M42 Timing Help

[MrSalumi]

OK guys.. About to finish up the top end rebuild and need some help getting the timing right.

1) First I have the number one (furthest forward to front of car) piston at tdc (determined by having a steel rod through the sparkplug hole touching the cylinder and it being past the upstroke and before the downstroke)

2) Both my cams have been off and are not marked well. I have read that I need both most forward lobes pointing directly at each other inwardly. Is that right?

3) I need the cam tower torque specs. Those nuts holding on the top half of the cam clamps. I know there is a special sequence as well so as to not snap the hollow cam.

4) anything else i need to know? Apart from manually taking it through a whole revolution to make sure nothing is binding or bending..

THANKS GUYS!!!! I cant wait to get her all back together and snap some photos!

[FredK]

1) There should be a TDC mark on the crank, right where the front timing wheel has a gap in all the teeth. In that gap, there is a line. The line should line up with a marking on the front timing cover. This is more precise than determining TDC with a rod.

2) Yes, the cam lobes should be pointing towards each other on the front most cylinder (number one). The cams have flats on the opposite end at the back of the cylinder head. These should be completely in the same plane as each other. You can use a steel rule to determine this, or use cam blocks if you want to set it and forget it.

3) not sure

4) Get a helper when you're setting timing to avoid having the cams shift while you're torquing down the cam gears etc. You might want to turn the bottom end 45 degrees past TDC, then installing the cams. That way if something rotates, you don't smash the valves into the pistons. After installation and getting the cams to point at each other, you can turn it counter clockwise 45 degrees back to TDC, and set timing.

This is a delicate procedure. If something doesn't feel right, STOP.

[MrSalumi]

FredK

Thanks so much for the info. Tomorrow is the big day that I am putting all this stuff back together. I'm just going to take it as slow as I can and triple check everything.

thanks
Sal

[MrSalumi]

OK, got the cams all aligned and tightened up. BTW the Master Tech at the dealer confirmed that the torque specs on the cam towers are 14 nm or 10.38 ft lbs. Everything came together well, nothing felt forced. So for future reference both cams have drilled holes on the rearmost square lobes. Those should be facing in parallel plane with the top of the piston surface, at TDC. Also the lockout on the bell housing is far easier to use to put the car at TDC than the rod method, since all my pully's are off and both timing covers, lower and upper are off as well. No reference points.

However I did end up breaking off a bolt in the block. A stupid waterpump bolt head came right off with the stud sticking out a quarter inch. I tried vise grips but seem to be doing more damage to the bolt than anything else. Going to try to hacksaw into the head and use a flat head screwdriver tomorrow. I hope hope hope that I don't have to tap that damn thing out.

-S

[FredK]

Great. It sounds like you have this job well under control. Using a pin is definitely the easiest way to lock the bottom end, especially since the timing covers are off!

Good luck with the rest of the job. I hope you don't have to tap that bolt out. Ugh.

[jeff_b]

I'm facing that very problem, but I have two bolts snapped. This is step one of my fix; blow a wicked small hole into those pricks. Then, I'll just drill and retap 6mm, praying the pilot holes are close enough through the bolt center so the new bolts run straight. I'll be doing that this weekend, will post pics if you're interested.