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Discussion Starter · #1 ·
Hi I hope somebody can help!!:cry:

I have bought a astra (1999) 1.7 tdi with cambelt failure. Its the GM low blow engine, found 2 rockers broken, removed head, valves and pistons ok.

I have re-assembled the engine with new gaskets etc., but cannot get the crank up on TDC,( also pinned the flywheel) with the exhaust valve camlobe upright, without one of the pistons hitting a valve.

Please help me, this car has been bought as a non-runner - could it be possible that someone has fitted the wrong camshaft before it came to me???

Head was removed, all valves were not bent, and lapped backing. nothing protuding the head before fitting.

thanks in advance

Barny
 

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Hi I hope somebody can help!!:cry:

I have bought a astra (1999) 1.7 tdi with cambelt failure. Its the GM low blow engine, found 2 rockers broken, removed head, valves and pistons ok.
Rockers broken without damaging a valve or valves?
I have re-assembled the engine with new gaskets etc., but cannot get the crank up on TDC,( also pinned the flywheel) with the exhaust valve camlobe upright, without one of the pistons hitting a valve.
If a piston is hitting a valve at TDC it indicates gross mistiming to me. Don't know what the official method is, but what I'd say is rotote the engine in the forward direction until the pistons are at midstroke. Now fit the cylinder head! Note how far the crankshaft timing mark is from the correct position and position the camshaft mark half that distance in the forward direction. You're nearly there and I don't think I need to continue.

Ill considered rotation of the crankshaft and or camshaft I'd say is bound to lead to tears.
 

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If my memory is correct you need to time the camshaft once the head is on the engine. You need a special tool set that enables you to do this.

Ive done several on the GM 1.7TD engines myself. Never on an Isuzu engine though...not sure which the low blow is personally.

But if you removed the camshaft bolt then you should find that there is no woodruff key.

The idea is to time the bottom end, then time up the cylinder head using the special tool and dial gauge, WITH the cambelt actually fitted... you crack off the camshaft pulley bolt and then rotate the camshaft directly... Its done by angles on the gauge, NOT markings on the top.

Been awhile since ive done it but i can give a better impression tomorrow if this applies to you?
 

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Discussion Starter · #4 ·
Hi V6Cav, yes this applies to me the low blow is the GM1.7TD engine (x17DLT). Problem is if I time up and lock the flywheel at TDC, I cannot rotate the camshaft to achieve the lobe position:( (autodata says cylinder 1 at vertical pos.)

there is definatley no woodruff key on the camshaft.

i did not drain the tappets before refitting the head and the cams, would this be causing problems??

any help greatly appreciated M8

cheers

Barny
 

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Discussion Starter · #6 ·
OK guys, I drained the tappets in the vice and set the cambelt timing with a Dti gauge. She starts and runs, but when warm, and bringing up revs, it snaps a rocker/cam follower. Ive done this 4 times now and running out of rockers!! never the same one that breaks - inlet and exhaust - seems like not enough clearance btw pistons and valves - possibly supplied the wrong headgasket?? I replaced the original for the same, but purchased the car with a broken rocker - any ideas chaps??
 

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I have the identical problem on a 1997 astra with low blow GM engine. What is the special tool, and what does it comprise?
TIA

Mike
 

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hi there,these engines will break a rocker if the timing is even slightly out,the rockers are very weak and will snap without doing any valve damage,they must be timed up using the correct timing kit and double checked before running.
 

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Can you suggest a supplier for the timing kit, and I've read about the tappets having to be squeezed to do something that I'm not sure about. Do you know about this?

I'd appreciate any information you can give me on this one.
Thanks,

Mihai
 

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1.7 cam timing

I sufferred a cracked cyl. head so rebuilt with one from breakers. Its a 1996 LTD engine. I didnt use any special tools, have done 3 yrs and 25k miles since.

I set TDC by setting pistons at top, then checked by "rocking" them with socket bar on the crank pulley nut (head off). If head is on, a thin stiff wire (bent) can just be inserted through injector hole, but assistance is needed to rock crank, No. 1 at TDC on firing stroke. Also marked up ring gear with bright orange paint.
With belt tensioned up and No 1 exhaust cam set to open valve, I rotated camshaft (nut slightly slackened off, using mole grips on shaft with protection on jaws) to its stop in both directions, marking with a tiny spot of quick dry paint on cam and pulley. Then, mark cam and pulley halfway between these spots and rotate cam so it exactly lines up, and tighten enough for hand cranking test. So now the cam is clear equally in either direction of the valves touching the piston, and should be close to correct timing. I used alloy chock blocks between cam and case on the final tightening.

Do several hand cranking cycles to ensure that all sequences are correct before any attempt to start is made, and everything returns to its correct position at TDC on No 1 cyl.

NOTE: Its a while since I did this and mght have forgot one or two details. I hope it helps a little.
Also, I never touched the tappets when I transferred onto other cyl head.
 
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