Why did they need to install an Anti-Run-On -Valve? Was this a part of the emission suit ofequipment? Did the timing have to be settoo (advanced?) for emissions sake? Idon't see this kind of thing on other engines and I want to eliminate it. So how much trouble am I getting myselfinto. My plan is to get to carbs andheaders, that's it.

1977 XJ6-C

What opinions have you?

Thanks geneo

 

My S2 cars had them, once.

I ditched them waaaaay back.

SERIOUS MEMORY HERE.

Basically on RHD cars there are 2 wires tucked under the battery tray, and one is dead at Ign ON, and live at all other positions. This live travels all the way round the front cradle, and appears at this dump valve one side. The 2nd terminal of that valve is earthed via a "reverse" oil switch. \\When the engine is switched off, the live wire supplies volts, and the oil switch supplies earth for a few seconds, and this OPENS that valve, thus supplying huge amounts of air into the vac side of the manifold, effectively stalling the engine.

Without that valve, some engines tend to run on a tad. Our Daimler did, and timing fiddling was only partly successful, but performance did suffer. I simply got in the habit of leaving it in "D" when I switched the engine off, and that worked 99% of the time.

Idle speed is also critical, so fiddling with that speed will also assist the shutting down.

 

thanks grant. That the engine runs on at all is probably the question. Race engines don't have the valve. So, what do we have, ignition timing, valve timing, too long of an intake manifold? what carbs were you running on yours?


With no spark, ignition must be from hot head or carbon buildup.


any comments from the gallery? i'll be into it soon.


geneo

 

Series 2 cars had a big aarse flywheel that loved to rotate on its own.

My cars eventually got the S3 flex plate (tin plate by comparison, problem solved.

Add to that a very long stroke engine, etc and it just didnot shut down as we wanted.

OK, hot spots etc always cause such issues.

Carby mixture etc all play into it, and I seriously doubt there is ONE item that is the culprit.

My MK10, 3.4 S Type, etc all did it a some time, and usually in our Summers.

The old MK7 back in the '60's did it also and since it was a manual transmission, easy fix.