Distributor Caps

[Jules]

[Jules]

Some pics in case it helps! It would appear the common denominator is me!

[wilf]

Jules - can't quite see from your pics the failure you described.

[Jules]

The circular scoring on the rotor arm is the main thing to see… is that normal?

[richardthestag]

rotor arm on the left is cheap nasty chinesium, widely available through most main suppliers

rotor arm on right is a nice DD rotor arm for electronic controlled lucas distributors.35DM8 35 DLM8 etc etc, it is slightly shorter in height because the centre shaft in those distributors is slightly thicker. Put a wide tail point rotor onto one of those distributors and the cap will wobble when the engine is running.

You also need to use the thin tail rotor arm is you have pertronix or a cheaper substitute where a cap fits over the top of the centre shaft, see below for a robbed image of the cheaper powerspark setup. the black trigger ring sits over the top of the centre shaft of the distributor and on top of the original 8 pointed cam, so you loose 1-2mm in height.

s-l1600.webp

On the luminition and newtronix setups the trigger sits around the centre shaft and not on top of it, so you still need the original wide fan tail rotor arm, as if you are still running a points system.

when you talk about failed, is the car failing, no spark?

[richardthestag]

This might help

https://youtu.be/nr1_jFssay8?feature=shared

[richardthestag]

I think maybe a little more information about the ignition coil you are running also.

A very long time ago I had a ballast resistor (EUREKA) wire failure on my mk2 stag. I proved that by running a 12v feed from the battery to the coil +ive terminal. The coil was designed for ballast systems. so there fore I ran it outside it's design spec. Constant over supply to the coil, during my 20 minute test drive, caused damage to the cap and rotor arm, both of which had to be replaced.

Your 1971 stag engine should have a white ceramic block that contains a ballast resistor


s-l1600 (1).webp

Wiring is simple as one side takes the ignition switch feed and the other takes the starter solenoid feed and the supply wire that goes to the ignition coil +ive terminal

Do you have this resistor block?

What ignition coil do you have?

[Jules]

Thanks for the responses above, so it looks like the issue has solely been the rubbish quality caps and rotor arms. When I first fitted the distributor doctor arm and cap i didn’t lock the cap into place (small channel/cut out on dizzy). I think because of the much tighter tolerances and the other caps were so loose I didn’t pick this up. I’ve since removed all the least, re fitted everything properly after phoning the distributor doctor and everything is now working nicely! I think because the electronic ignition lifts the rotor arms a touch you need the fit to be exact which when I was rushing to fit the new cap at the side of the road with 3 little ones in the car I didn’t do! For reference it does have a ballast wire but that’s fine, I have however ordered a new coil as I’ve never replaced this and a spare cap and arm from the distributor doctor so I can throw the other cheap rubbish away! If I get a few minutes I’ll try to phone rimmers and Rob sport to tell them! Many thanks for all the help and advice!

[richardthestag]

Pleased you got it working.

If the coil is working I wouldn't change it! seriously.

I am slightly confused though; your car is 1971? Ballast/Eureka White/Pink wire to coil positive terminal to replace the ballast resistor block didn't come in till 1973 .. or so I thought.

Lean on the suppliers to get parts returned where still under warranty for full refund. bring some of the pain back to them for selling the rubbish in the first place.

[Jules]

The car is 1971 but a bit of a mish mash of bits. It was rebuilt in the 2000’s (have a huge written file, a diary of all the work) and essentially the guy from the looks of it didn’t have cash but really spent the time, so made 1 good engine from 2, stripped the entire underbody and treated it and then painted it with hammerite. So it’s a genuine mk1 body but engine, seats etc mk2 and it looks like a mk2! It’s very far from perfect but I love it to bits as do my girls and I have had many happy (reliable) times in it!

[Jules]

P.s, will keep the coil on the shelf as a spare!!