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Question Problems tensioning the timing belt

Into the final stages of replacing a blown headgasket on my 86' 951. I'm following the procedure as outlined on Clark's Garage and the factory manual, but using the Krikit tool instead.

After I get 4-5 readings of ~37-38 lbs and I turn the cam sprocket back to TDC (from the 10 degree or 1-1/2 tooth counterclockwise position) I loose the tension on the belt. If I continue to rotate the sprocket 360 degrees clockwise back to TDC there are times when I recheck tension and it will be OK again, but it will also fluctuate from a low of ~20 lbs to 60-70 lbs.

My balance shaft belt is tensioned properly and does not fluctuate in tension like the cam belt as I rotate the cam 360 degrees.

any idea what I'm doing wrong?
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Last edited by murn; 07-03-2005 at 05:05 PM..
Old 07-03-2005, 01:32 PM
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Do a search in the 924/944/968 technical forum, user's name: Taz's Master, and key word: timing belt. I asked the same question (because I was in the same situation), and the Belts Again thread contains an answer that allowed me to properly tension my timing belt. (I think it was to do 2 complete revolutions, back up 1.5 teeth from TDC and tension the belt, but check the response).

You are using/reading the tool properly, but your procedure is wrong.
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Old 07-03-2005, 06:00 PM
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Yikes......... yup
Taz is correct.

2 revolutions and back 1.5 teeth.

Then you tension the belts......

Turn it a couple of more turns.......... and back 1.5

Check tension.

Do this as many times as you need to get comfortable with the readings you are getting....
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Old 07-03-2005, 07:18 PM
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yeah I was doing the correct procedure all evening. Just got your posts, and the tension held this time. Thanks.

I'm not out of the woods yet. The car cranked over and sounded like it always did (before the headgasket failure) but then died after running at about 1000 rpm for about 5-10 sec. I tried it another few times and it would crank and abrupetly stop without starting.


Any ideas?
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Old 07-03-2005, 08:02 PM
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You never rotated the cam without it connected to the timing belt right?
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Old 07-03-2005, 08:17 PM
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No the cam was never rotated while on the head. I had the cam seals replaced when I had the head serviced, so likely rotation there and when I was putting it back on in the TDC position.

I think you are suggesting that I might have rotated the crank without the belt attached. Answer is no.


Could the car be flooded? As I mentioned in a previous message to AE1969 my first attempt failed and there was a lot of noise and shut the car down. took off the belt covers to find no tension on the timing belt. There was a substantial amount of gas in cyclinder #1 (probably the same for the others) when I retensioned the belts properly this time.
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Old 07-04-2005, 04:52 AM
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Check compression.
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Old 07-04-2005, 06:22 AM
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Sounds like your timing slipped.

Roll the motor over by hand to TDC#1 look on the joint between the engine and the bell housing - you shoud see a notch in the flywheel. Additionally, the mark on the camshaft housing should line up perfectly. If they are not lined up, your timing is off.

If you are not lined up, you likely bent a valve. if you are lined up, do a compression check it (as previously stated)

Many times, especially if you are unaware of the possibility of it happening, the camshaft can roll slightly when you are installing the camshaft housing on the head, - not much, just a tooth or so. Couple this with the crankshaft not lined up exactly (I use the mark on the bottom of the flywheel) you can easily get 1 - 2 teeth off on your timing.

Fingers are firmly crossed for you.

AFJuvat
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Old 07-04-2005, 07:14 AM
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AFJ, I triple checked the position yesterday with the third method that was suggested by AE1969 (since I could not lift my car enough to see the flywheel, I need a new jack). I took out spark plug #1 and inserted a long dowel. The dowel continued to rise to the TDC mark on the cam sprocket and immediately fell after the mark was passed, I could also visually see the piston rise and fall as TDC was passed on the cam sprocket.
So I think I'm good there.

I will have to check compression when I get home later today. I've been told there is little value in cold compression numbers. I'm assuming that if I get some really low numbers I'm gonna be replacing some valves.

One followup question. The belts are tensioned fine now but while hand turning the crank there are positions when it turns very easily and some postions that require much more effort. Can anyone offer an explanation?

Crossing fingers too.

Thanks for all the advice so far, stay tuned.
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Old 07-04-2005, 08:45 AM
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turning the crank will be hard when the motor is creating compression and then will be easy, even continue the rotoation, as the compression is released. did i understand your question correctly?
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Old 07-04-2005, 08:52 AM
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My toes and fingers are crossed as well............

You are feeling the compression strokes. Even with the plugs removed you will have resistance.

If you are off 3+ teeth. The valves will hit......it will be obvious. AF is right ....... the timing more than likely slipped with the loose belt.

We are all hoping no major damage was done the first time.
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Old 07-04-2005, 08:55 AM
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Taking just about any and all offers.

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?# screwed valves.

Damn compression numbers were pathetic. I got it running ruffly with full throttle came off and it died.

guess the next step will be to strip it down and visually confirm which ones but it could be all of them. Looks like it will wait to next year. To add insult to injury the drivers side mirror feel out when I slammed the door. A sign that I should quit now.

thanks for the help.
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Old 07-04-2005, 06:14 PM
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Awwww hell.

What were the numbers?
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Old 07-04-2005, 07:24 PM
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kinda weird actually

Cyc #1: over 300, 105, 90. Each took about 4-5 cranks to achieve. Each time gas ejected from the release valve on the gauge.

Cyc #2: 120 (10 cranks), 60 (7-8 cranks), 30 (7-8 cranks)

cyc #3: no reading

Cyc #4: no reading.

Not sure if I toasted the gauge after that first reading.
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Old 07-04-2005, 07:50 PM
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Old 07-06-2005, 06:01 AM
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Well..........I figure you bent 4 exhaust valves...........

I do have a spare head............

Take a deep breath murn............ and put the gun down.

It can always be worse.

...........but if not.......... I can always use another car.
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Old 07-06-2005, 09:06 PM
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Will the entire head really be ruined? I thought the valves themselves can be replaced individually when this happens, and the head can usually be saved.
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Old 07-07-2005, 07:41 PM
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Hey, mate,

I'm in Wainwright - not too far from you. If you decide to get rid of the car, let me know because I may be interested in it.

Judging by your compression numbers, I'd guess you've bent some valves. It's really important to get the timing belt right. Head over to clark's garage (don't know the internet address off-hand, but a quick search should do it for you) and read everything he's got on his site about t-belts.

If you do decide to fix the car, keep in touch with me and let me know what you're up to. I've been doing my own belts for years and could help out if you need it.

HTH

S.
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Old 07-17-2005, 07:59 PM
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Actually she fired up tonight but ran rough (not sure what the problem is now). I went to replace two dirty plugs and noticed that I mixed up my ignition wires. Also some smoking from the crossover pipes maybe (lose?) or the engine degresser (smells like Gunk), has me a little worried. The smoke was white and did not smell like glycol, wasn't blueish either. Hesitant to idle it again due to the rough idle and smoking.

If you wanna come check it out, anytime. I could probably post a picutre or two aswell.

I think I'll try another cold compression test first, think I blew the gauge the other time. We'll see.
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Old 07-17-2005, 08:38 PM
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Ran rough? Check timing again. You can run one tooth out on the cam (not the crank) and not trash your valves. Ask me how I know... But your compression test worries me (and the gang).

Smoking from crossover pipe? Burning off degreaser? Could be. The smell will tell you what it's burning. Is it smoking out the tailpipe? Black means too rich, white means coolant, blue is oil.

IF your t-belt is tensioned properly and you've turned the engine over by hand and not had valves strike the pistons, idling the car shouldn't hurt it. Then you can see if your smoke clears (so to speak!).

The most important thing is to be methodical. Don't chase ten things at once. Knock 'em off one at a time. I'd double check timing first, then belt tension, then look at compression. If your timing's out, a compression test won't tell you a thing, and so on.

Good luck and keep us posted!

BTW - are you military posted to Cold Lake?
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Old 07-17-2005, 09:58 PM
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Old 07-17-2005, 09:58 PM
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