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Opeler
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Discussion Starter · #1 ·
I recently bought a '70 GT with 1.9 l that was not running, and have been working to get it back on the road again. I pulled the timing chain tensioner the other day to take a look at it, and the plunger had come loose out of the plunger guide. Luckily, the plunger came out with the guide when I pulled the tensioner, and I peened it back into the guide. I cleaned everything up, made sure that the plunger moved freely in the guide, and put it back in the timing chain cover. When I took the car for a test drive, it seemed to run fine, however at low rpm and decellerating, there was a rattle in the front of the engine. After reading some of the posts in this forum, I assumed that it must be a loose timing chain, and started to look for the discussion on how to extend the tensioner plunger (I still have not been able to locate it, however). I did some other work on the car.. pulled the manifold and carb to remove broken bolts in the exhaust manifold flange (the flange to the downpipe), etc. I replaced the manifold and carb using new gaskets. Now, when I try to start the car, it fires a few times, tries to run, backfires a few times, etc. but never starts. I have checked the distributor timing, and it looks OK. I am suspecting that the timing chain has skipped on the cam sproket, and the valve timing is now incorrect. Does this diagnosis make any sense? Is this something that happens to these engines? Is there a way I can check the valve timing without pulling the head or timing chain cover? Thanks in advance for your help.
 

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Opel timing is weird but once you get it, it's simple. I think I can even explain it now without straining something. Pop the valve cover, bar the crankshaft over clockwise watching #4 (rear) intake valve open and then close. Bar the crank clockwise some more watching the timing mark on the flywheel thru the window on the right side of the block. Stop when the mark lines up with the pointer. The cam gear mark should be just above the line on that little tab sticking out of the block under the gear, using the center of the cam to ensure the linup is straight. The points should have just opened and the rotor should be pointing to #4 plug wire.
Somebody straighten me out if I got that wrong...
I suspect you have timing chain rails worn out, tensioner block, too.
Better pull the pan and cover and have a look around before something blows up. :( If it needs a rebuild, it's WAY cheaper to do it before the hard knocks start.
 

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Old Opeler
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amishhacker said:
After reading some of the posts in this forum, I assumed that it must be a loose timing chain, and started to look for the discussion on how to extend the tensioner plunger (I still have not been able to locate it, however) Thanks in advance for your help.
A small metal cap can be fitted to the end of the chain tensioner to give the tensioner a bit more lenght. I think something like the cup out of a rear wheel brake cylinder has been used by others on this Site,.
 

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OPEL-LESS!!!
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this sounds silly, but i've had the same "symptoms" which ended out being a rotted out alternator bushing. few weeks later another posted with this problem and had found the same thing happened to his car also. may very well be worth a check. just see if the bushing is shot between the alternator backet and the timing chain cover, quick, easy, and best of all free to check.
 

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TC tensioner fix

Here's that fix you were looking for.
 

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Opeler
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13 Posts
Discussion Starter · #6 ·
Thanks for the advice folks. This evening I pulled the valve cover, and looked at the cam timing using Jeff's technique above. Everything checked out OK. The cam gear timing marks lined up as he noted, so that looks OK. While I had the valve cover off, I had my son crank the engine with the plugs removed to see if any of the valves might be stuck. All seemed to be operating correctly. All of this is good, however I still can't start the engine, and I get backfiring through the carburetor. The firing order seems to be correct 1-3-4-2, so I am still looking for what I have done wrong.

Since I removed the carb and manifolds, and everything else (that I can think of) seems OK, I'm now suspecting that it is something I did when I had the carb and manifolds off. Is it possible that somehow a vacuum leak at the carburetor baseplate gasket or intake manifold gasket could be causing the problem? Would moving the carb aound shake loose some dirt inside and clog a passage and cause a problem like this? Anyone have any other suggestions?

Thanks
 

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ok been there done that so many times it's like habit now. Try 180 out or swapping the plug wires 180. Not that I've done this enough times to know how the carb acts or anything when you do it.
 

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OPEL-LESS!!!
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i've changed many many dizzys in the opels with numerous cars. and only ONCE have i got the dizzy in right on one time, the rest have been 180 out as dave stated, no matter how much care i take to try and get it right. the cap has a notch in it that fits into the distributor, so you can't just flip the cap 180, but change the wires on the cap 180 degrees as dave stated, very probable cause.
 

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Opeler
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Discussion Starter · #9 ·
I finally got a chance to work on my engine today, and got it running again. It turns out that it was either a carb or carb gasket problem. I wound up pulling the carb and cleaning it by blowing out all of the jets, passages, etc. I also noticed that the carb base (it's a Weber) was not completely flat, so I wet sanded it on a steel block until it was true. While the carb was off, I ordered a thick base gasket from OGTS. The previous one was from a local parts store and was very thin. When I put it all together, the engine idled great, so I think that it was probably a leak at the carb base that was causing all of the backfiring/non running problems. Anyway, thanks everyone for the advice. It's now on to putting in a new exhaust and trying the timing chain tensioner trick mentioned previously in this thread.
 

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Old Opeler
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amishhacker said:
..........trying the timing chain tensioner trick mentioned previously in this thread.
Realise that the "timing chain tensioner trick" just compensates for wear and is an interim measure - a keep it going for now fix. Plan on a timing chain and tensioner replacement in the next wee while. BTW: the "fix" also has an effect upon cam timing too. It works but is not a permanent repair!
 
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