Astra cambelt kaput!!

Very good chance of engine damage ,

GM 1.7 low blow, or the Izusu version?

The former- afew broken rockers, and it will go again, or the latter- broke i am afraid..

Tim.

It's the GM low blow engine. I think it's engine code X17DTL fitted with the bosch pump. Would that involve just taking the rocker cover off to inspect / replace rockers or does the head still have to be removed? According to Autodata there's a few special tools needed to replace the belt;

Flywheel locking tool TDC position tool Measuring bar Holding tool Dial gauge Flywheel timing pin

does the cambelt still drive the water pump on these vans , if so it may pay to change this at the same time

Just had a word with my local mechanic. He did a broken belt on this type of engines and it had only smashed a few rockers. He says with a tool to press down the valves you can get the cam out and replace rockers by just the valve cover removed without touching the head bolts and suggest I try that first, and prey it starts without any misfire.

I've always done them with acouple of modded stout screwdrivers- as you say without disturbing the head bolts...

Tim. .

Got the top off and retrieved all the broken bits. There's 4 broken rockers, from left to right;

I removed the bracket at the right holding the camshaft (nearly lost it down the side of the engine!) but looks like I'll need several pairs of hands trying to get it slide past the remaining rockers.

P.S Are the shims specifically machined for each individual valve? Just wondering as No.4 cyl had both rockers broke so not sure which shim went to which valve?

No. Shims are normally made in diffent sizes. The correct shim or combination of shims are selected to give the right valve clearance.

Just

Doesn't matter. After fitting new rockers the clearance will need to be checked. Once you know the correct size, you can buy the right sized shim from a Vauxhall dealer. Mike.

On closer inspection I don't think they are shims as is fitted to the Isuzu engine. They have a grove in which the rocker finger sits in and doing a bit of google looks like I need a dial gauge to set it up.

Anyone know if the crankshaft pulley has to be removed for fitting cambelt & setting up? The large centre bolt looked partialy rounded before I even tried getting it out and even with an impact wrench the bastard won't budge!! There's a hole at the bottom of the flywheel housing to insert a bolt to locate TDC. Would that do without removing the pulley?

the little things with a slot in them are to avoid the rocker wearing out the valve, very cheap item to replace while you are there. from the pictures it looks as if the pulley can stay there, but autodata says it has to come off. on some engines you can use the camshaft gauge off the early vauxhall engines, but it should be done with the dial gauge for accuracy.

In your position why not put the new rockers in and roughly time the camshaft as you put it back and get a mobile cambelt man round to time it up properly.? Bear in mind that a half tooth out on the timing means the valves can hit.

Have you checked that the valves are not bent? You can do it quite easily with the cam out. Get compressed air into the cylinder via the glow plug holes or injector holes, it shouldn't leak out of inlet or exhaust, a bit of a leak around pistons and into the oil area is normal for a cold old engine.

Thanks for that. Yeah I've read that it's critical to get it right as there's no room for error on these engines. Might give the compressed air a ago when I get the cam out, waiting to get hold of the tool to help slide that out. At the moment it's positioned so non of the valves are in contact with the lobes (the ones that should be are broke off). With the valves not touching the cam lobes is it normal to be able to turn a diesel engine at the crank pulley without too much effort? When locating the TDC locking hole I could turn the crank one complete turn without too much effort with a

Nope, twice per turns normal for a 4 stroke 4 cylinder.

every half a turn you should get a roughly equal amount of resistance. If the valves are not moving at all then you won't have the compression effects that would be there normally (not much to squash) It would not be a very good guide just turning it, but if you hear a load of air being blown out of the inlet or exhaust then that would be a very bad sign. You are squashing the air in two cylinders at a time, the spring forward is good, showing some squashing on that pair of cylinders, but it might be only on one of the pair.

One cylinder at a time, surely? With another cylinder going up, but on the exhaust stroke.

Thanks, so far so good. I'm having a blonde moment and just want to confirm if the pistons are always in the same position after one complete turn of the crank? For e.g. does it go through it's full cycle in one turn or does one turn bring the outside pistons to the top and then another full turn bring the middle to the top? Just want to make sure that when the timing pin fits into the flywheel housing then that's TDC and can't be a complete turn out?

Ah I understand now. Bad thing is I think there was a hiss sound coming from the top as I turned!!! Will get someone turn it tomorrow while I have a closer listen.

No. two pistons at a time go up, while two go down,

usually only one at a time would have compression, but since the valves are not in use at present then both pistons will squash stuff at the same time.

In the OP engine there is no intake stroke, no exhaust stroke, no power stroke, there is a vacuum inducing stroke and a compression stroke on two cyliders at the same time, then repeated for the other pair.

A normal engine has effectively two TDC but.......... There is only one TDC that you are interested in, which is for number one cylinder (which on most engines is the same as for cylinder 4) cylinders 2 and 3 will be at the bottom when this occurs.

One complete turn from tdc will bring the same two cylinders back to TDC

If the pin can only go in at one point then it will be the correct point.