1800: Webers or SU Carbs

[classicswede]

If you did not notice much of a power difference then there must have been something wrong with the setup.


As your car is a Jensen produced car then I can see the sense in putting it back to original. You would want the early version SU's with 2 bolt air filters. You would also want to go back to a early B18 engine with correct age dizzy dynamo and rocker cover etc.
Are there other modifications? If there are lots of mods it will probably be more work than it is worth going back to original.


The big question is what do you want from the car?

[Steve121]

nothing wrong with the setup, overal power slight increase, torque, a BIG increase.
Had standard B18 valves with K-cam and head mods, bigger valves would have been the next step for mine.

[redcar]

hi, i dont want to hijack a thread, but in the same vein, i need to do something about my twin SU's. the throttle shafts are worn and will require attention soon.

Seeing as ireland is the most expensive country in the world for this sort of thing, would it be worth getting them overhauled for about €400, or buy the downdraught weber kit from the US for about the same money? like this: -


http://www.ebay.com/itm/300916044324...fe7224&vxp=mtr

noise is not my biggest concern, but anything to improve my mpg average is...

[Burdekin]

Gareth is it only the shafts that are worn? If so just do it yourself there is nothing hard or complicated and the guys at SU are helpful. I did a write up in my Amazon build but pics are gone but could repost if interested? If the shaft bush/housing is worn I maybe able to help once I get my milling machine properly set up but won't be for a little while.

[940_Turbo]

That Weber down draught kit is as best a step sideways and in truth probably a retrograde mod.

I can see the point in the twin side draught Webers, I'd use them on a fast Rally car for instance. That downdraught is strictly for incompetents who can't figure out how to balance a pair of SUs

[redcar]

Originally Posted by 940_Turbo

That Weber down draught kit is as best a step sideways and in truth probably a retrograde mod.

I can see the point in the twin side draught Webers, I'd use them on a fast Rally car for instance. That downdraught is strictly for incompetents who can't figure out how to balance a pair of SUs

tbh, i think i fit into that category quite well, 940...

thing is, i can spend a shed load on an irish refurb whose quality may be questionable, or just buy a brand new system for the same money and probably get a few quid back the SU's.

you guys have it easy in the UK with regards to choice of craftsmanship. we have 1 guy on our island who knows he has a monopoly, so price = quality does not always tally.

mitch, i the shafts rattle around a little in their housing, my idle is iffy and fuel consumption poor. i dont think they've been done before, so i think the bores need bushes/liners, etc. and whilst they're out, i may as well get them fully overhauled. i'll have a dig through and see if i can find your post on this.

[Derek UK]

For Euros 400, or less, I'd think that Burlens would bring your carbs back like new including having all the metalwork replated etc. If you think you just need new bushes and shafts it would be a lot cheaper and there are several other companies that can do this too. Breaking the carbs down to bodies only would reduce your postage costs which for you is a factor. I'm sure that your man over there, monopoly or not, would also be able to do just the shafts. A pair of worn carbs could also be bought here in the UK (£30-50?) and sent direct for refurb to your requirements before being sent to you, and could also be considered.
As said the Weber downdraught conversion is a bit sideways and is rarely good straight out of the box. Jetting to suit the car can be time consuming and costly if you want the best out of the install.

[P1800Ray]

Great feedback guys ! I've tried a regular P1800, one with high lift cams (on SU - it idled at 2000 revs !) and my standard B20 on Webers and they all seem similar in performance to me.

Inevitably, the decision is whether to go original or make it more useable. With a B20 engine and (I think) a B20 rad, I think useability is my preferred option. The Webers are loud and the car is in an integral garage so it would be nice to reduce the smell of petrol. I guess the other option would be to port the head etc so that the Webers have something to play with. Anyone done this ? Guide price on cost ?

The Weber set up has been tuned by Track n Road in Essex who I know from experience are top notch at this sort of stuff.

[Faust]

Originally Posted by Derek UK

As said the Weber downdraught conversion is a bit sideways and is rarely good straight out of the box. Jetting to suit the car can be time consuming and costly if you want the best out of the install.

I have a Weber 32/36 downdraft fitted to my car (B20 engine) mated to a Simonz 4 branch manifold, performance exhaust and K&N air filter.

I did have twin SUs fitted but they were past their best and I was tired of tinkering with them. I made some enquiries about having them re-furbed, but the prices I received from Burlen, Southern Carbs & some local specialists were quite high (ranged from £250-400) which made me think that the Weber was good value (450 for the brand new kit including inlet manifold).

I know the Weber downdraft is not a popular choice (they seem to love it in the states for some reason) but I’ve been really pleased with mine. I set it up properly when I fitted it – it was jetted correctly out of the box – and I’ve not had to touch it in 18 months apart from dealing with a dodgy choke cable which was not letting the chokes open and close leading to excessive fuel consumption (hardly the carbs fault, mind).

As it’s a progressive carb (one choke opens, then the other under hard acceleration) I find the fuel economy is better than I was expecting. About 25 mpg in ‘spirited’ town driving and approx 37 on motorways at a steady 70 (I use super-unleaded and Castrol Valve master plus). The performance of the car certainly surprises a lot of moderns, but as I’ve not driven an Amazon with decent SUs fitted, I can’t really compare the two types of carbs re. performance... But what the hell, I’m more than happy with the amount of power my car has got!

In fairness I’d say that the SUs are probably the better choice for power, but as (and I freely admit it) I’m not used to working with them & I find them hard to adjust, I went for the Weber as it’s a ‘fit and forget’ part.

I have not regretted it one moment and I’d certainly recommend the kit to others.

This is a good review of the kit: http://www.vclassics.com/archive/weber.htm

[david sharp]

I totally agree with Faust. I fitted the 32/36 DGV kit to my B20 122S three years ago and it has been reliable and trouble free ever since.
I have today completed the mods. I discussed in the "KG10 camshaft" thread earlier this year and am off to Peter Baldwin's rolling road next Monday morning for the final setting-up. It will be interesting to see how this carb. copes with my modifications although I do have a good pair of SU's in reserve.

David (another incompetent!)