So, yesterday while exploring how to replace the original distributor when the Pertronix unit arrives, I actually found the crank pulley timing marks. So, sprayed it down with brake cleaner and can now read the markings. Hooked up a timing light and fired her up. Got a reading of 13 degrees BTDC (vacuum still connected). Did not want to unplug the vac line until the new distributor goes in so left it alone.
Took her out for a spin and noticed the voltmeter reads higher than it ever did before. At idle (800 RPM) in the garage, battery voltage (and what shows on the gauge) is 14.2V. Hi-beam lights on, drops to 13.6V. Although never checked before at the battery, it always seemed to register about 13 V at the guage. The output seems stable at around 14.2V even at 2500 RPM.
Since I did nothing except spray some cleaner around and wipe down the pully area, I have no idea what caused the change, unless I moved some wiring down there while cleaning. Any thoughts and is this reading higher than it should be?

 

Nothin' wrong with 14.2v

The low side of normal/acceptable/typical is about 13.6 volts

I can't explain the increase unless the belt was slipping and your cleaning efforts made the belt grip again

Cheers
DD

 

The fiddle factor as Doug calls it.

14.2 is topside on most systems of this era. They settle to around 13.6- 13.8 after about 30 minutes. BUT, there is so much depending on that. Lucas components and wiring for starters.

Cleaning anything in that area can do what yo have now, and probably some grime on the belt?? and now its gripping a small tad more, thats a stretch of the reasoning, but its out there.

Moving wires etc more the culprit.

I would put a DVM across the battery with it running and see what its actually showing.

Over 14.2 and 14.2 actual for long periods (as in hours) will damage the battery.

 

If the battery is low on charge, the alternator will compensate by raising the voltage. When the internal resistance of the battery rises (eg. the battery picks up current), the voltage will drop to 13.6.
This is normal behaviour and should not be corrected.

 

My vote is Leave it alone, all is well.

Wire wiggle or belt and pulley cleansing. the brake cleaner worked as a belt dressing and made it "stickier " and thusly reduced slip.

I don't get the 13 BTDC with the vacuum connected? Sounds like that is where it oughta be with no vac advance. perhps the vac can is busted and your car has only centrifugal advance if any?

What is the issue with trying it with the hose off and plugged?

And, as to an issue before th Pertronix swap??

Carl

 

I'm told the timing should be 17 degrees BTDC with vac. disconnected. Mine shows 13 BTDC with vac connected.

I cannot complain, as the engine is smooth both at idle (800 RPM) and throughout the RPM range.

I need to invest in some long needle nosed pliers to reach the vac hose and not lose it if it falls. That is the only reason I did not disconnect it.

When the Pertronix arrives I will have to set the timing at 17 BTDC.

 

"I need to invest in some long needle nosed pliers to reach the vac hose and not lose it if it falls. That is the only reason I did not disconnect it.
When the Pertronix arrives I will have to set the timing at 17 BTDC. "

You will set Pertronix at 10 BTDC with vacuum disconnected
Take a golf tee and drill 1/16 hole in head ... insert 18 inches of safety wire; and you can plug vacuum line and retrieve itwhen you are finished with the timing set up.
Rgds
David

 

Thanks David, You said set to 10 DTDC disconnected? The standard is set to 17 DTDC as I understand. The car now runs at 13 DTDC connected and runs fine. Once I get the unit I will set as you say at 10 BTDC disconnected and plugged at 800 RPM.
Do the actual Pertronix units differ as to their settings. Mine will be the D171618 as recommended by Pertronix.

 

Hi Iramphal,

Manufacturers (Jaguar in this case) timing for this era of vehicles was based on leaded petrol.

We use unleaded petrol, so timing doesn't need to be quite so advanced.

Cheers,

Nigel

 

Ian,
The mechanical advance range is greater in the Pertronix distributor curve for jaguar engines, so they set idle at 8-10 degrees. There will be instructions with Distributor so setup is two wires and timing. When you get in the range of 2000-3500 RPM, both the OEM distributor and the Pertronix total advance will be very close to each other. ( I have seen recommendations to set it at 8 degrees, but I would set to 10 degrees for low octane & low compression EFI XK engine)....Remember they don't technically market to EFI systems, only carb'd engines
Rgds
David

 

Hi David, Thanks for the clarification. Once the Dizzy arrives I'll let you know how it goes. Will follow your initial recommendation of 10 degrees and see how that works.
Cheers, Ian