Hey folks, I'm considering doing this to my '73. I'm aware that it's not gonna magically turn it into an E-Type, but the fact that I'm into a complete bottom-end rebuild (all 6 liners were cracked) and it's already 9:1 compression with a pr. of 2" SU's I thought hell, why not just get all silly-like.

It seems that locating a complete 420G setup is the only reasonable way to go, but before diving into that I thought I'd see what your thoughts and/or experiences are on this.

...and fwiw, buying a complete new setup is out of the question...waay too pricey.

Thanks in advance!
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A friend of mine (sadly now deceased) fitted triple SUs onto a series 3 and it was very successful.
Obviously, he changed the fuel pump etc. from the original high-pressure fuel injected system.
He claimed that he had improved mileage per gallon and improved acceleration.

 

Hey thanks for that Bill....just the kind of info I'm looking for.

 

OK Chris, I am hoping to shine some light on your proposal. To give you some background, many years ago I had an E type which I tuned as a performance car. I have now had a 73 series 1 (auto) for 40 years. My current project is to try to recall just part of the E type driving experiences by converting this car to manual transmission. Like you said, I do not hold out great hopes.
The main benefit of the triple setup is in the manifold. It will perform way better at high RPM. The twin HS8s on my XJ6 give good performance in the lower range and also excellent fuel mileage. I am not considering changing this setup.
I just want better response from the transmission, and will work towards a really neat exhaust note. Those are my objects.
I cannot ever imagine reproducing the driving experience of the E Type that I had when I was younger. I drove that car like it was the Mille Miglia. The enforcement technology of the day was not up to the performance of the car and that is how I got away with it.
In summary, I do not think a triple SU setup will help you unless you already have a manual gearbox and are looking mainly at high end performance.

 

You will want to look at the distributor also, as by 73 they were are tailored to smog curves, not performance. Go to XJ6 S3 distributor (requires an S3 ignition amplifier) but has good performance. Or go with Pertronix after market distributor (high performance, with matching coil).
Rgds
David

 

To both Mekon and David...

My car already has a manual gearbox (with o/d), as well as a Pertronix ignition module.

The biggest issue I'm facing, seems to be finding a set, with the manifold etc for an amount somewhere south of stupid money.

We shall see....hope springs eternal.

Thanks everyone so far!
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E-BAY
Jaguar 4.2 Triple Carb Intake Manifold 3.8 MKX MK10, XJ6 Conversion

UsedUsed
Time left:5d 12h|Saturday, 08:24 AM
Starting bid:
US $125.00
Would not expect too many bidders
Bought mine for $175 about 7 years ago
Rgds
David

 

Triple SU's are over carburetted for the engine, so I wouldn't bother. A friend of mine built up a 4.2 race engine for an E Type and actually achieved 265hp - with 12:1 compression and 115 octane fuel. Even at full throttle the dashpot pistons had not lifted all the way, so for a road car a pair of SU's would not be a restriction.

The triples look pretty, but there isn't a technical advantage to having them. Consider that on a dyno a good triple E Type engine in standard form is about 180-190 hp. The intake area is about 9.4 square inches on the triple SU's. The most powerful version of the engine was the EFI XJ6, with a 65mm throttle body producing 205hp, or potentially 230hp without the restriction of the air flow meter. That works out to 5.1 square inches for the EFI engine. Throat area isn't directly comparable between a carb and EFI throttle body, but the engine doesn't need the size of the triples to make power.

 

I did the 420 manifold on 1968 XKE 4.2 smog engine, but used 3 ZSs as apposed to the traditional 3 SUs; the problem with the SUs was bonnet clearance. Two carbs flowed enough for the engine performance. The improvement comes from the near straight, "balanced triple manifold", as compared to the dual carb "log manifold", with 90 degree turns.

IMO, the 420 manifold flows better than the standard triple E manifold, as it has less curvature between cylinder head and carb body.
On a XJ6 you would not have a carb height clearance issue; you just need to go to Triple SU needles, jets and dampener springs.
Rgds
David

More discussion on the project:
https://www.jaguarforums.com/forum/e...retion-214389/

 

I think you mean a 420G, as opposed to a 420? The 420 is the small saloon that has the same 2 carb manifold as the early XJ6's. The 420G/Mark X is the large car that came with triple carbs.

 

Yes, David84XJ6 had me researching 420 manifolds to see if there was anything special about them!
420G/MkX manifolds are available at a reasonable price, but getting the 2" SUs may be the problem. Used they seem to go for around $300 each over here, with a re-furbished set of two at $1800.

 

I found a couple of 2-inch SUs off a S2 XJ6 in my shed. I would love to get $300 each but will take that for the two.
Cheers

 

Hey thanks again everyone for chiming in...I've been going back and forth on this for a while.

It's basically down to wow-factor vs data on this one - part of me says screw it, it looks fantastic. And, with a bit of work, it'll run more than well enough to not be a distraction. However, my competition experience (and seemingly terminal pragmatism) respects the figures that Jagboi shared in post #8....that being that as a pump, the engine is quite well served with the two HD8's.

Does this mean I've decided to walk away from this, and let the facts and figures guide me towards a sensible outcome?...

...maybe, we'll see....any other ideas are certainly welcome, as the truth is that I've always had a deep abiding love of the cool.

 

It all comes down to money! Not that there is anything wrong with a nicely polished pair of Su's...

 

Had my 2 refurbished for $1k down here….John is on the money.