Self Grenading M42 Part 2 : The FIX....

[fiftytakedowns]

A continuation from:

http://www.r3vlimited.com/board/showthread.php?t=190274

So now I have a spare long block that needs a couple parts, but is in good shape, and some other parts that can help me do this, as well as a place to work. I decided to get it towed back to marin and get to work.

Well today I found some interesting if not good results from the teardown.

I pulled the Plugs today and cranked the engine over by hand as advised to by a family friend mechanic. and felt for any resistance or seizure. luckily, I found niether, and the engine turned over extremely smooth. this points me to think that there was no contact between the valves and the pistons.

Secondy, Looking at the plugs, there was no shrapnel damage, or any for that matter on the spark plugs. This also points me to believe that the pistons and valves never touched.

when taking a mini LED flashlight and poking around the combustion chamber through the spark plug areas I didnt see any damage on the pistons, jsut a we bit of carbon coating.

im about to start pulling off the timing cover gasket to see what rails are damaged ETc..... Anyone have anything else they think I should look out for?

[KenC]

What happened to the engine again?

I'm not sure that any of your tests can rule out a piston/valve collision. If you can't see the entire top of the piston, you can't tell if the valves hit. And unless a valve head snapped off, there usually isn't a whole lot to see anyway... just small impact marks (enough to cause hotspots though). Also, the valves are usually only going to hit once, and you won't feel that resistance.

Better tests:
1. With the plugs IN, crank it over by hand. Especially in an M42, the compression will make it difficult to turn all the way over without a long handled ratchet or breakerbar.
2. Get a heavy duty impact to turn the motor over and look for equal compression with a gauge.

[fiftytakedowns]

Im going to check to see if the Crank and the Cam sprockets Are at TDC maybe then I will actually see if it has skipped a tooth or not. Ill pick up a compression tester and see what the numbers are. and report back.

- Is there a problem with using the Starter?
- how can I find TDC on the Crank pulley, is it the same like the M10s with the timing cover?

[KenC]

If it's still in the car, just use the starter. A compression test will tell you if the valves or bent or not.

Just put a probe down cylinder one and rotate until you're at TDC.

[fiftytakedowns]

Just slapped in the probe, the Chain sprockets were consistent with the TDC of the piston. Doesnt look like the chain skipped....

[KenC]

Sounds like you just have to replace a chain guide or two.

[fiftytakedowns]

WOOOOOOO!!!!

BTW go oregon!

[harv]

Im going to check to see if the Crank and the Cam sprockets Are at TDC maybe then I will actually see if it has skipped a tooth or not.

Engines don't "jump time" or skip a tooth.

This is a myth created by fat stupid red necks while they were trying to figure out what spark plug wire goes where after putting on a new cap and rotor on a Saab.

Now something could have broken to the point of things hitting one another but I have never in my life seen a motor jump time. Even with a belt.

John

[Ryann]

This is a myth created by fat stupid red necks while they were trying to figure out what spark plug wire goes where after putting on a new cap and rotor on a Saab.

I've seen this happen once on a 300k mile 5.0L Ford F150, but it was so far off it wouldn't run. So yeah, it's kind of a fat redneck myth.

[fiftytakedowns]

I could see it happening in the m42 though. If the tensioner went out slightly, or pressure dropped per se... OR they have adjustable cam gears, so if it got loose, and spun +3 or-3º in one way or the other.

But anyway..

found the problem..

It was a timing chain guide rail that was KAPUT.

Wondering if I should replace the crank sprocket.... it's teeth are spikey...

[Ryann]

Wondering if I should replace the crank sprocket.... it's teeth are spikey...

The crank and idler gear teeth are normally "spikey-er" than the cam gears.

[fiftytakedowns]

the idle gear was in perfect shape, should I just pass on the crank gear then?

[fiftytakedowns]

Okay, So how far into the replacement parts should I go...

I already have 4 new camshaft sprockets, and hte idler gear and crank gear look to be in some good shape........

I mean I know I will be replacing the rail.
but is the chain and the tensioner/ tensionor guide necessary?

Thanks.

[Ryann]

Gear tooth wear and chain wear/stretch are married. If you replace one and not the other it will speed the wear of the newer component. Best thing to do IMO is to replace the guides and tensioner while leaving the rest alone, unless your cam gears are completely shot. In that case, it's best to replace everything.

[fiftytakedowns]

So today I nearly finsihed the entire timing chain rebuild.

all I have left to do is Torque the 22MM Crank pulley, and add the eight bolts on the pulley. I got rid of the front dampener for the power steering and AC cause I have niether. 3lb ROTational WEIGHT LOSS FTW.

How does one torque that 22mm bolt without a gun?



I did find a puncture; A tiny tiny leak in the radiator. I threw in a raw egg cause I was so fed up. anyone else know how to fix a little leak in the radiator?