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GoodCat · Joined: 11 Apr 2009 Posts: 31 Location: Indianapolis, IN

I was having trouble getting the timing belt on as the top seemed very loose. As it turns out, someone (naughty roommates... ?) had moved the cam gear manually while I was away and that's why. Now I have to reset everything. I found the notch on the cam gear, however I see no notches on the crankshaft pulley.

How do I align everything so it's safe to put the belt on? The only timing belts I've changed was just an on and off job...
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1980 Porsche 931

Rasta Monsta · Joined: 12 Jul 2006 Posts: 11733 Location: PacNW

Better get a manual. Better also create a signature in your user control panel, so we can see what year your car is. Not sure, but I think the flywheel marks might change between years?

Anyway, there is a window in the block (left side) that lets you see timing marks on the flywheel for TDC.

Oh, and kick your room-mate's asses. They almost cost you a small fortune.
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flosho · Posted: Sun Apr 12, 2009 2:20 pm Post subject:

lol, why the hell would your roommates do that?

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GoodCat · Joined: 11 Apr 2009 Posts: 31 Location: Indianapolis, IN

Thanks Rasta, I added it to my sig. I'm going to look for the window now.

I did open up spark plug on cylinder 1 and stuck a thin dowel rod down it. I turned it until it was at the top of it's path assuming TDC then tried to fire up and blurgh, nothing.

Does the cam shaft need to be at TDC or alligned with the timing mark (I assumed that's the large metal notch just to the left of the cam gear (11 oclock) ? Sorry, new to timing

Funny how you can have a number of engine swaps behind you and realize you don't know how to reset timing. lol

The issue I'm seeing is while trying to set the cam shaft, after turning so much, it 'jumps' to the next position. This position is neither at that notch or TDC. Should the cam gear be aligned out of one of these 'jump' spots? Hope that makes sense. I'm frustrated, but trying to get this up by morning. All of them deny touching it, but there's no way I bumped it hard, I'm too careful.
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1980 Porsche 931

GoodCat · Joined: 11 Apr 2009 Posts: 31 Location: Indianapolis, IN

Just realized I was looking at a dot on the front of the cam gear, instead of the dot on the back of it. UGH Forgot I got a manual with this thing and noticed it said 'notch on the back' doh! So forget that question. Thanks for all the help! I have yet to locate the window, but found a few pics, so I should be good to go.
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1980 Porsche 931

924RACR · Posted: Sun Apr 12, 2009 10:13 pm Post subject:

The cam probably moved from spring pressure.

The window on the block is actually on the bellhousing, not the block - Rasta must've been into the grappa when he posted that or something.

Look on the bellhousing directly below the ignition coil. You'll probably have to move some wires out of the way to see it.

Don't be so cavalier about setting the timing; get it wrong, you could be hunting for new valves. The 931 IS an interference motor.

Find the marks, get it set right. Don't run the engine unless you're sure you're using the right marks!!!
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924RACR · Posted: Sun Apr 12, 2009 10:15 pm Post subject:

One more thing which has thrown me out on occasion - make sure when setting the marks and belt that all the slack is on the same side as the tensioner! Otherwise it'll be all lined up till you tension it, then it could be off a notch...
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GoodCat · Joined: 11 Apr 2009 Posts: 31 Location: Indianapolis, IN

Well I found the window, but I've been sitting here with my buddy having him turn the crank and watching, no lines, no zero, nothing... urgh! Any clues? Is this a tiny dot? A thick notch? I do see all those half crescent indents but there are many of them so I assume that's not it. Any other way to tell?
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1980 Porsche 931

GoodCat · Joined: 11 Apr 2009 Posts: 31 Location: Indianapolis, IN

ok, found the notch on the crankshaft pulley now that's it light. When I align it perfectly with the outdent notch behind it, the top of the belt is loose. So both crank and cam are aligned with their notches and the top belt is way to loose. In order to make the non-tensioner side tight, the crank notch has to go way out of alignment...

edit: Now the assumed 'window' I'm speaking off is what I found on the bellhousing on the left, BELOW the car (just to the side of the starter motor) Is this the correct hole to be looking in? After all this, I'm assuming not...

update: Did find on top of the engine a stop to look down near the firewall into the bellhousing a believe, a small window.

Saw marks for Z1, 20, 25 then nothing the rest of the way around. When it's on Z1, the timing marks align on the crank pulley, but the belt is not tight...

this picture appears to be the window I'm looking through when I see Z1, 20, 25

http://img262.imageshack.us/img262/3343/timingmarkskp2.jpg
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1980 Porsche 931

Smoothie · Posted: Mon Apr 13, 2009 8:20 am Post subject:

No, the window is a small rectangle and you view it from above, with difficulty, down between a bunch of wiring and hoses at the rear-left of the engine, below the coil.
The flywheel TDC mark is a line with "Z1" engraved next to it. Make sure you can see both it, and the front crank pulley mark lined-up at the same time, then make sure the mark on the rear of the cam pulley and pointer on the valve cover line-up..
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GoodCat · Joined: 11 Apr 2009 Posts: 31 Location: Indianapolis, IN

update: pieced her back together when everything was lined up and it started after some trouble and ran like it was 100 years old and dying. At maybe 100 rpm. fail, ugh So confused

update: started over again, now when I align everything, the belt is VERY loose. Z1 is lined up, both gears are aligned with their pointers....

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1980 Porsche 931

Grenadiers · Posted: Mon Apr 13, 2009 12:21 pm Post subject:

THe trick to installing the belt, is to turn the crank pulley a few degrees, then tighten the tensioner. Can't recall which way at the moment, but you'll figure it out. This takes the slop out of the top of the belt. Just check your marks on the cam and crank pullies when done. It might take a few attempts.
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flosho · Posted: Mon Apr 13, 2009 12:51 pm Post subject:

I would check the compression once you get it all lined up again and tensioned properly.
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GoodCat · Joined: 11 Apr 2009 Posts: 31 Location: Indianapolis, IN

Thanks guys! Grenadiers, I figured out your trick about the 25th time I removed the belt and redid TDC trying all sorts of tricks (literally) lol. However, car won't start. Finally got the belt on and the crank pulley, cam gear, and flywheel marks all align. Seems like it's some sort of timing issue, so I'll take it from here and go with what I can.

I appreciate the help guys. I might just bite the bullet and take this to Car-x tomorrow. Funny how many overnight transmission and engine swaps I've done on fun cars, but when I get something for my daily I can't figure out the issue. lol Thanks again, glad to join the Porsche family! Even if it only ran for a day

Bed time for me.
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1980 Porsche 931

924RACR · Posted: Mon Apr 13, 2009 9:49 pm Post subject:

Car-X? You don't mean taking it somewhere where someone else who has no clue can tell you what they think is wrong, do you? 'Cause that'd be a collosal waste of time and money.

Your second-to-last post sounds like it'll be with the timing belt off one notch.
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Vaughan Scott
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'79 924 #77 SCCA H Prod racecar
'82 931 Plat. Silver
#25 Hidari Firefly P2 sports prototype