What happens if I remove the air pump, air rail, EGR valves and most of the vacuum lines from my 1976 XJ-S V12 engine? Will it run any differently?

I assume I do need the vacuum advance for the distributor (or an electronic ignition). What other vacuum lines should I keep? Can I recycle the air pump, air rail, EGR valves and most of the vacuum lines? Anything else I can throw out to make this engine simpler?

I have seen hot rods with a Jaguar V12 engine that only had the bare engine block, ignition, cooling system and carburetors. None of the air and vacuum stuff.

 

Can't give you an answer but I'm wanting to know as well as I'm looking to ditch weight and clean the bay up

 

I just took the entire fuel system, air rails and intake manifolds off the engine. Now I can actually see this beautiful engine.

 

It will run sweeter and luv you way more.

All of mine were/are lean and mean.

Removed were:

Air pump and plumbing.
ALL the vac junk.
AAV and balance pipe.
Over-run valves.
Engine driven fan, and the front "V" of the crank pulley.
Compact a/c compressor in lieu of the "monster".

We never had Cats on any of ours, so the exhaust was always simpler.

Vac advance from the RH throttle body underside inner port only.

Trans, brake vac, and a/c vac stayed where it was from the rear of the RH Inlet plate.

 

Foggy memory here....might be bollixing up the conversation.... but.....

Didn't the pre-HE V12s have a vacuum retard system rather than vacuum advance? if so, I'd think keeping correct operation should be part of the plan.

Or am I going back too far, into V12 E-Type territory?

Cheers
DD

 

Is the a/c compressor needed?

 

If you want AC, obviously! It also runs a fuel cooler, the cars are actually not emissions certified without AC due to it being needed for the fuel cooler.

 

What did you do for the idle speed control?

 

l think the retard/advance capsule was more a market thing Doug.
I know my series one xj12's are all vacuum retard but l thought that was an Australia only setup.

 

so do xjs without a/c not have the fuel cooler then? If I remove the air pump, and a/c compressor I can remove the fuel cooler as well? I bought the car and it didn't even have the ac belt on and doesn't look like they have had one for a while.

 

For North America certainly, there wasn't an XJS without AC from the factory. Not sure about the UK market, but I think they all had AC too. I stand to be corrected on that as I'm not certain.

Yes, you can remove the fuel cooler, or a better alternative would be to to leave it in place. Saves making up new fuel lines.

 

Is there a write up on deleting unnecessary vac lines? I have an 89' with lines going everywhere and some are just dead ends with a bolt in them besides the one for the ecu and abs computer I can't imagine why most of it would be needed?

 

Both Pre HE Fuel Infected cars were vac retard, and I simply converted to vac advance and retimed accordingly.

The E was advance and retard, and never really worked properly, and I moved the car on. Lost interest.

 

Forgot that sucker, also removed when the new hoses were made for the newer a/c compressor and 134a retro.

 

Aussie special secret, hahaha.

HUGE QUANTITIES OF ALCOHOL FIRST, everything looks and sounds better and smoother from the go get.

Balanced both throttle bodies just as I did/do twin carbies, and mine all had the BIG throttle discs.

Electric solenoid, switched from inside the cabin for cold start extra air, simple. Actually used 2 of the "extra air" solenoids that once resided in the backing of teh RH air filter box. One for each bank.

 

Every market in unique, and then there was the "try this" mentality from Jaguar along the life of the V12.

I basically removed one line at a time, and ensured it still ran, etc, then another, and so on until I ran out of hoses and junk.

Like you, most of mine was plugged, broken, etc.

This was waaaaay back, and I had no books, Internet was not invented yet, and so seat of the pants stuff really.

Once finished, MATE, they really snapped into life.

 

What is actually the intended purpose of the small diameter balance pipe going over the fuel rail and teeing off to the crankshaft breather on the left air filter housing? There is a one way valve just before entering the tee between breather and air filter housing.

 

snap Grant with the choice of a/c compressor, but I had a lug sawn off on mine

 

That pipe activates the crankcase ventilation valve. When your engine is idling, it will leave the valve closed (IIRC). Once the vacume has gone (open TBs) it'll open the valve and allow for the crank case to be ventiliated.

That is the entire purpose. You could, if you wanted to, blank it all off and have a little filter on the end instead...

 

The ABS does not have any vacume connection. You have, if refering to a Marelli car, a hose going to the ECU for the ignition. That is mandatory for the ignition system to work correctly.