Misfire at higher load

[Aleco]

Thanks for the support!

I've got one more thought up my sleeve. The dizzy cap, rotor arm and leads are relatively old, I've ordered a new set so I'll see what happens.
Interesting I swear I can hear a ticking noise coming from the dizzy.
The rotor arm looks ok but the contacts on the cap look worn and there is a little brass? dust in the distributor where it looks like the rotor and cap have worn.

Clutching at straws?

Oh and to add to my joy it looks as if the cooling circuit bypass tube to the inlet manifold is leaking.

[misterp]

If the dizzy cap is cracked, then a good tip is to when dark, turn off all the lights and look at all the parts of the ignition system.

You will, if the ignition is tracking, get a blue 'aura' around where the energy is leaking and so any cracks in the cap will show up.

This also works for ignition leads where the insulation has broken down as they glow a blueish when they are past their best.

[Aleco]

My drive home was even worse than the journey in, it struggled to keep up a decent motorway speed.

I've just got back and had a look at the dizzy and rotor arm. It's been a while since I had a car with a rotor arm and dizzy cap but​ this looks pretty poor to me. Any thoughts

[mahony]

My drive home was even worse than the journey in, it struggled to keep up a decent motorway speed.

I've just got back and had a look at the dizzy and rotor arm. It's been a while since I had a car with a rotor arm and dizzy cap but​ this looks pretty poor to me. Any thoughts

That cap looks way pass it's best, never seen rusty screws inside a dizzy cap before , time for a new one i think

[Aleco]

I thought it was ropey, pics don't really show it but it looks like it's been sparking across two terminals and then hitting another.

I've got a set on order from Rimmers ready to be joined with my new leads from the club.

After a number of false dawns I don't want to get my hopes up!

[Aleco]

New cap, rotor arm and leads fitted. Bugger all difference higher up the rev range.
Perhaps slightly smoother lower down.

I'm so frustrated!

I know I now need to check the cam timing but to be honest I don't have the time - kids/home/work etc. I can't justify the time.
I'm at a low ebb.

I'm thinking of saving up again and getting the engine professionally​ set up (again).

I live in kent, anyone know of a decent engine tuner/builder in South East?

I was thinking CCK in Uckfield.

[Jon Tilson]

If you are seeing brass dust in t he old cap it means the dizzy spindle bearing is flopping about and this will not lead to good running. Can you feel sideways play on the rotor arm?

I would have a look at rebuilding the distributor. There are some good threads on this in the resto section.

Jonners

[Aleco]

Hmmmm that's got me thinking Jon.

Will investigate!

[Galileo]

I don't know if this adds any value, but as AlanH mentions in a previous post in this thread, how much do you trust your carbs?

Here's a tale (I'm prone to waffle), my Sprint struggled to rev past about 4k, so I assumed ignition and checked all settings, all fine but plugs were a bit tired so replaced plugs, and then new leads, coil, distributor cap, all with no change. I'd just bought a spare engine with all the ancillaries so I swapped the distributor over from that one for good measure and still no change. At this point I had kind of given up on finding the cause for the time being, and independently of the issue whilst struggling to set a decent idle speed I decided to see what it was like with the spare engine carbs on instead. Put the later model carbs on (Waxstat), took it out for a spin and was amazed at the snappy response and it revved up right to the red line, wtf thought I.

I have no idea why this made any difference, sure they were the original ones with the side pull springs and there was wear in the spindles, but that surely would mostly effect idle speed and mixture setting only? Anyway, this inane ramble may or may not help you!

[Aleco]

I like a bit of waffle, brings the story to life!

To be honest I'm not sure of the carbs either. Perhaps a rebuild would be an idea.

Or (I've had a beer or two to console myself) a twin 45 dellorto conversion?!

If only I had £1500 spare!

[Aleco]

Coincidentally my idle speed is pants. I spent ages trying to get it right with no luck. Always seems high.

[Galileo]

That's what I had, I'd balance the carbs, set the right idle speed, couple of blips or a drive and it would then be too high, classic spindle wear pattern in hindsight, but I'd got used to fuel injection for 15 years and filed away my knowledge of dodgy carbs, along with setting fire to bonnet soundproofing with a dodgy Peirburg overhaul and a backfire but we don't talk about that. I don't know if yours is the same but my Sprint just seemed to 'bog down' when trying to accelerate past about the 3,500-4000k mark, seemed to pull just fine at low revs though. I wonder if it could be fuel starvation from a dodgy float valve or float height setting as the genuine culprit though?

I wonder if someone in the club could lend you a pair of carbs to try? I haven't got around to doing anything with my original carbs as I had thoughts of sending them off to SU (Burlen) to recondition them until I saw their pricing and shall we say re-prioritised a touch...

[Aleco]

You've just perfectly described my car!

I will look at were I can get hold of a pair of overhaulled carbs

[Jon Tilson]

If you can get your car to the Hampton area of west london towards the end of a chemo cycle I will happily have a look for you.

PM me re dates etc..

Jonners

[GrahamFountain]

I get a higher load, higher rpm misfire on my sprint as the points close up. I admit I've not read every post in this thread, but I did search for points and contact breaker and can't see it's been mentioned.

If it's carbs, does pulling the choke out when it's missfireing make it better for a bit, or worse?

It's a pain, but it's somtimes worth checking the gap for all four cam lobes. It can show some problems with the distributor.

Graham