"Missing" under acceleration.

Patrick

CCCUK Member
Hi all. I have a 1960 C1 which has been driven very little over the last few years as I was based abroad. I returned in mid August and have been taking every opportunity to take it out for a spin. Over a period of about three weeks it started to "miss" under acceleration. This condition continued to develop but the car ran very well otherwise.
I took the car to the garage that has been maintaining it for me for many years. He maintains a lot of classic cars for a storage facility nearby and is also a personal friend whom I trust implicitly.
He stripped down the carbs and cleaned them and also replaced the spark plugs but the problem is still there. He has suggested replacing the HT leads, the theory being the leads are "breaking down" and not getting a strong enough charge through to some of the plugs. My only concern here is that we replaced them 4 years ago.
Two questions:
1) Whilst I do trust him, I'd like to get a second opinion on what might be the cause of the problem;
2) Where can I get a good quality set of the correct HT leads?!
 

Oneball

CCCUK Member
Does it miss the moment you put your foot down or is it doing it all the time under constant acceleration.

Have you got the stock ignition system?

When was the last one you put fuel in?

Have you got a fuel filter?

I’d check timing, points, mixture and fuel delivery are all correct before changing anything.
 

BobbyV8

CCCUK Member
Don't know what ignition system is on it but we used to get that problem with a faulty condenser with a points ignition system.
 

Forrest Gump

CCCUK regional rep
I’d suspect a damaged HT lead. Check carefully where the leads get close the exhaust manifold, looking for a burn on one of them.
 

Patrick

CCCUK Member
Does it miss the moment you put your foot down or is it doing it all the time under constant acceleration.

Have you got the stock ignition system?

When was the last one you put fuel in?

Have you got a fuel filter?

I’d check timing, points, mixture and fuel delivery are all correct before changing anything.

Whenever I accelerate it does it. It is the stock ignition system. Yes it has a fuel filter. He gave the car a service as well - no other issues came to light.
 

Patrick

CCCUK Member
The HT leads that are on it now were part of a "servicing kit" supplied by Corvette Central - may be the quality was not so good.
 

Roscobbc

Moderator
Andy's comment is worthwhile following - I had this issue on and off for quite a while before figuring it - plug boot (and HT cable exiting it) was close to header - not ever a real issue in normal driving - when 'booting it' there would be a misfire. It was only driving at night without the hood that it became apparent - the boot/lead had been burnt through and was arcing against the header flange when a load was put on the engine. And this was with an MSD system (also had it previously before MSD was installed) - electricity will always take the path of least resistance (a scientific fact) - under normal and light throttle use the power would go to the spark plug as normal. Put a load on the engine (i.e it firing an enriched mixture) and actually driving the car (not revving whilst parked) was sufficient for the 'spark' to at first be weakened when shared with being earthed against the header flange - to entirely going to earth once an increased load was applied to the engine. Easy to see at night without a hood.
 
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