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Carbs - Which ones to buy?
speedyxjs - 4/3/09 at 08:24 PM

Im looking at SU carbs on fleabay but have noticed there are different types.
Im planning on modifying my current (EFI) manifold to use on my 3.6 and wanted to make sure that getting twin SU's off a 4.2 Series 3 XJ would be up to the task

James - 4/3/09 at 11:00 PM

Your fuel economy is going to be bad enough... don't you want EFI to maximise it?

Cheers,
James

02GF74 - 5/3/09 at 08:13 AM

what's the engine, make/model./year - I have SU books so can take a look and tell you what was fitted at factory.

from memory the 6 cyl jags had twin 2 inch SUs, I think the E-type had triple 2 inch.


oh, just remembered, go over to burlen.co.uk - the peeps who took over SU - they have online application page where you can enter ^^^^ info. - saves me remembering and looking in my books - it may be more up to date too.

[Edited on 5/3/09 by 02GF74]

britishtrident - 5/3/09 at 08:24 AM

I don't think it will work
(1) Jag SU carbs have no cold start facility, so you would need to fit the electrically operated SU cold start enrichment carb and its thermal switch.
(2) Your manifold won't be water heated so the above won't work properly.


Megasquirt or micro squirt it.

[Edited on 5/3/09 by britishtrident]

speedyxjs - 5/3/09 at 09:01 AM

The engine is a 3.6 AJ6
I want to have it on carbs as it looks so much nice imo.
Fuel economy??? Who cares, the car wont be used much anyway (plus i have a 50l tank ). Anyway, i want to encourage global warming so i have nice weather to drive in

ETA - i thought about megasquirt for it (i read that some bloke up north megasquirted a 4.2 Etype and is getting 48mpg combined ) but it looks quite expensive, confusing and teh horror stories i have read about locostbuilders trying and failing to set it up.

[Edited on 5-3-09 by speedyxjs]

britishtrident - 5/3/09 at 09:57 PM

Sorting out a Mega Squirt is nothing compared to trying to find the most suitable SU carb needles ---

paulf - 5/3/09 at 10:31 PM

You could always use the SUs as throttle bodys and discretely fit a set of injectors.
It is much easier to set up injection with an AFR meter and PC than having to guess at different needles and springs etc.
Paul.

quote:
Originally posted by speedyxjs
The engine is a 3.6 AJ6
I want to have it on carbs as it looks so much nice imo.
Fuel economy??? Who cares, the car wont be used much anyway (plus i have a 50l tank ). Anyway, i want to encourage global warming so i have nice weather to drive in

ETA - i thought about megasquirt for it (i read that some bloke up north megasquirted a 4.2 Etype and is getting 48mpg combined ) but it looks quite expensive, confusing and teh horror stories i have read about locostbuilders trying and failing to set it up.

[Edited on 5-3-09 by speedyxjs]

coozer - 5/3/09 at 10:37 PM

What about bike carbs? Same principle as SU's but easier to setup and better mpg...

ss1turbo - 6/3/09 at 07:04 AM

quote:
Originally posted by coozer
What about bike carbs? Same principle as SU's but easier to setup and better mpg...


It'd look like the underbonnet of a TVR Speed Six..

The injectors-inside-carbs has been done a couple of times by people who want the "factory" look. Think there's an MGC somewhere that had a pair of SU's as throttle bodies, but port injection. A nice tidy cover over them and you'd think it was carb'd unless you looked very closely.

The only HS8's i can think of with a cold start/choke on them are those from a Rover 2000TC (robbed for many a Dolomite Sprint). Jag and RollsRoyce ones came with an AED (effectively an additional, very rich carb which chucked even more fuel in when cold) from memory.

I'd keep injection, but try and hide it; then use a couple of SU's just to throttle the air...

speedyxjs - 6/3/09 at 08:48 PM

Ok, what bike carbs are best?