]

Rob, or anybody - would you know which specific mustang injectors is required for m42? or do you know a place or link and part numbers to place an order? I want to replace mine with mustang injectors but doing a search is confusing me.

[Simon S]

Dude - read post #22 of this very thread.

[aworthybrother]

Dude - read post #22 of this very thread.

Yeah, found it. It was a very informative post. Thanks.

Bosch MPI injectors 0280150556. How long have you been using these injectors? Any gains (idle, mileage or performance wise)? Thanks.

[Simon S]

To be honest - I haven't installed them yet.

In theory - any gains will be negligible/marginal. Most guys putting them in are usually doing other mods or maintenance of some sort at the same time. If you’re looking for specific documented differences resulting from swapping in just these injectors – I doubt you will find it. If you were to find it – it would most likely be on m42club – which is a place you should check out anyway. (m42club is where I found that pn – and learned about Motor Man)

If I were to guess – they’d be worth like +1/4 hp and maybe + 1-2 mpg. Again, pretty marginal. Think of it this way – they are the exact same injector – with a slightly more-optimal design. If your current injectors were partially clogged or unbalanced…

I am an optimization freak. I’m completely fine with negligible/marginal gains. I partially justify swapping these in under a ‘preventative maintenance’ category.

Anyone telling you you’re gonna get 5+ hp and 6 more mpg by swapping in ANY injectors on a stock-spec engine is bull shitting you.

[Dj Buttchug]

basically if you wanna rock m42 just know that you gotta put some time and effort into it to make them right. Just like any other production engine, the m42 has flaws. Consider the fact that most the engines had by us are well over 150k miles. With that kinda of mileage expect leaks/ worn timing components.