mbomberz1

I'm doing some maintenance on my 3vze, which includes a new timing belt since I will have it opened up that far. I am putting it all back together and when lining everything back up to get my cam marks lined up my crank was at about 5 degrees BTDC. If I put the crank at 0 degrees, my cams are off a little bit, maybe half a tooth or a little less.

My question is, is this within a reasonable margin for error? Do the marks have to be dead on? Not sure if I'm being too critical. Shifting the belt one tooth either direction would end up in things being much more out of alignment.

I did not pull the cam gears off, but wondering if it might just be some slop in the keyway on the cams and crank that allow for this little bit of variance in the marks.

Anyone have any advice? I saw some people with similar issues, but didn't see any resolution to those posts.

Thanks for taking a read!!

The images below are with the crank at 0 degrees.

AKHeathen

make sure that the belt is riding in the shiny area. i've had it be off because of buildup on the sprockets. make sure the tensioner is properly tight, and rotate the engine over twice and check again. it's possible the ballancer is off a few degrees. you would verify it with a micrometer guage measuring tdc on the piston. you could still set the distributor base timing to the marks and the computer will adjust it.

scope103

The cam sprockets don't have "keys" in the usual sense. Instead, they couple to the cams via a 5mm round pin called a "knock pin." http://personal.utulsa.edu/~nathan-b...67timingbe.pdf

The FSM method of removing the cam bolt is to hold the sprocket with an SST. The cam bolt goes on with 80 ft-lbs, but lots of folks find them REALLY stuck on. In that case, all of the undoing torque (I've heard of people using 5' long pipe!) is carried by that little knock pin. (You can imagine the load on the knock pin if someone uses a big-ass impact to put the bolt in or take it out.) When I first removed mine, I found a 2mm shear bend in the pin -- if you have that, it could account for a few degrees of cam timing error. That error (if you have it) would be constant; it's not "slop."

So I think you have reassembled it as best as can be done, and while your cam timing error might make a difference it won't be one you can detect. If you're interested in removing the cam sprockets to look, here's a much better (IMO) method for removing them: https://www.yotatech.com/forums/f116...l#post52283495

mbomberz1

Thanks a bunch for the responses. I think i am going to just see how this goes, as I am pretty confident at this point that this same problem was there before I tore it down and it was running great. Got 20.5 mpg on a trip up to Gold Lake and back a few weeks ago. Was pretty thrilled with that!

My last question is this, should I now account for this ~5 degrees of Timing error manually when adjusting my timing? If my cams are dead on when my balancer is showing around 5 btdc, does that mean I have actually been running more advanced than I had thought? So if i adjust stock to 10 btdc, that is closer to 15 in reality? Might explain why I had to retard my timing more than expected when getting it smogged last time

AKHeathen

well, you have to physically verify tdc to know exactly. it could be the woodruff key or keyway, too.

RJR

Assuming the mark on the crankshaft pulley is accurate, then no, you don't want to compensate for the shift with your ignition timing. The ignition needs to be timed to the piston position, which is set by the crankshaft. If your cam pulleys are indeed off, that will affect valve timing, but that's a different thing than ignition timing.

On the other hand, if it's the harmonic balancer on the crankshaft that has slipped, then yes, you should compensate the ignition timing to match. Better still, find out which one is correct by finding the real TDC.

scope103

No. This is getting pretty esoteric (cam timing v. ignition timing), but generally you set the timing to the position of the piston (10° BTDC). The distributor is driven by the cam, but you're COMPARING it to the position of the crank; your distributor will be twisted by a few degrees to get the timing mark in the right place, but it's still the same with respect to the piston.

The harmonic balancer (with the timing mark) is keyed to the crank with a woodruff key, and that you're NOT going to bend. BUT -- the harmonic balancer has an annular rubber piece which has been known to fail, so that the timing mark says "TDC" when it's really off by 30° or more! I doubt that's your case (if it's going to fail like that, it's going to move more than 5°), but it's easy to check. Drop a plastic straw down #1 plug port, and wiggle the crank until it's at the top. (Why not a screwdriver? If you get too energetic, you'll scar the heck out of the top of the piston. The straw will just bend.)

RJR

You know, I was going to suggest the same thing, finding TDC with a straw or a wooden dowel. Then I went through the math, and realized doing it accurately is actually pretty tough. The stroke on a 3vze is about 3.5 inches, as I recall. Even at the 90deg point, when the piston is halfway up or down, it only moves about .03" per degree, which is pretty hard to see on a plastic straw or even a wooden dowel. At TDC, the sensitivity will be even less, by quite a lot. My guess is you'd need a dial indicator with an extension, or a similar precision instrument, to find TDC within a degree.

I expect that's why AKHeathen mentioned using a micrometer.

scope103

Damn! I knew I'd get called out by an engineer!

I'm pretty sure if the annular ring failed, it wouldn't slip by just 5-10°. Unlike RJR, I didn't do the math, but I still think the straw/chop stick method will detect an actual problem with the harmonic balancer.

Or maybe I'm just thinking of how hard it would be to get a good set-up with a dial indicator ....

AKHeathen

yes dial indicator. got woken up by bull moose tearing up the trampoline, grill, and power ped, etc in the yard early this morn, so my brain has been drawing blanks today, lol...... but you could get it close by making sure the ballanceer doesn't have slop on the crank and placing a clamp in a way that it gives you a solid point for the dowel to move against. make a mark when you think it's at tdc by feel, than a mark 1mm down. rotate clockwise till it hits that 1mm mark and scribe a fine line where the 0 points. then go ccw and do the same thing. the factory notch should be right in the center of these 2 marks. it might be off like 1 degree, but close enough to give an idea..... i have seen the woodruff keys worn down, and it may be possible someone in the past glued the pulley back on. i know i seriously considered it.

mbomberz1

Just wanted to post the results:

Ended up finishing all of the repairs, with the timing belt like in the pictures. Runs just as good as before. After a lot of thinking about that timing belt, the only thing that makes sense to me is the missing material from when the heads were shaved, bringing the cam gears lower, reducing the distance slightly could cause the slight variance like mentioned before.

If any of you guys are good at wiring, I just posted a question about that

https://www.yotatech.com/forums/f115...ng-job-291370/

I know.. wrong forum.. Hoping someone moves it for me

Marsheen

you know, I just had the same problem, I couldn't line up one of the cams with the mark on the cover. I spent a good 2 hours trying and adjusting, but no matter what one of the cams would skip a tooth. Got tired and put it back the way it was. cranked it up and seemed to run fine. Making some noise at first but I had the car apart for 6 months.

Marsheen

ohh and your closer then me on your markings