Ok. So spoke too soon However, there is an interesting development - I was driving at night and each time I experienced the drag/hesitation the headlights and dash lights became dim. When the hestation went away the headlights and dash lights became bright again. Interestingly too, the issue occurred constantly - not just uphill. I think it was just more noticeable previously under load - as you need all that the 998 can give you up hills at times

Checked a few elementary things when I got home - like fan/v-belt on the alternator (yes I have replaced the gennie with an alternator), checked and cleaned up the earth points. They all seemed nice and tight and cleaned.

Any other suggestions? Could it be a voltage regulator issue?

I would not expect it to be voltage regulator related... but it could be.

I suggest that you remove the belt and try spinning the alternator and the water pump by hand. You may find that one of the two has bearings that are beginning to fail.

Would the belt not slip if the bearings "stuck" and make that awful screeching noise of a slipping belt?

The belt may not necessarily squeak. I can't say with certainty that the belt would slip or even that the bearings are your problem. I'm only suggesting it as something to check.

Many years ago I owned a Honda Accord. It seemed to be having some pulsing when driven. I couldn't find the cause. While driving to my father-in-law's house the car practically did a nose stand while cruising at about 35 MPH. It was as if I'd punched the brake pedal and then suddenly released it. It did this three times in quick succession and then the car started moving again with pronounced bucking and surging. I limped the last mile to his house. When I checked under the hood I found the water pump had completely seized. When I fit the replacement water pump all surging and bucking was gone. Had it not been for the water pump bearings finally failing I wouldn't have thought to look at it. The car was otherwise running fine... no belt squeaks, no charging problems, and no overheating.

Thanks! Definitely worth an investigation. Will feedback after the weekend.

A friend of mine pointed out another thing to check. On most of the Lucas distributors there is an earth/ground wire INSIDE the distributor. This goes between the breaker plate and the dizzy housing. It's typically a cloth insulated piece of high-flex fine stranded wire.

If that wire is missing, the coil current has to pass through the bearing in the breaker plate. This can create intermittent problems. It may work for days without issue and suddenly the engine might start surging or may even stop. You can't just go by "oh it looks like it's there", you need to give it a gentle tug to make sure it isn't broken beneath the insulation.

sounds like you have a problem with some cable earthing out somewhere

Thanks for all the help everyone.
I tried all the advice here - took off the belt and checked the bearings on the alternator (only done about 2000 mi). No issue. Same with the waterpump - new from the rebuild, so also only about 2000 miles old. No issues.

Removed all earth points - cleaned and tightened up. Removed fuse box and cleaned and wire tightened. Battery terminals checked and tightened.

Recently replaced the points and condensor with a Lumenition electronic module. That all checked out ok.

Leads me to think I may have a sticky valve? Any thoughts on this angle?

Could it still be a fuel supply issue? The lights going dim could be a side effect of the rpm drop when the engine drags. Did you run through the filter, etc.?

Lumenition? Ok, I have one more long shot for you.

An acquaintance of mine on another board had problems with his ignition system after changing to Lumenition. As it turned out, he used the crimp terminals supplied with the Lumenition kit. Eventually he replaced the Lumenition terminals and all his ignition problems went away.

I know it's a long shot but it is an easy thing to try. Don't forget to try refitting the points and condenser again.

I still recckon it is more than likely a wiring problem only way it can affect both ignition and lighting at same time,either a main earth lead not earthing properly or a power lead earthing out with movement of the engine,thus pulling the headlights and panel lights down,as it has an alternator the engine revs should not affect the output from the alternator so doubt fuel problem.if this has only started since you changed to lumenition then it could be something to do with the lumenition going down to earth.

The problem was occuring before I changed to electronic ignition. So I do not think it is an issue with the ignition system. I have booked the car in with an auto electrician to check all the wiring et al for me. Will keep you posted.

OK, so it's not the Lumenition then.

As Mike said, this really does point more to some weak or damaged electrical connection since you reported on 5/8 that the headlights were also affected. Of course... it could also be something failing in the alternator.

With an intermittent problem, bench testing the alternator may not reveal any problems. However, it sure sounds like it would be a good idea to check the wires to and from the alternator and be sure to check the battery cable where it exits the channel under the car (near the exhaust pipe). I know several people who's car died because this cable came out of the channel and shorted to the pipes.

Perhaps the uphill missing/surging you've got is the alternator kicking in/out as a connection is made or broken... particularly if its a short of the main battery cable.

She was dead this morning. Just plain refused to start! Motor turned, by not even a hint of life. May be easier to trace the fault now... Will keep you posted

DOH!!!

Do let us know what you find.