Peter Zimmermann

...oh, boy...this is going to be fun...

dsmith

relax, i have the proper holder for mine...

what is this? every time i think i'm ready, you through in some didbit like this. is this to keep carbon chunks from falling down?

theiceman

oh oh I know this one ... ( my best Horshack impresion )

yes , it is to stop tiny chunks from falling down and lodging in the valves and giving a false reading during measurement ... see Pete I do pay attention .... sometimes ..

Peter Zimmermann

David: Yes, indeed! ice remembered and you are exactly right. When you remove the spark plugs little bits of crud can break off and fall down. In a combustion chamber where the exhaust valve is open that crud can get in the opening, stick to the valve seat and hold the valve in a false open when you turn the engine to that cylinder. This is why, when you do a leak down test, for absolute accuracy always turn the engine to the cylinder you're going to test before you remove the plug.

dsmith

Well, I decided to do the deed today and replace the cam plate seals/gaskets. I used Wayne's rebuild book and the Bentley manual without a problem. The only thing I noticed was that the left side aluminum cover that the o-ring slides over and the 3 bolts go in had some scratches on it. Sorry, Pete, I chickened out and put some Curil-T on the o-rings. I also applied loctite 574 to the paper gaskets, including the chain cover gaskets. I adjusted the valves again, using the tool and checking with the go/no-go method.

On timing the motor, I marked the sprockets to chainlinks and the dowel pin. On reassembly, the left side looked exactly like it did to start, which kind of made me wonder, but I guess it's entirely possible, I guess. The right side needed a small adjustment after reassembly. I checked both sides several times before and after.

Pete: Question for sanity on 83sc 930/10. I set #1 to TDC, turned cranked about 360 deg, then moved crank to Z1 (about 1 deg). Then when I rotate 720 deg, should the gauge read 1mm when returned to Z1? it does, over and over. Same with the right side. both cams are pointed the same direction. No resistance was ever felt. If the timing was off so that engine damage would occur when started, would there be valve/piston resistance when turning by hand?

The best part was the Stomski Racing mechanical tensioners. I used them to hold tension while timing. They are anodized blue and look great. I SO wanted to leave them in...

I'll probably wait until Saturday to put the motor back in. 1 week 'til the next race. Hope this stops the leaks until rebuild time...
David

Peter Zimmermann

720 degrees crank rotation is one engine revolution, so the dial indicator should alway return to the same reading. Cam timing is done at Z1, after 360 degrees crank rotation. Put the engine on Z1 for cyl #1, adjust cyl #1 to .004" (0.1mm) rocker clearance, attach and adjust your dial indicator to "0". Turn the engine clockwise just short of 360 degrees, then sneak up on Z1 so you don't go past the mark. Stop when at the mark. Read the dial indicator. The number (between .9 and 1.1) is your cam timing. Turn the engine (360 degrees) back to where you started before you loosen the cam to make a change. The left and right cams should be as close to the same as you can get them, I write down the number for the first cam, then match it with adjustments as necessary when I do the opposite side. I've had to loosen, move a tiny amount, and retorque that second cam as many as five times on some engines that didn't want to co-operate! A little Curil T is OK on the o-rings, especially if the plate is a little scratched. For gaskets with a somewhat shiny, pebbled side, using sealer is not recommended! If you have done something wrong with your basic cam installation you will know immediately because you will get piston/valve contact. Hope it comes out OK!

dsmith

I believe I got this part fine. Stay with me now and I'll explain exactly what I did. I'm looking for a comfort level that valves/pistons won't collide on start up! This is definitely a procedure where seeing it done once would answer most questions.

The book says to turn until the overlap reading on the gauge (.9-1.1), so I was using 1mm. When I did this for the left side, 360 deg was exactly 1mm, starting with cam pointing up (930 dot) and crank at Z1 and dizzy rotor pointed at the line. So no adjustment, correct? After 2 more rotations Z1 was still at 1mm. So all good on the left, correct?

After the 720 rotation on the left, the right cam was pointing down, like the left, and I repeated the same process. This time, the gauge (mounted on the right) read 1mm about 3-5 deg before Z1 lined up. So, based on the manual instructions, I removed the cam bolt and dowel pin at this point, rotated the crank to Z1 then replaced the dowel and bolt, then turned 720 deg and the gauge showed 1mm. Was this correct? This did take a couple tries.

So, I check both sides a couple times. I rotate the left 360 deg and it shows 1mm, I rotate the right 360 deg it shows 1mm. Does this sound correct?

Huge thanks,
David

Peter Zimmermann

David: Yes, it sounds correct - as long as you deal in 360 degree increments, to achieve overlap of the cam that you're checking, you should be OK. The left side is definitely good, just make sure that you double check your setting after torquing the cam bolt. The right side will also be good, as long as you started with the crank on Z1 #4, adjusted the #4 intake rocker to 0.1mm, then set your dial indicator to "0". I would say that, if you've torqued both cam bolts, you're ready to button it up!

dsmith

Thanks, Pete. That's reassuring, though I know you can't be positive of what I did. I double checked each side 3 times after final torque. Well, I'll put it back in tomorrow morning and let you know if it explodes!
David

dsmith

so, in conclusion, i put the motor back in yesterday, then decided to also replace the oil return tube orings. after an hour of messing with the first one, i only ended up doing the right side. that was one of the hardest jobs i've done! push, pull, pry, grunt...

anyway, i started it up last night and nothing broke! i drove it today and no leaks, except a drip from the return tube orings at the case . i told my wife i would only be happier when she pops out a healthy baby in October! thanks for the info, Pete. i will be doing a two race weekend 5/26-27 and put it to the real test.
ice, your turn now.

theiceman

So you took the whole engine out David just for those leaks at the cam ? if you did I have no excuse..

dsmith

yep. i think people are nuts for working on these motors in the car. it takes me about 3 hrs to r/r the drivetrain at leisure. i've tried adjusting valves and removing rocker shafts in the car. i spent way more time trying to work around stuff than it takes to drop the motor. it's not just the time, i found my repairs were much more accurate, especially cleaning gasket surfaces with the motor out.

granted, i bought a scissor lift and atv jack. remember, i r/r'd it 3 times last june. it's only 4 bolts...

Amber Gramps

OK, so I am all warm and fuzzy over CV boots over on the novice posts and you guys over here in expert are talking about 720 degrees like its no big thing. some of us explode when we see intake valve durations that exceed 360 degrees. in high school I remember a duration of 420, but I think we were smokin' something.

dsmith

douglas, i used to live around Upper Arlington. i went to Ohio State. that's right, i'm a poison nut (buckeye). i don't know anything about timing motors, so don't call me an expert. i just followed directions. might as well be 900 degrees, wouldn't mean anything to me. i only owned my repair shop. i wasn't a mechanic, but i learned tons. with 500 cars per month, it's hard not to.
david

theiceman

David , did you lift your motor onto an engine stand ? how were you able to work on it after dropping it ?