Peter Pompiliis Zagato JHT 909L camshaft timing issue

[Mark Webb]

Having run Peters Zagato for the past 25 years and had little trouble with the engine (bar a persistent  slight rattle on light load,more later). The introduction of E5 has made misfiring on the overrun worse and now any early down changes at speed can result in a backfire! So having checked the ignition timing and distributor condition etc I can rule that out. So I decided to look at the valve timing. The results are a bit odd, measurements seem to be even at 10 degrees either side of the tdc Mark. Exhaust about 10 degrees early and inlet 10 degrees late. This is using a genuine British standard Manning feeler guage bought from the man himself. The camshaft marks line up at the on the inlet camshaft at tdc but are advanced at the on the exhaust which tallys with the measured timings on that cam. Consistent and checked several times, so nothing really rings true.I know Peter had some 'hot' cams fitted originally and found then too radical, I understood that he refitted standard cams. However on inspection those fitted appear too good to be true. No wear markings a I would expect more from old cams, maybe new/ reprofiled new cams were fitted about 30,000 miles ago? So does this ring any bells with anyone? Or can anyone remember what cams he did end up with. I certainly cannot , but I do remember the 'hot' cams with green paint marks (from memory) in the contents of the garage that I sorted out for Kim at the time. They may have been destined for the 1600 Zagato project that was ongoing at the time he died. I also wonder if the rattle on a light load at about 2-3000 rpm is actually valve/ piston contact. Though I doubt it would have lasted 25 years without getting worse! I always discounted valve timing as an issue, I suppose thinking Peter had set it up, but maybe it was done in haste? The fact that the exhaust timing is advanced would rule out chain stretch as if anything it was even more advanced back then. The late Peter Gerrish may have known, I think he was involved with the engine build. Anyway I am reluctant to set it to standard timing, check for interference then run it and cause any damage without checking first. Sadly cam timing has always been a 'black art' to myself, I find TV and radio transmitters are far easier to understand and  tune up, each to their own! Any ideas?

[lancialulu]

Not sure what series car engine you are referring to, S1 or S2? Anyway with unknown cams I would recommend making a protractor disk for the front pulley and use a dial test indicator on #1 inlet and exhaust to find the max opening point by setting the closed gap to .4mm and noting the opening angle and closing angle and calc the halfway point. Difficult to do on a Sport with radiator in place. Standard cam MOP is around 109degress btdc (ex) atdc (in) other cams may vary around 104 - 112 but you will be in the right ball park.

To do a crude check for valve fouling go 10deg btdc and lever down on the exhaust valve and 10 deg atdc for inlet noting free travel of valve.

Popping and banging also is not helped by air leaks in the exhaust sytstem.

[nistri]

I am a bit confused: the "Manning" feeler gauge which I also got from Harry is 2.2 mm thick and used for the 1.3 engine. The 1.6 engine should use a 1 mm gauge or am I wrong?
Popping and banging may have multiple causes like indicated by Tim, I would add heavy carbon deposits on valves and pistons that glow after ignition and fire fuel residues at the wrong cycle time.

[Mark Webb]

Hi Tim and Andrea

The engine is a 2nd series 1300 (bored to 1310cc) with flowed head and an upgraded exhaust manifold with springs holding the sections together, not great for seal, but silicone helps. It's sealed at the moment but needs doing every 18 months or so, not fit and forget like the standard system. My 1.6HF engined S3 coupe pops and bangs a bit on the overrun (std system) but not that badly, I think it's worse with ethanol in the petrol but the Zagato is something I now have to drive around, not ideal. Heavy deposits are unlikely as it was rebuilt 30,000 miles ago and mostly run on Shell optimax and now Esso E5. The feeler guage is the Standard 2.2mm that Harry sold so is correct for the engine. I think I'm going to have to bite the bullet and use the protractor, maybe take the bonnet off for a start, the Coupe seems so much easier to work on! Good point on the clearance check at 10 degrees will give it a go. Sadly Peter did not mention what was fitted in any documents and I can find no bills for Camshafts in the extensive file of bills etc. It was rolling road tuned at 113bhp in the late 90's, so in a fairly high state of tune, but how much of that was flattery to the customer, who knows. I certainly remember it being smoother and reving more freely when I first used it. So maybe something has changed. Anyway I will have a look over the next few days and see what I can measure. But I am wairy of causing damage, it could be just on the edge of interference hence the noise on light loading. Given that alternative cams are not common on Fulvias I wondered if anyone could make any sense out of my results. I will report back on my findings. Thanks Mark

[Mark Webb]

All sorted, they did turn out to be standard cams, measured at 270 degrees pretty close to 273 degrees considering the accessibility. So I timed them up as standard and the car runs much better, no backfiring and more like my 1600 engined S3 coupe when it comes to over run noises. Not sure why they were so far out, maybe Peter was experimenting with timing or just timed them in haste. Anyway no harm done and it's only taken 25 years to find. Hopefully the next 25 years will be just as reliable, though I may need a lifting frame by the age of 92, the car seems to get lower everytime I get out of it these days! Thanks for the advice.