Was reading through an old copy of Jag driver where it was said that replacing Stroms with a new set of SUs would give a 40 BHP uplift ….sounds a bit optimistic ( IIRC a review in 68 gave a figure of 168 bhp for an emissions car , as compared to around 195 for the SU equipped version ). One thing Im puzzled about - with the SU inlet manifold the tract from the carbs to the inlet valves is nearly straight ( ok it has a gentle curve ) , but on the Strom version , the mixture looks to go round a couple of 90 degree corners before it gets to the valves - not sure why they did it this way - must make it more difficult for the engine to breathe and produce less power as a result
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Well they fitted two carbs instead of three, but the inlet ports remained the same so given that the carbs are laterally separated further from the head ports, flow needed to go through a couple of turns.
My Triumph GT6 was an inline 6 with two ZS’s. I actually thought the intake manifold was kinda neat, given that the head had six intake ports arranged in three pairs. The runners from the front carb went to the front two and the forward one of the middle two, in such a way that all three were the same length. Same for the rear carb.
My 69 Series 2 OTS came from Texas with Strombergs. It ran OK-ish but as it was the first and only E I’d ever driven I assumed that was how it was.
I have a friendly very local tuning guy so took the opportunity to put it on his Dyno. As you can see from the attached PDF It was clearly a little short of where even a Stromberg equipped E should be. So – three possibilities 1. Sort the Strombergs 2. Fit SU’s 3. Fit Webers.
As it happens, the Tuning guy is a Weber main dealer and at just under £2K for the full kit, set up specifically for a 4.2 XK engine, compared to SU’s at £5k new or £3Kish used they seemed like good value.
Fitting was straight forward only adding a fuel pressure control and gauge. They are a proper ‘mugs eyeful’ next to the engines cam covers and the intake noise without filters is glorious but best of all the increase in performance was astounding.
Again without any fiddling I took it back to the Dyno guy and it produced the second set of numbers which I have extrapolated onto the first to make for easy comparison. Since then I’ve added a 123 distributor and a set of HT leads and will one day get around to another Dyno session.
The Webers do randomly pop and spit occasionally on a light throttle and average around 15MPG but I should add that since fitting them it’s very difficult not to drive everywhere with your backside on fire.
E Type Weber V Stromberg.pdf (2.7 MB)
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Wow. Clearly your Strombergs were sucking.
I certainly hope you’ve fitted air filters to the Webers.
Nice roads around Northallerton. No wonder you have fun…
Is this on a stock engine?
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Indeed we do Peter; some of best B roads in the UK, especially over the North Yorkshire Moors.
As far as I know it is stock Wiggles. I believe it had some engine work done in the US before I bought it but no reason to believe it was anything special. Standard exhaust manifolds. Denso Iridium IW16 plugs. Compression test indicates a CR of around 9:1.
Runs noticeably better on Shell V Max Power 99RON Octane.
WOW Bob -I knew my S2 was a pooch before I made changes to S1 specs.
Now if we just had an 3xSU dyno number.
Any ignition changes from the stock 69 distributor with the Webers?
Interestingly, if you allow 20% for drivetrain losses on the dyno…220 x 1.2 = 264hp.
You don’t suppose Jaguar had Webers fitted when they rated the original E type?
Nah, they’d never do that.
The 220 number was at the flywheel David. From memory I think the drive train loss was estimated at around 15% so 190-ish at the wheels.
You would have had a hard time finding any Dyno, never mind a correctly calibrated one you could hire for an hour back in 1970, so I guess Jaguar weren’t overly worried about being a little optimistic.
I spent 15 years racing an E Type, and have competed in Autocross events with my E Type for at least 30 years. All with both Weber’s and SU’s. The only criteria to judge the difference between them from a performance perspective is lap times, and I’ve been unable to find any difference BUT, and it’s a big but, you need to compare apples to apples. The stock SU setup with UM needles, and factory issued air cleaner system is a dog. Even Jaguar admitted the air cleaner system, built for quiet, sucked 16 hp. We confirmed that on a dyno. UM needles are installed with an eye to fuel economy only - they are way too lean for performance, so if you say Weber’s burn more gas - that’s why. Install a good set of air cleaners, proper velocity stacks, and richer needles on your SU’s and you’ll see a real improvement in performance. Weber’s have certain advantages, explosive noise and acceleration from the pump jets, very smooth running at low rpm, great appearance, cheaper than triple SU’s if you are converting from Strom’s etc, and oh, by the way I have a set for sale.
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1966 Road & Track article on Webers.
Also There’s a D type for sale in the RT classifieds for $7K, and an ex Ecurrie Ecosse D type for $12K.
Hi Terry,
I think I might have asked this before so if the case, apologies. The Stroms have B1E needles fitted I believe. Have you any idea what the next richer needle might be? I asked Joe C and he couldn’t help.
Q’s:
Are they set for a stock 4.2 motor? Are they in good condition? Do they come with the appropriate manifold and linkage? If answers are ALL yes, how much?
Please PM me with answers.
Hi Terry.
Could you please pm your contact details.
Cheers Craig.
Hi Les There is an ad for these in classified: Weber carbs for E Type
As for Stromberg needles I don’t know the answer, but I do know somebody who may be able to help https://www.sucarburetors.com/
Give Rhys a call - he’s very knowledgeable and very friendly and helpful.
Funny David about a week ago I came across this same article in an old Road and Track publication reproducing their Jaguar stuff over the years. Coincidence - maybe.
I’ve had the article for years, Terry. Not a big difference in acceleration but enough given the cost. The sound alone is probably worth the effort. Maybe not the engine rebuild of an unfiltered intake tho".
Good point about putting fuel into an E. I’m going for UE needles before Joe Curto retires.
The real fun in that R&T is the classifieds. A D type for $7K? Even adjusted for time/value/inflation its a wicked bargain. Nothing cheaper than an obsolete race car, until its a vintage racer.