Distributor Flash guard

[Fspp369]

Hi everyone,
What is the forum opinion on the need/efficacy/desirability of the V12 Distributor internal flash guard.
Mine is partially broken and they seem hard to find, thus making me wonder do I really need one?
If the general consensus is that they are needed,where might I get one, at a sensible price......if only!
Peter

[lowact]

For the CEI distributor?
AEU1722 GBP9 from SNGB.
Otherwise I do have a spare for twice the price?

[jagwit]

The OPUS dissies did not have such a flash guard did they?

They also did not have the ventilation system the HE LUCAS dissies had?

Should be easy to implement the ventilation system by using an HE cap (or drill holes and fit pipes to the OPUS cap), connect one fitting to the clean side of the air filter housing, the other to atmosphere via an inline fuel filter.

I've never heard of dissy fires on the carburetted V12s. Does it happen?

[lowact]

Problem with the ventilation system, when the shaft seal wears out, crankcase fumes are sucked into the distributor ...
http://forum.etypeuk.com/viewtopic.php? ... or#p123206

[jagwit]

Problem with the ventilation system, when the shaft seal wears out, crankcase fumes are sucked into the distributor ...

Surely A LOT more fresh air would be sucked in together with crankcase fumes rendering the crankcase fumes too lean for combustion? The fresh air route being the path of least resistance (or should be).

[ReconPilot]

Peter,
The Flash Guard was not fitted to S3 E-type dizzy units. IHMO Jaguar tried to fix their "mistake" on later XJS and XJ12 motors outfitting them with the Flash Guard.
If you have an Official S3 parts manual you'll note there is no depiction for a shaft seal within the dizzy. Trust me, Lucas did install a seal on the shaft for the purpose of keeping crankcase fumes from migrating into the dizzy. Yes, there have been small explosions where those fumes have ignited, blowing the dizzy cap off! Over time that OEM seal becomes hard as a rock, ineffective, allowing fumes to penetrate the dizzy. The result -- KABOOOMMM. How much good the Flash Guard did is debatable. I've seen several melted Flash Guards that were installed on S3 E-type dizzies without the seal mod. Regular maintenance on the dizzy is your best insurance.
Enthusiast have replaced the OEM seal with a Viton Chicago Rawhide seal. You'll have to search the archives for the part number. If you do a tear down of your dizzy and find the OEM seal, replace it.

Stay Safe and Happy Trails,

Dick

Don't let the Old Man in ! ! !

[Fspp369]

Thanks Dick for that, I should mention that in the original post I forgot to say that I have an efi v12 from an XJS that had done 42k miles when it was removed, following an RTC! So perhaps the seal, if it’s there, is ok. I’ll take a look when I’ve got to the engine , at the moment I’m into the bodywork.....may be here some time!!
I wouldn’t have thought drilling holes in the dizzy was a cool...te he... thing to do, thinking condensation etc etc.i do know that some caps come with grommets and such mine didn’t.
The debate continues, I may just put my guard in the drawer. Watch this space.

[lowact]

I was told that the flash-guard in dizzys of HE engines was extra protection for the electronics (reluctor sensor) against HV arcing between the rotor and the terminals (if badly tuned). Not needed for preHE 'cos the coil is relatively low power. For HE the power was boosted (twin coils) to be reliable with the higher compression.
Before 1980 efi cars had a trigger circuit board in the distributor. Later cars didn't, instead the flash-guard was introduced, mounted in place of the efi trigger board.

[Fspp369]

V useful info.

[ReconPilot]

Indeed, Very good info. Having never experienced work on an EFI motor the Flash Guard makes sense to protect internal electronics. Never too old to learn from other's experiences!!!

Question: Does the Official Jaguar XJS Parts manual show a breakdown of the distributor? If so, is a shaft seal depicted/Part Number? XJ12 series cars did have the seal but, like the S3 E-type, it wasn't depicted in the parts manual drawing!

Stay Well and Happy Trails,

Dick