Timing / balance belt change - setting TDC

[Wicke944]

So I decided to change out the belts and rollers, seeings as it’s been probably 40K since I was “told” it was last done.

I pulled everything off to get at the belts and tried to find TDC… I set the cam pulley at the mark, could not see the scribe or “OT” through the top inspection hole, spun it a second time and no scribe, I even checked the bottom inspection tab by the starter starter. Could my flywheel not have the scribes?

So I made sure the cam pulley was set at the notch, the lower balance shaft pulley scribe and upper balance shaft scribe and all set at their respective notches and pulled the belts off and changed out the worn out idlers and rollers. Seems my water pump is ‘good for now’… knock on wood :bang:

My question is should or can I keep spinning my crank to find tdc!? Will I damage anything without the belts on?
I want to pull my spark plug and check there for tdc… do the other pulleys ie cam/balance have to rotate in unison?
I also don’t have a tensioning tool, was going to just do the twist method. My old belts seemed very loose, I could almost take the balance belt off with loosening the tensioner roller.
Thanks in advance!

[Tom]

So I decided to change out the belts and rollers, seeings as it’s been probably 40K since I was “told” it was last done.

I pulled everything off to get at the belts and tried to find TDC… I set the cam pulley at the mark, could not see the scribe or “OT” through the top inspection hole, spun it a second time and no scribe, I even checked the bottom inspection tab by the starter starter. Could my flywheel not have the scribes?

So I made sure the cam pulley was set at the notch, the lower balance shaft pulley scribe and upper balance shaft scribe and all set at their respective notches and pulled the belts off and changed out the worn out idlers and rollers. Seems my water pump is ‘good for now’… knock on wood :bang:

My question is should or can I keep spinning my crank to find tdc!? Will I damage anything without the belts on?
I want to pull my spark plug and check there for tdc… do the other pulleys ie cam/balance have to rotate in unison?
I also don’t have a tensioning tool, was going to just do the twist method. My old belts seemed very loose, I could almost take the balance belt off with loosening the tensioner roller.
Thanks in advance!

Good call changing them....

Assuming your car has a factory flywheel, it will have the OT line. It's not easy to see in the little rectangular window in the bell housing. Sure you are looking in the right window? I usually stand on a stool or something so I can get my head right over the back of the motor and look down -- even then there is usually stuff that needs to be pushed aside to see the TDC mark. A flashlight helps a lot too. Keep looking, it's there. Maybe have someone else rotate the motor as you watch for it? Make sure you can see the flywheel moving past the window to know you are looking in the right place.

You cannot spin the motor with the belt off, when the camshaft is still on the motor. I'd have to think about whether there is a cam location that keeps all valves out of harms way from the pistons, but if you just start cranking the motor, chances are good you'll make piston-valve contact at some point.

Have you moved the crank since taking the belt off? If not, you could put the belt on to keep the motor in time (at least as close as it was before anyway) an then turn the crank. I'd be super careful the first few times around, however, and stop at any sign of mechanical contact since you don't really know if the motor is in time. If you have moved the crank and don't know where TDC is, the safest approach would be to remove the cam tower so you can turn the motor, find TDC, and then assemble everything back in time. Alternatively, you might be able to pull the #1 spark plug and use a long wooden dowel to see if the #1 piston is close to the top and, if so, whether to can high-center it without moving the crank much -- doing that would be close enough to get the belt on so you can then turn the motor safely and find the TDC mark.

Did you see the 3D-printed tension tool here on Carpokes? It won't necessarily have the accuracy of the factory tool, but it will definitely get you closer than trying to go by feel on your maiden voyage!

[Wicke944]

Yes I was looking from the top in the inspection hole by the speed/reference sensors. (Photo atta he’s, but not in focus enough to see the small line)

And ya too late I had already turned the crank without the belts on. I did not feel any heavy resistance.

I checked again with the help of my 9 year old, and from the passenger side looking into the TDC hole I saw the finest scribe, which mates with my mark I had on the crank and confirmed with the #1 cylinder at TDC.

So with what I believe to be TDC I installed both belts and tensioned, turned over by hand twice and appears all good…

But has this been all for nothing? Did I screw something up by spinning the crank around without the belt on? Even though the cam was set at the top notch?

I confident I’m there, and just assume I have an aftermarket flywheel that doesn’t have OT or the secondary tell from the underside. I did however notice another scribe on the flywheel only visible from under which lined up with a line on the pan. To the left of the clutch inspection hole, I painted it white. See photo.

I’m frightened to turn it over now and to pull off the cam / valve cover will I see the damage?
Seems like a lot of work to just confirm TDC.

[Tom]

My strong suspicion is that you have a factory flywheel and that the surface rust on the outer edge is making the OT and line difficult to see. There is a rumor that they made the marks deeper on the later flywheels for that reason, though I can't confirm that. I can't really tell from those pictures if you are aligned, and that bottom line does not seem to look like the notch people generally use - see Clark's below.

http://www.clarks-garage.com/

Did you spin the motor a full 360 degrees with the belt off? Seems hard to imagine you'd bend a steel valve without knowing it.... the valves for cylinder #1 and #4 are closed with the cam at the tdc mark so they should be fine; but #2 and #3 each have one valve partially open. My guess is that they just are not open far enough at that point to make piston contact. I really think you would have felt it unless you are Superman and bend steel without noticing....

[Race5103]

I agree with everything Tom is telling you. With ANY engine that is interference you may never spin the crank without the timing chain or timing belt installed and with the timing correct. I would say it is unlikely you haven't already bent a valve but it is possible.

I just finished this job on my car last week. The questions you are asking indicate a lack of experience with this type of work and this is not an easy car. Go slow. Question everything and don't do anything until you ask all the necessary questions and make certain you understand the concepts.

I had all the same difficulties finding TDC on the flywheel that you did. But the mark on the distributor is easy to see and just following the rotor will at least let you know when 1 is at TDC and not 4. By spinning the crank with the belts off you have moved cam timing and crank timing out of phase and that must be corrected.

I agree with Tom it should be impossible to bend valves and not know you have done it, so maybe you are good. Get under the car and look at Clark's garage and use the flywheel mark that will be visible almost straight down, It will be visible even with a rusty flywheel and it is accurate. Do you have any idea what the alignment of the crank and the cam was when you took everything apart? Email me [email protected] if you like. Tom also seems familiar. There are good vids on youtube that will be very helpful.

[Race5103]

I read your post more fully and it seems you found TDC and just didn't have the flywheel marks to confirm. But it sounds as if you may have it correct. Since you think valves and pistons have not hit already I would rotate the crank back to TDC using something inserted through #1 spark plug hole. I would put a dial indicator on it so you can be very accurate. After that find the marks on the flywheel and make the marks bolder. I had all the same problems and once I was under the car with the flywheel cover off I could see everything easily. Use some paint and make them bolder so this won't happen again. IF you get the crank back to TDC without bending anything you should be good to go. I assume you won't bend anything based on your remarks that you didn't feel any resistance when you rotated the crank previously. Rotating now won't do any more damage that what has already been done and if no damage has been done you'll be good. Good luck.

Lou

[Race5103]

Regarding Tom's statement all 1 and 4 valves are closed when 1 is at TDC I don't think that is correct but I don't have a way to check now. PIstons are both at TDC but cam timing is 180 degrees out. I think both valves are open but I'm not pulling my valve cover to check. Perhaps you'll pull yours and let us know. You may find it helpful to pull so you can see the timing there anyway.

[Race5103]

If valves are bent you won't see bent valves by pulling the valve cover but you may see valves that don't fully close when they are no longer on the cam. But personally if the are bent the damage is already done. I would probably try to get timing right, pull all the plugs and run a compression check. If compression is good you are fine to start. If not, I'm sorry you have a longer and more expensive road ahead.

Pulling the valve cover is not at all difficult, especially compared to everything you have undertaken so far and you probably will find it educational.

Lou

[Tom]

Regarding Tom's statement all 1 and 4 valves are closed when 1 is at TDC I don't think that is correct but I don't have a way to check now. PIstons are both at TDC but cam timing is 180 degrees out. I think both valves are open but I'm not pulling my valve cover to check. Perhaps you'll pull yours and let us know. You may find it helpful to pull so you can see the timing there anyway.

Hi Lou and welcome to Carpokes! Give that a little more thought and I think you'll agree with me. We are agreed that both pistons 1 and 4 are at the top of their stroke at the same time, so whenever #1 is at TDC, so is #4. See video below of a motor I built 15 years ago that confirms that. With the cam installed and timed, when #1 is at TDC on the compression stroke, #4 will be at the top of the exhaust stroke, but nevertheless both #1 and #4 will be at at TDC. It goes without saying that the cam is designed to keep the valves from being open (more than a crack anyway) whenever a piston is at the top of its stroke, otherwise the piston would hit a valve.

If you take the cam tower plugs out of the top of the cam tower you can actually peek in there and see the lifters all the way up on the #1 and #4 cylinders. Not sure what part you mean when you say to pull the valve cover to check if the valves are open/closed. There's no valve cover, per se, and if you removed the cam tower the valve springs would close all 8 valves.... I suppose you could flip the tower over and look at the lobes to confirm that none of them would be be holding a valve open in #1 or #4 when those pistons are at TDC....

[Race5103]

I agree with you pistons 1 and 4 have identical timing but it doesn't mean the valves do and open a bit or a crack is still open and absolutely makes a huge difference. So valves aren't closed if they are open a crack. They are on the cam. I don't know and don't have the time to be honest to find the exact cam timing specs but I'd be interested in seeing them.
Either way I think it is really academic and doesn't apply in this case.

Neither of us seems to know the specs that will tell us how far the valves need to be open before they will contact a piston and just knowing an engine is an interference engine doesn't tell us that. So I am guessing but I think that with the cams set at the no. 1 TDC position some valve, won't know which one is open far enough to contact a piston when the engine is rotated through a full rotation. Whether anyone felt it or not.

I'm certainly not going to run the experiment on my engine so we'll just have to wait for a report. My bet is one of the cylinders at least will have zero compression. But it will be interesting to find out.

what you and I are disagreeing about is pure academics and really won't affect the outcome here.

Nothing will change the rules. With a interference engine I would never spin the crank without also spinning the cam or cams with the cam timing correct.