Does anyone have any experience with this conversion?

What jets should be used.

It's a long story. The engine of my E-Type was swapped out and have until now, not been able to get it to run. It misfires up to 3000 but when the main jets kick in, its OK. Compression is a bit down on one cylinder. I have replaced rings, sleeves, bearings, valves, valve guides and valve seals.




I'm not very good at this so be patient if I don't supply sufficient info.

The car I have is a 1972 E-Type Series 3 that had the motor switched out with a 1986 ? HE. by an ignorant expert. For the past 5 or so years I have been trying to get it to run. First with the Strombergs and now with these Webers.

If I cant get it to run properly I will look for a standard V12 or a fuel injected one that is running. I would prefer not to give up and fix it.

Any suggestions would help

 

Eric,

Despite being an E-Type, I think our experienced V12 owners in XJS forum are those most likely to have the knowledge to resolve this issue. I've copied the information from your Intro to this new thread.

Graham

 

Some points:

1. the combustion chamber configuration of the HE engine makes it entirely unsuitable for carburetors. It relies on the atomisation from the injectors to give a burnable mixture around the spark plug. The reason your engine goes OK on the main jets is that it is getting enough fuel vapour round the spark plug (which is very recessed in the chamber) to make the engine run. The HE relies on a locally concentrated fuel area immediately round the plug (which WILL light as it is rich enough) to burn first, and in so doing set alight the VERY weak mixture elsewhere in the chamber - which would NOT burn on its own.
2. tuning Webers, let alone 6 of them, is a very specialist job involving many different jets and parts that only Weber specialist tuners carry. In the UK, at least, such people still exist, and to see what can be done (as in make the best of a bad job) with the HE engine, one of these specialists must be used.
3. Carburetors work far better with a pre-HE, so called "flathead" V12 engine, and if you want to keep the Webers, source a pre-HE engine, or swap your HE heads for second hand flatheads and new pistons - which are still available.
4. If you keep the HE engine, you will be far better off reinstalling the fuel injection - using either second hand factory parts, or an aftermarket system that works (not all do).

 

Eric,

My mate AKA The Pest from the West rang me back.

His is a 1988 XJS HE Coupe.

He has the OE Carby Inlet Manifolds with 4 SU HS8 carbies.

Also, he retro fitted the Carby engine camshafts, no idea where he found them.

It also has a Manual Transmission.
Originally it was a Dog, and bogged dopwn like yours is. The Camshaft change sorted that.
He played with Needles a LOT, finally found an enthusiast with a Dyno, who actually knew how to use the Dyno, and the rest was simple.and is now more than satisfied with it.

Greg is spot on with what he said.

 

A further point, that I forgot to make above, is that your Webers are sitting on VERY short intake runners. This means that there will be very poor flow at anything but high revs. At low revs, you need (a) long runners to get the air flow moving - something to do with sonic waves - and (b) properly tuned lengths at that. So your poor low rev performance will not be cured by just carb tuning, as the intakes you have are just not able to deliver airflow at a high enough velocity at low revs, to get proper cylinder filling.

 

Even if it doesn't run, it's a thing of beauty.

 

Now wait a minute Greg, Not to say you're wrong with the short intake runners, but didn't the V12 Ferraris of the late 60's use almost the same exact set up with the Webbers? I'm not a Webber Expert by any means. But they made it work??? I'm thinking as Grant mentioned the cam may have a big effect on all of this??? It raises more questions then I can answer. LOL!

Jack

 

Jack
No idea, but I expect you are correct; BUT Ferraris did not have the HE combustion chamber; plus Ferraris of that era were semi-undriveable at low revs/in traffic.

 

Thanks,
I think I'll sulk for a while.
I am in Cape town and do not know of any weber experts.
It seems as if only one of the carbs is playing up at low revs. It seems to be the one with the lower compression. I will try different settings and jets and see if I can get it right.
I might be able to find fuel injection ( have to buy the whole engine) but no guarantee it works.

 

what camshaft did he use?

 

Eric
You could try asking Rob Beere at Rob Beere Racing, very decent guy, if he has any data on Weber jets, or any advice on how to proceed, they used to race a very heavily modded V12 E Type on Webers.
Rob Beere Racing: Performance Jaguar Parts

 

Greg,
I will mail him today
Tks
Eric

 

Are you certain that your timing is set correctly and that the mechanical advance is working? A stuck advance could also cause poor low speed running.

 

Doug,
I have double- checked the timing and the distributor is a new upgraded one from SNG Barratt.
I think the problem lies with the Jet size ... I don't know which one's to use and have tried downsizing with limited effect. It still runs rich.
Not given up yet.
Eric