1982 380SL timing

[JustJim]

Bought a 1982 380SL with the fuel distributor missing. Was told it was removed for repair and the "mechanic" didn't return. Replaced the fuel distributor, then replaced all 8 injectors with new injectors. Still wouldn't run right. Checked fuel pressure at all injectors and is good. Checked the timing, was set at about 20 degrees after tdc. Tried to re-set it to 5 degrees before tdc, but had to stop at tdc because it wouldn't run at all if before. Shut it off and it wouldn't start again. Re-set it to 20 degrees and it starts, but still has the problem with not being able to develop any power. Removed the passenger side valve cover and has the double row timing chain already installed, but can't find the timing mark on the tower or the gear.
1) Where are the marks and what am I looking for (dot? arrow? line?)
2) Am I going in the correct direction with this, or should I be looking elsewhere for the problem?

[rowdie]

Left cam tower timing marks.

[JustJim]

Thanks for the help. I'll look again after work....

[Frank Reiner]

JJ:

While checking for the left side cam timing marks as indicated by rowdie, also check that the right side marks are aligned at the same time, and that #1 piston (right front) is at TDC.

If both cams are synchronized, but #1 piston is not at TDC, consider that the chain is off by one tooth at the crank sprocket (or two teeth at the cam sprockets). The pistons have valve reliefs that are deep enough to accommodate a 20 deg (one crank tooth) error without piston-to-valve interference. And 20 deg is what you are looking for.

[JustJim]

pulled the driver's side valve cover too. Both sides have the cam gears line up exactly with the mark on the tower, but the crank mark is about 12-13 degrees before tdc. does this mean my cam gears are each off a tooth?

[JustJim]

Just another quick note: I rotated the engine by hand 2 turns and stopped when the timing mark on the crank shaft hit tdc. Checked the marks on the cam towers and they were lined up. Turned the crank to 10 degrees after tdc, and the cam marks still line up with the towers. I haven't touched the chain tensioner, but the chains seem to have more slack than I'm used to in other vehicles....

[Frank Reiner]

JJ:

The 22-23 deg total variation (12-13 before to 10 after) that you have observed is quite unusual. Even if the chain and sprockets are very worn, and the tensioner is tight, the marks on the rim of the dampener will be consistent from rotation to rotation, albeit retarded. The engine has always been turned in the running direction (CW looking at the front of the engine), yes? Turning the engine "backwards" with a loose chain can lead to jumping over a tooth.

If you can, hold a small mirror behind the back of each camshaft and read the two-digit code # on each. The numbers will be in pairs, left/right, example: 62/63, 68/69, 70/71

[JustJim]

I'll try to see the numbers this afternoon when I get home from work. Do the different numbers make a difference for chain slop?

[JustJim]

The car wasn't running when I bought it. If it jumped a tooth on the crank gear and they rotated the engine in the reverse direction would that make the chain jump back one tooth on the cam gears?

[meltedpanda]

not a real good chance that it will "jump" a tooth without other consequences. I would think that if the slop was that bad that it could occur, other things would be very broken

[Frank Reiner]

JJ:

A tooth jump could occur any time the crank is rotated backwards when the tensioner is loose. Sometimes a jump may occur, other times not.

The question about the cam codes is to determine the intended valve timing.

[JustJim]

I'll try to get the cam codes when I get home from work.

[JustJim]

Driver side cam number at the back of the cam is 62, passenger side cam number is 63. I'm still concerned that the crank can move 20 degrees without the cams moving noticeably. I haven't loosened the chain tensioner. Does the chain stretch this much on these cars?

[Frank Reiner]

Originally Posted by JustJim

Driver side cam number at the back of the cam is 62, passenger side cam number is 63. I'm still concerned that the crank can move 20 degrees without the cams moving noticeably. I haven't loosened the chain tensioner. Does the chain stretch this much on these cars?

The cam codes are the ones most often seen (in US engines); they are very short duration, which is why there is no real chance of piston/valve interference.

Chain "stretch" is actually accumulated wear of the rollers, pins, bushings, and the teeth of the sprockets. The side plates of the chain do not become elongated.
The 20 deg. movement of the crank, as noted before, is unusual, and points to a lack of travel in the tensioning components. If you remove the tensioner from the RH cylinder head, the tensioning slide rail/shoe can be swung back so that the slide surface can be examined. It should show some grooving, but not more than 1/2 the thickness of the slide facing.
As you remove the tensioner from the head there should still be spring force against the rail.

[rowdie]

Are you only rotating the crank bold clockwise? If you are rotating back and forth it means nothing. As mentioned, I think, never rotate counterclockwise.