SU-HIF 44 carbs

(Neville, S1 XJ12, Megasquirt ECU) #1

My S1 XJ-12 has been in storage for a while, and after recently repairing the brakes I thought I would crank it over and see if I could raise oil pressure in readiness for re-commissioning. No result but a flat battery (I hadn’t bothered to pull the plugs first). But I was annoyed to step out into a pool of petrol, and that’s when I remembered that the die-cast float chamber covers on the bottom of the SU-HIF 44 carbs it’s fitted with are badly distorted, and if the engine doesn’t run regularly they leak.

What to do? I checked and found new covers are readily available, but are the same light-weight affair and will doubtless suffer the same fate, so I decided to CNC machine replacements out of billet aluminium.
This is the inside of the bowl. It seals against the carb body with an o ring. And this is the outside:
Carbs are re-fitted now, and I’m back on track with bringing the old girl back to life again.

It hasn’t been a cheap exercise, but I’m pretty confident that the float bowls won’t be leaking in future.

(Paul Wigton) #2

Betcha there’s a market for those!

(Ole Würtz) #3

Count me in. Engine jewelry right there !

(Kirbert - author of the Book, former owner of an '83 XJ-S H.E.) #4

Seriously, that’s over-the-top awesome. Since you seem to enjoy such projects, do you think you could put together a shutter wheel for the FAST XR700 ignition system? When it was offered by Crane it came with a shutter wheel for the Jaguar V12, but since Crane went belly-up and the same ignition system is now offered by FAST, they have dropped support for the Jaguar V12.

We had a discussion of this problem here on the v12-engine forum a while back, but I don’t think anything ever came of it.

(PeterCrespin) #5

Yeah - gorgeous…and ideal for picking up added heat from the exhaust manifolds below LOL

(Ole Würtz) #6

Off course. Duh :roll_eyes:

(Neville, S1 XJ12, Megasquirt ECU) #7

Hi Kirby, I have a couple of Crane V-12 discs. I’ll have a look at it but no promises yet.

Peter you raise a valid point and I’m sure heat soak from the exhaust manifolds was a contributing factor in the demise of the old float covers. However I’m of the opinion that the heat transfer will transition through the warm-up - cool-down cycle, and that heat transfer out of the fuel will be beneficial while the engine is running, and negative when it stops. I think I’m better able to control that cool-down environment through my header wrap, programmable electric water pumps and electric fans. If all else fails I’ll just have to rely on the fuel temperature compensation facility built into the HIF carbs. While the fuel is maybe boiling away I’ll take comfort from the structural rigidity I have gained with the fins.

(Ed Sowell) #8

Kirby’s alluding to the prospect of stamping/cutting the NLA 12 slot shutter. I posted some graphics that are probably good enough for doing it. I also got a price for making them, but decided against going forward when I managed to get my dizzy back together and running with the one I have. But the issue will keep coming up.


(PeterCrespin) #9

Wrapped pipes may do the trick. Anyway, one spare Crane shutter will seal my lips on the topic!

(Kirbert - author of the Book, former owner of an '83 XJ-S H.E.) #10

Hey, if he’s got a couple of Crane shutter wheels on hand, he doesn’t need your graphics!

I’m betting that the issue with CNC’ing a shutter wheel will be creating the 12 narrow slots. If those slots could be made a bit wider, they’d be easy. Q: Would wider slots work? I’m betting they would work fine. Anybody know for sure?