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

[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.

[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

[fiftytakedowns]

WOOOOOOO!!!!

BTW go oregon!

[KenC]

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

[fiftytakedowns]

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

[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]

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]

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]

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?