I just bought a signal red 1974 xke roadster with manual, wire wheels with removable hardtop with 28,000 miles. It has been in dry storage for over twenty years. It has no rust and except for a little garage rash looks like an 8 inside and out. I have restored the gas tank, rebuilt pedal box and replaced the master cylinder and clutch master cylinder. I am rebuilding the Zenith carbs and replaced some of the water hoses. ( Should I put SU carbs on and ditch the Zeniths?) I have replaced the oil and filter. I filled each cylinder with Marvel mystery oil and let it sit for two weeks. I looked in the cylinders and it was apparent it was running way too rich for a long time. Lots of carbon build up. I replaced the plugs. The engine starts immediately as proof of life, but I only let it run for a few seconds. It sounded awesome. I am trying to get away without replacing the brake servo and pressure differential warning actuator. We'll see. I think I am going to have to rebuild the front calipers. I hope I will not have to do the rear. That may be a bridge too far. I am concerned about the radiator sitting that long. I am going to back flush it, but perhaps I should just recore it now. I am replacing the rubber fuel hoses but it is getting overwhelming. I am trying to get it running to evaluate what it really needs. Any advise is greatly appreciated. I need advice on the best tires to put on the car. The size is hard to find. Should I go to 205 65 V15? I think I found a unicorn. I just hope it doesn't kill me.

 

Hi @egold56 sounds like you've made a great start to what will be a truly superior car. As the owner of a '73 OTS E-Type that was converted to SU carbs by a PO, I do not recommend the conversion. In fact, I'm commencing a conversion back to the original Zenith Strombergs once I've rebuilt them (fortunately the originals were included with the purchase). The car runs ok as it is, but I see no advantage, and several disadvantages to the SUs:

• Much of the under-hood emission control and fuel piping, as well as linkages have to be changed / re-routed to accommodate. And it is very difficult to diagnose the correct routing because of a lack of other cars to reference.
• My gas mileage is currently about 7mpg. Diagnosing this problem is similarly tricky. You would think it must be running very rich, but I can't find evidence of that. Literally YMMV, but again, diagnosing it is doubly difficult because of the paucity of other knowledgeable owners with similarly configured cars.
• The fit of the air cleaners is not, well, clean. Lots of re-jiggering needed to make that work as well.
• And of course, there's the issue of originality. Something you may or may not care about.

If you do decide to proceed, I'd offer up the following:

• Let me know because I can point you to a couple of examples I've found on BringATrailer that have the conversion. The under-bonnet photos of those auctions were invaluable in helping to get the hoses right. Here's one example: 1971 E-Type with SU carbs on BaT.
• I'd be happy to share photos of my own rig as well.
• I've also obtained the installation instructions for the conversion and can share them with you if you want to take a look before proceeding.
• Keep the original carbs. If for no other reason than they could be included in a sale down the road by your heirs .

Good luck!

Rick

 

Now that I have taken off the carbs I am shocked at how many vacuum hoses and connections there are. Given four carbs and leaks are the nemesis of tuning, I can't see how these carbs work for any length of time. SU carbs look like the better choice if you patiently seal off each of the emissions vacuum hoses and ports and remove the airpump etc. to simplify the entire works. The zenith carbs are made with the emission attachments and quite frankly unless perfectly maintained I doubt the zeniths with all of the emissions connections will be reliable.

 

I've had very good luck with my original Zenith carbs with the exception of a few O-rings that have degraded largely due to ethanol laced fuel. You're quite right that the rubber hoses all need to be in good shape but that's a relatively simple replacement job. The trick is to run your car frequently and keep the fuel fresh. I try to drive my car at least every other week, and at least so far have had zero problems with my original carbs (knock on wood).

 

I'd definitely recommend not removing all of the emissions & vacuum hoses etc. without understanding what each one does.

That's because some of them serve the purpose of recirculating gas tank and engine fuel vapors through the charcoal cannister and/or the carbs. When I bought my '73 E-Type it had been converted to SU carbs. In the process all of the hoses, air pump, air rails, charcoal cannister and other emissions equipment had been disconnected. It stunk up the garage with the smell of fuel, and it even smelled while driving it. It was bad enough that my wife couldn't join me for drives because it made her nauseous.

So I researched the various connections and hoses and reinstalled the charcoal cannister as well as rerouted / connected the hoses that trap and/or recirculate the fuel vapors. No impact on performance, but a significant improvement in the odors. The garage smells a lot better, and my wife can now join me for drives. And that's a good thing...

I didn't have to reinstall the air rails and air pump, so the look under the bonnet is much cleaner than stock (although IMO the air rails do give the engine compartment a sort of retro-Jetsons look)

Nonetheless, I do eventually want to refurbish and reinstall the original Stromberg carbs.

 

Then of course there is this alternative to SU or Stromberg.....
EFI from a XJS. Very nice, no choke, instant cold start and run without coughing. Very nice.

 

How expensive is that? How difficult to install?

 

Now that's an awesome mod. Question: how did you pull it off? How did you source the EFI? Who did the work? What did it cost?
I'm interested!

 

There is another post on this I did a while back:

https://www.jaguarforums.com/forum/e...?highlight=efi

But briefly, AJ6 Engineering, Roger Bywater wrote a conversion guide that I used. I did the work. All the bits came from a ruined 1988 XJS engine, including the induction, injection, ECU, wiring. I had to fiddle a bit with the water rails (they go thru the carburetor inlet manifold and had to be replaced with the XJS components that don't quite fit right) and restructure the harness for component location. The Series 3 fuel tank already has baffles around the pickup to insure fuel at the pump at low fuel level and a return circuit in place. The fuel pump was replaced in the same location with a high pressure unit. The ECU is under the passenger seat, the injector ballast, control relays and inertia safety switch are located on the right side firewall. I added lambda sensors on the exhaust, all the other sensors came with the XJS hardware. I modified the airboxes to fit the frame and fabricated a larger diameter inlet horn to mount in the same location as the original.
As it happens, the history is that the Series 3 cars were originally contemplated with EFI, but development delays prevented that from taking place. The program was deferred to the XJS. So I tried to make everything look like it may have been (should have been) in 1974. If you are not familiar, it looks like it came from the factory.
Roger also will re-program the ECU for this configuration, however the XJS programming seems to work fine. He has an ECU of mine for that purpose, and he also modifies the throttle body to a larger diameter that will finish the program.
It took quite a bit of calendar time because I only worked on it a few hours a week. Full time, maybe 6-8 weeks. In my case expenses were components: replaced the sensors, had the fuel rail and injectors rebuilt, and had to fabricate a few components.
There you have it. All in all a good result.

 

Awesome persistence. When it works properly it would be great. I wonder the difference between a pre HE and He engine considering the difference in heads and efficiency.

I am overwhelmed with the original configuration of my car. Modifications at this point are too much for me. I do like originality and since this is a 28k car I am getting a lot of that. I am replacing all of the vacuum hoses and cooling hoses and learning what they do and where they go. (Nothing comes off easily) The carbs are now rebuilt. We will see if I did them correctly. I predict another four scrapped knuckles getting this car back together. Then on to the radiator, brakes, tires and wheels.

 

As an aside. What tires are you using on your car. I am stumped as to what to put on.

 

I have two sets of wheels and tires. The original steel wheels have Dunlop SP Sport ER70/R15. That's the OEM look. The alternate is alloy wheel, reminiscent of the wheels on the D-Type, I believe slightly wider and the tires on this are Goodyear Eagle HP P205/65R15. That's about the biggest tire I can get on the thing, I had to take about an 1/8" off the center of the wheel to get the tires in far enough to avoid brushing the tire side against the inside of the rear fenders. It would just brush the fender when the suspension bottomed on a high speed dip in the road.
I don't drive the car aggressively enough to be able to see any real difference in performance of the tires.

 

Following on more than a year later. On my 73 OTS I finally (as threatened) refurbished the original Strombergs, pulled the "upgraded" SUs, and put the Strombergs back on the car.

I researched and reconnected all of the various vacuum hoses and other connections. It took about 5 weeks of on-again off-again working on it. Much of that time was the research.

Much to my surprise, the car started immediately. Of course I had to go through the process of balancing the carb idle and choke settings. Once I did that and took it out for a drive, here is my experience:

• Starts better and faster
• Warms up faster
• Accelerates faster
• Runs smoother
• Less odor
• Sounds better. A real thoroughbred "burble"

And that's all without (yet) going through the process of tuning and balancing the carbs.

Of course some of this improvement may be due to the way the SUs were originally installed and connected by the PO. I have no idea their tuning history or whether the vacuum connections were optimal.

What's not to like?

Soon I'll be putting the SUs up for sale. They're very pretty, and only have about 1,000 miles on them. So @egold56 if you're still contemplating swapping out your Strombergs for SUs, I might have a deal for you! . On the other hand, if you still need help with how the various vacuum hoses and connections work on your Strombergs, I know quite a lot about it now.

All the best,

Rick

 

Thanks
after a year I have learned a lot. I am about to take off my carbs again and fix any vacuum leaks. I am going to plug the temperature compensators and inspect the bypass valves. I am putting thread lock on the starter box screws as they seem to constantly work loose. After just replacing the torsion bars and transmission mount it should be easy.