Club 80-90 Forums

I think my engine is finished. It's not a fuel problem. I'm thinking burnt valves. Wouldn't tick over when cold, got it warm, revved the knackers off it and BANG, it was like a shot gun going off! Couldn't get the bugger to start at all then. After a minute or two got it started and it will tick over now although the engine is sound ing rough, bouncing from side to side and pops through exhaust if revved.....

Decided to re re re re re re check the tappets now it will tick over and they are acting differently now - they are rising as I wind off the pre load or expanding as you would expect. I've now re-set at 1.5 turns, the engine will still idle. I will now road test it. Got my RAC card.... Could my tappets be knackered?

After a few days use, it's happening all over again, sounds like a bag of spanners and won't tick over. Took the carb off yesterday and cleaned / blowed it out. Drove to work this morning and still the same. If I floor it there's plenty of power but sounds rough. As I let off the throttle there's a small back fire, think out top of the carb. Any ideas before it gets junked?

Mate, 1.5 turns is far too much, those valves are open if its backfiring, do yourself a favour and do them again, this time just put them in so that there is zero gap and try it, do not load them at this point, if that then cures your problem then you need to set them properly, you will find that the hydraulic tappets on these motors are not a set commodity, each one will act completely differently to the next especially if they are worn, adjustment is on an individual valve by valve basis, adjust until zero gap and then turn until tight, a fully pumped up tappet will need a quarter to half a turn whereas a new one will need up to 2 turns, watch the valve when you adjust it, if it is open on adjustment its wrong and will produce backfires and no idle

steve8090 wrote:Mate, 1.5 turns is far too much, those valves are open if its backfiring, do yourself a favour and do them again, this time just put them in so that there is zero gap and try it, do not load them at this point, if that then cures your problem then you need to set them properly, you will find that the hydraulic tappets on these motors are not a set commodity, each one will act completely differently to the next especially if they are worn, adjustment is on an individual valve by valve basis, adjust until zero gap and then turn until tight, a fully pumped up tappet will need a quarter to half a turn whereas a new one will need up to 2 turns, watch the valve when you adjust it, if it is open on adjustment its wrong and will produce backfires and no idle

Thanks for the reply. I'll do this tonight. If there is damage in the cylinder head or valve burnt the engine would not run at all would it? As it is, when it does run ok, it runs really well with plenty of power. Guess I'm after piece of mind that it's not terminal.

Backed the adjuster off, can feel the tappet expanding. Set to just contacting, still won't tick over. If I rev it, you can here a faint pop on releasing throttle. Don't understand this. Day before I removed rocker gear to replace a pushrods tube, rather van did a 60 mile round trip with no issues. If I've set the adjustment to 1.5 turns and had a valve open, wondering if it's now damaged. Unlike air cooled, I can't whip the head off to check.

Next step then is a compression test, this will give you the answer, i have seen tappets set far too tight destroy camshaft lobes but thats after a few thousand miles.
And if you can feel them expanding you could still have a tight tappet, a fluffing on the i let is a tight valve or pop in the exhaust is also a tight tappet.

Hi, cheers for that, I'll contact some one tomorrow to get compression test. I've re adjusted to zero lash, revved it a couple of times and it's ticking over nicely. I'll get the tappets set and checked for leak down.

Sorry to jump in again. Had a good read of the link that was kindly provided and did a bit of exploratory work. Essentially, they are all new tappets, and when left for a while they are quiet on starting, but one of them gets noisier as time goes on which is odd. I realised the mechanic had put really thin oil in so changed it and initially all seemed a bit better, but then the single noisy tappet started again. I therefore took the rocker covers off and checked them all in sequence. It seems that number 4 inlet valve has 'play' in it even though the rocker is in contact with the valve. I tightened it but it seems like the 'slack' is at the tappet. none of the other rockers could be rocked at all at their TDC, but this one could. It felt like I was pressing against a weak spring.i tightened it one whole turn and ran it - tiny bit quieter but i did note that it was wound in a small but noticeable amount more than the others. Do I need to get it looked at?? It is running ok (well actually). Can i do much harm?

gasman78 wrote:Sorry to jump in again. Had a good read of the link that was kindly provided and did a bit of exploratory work. Essentially, they are all new tappets, and when left for a while they are quiet on starting, but one of them gets noisier as time goes on which is odd. I realised the mechanic had put really thin oil in so changed it and initially all seemed a bit better, but then the single noisy tappet started again. I therefore took the rocker covers off and checked them all in sequence. It seems that number 4 inlet valve has 'play' in it even though the rocker is in contact with the valve. I tightened it but it seems like the 'slack' is at the tappet. none of the other rockers could be rocked at all at their TDC, but this one could. It felt like I was pressing against a weak spring.i tightened it one whole turn and ran it - tiny bit quieter but i did note that it was wound in a small but noticeable amount more than the others. Do I need to get it looked at?? It is running ok (well actually). Can i do much harm?

If you use too little preload you will stress the lock ring that holds the lifter together when the lifter socket makes contact with it. If you use too much preload, the plunger may bottom out at first, then as the lifter pumps up to compensate the valve may not close properly and compression, performance and valve life will suffer...is the worst case.
Not all the lifters will adjust the same, but I would say they should be within a quarter/eighth turn of each other.

Thanks for that. I think it is a dud tappet. Will get it looked at.