of course MG will have his retoric bs.

 

Stock seats are said to be only 7 kg. I had the driver seat out of mine a few months ago. I didn't weigh it, but it did feel pretty light. There is a lot of sound deadener that you can get rid of for weight reduction.

 

[QUOTE=Dleit53;2249830]Why the early distributor? Look at the advance curve it has compared to the advance curve of the HE
I have a distributor machine and am well used to modifying the advance curve but there is only so much you can do. I grind weights, change springs, silver solder added weights etc.
I can never replicate the same advance curve unless I use all the early distributor internals. At that point why not start with that?

 

Apparently on Marelli cars you can just physically turn the whole thing to Adv timing, is this in any way applicable in Lucas cars?

 

YES Van , like a chevy you can rotate the distributor to adv. or retard, but you still will have the timing curve thats built in, of course you can always change curve , summit has some nice parts for custom curves!
a DYNO would be awesome for that, but not absoluty nesessary!
ron

 

Power? It’s a function of money and skills. You can reduce a lot of cost if you can do the work. 96 MM is possible but requires special liners. And block work. Plus pistons ( more in a bit )

I have a computer program ( Performance Trends) that tells me what individual changes yield in additional power. Through careful adjustments over the last 40 years I’ve been within 2% of actual output. Before the program I’d buy parts put them in the engine, put the engine on a dyno and see if it was better.
With the program I can compare cost vs power gained. A bigger bore does make more power but the cost ( starts at $1500-2000 and goes up) is very high compared to the power gained. But by itself only has modest gains.
A longer stroke gains more power but that means machine work ( not everybody who grinds cranks can successfully grind a hardened Jaguar Crankshaft and then reharden it ) replacement rods ( and pistons) so again the cost is high compared to power gained Add approximately $1000.

Realize these may be old numbers and do not reflect minor costs such as bearings, rings, gaskets etc or any labor.

Head work such as porting Is extremely labor intensive. It’s not something that unskilled guy should attempt. It’s easy to lose power. It’s not just making the ports bigger it needs be even flowing and the right size. Plus most important, the flow between cylinders must be equal.
It could be easily 200 hours of a skilled technician with flow bench equipment. Plus the power comes not where it’s useful on the street, but the race track.

Same with regard camshafts. Jaguar engineers knew what they were doing. More lift, more duration gives more power but at high RPM. Not at the engine speed most often used on the street.

The formula changes when you are racing. Instead of I can afford this and afford that on the street, when racing its’s, I have to Do all that to be competitive.

 

Ron,
A distributor machine is absolutely required to maximize any changes made. With regard the Lucas distributor it’s not unusual to have to pull the distributor and advance a tooth or even 2 in order to get full power.


Performance Trends is the Computer program I use to evaluate Changes. It’s wonderful to be able to do a cost/ power benefit analysis before spending money.

 

Stock seats may only weigh 7 kg ( I don’t know, seemed heavier when I tore out my old interior. Does that include the power seat adjusters weight? )

But how much do you think a racing seat weighs? 10 pounds, or 2&1/2 kg

The point is there are a lot of nice things to have but they all add weight.

To go faster reduce weight first, ( that costs next to nothing) then add power.

 

Can you do that? I understood that you have to slot the existing holes.

 

The picture shows how much to drill out on a marelli system I don't know about lucas distributors I wondered if the concept is applicable to those units.

 

Power seat adjusters? Mine doesn't have power seats. I didn't know racing seats were that light. I ditched my AC compressor and saved 37 pounds (I weighed), so I'm on that path, but it needs some other stuff done before I get heavily into that.

 

The doors by themselves are very heavy. Door skins are much lighter. About 1/2 the weight of Steel skins is fiberglass and 1/2 the weight of fiberglass is Carbon fiber. Replacing a pair of doors can take more than 200 pounds of your car. Trunk nearly 70 and hood( bonnet to the British ) more than 100.
that’s for American cars. Since the British don’t use side door guard beams maybe not as much.

My point is we try to get down to 2700 pounds in race weight which is 1900 pounds less than stock. So the weight is there to remove. You just need to want to go fast more than you want the quiet elegance Jaguar’s offer.

 

Actually, the XJS does have side intrusion beams in its doors, and did from the start.

 

my 1978 XJS did have side intrusion beams, i cut them out , a guess about 10 lbs, sprayed the inner skin to reduce slam sound! add 1 pound!
​​​​​​ to each his own,
MG is much to radical in his ideas, for a street car!

 

You are right Ron . I do state repeatedly that I’m a racer. Weight is my #enemy. So yes I’ll focus on that over any other consideration.

 

MG its very simple ,always has been , POWER TO WEIGHT RATIO!
its nothing new!

 

Hi everyone. Does it make sense to Polish the pistons and combustion chambers? Or monkey business?

 

No, it does not. But Total Seal rings are meant to be good!

 

That is, just remove all the irregularities and that's enough.
No mirror shine needed?

 

Nothing at all needed if they are as-factory.