Timing belt off by one tooth?

[Isotope9]

I've been chasing a lack of top end performance on my de-smogged '79 and it looks like the timing is off by a tooth.

Some background...my father restored the car and engine was rebuilt by a local Fiat "expert" with "big valve heads" from somewhere in California and possibly a different cam. I don't know any particulars or either the size of the valves or the cam (if it was indeed installed) as I can't find any receipts/records etc and my father passed a few years ago. The car starts, idles and runs fine, except at the top end of the rev range, 5K and up, where is seems to fall flat on it's face. Carb was new at time of engine rebuild.I pulled the carb jets and cleaned them, cleaned the carb and with no improvement, changed fuel filter etc.

In searching the forum, most threads referencing poor performance indicate to check the timing, so I did and it looks like the timing is off by a tooth. When the mark on the cam is aligned with the arrow, the flywheel mark is just entering the window, at the 10deg mark (pics 1 & 3).

Pic #2 is when I align the flywheel at 0deg. Also my dist. cap seems to be at an odd angle from other x1/9s I've seen. I'm guessing that the engine builder had to compensate for the timing being off? I have not checked the timing with a timing light.

What is the procedure to fix the timing? I'm hoping it's as simple as removing the timing belt and aligning the cam pulley correctly...but I know that it's never that simple!

Any help is appreciated.

Thanks in advance,
Rob.

 

[Isotope9]

I checked the workshop manual and followed the timing belt replacement instructions and when the cam sprocket is aligned with the mark, the crank pulley mark is not aligned with the indicator. It's off to the right, so it does indeed look like they didn't set the timing correctly when the engine was rebuilt.

That said, if I follow the timing belt replacement procedures, how do I ensure that the timing is set correctly? Set the crank pulley to the mark and rotate the cam back a tooth and bolt everything back up and then set the distributor?

Thanks in advance,
Rob

 

[Pete Whitstone]

That said, if I follow the timing belt replacement procedures, how do I ensure that the timing is set correctly? Set the crank pulley to the mark and rotate the cam back a tooth and bolt everything back up and then set the distributor?

That's pretty much it, yeah. It's not a difficult procedure. Some things to watch out for, however.

1. Replace the timing belt, don't reinstall the old belt.
2. Might as well replace the tensioner bearing while you're in there. Be careful here, one of the bolts goes through to the water jacket and if you don't use teflon sealant on it, it will weep and you will be doing all this again.
3. Be very careful about rotating either the cam or crank with the timing belt off. On a stock 1500 it's fine, but on a modified motor, it may now be an interference engine. So move them as little as possible, and certainly don't spin either thru a full revolution. Or if you find you have to, then set the crank to 90 degrees past TDC so all the pistons are halfway down the bore.
4. You will probably find that the aux shaft is going to spin around a little, since without the belt on, there's not much stopping it from turning. This will throw the ignition timing out. My advice on that would be to ignore that for now, since you said your dizzy sits at an odd angle. Get the belt squared away, then pull the dizzy up enough to clear the gear meshing, and rotate it to whatever position you want. Since the engine will be at TDC, stab the distributor back down wherever you want the rotor and cap to be facing when it's pointed at #4 (pretty sure the SOHC motor is timed from the #4 after a cam belt change, but keep me honest guys, it's been a while since I messed with a SOHC). Then bolt the dizzy back down loosely, it should be close enough to start the engine. Then you can time it with the gun.

Pete

 

[dllubin]

Assuming they put the flywheel on correctly, I would go with that mark. If it is about 180 degrees off from the crank pulley mark, they put it on wrong. However, if it is not too far off, the problem may be with the calibration of the crank pulley pointer. It is very adjustable. If you want to use the crank pulley to time the car, adjust the crank pulley pointer so it is consistent with the flywheel mark.

As far as the distributor cap goes, it can actually be positioned in any orientation as long as you can make it fit. The critical relationship is where the ignition fires relative to where the piston is. Since the auxiliary shaft position can be set independant of the crank and cam, and the distributor splined shaft can be inserted however you like, the axial orientation of the distributor body is arbitrary. I try to pick an orientation that makes the routing of the plug wires the easiest.

 

[Dr.Jeff]

Rob, I agree from the pictures it appears like it might be a tooth off. However on my '79 there isn't a perfect alignment of all markers/indicators no matter where things are set for the timing belt. It always appears to be half a tooth off (and I've verified everything is correct with the engine out of the car and partly disassembled to see first hand). There is no adjustment for the pointer at the timing belt pulley (top of engine), so it must be a manufacturing issue I guess. However that does not mean yours is like mine. I'd suggest you attempt to change the belt one tooth (in the manor you described, follow the guide in the Wiki) and see if it all aligns correctly.

As for the ignition timing, distributor position. That can vary significantly depending where the drive for the distributor is installed when the dizzy is put in place. So it does not matter how it looks on the outside, so long as the ignition timing checks out correctly (with a timing light).

EDIT: I just saw the posts from Pete and Don, all great advice to follow when changing the position of the timing belt and ignition timing.

 

[NEG]

Yup, but in this case it looks to be a tooth off. New belt and tensioner don’t skimp, get the rotor arm on the distributor pointing to cylinder #4.

 

[dllubin]

If the head or cam box was milled, it could have thrown a few things off but then I would expect the motor to have an adjustable cam pulley.

 

[kmead]

To be clear the engine timing mark on the flywheel should be at 0 and this allows you to verify the other end to ensure it is also pointing to 0.

As was pointed out, if the head was milled you may not be able to get the cam to properly align with the pointer for the camshaft wheel. You may need to degree in the cam with an adjustable wheel to get the mark to the correct place and have the cam properly timed.

In regards to the distributor, there is a screw for the vacuum advance which aligns with #4 cylinders post in the distributor cap. You can loosen the distributor, rotate it to where you want it to be and then when the belt is off, rotate the Aux pulley to get the rotor to point to the screw (and therefor #4).

 

[Dr.Jeff]

Not to get side tracked here, and hopefully not to confuse anything, but to be a bit more clear about what I noted earlier. On two of the four 1500 engines I have - all completely stock, heads not milled, cam boxes not milled, standard head gaskets, original factory cam pulleys, correct timing belts and tensioners, flywheels in correct orientation, crank pulleys properly installed, belt covers/timing indicators installed correctly and in good shape, no damage or alterations, everything verified with the cam covers/heads on and off, etc, etc... the timing belt pointer (at the top of the engine/head) does not line up exactly with the mark on the pulley - it is about 1/2 tooth off no matter how everything is adjusted. One of those two engines is still as it left the factory, in that it had never been opened or had major work done to it before me (aside from normal maintenance). And the fact that two engines are this way (plus I recall others have mentioned the same), I have to assume it is just manufacturing tolerances or some sort of inaccurate design/engineering. The only other possibility that I can think of is the timing belts are not the exact correct length, however the same results were found with different belts from different manufacturers. Otherwise I honestly cannot find any rational reason for this.

To be clear, I do not believe this is the case for "Isotope 9" (great name); as noted earlier it does look like his belt is a tooth off in the pictures. But I wanted to throw this out for discussion because it kind of triggers my OCD tendencies. Should I trust the timing marks and degree the cam with an adjustable pulley to match, or alter the timing marker location to match where things are, or just ignore it and have bad dreams that things aren't perfect?
Sorry if I've strayed off topic but I think it relates to some other comments above.

 

[carl]

I don't think you can adjust the timing pointer on the block without knowing true TDC so I wouldn't mess with it. Also, it's hard to get a true, proper angle vision of the mark on the pulley and the timing plate unless the motor is out of the car. Lots of spiders have the same issue, with the timing marks on the cams at a half tooth either way. Probably not a big deal for stock cams but a dyno day with readings of half tooth either way would be interesting. I agree that that motor in the original post is at least a tooth out.

 

[Dr.Jeff]

I agree Carl. In my case all of the engines are out of their cars and the heads were pulled to find true TDC. But I decided not to play with changing the pointer position and just ignore it. Setting the belt one tooth in either direction made the marks WAY off, so the "half tooth" position must be correct (at least on these two engines). I will be installing an adjustable cam pulley on one of them. And that one should end up on a dyno some day. But there will be many other vital things to get set before playing with little changes in other stuff (like cam degrees), so there likely won't be time (or money) to get that far.

 

[Isotope9]

Thank you everyone.

So if I understand everything above, it looks like I need to line the flywheel up with 0deg mark, replace the timing belt/tensioner ensuring I align the cam gear with the stamped steel pointer. And then set the ignition timing.

Seems simple enough. Time to order some parts.

Thanks again!

 

[Dr.Jeff]

You've got it as far as I can see. Be sure to look at the excellent guide to replacing the timing belt in the Wiki:
http://xwebforums.com/wiki/index.php?title=StaticTiming

By the way, I mentioned the "half-tooth" misalignment thing just to say don't get too nervous if yours ends up that way. You will know if it is a full tooth off (like it is now) vs a little bit off (like I described)...it's an obvious difference. Just be aware the timing pointer at the upper pulley might not be 100% perfectly accurate. However the one on the flywheel (for top dead center) should be (so long as it isn't 180 degrees out).

 

[Dan Sarandrea (Phila)]

Thank you everyone.

So if I understand everything above, it looks like I need to line the flywheel up with 0deg mark, replace the timing belt/tensioner ensuring I align the cam gear with the stamped steel pointer. And then set the ignition timing.

Seems simple enough. Time to order some parts.

Thanks again!

The "approved" (factory service manual) cam belt installation method has removal of the engine accessory drive pulley as one of the steps. Once that pulley is off, there is a cast-in downward pointing triangle on the seal cover that points to something in the vicinity of the nose of the crank. It might be a mark or dot or something on the crank or it might be the woodruff key slot, or maybe a dot on the crank's cam belt cog. Whatever it is, that was put there to help you get the crank in the right spot for doing the belt replacement.

The times I've done my cam belt I haven't removed the pulley, so I've only ever seen the triangle and dot in pix. Maybe someone will post a pic.