Opinions on the Weber 500 Carb

oport

oport

Member
Hello,

since i need to put new carbs on my P6 V8 Engine to fit it under the bonnet of an MGB GT, i spoke with RPI. They are heavily promoting the Weber 500 kit for the Rover Engine. Since i have no experience whatsoever with this carb, i am interested in opinions from people who either have it in their cars or have hands on experience with it.
How is it running under cold/hot engine environments, how is restarting a hot engine (heard some rumours about hot starting problems)?

Any information is appreciated.

CU Olaf
 
Have one in mine and it's a great upgrade only problem is hot restarts. More power instant pick up when accelerator is pressed good fuel consumption also.

Graeme
 
I had one on my old SD1. Wouldn't start properly from cold, no one could find out why. Wouldn't start when hot, no one could find out why. Made the car fairly swift when it did eventually start though, but with some loss of refinement and more noise etc.
I'll be sticking with SU's in the P6... :?

I didn't get on with it particulary well, but many others have. Depends on what you want really (SU's or EFI for me though).
 
I have the strong impression that Webers do not work at all well "out of the box". Equally people who have gone to the trouble of playing with the jet sizes and/or getting them set up on a rolling road that understands the engine and the Weber seem to be very pleased with them.

My strong guess is that those who sell the carbs don't have a menu in front of them for how to jet them or set them up for all of the permutations of Rover V8 - and there are a great many! My guess is that most carbs are sold with jets that will get you away from first fire up but are much less than ideal for most engine specs. Even in P6 world there are a great many specs commonly fitted to cars - viz 10.5:1 small exhaust manifold, 10.5:1 large exhaust manifold, 9.75:1 large and small manifold, SD1 heads with small and large manifolds. And that's before you start debating who has fitted what non standard cam, standard or sports air cleaners and all the other capacities imported from Range Rovers et al.

By contrast SU's by their design cope much better with these variations, as do the the common EFi transplants. But it's worth noting that BBLongman felt it necessary to go to a rolling road to set up his aftermarket EFi!

Also you must remember that many people have fitted the Weber as a result of not being happy with their engine in the first place. So it is likely that there was more wrong than just elderly SU's. Changing an engine didn't solve Gareth P6's problems - it took a new distributor to do that. So perhaps people who have trouble with the Weber are unfairly tarring it with other problems in their particular installation.

Moral of the tale is that you shouldn't expect to have a working car just from shelling out for the carb, but should allow another couple of hundred quid to get it rolling road set up after fitting (which should also sort out any other problems in the engine along the way).

From a technical perspective all carburettors are flawed in one or more load scenarios. SU's are an exceptionally good compromise, but are poor at full throttle and less than ideal in response to a sudden power demand. Webers are excellent at full throttle and are very good at sudden power demand, but are less good at steady part load running. If you want your cake and eat it the only solution is a well mapped modern EFi with the maximum available number of sensors (ie including lambdas in both bank's exhausts etc). This incidentally excludes the commonly used ex Range Rover systems!

Chris
 
I had a the weber fitted to my car before I went to EFI and although there were lots of roary noises and plenty of acceleration (possibly only perceived as a result of the noise) It was essentially a bit of pain in the bum. My main bugbears were starting, poor idle and a lot of smells from petrol evaporating when parked up with a hot engine.

If I could go back and do it all again I'd stick with SU's!

I'm very happy with EFI but as Chris said it still needed to go on a rolling road to be set up correctly. There is no other way to do it and the same is true of carb engine. I never had the weber set up on a rolling road but in retrospect should have done. The chap who mapped my EFI set up did say that they had got some good results with the 500 on RV8's.

If your putting it in MGB you obviously have some problems with the standard SU set up from the P6 so you have to do something. I'd recommend EFI over the 500.
 
My Weber is certainly more responsive than the SUs, but there are very few people around these days who know anything about them. I took it to 2 rolling roads, who both told me that they knew how to set them up, only to find that they had been a little over confident in their self opinion. One of them told me that the Weber was no good as you could not get the jets for it and I would be far better off fitting an EFI system. Strangely, he just happened to have an EFI system for sale :roll: The other put it on the rolling road then phoned a mate who knew something about V8s.

If you want one, don't forget you also need a manifold (The JWR Dual port is very good).

Have you the space under the MG bonnet?

Cold starting - no problem. Hot starting was once a pig, but fit the Mr Gasket heat dissipator (how do you spell that?) and it starts straight away, every time.

Jets and control rods (needles) are fairly easy to get and changing them is easy.

The big pancake filters do give a fair bit of induction roar.

If you wish to upgrade your engine, the first thing to upgrade would be the igniton system, not the carb.

As far as operating in a hot environment, you may be better off fitting a cold air induction system as this will give more usable power and produce less noise.

Richard
 
BBLongman said:
The chap who mapped my EFI set up did say that they had got some good results with the 500 on RV8's.
Click to expand...

Haven't got his name and phone number, have you?
 
Certainly have, the guy who does the tuning is called Adrian. The garage is a bit of shack to look at (aren't most of them) but I wouldn't hesitate to recommend him. He keeps the jet and spring sets in stock for the edelbrock range.

Not a million miles from you if your in Sth Yorkshire. Mention where you got the recommendation from if you go for it.

A B Garage,
Unit 167B Castle Close, Hawarden Ind. Park, Manor Lane, Hawarden, CH5 3PZ
M-F 9am - 6.30 pm Sat 10 -5 pm; Tel: 01244 537701;
 
Thanks BBL

Unfortuneatly Sparky was SORNed on Monday til May, but I will get in contact with this chap.

Richard
 
chrisyork said:
I have the strong impression that Webers do not work at all well "out of the box". Equally people who have gone to the trouble of playing with the jet sizes and/or getting them set up on a rolling road that understands the engine and the Weber seem to be very pleased with them.

My strong guess is that those who sell the carbs don't have a menu in front of them for how to jet them or set them up for all of the permutations of Rover V8 - and there are a great many! My guess is that most carbs are sold with jets that will get you away from first fire up but are much less than ideal for most engine specs. Even in P6 world there are a great many specs commonly fitted to cars - viz 10.5:1 small exhaust manifold, 10.5:1 large exhaust manifold, 9.75:1 large and small manifold, SD1 heads with small and large manifolds. And that's before you start debating who has fitted what non standard cam, standard or sports air cleaners and all the other capacities imported from Range Rovers et al.

By contrast SU's by their design cope much better with these variations, as do the the common EFi transplants. But it's worth noting that BBLongman felt it necessary to go to a rolling road to set up his aftermarket EFi!

Also you must remember that many people have fitted the Weber as a result of not being happy with their engine in the first place. So it is likely that there was more wrong than just elderly SU's. Changing an engine didn't solve Gareth P6's problems - it took a new distributor to do that. So perhaps people who have trouble with the Weber are unfairly tarring it with other problems in their particular installation.

Moral of the tale is that you shouldn't expect to have a working car just from shelling out for the carb, but should allow another couple of hundred quid to get it rolling road set up after fitting (which should also sort out any other problems in the engine along the way).

From a technical perspective all carburettors are flawed in one or more load scenarios. SU's are an exceptionally good compromise, but are poor at full throttle and less than ideal in response to a sudden power demand. Webers are excellent at full throttle and are very good at sudden power demand, but are less good at steady part load running. If you want your cake and eat it the only solution is a well mapped modern EFi with the maximum available number of sensors (ie including lambdas in both bank's exhausts etc). This incidentally excludes the commonly used ex Range Rover systems!

Chris
Click to expand...


Great summation there Chris. Like all things they arnt plug and play even Mr Gates would have to admit that! However you have to weigh up which is the easier to get usefull results from with the minimum of BST (blood sweat and tears) I opted for the Weber as it is a stand alone solution not an invasive injection system but that was just because I wanted less BST (and I am at heart lazy).
Ultimatly the best system would be the mapped injection system and if an off the shelf fool proof works with no effort system were out there I would have one .

graeme
 
Hello,

thanks for your impressions and advice. I will try to elaborate a little bit why i am considering the Weber 500.
First point: Space under the bonnet. Not much actually in an MGB GT, so a flat setup is necessary. The original manifolds for the SUs are almost impossible to get.
The SU carbs i have on the engine are due to a complete overhaul (like the engine itself), so i have to decide what to do. A Weber 500 setup with an Offenhauser 600 Manifold is more or less the best solution regarding to bonnet clearance. EFI is no alternative, because it would void the classic car status in germany, which has huge tax implications. So, carbs it is.
Since the engine will be done properly anyway, i am willing to take a chance with the Weber. I think when i listen to you and other people and take care of a proper heat insulation i will eventually get it to work. And if anything else fails Chris from RPI promised to come to germany and fix the setup :) :)

CU Olaf
 
One other suggestion Olaf - would it be acceptable to use an MGC bonnet to achieve clearance for the SU's in their Rover configuration? C bonnets are available new so shouldn't be a sourcing issue.

Chris
 
Hi Chris,

yes, thought about it too. But there are a couple of issues with that.
The car will stay at least for a while as a rubber bumper car. C bonnets look pretty stupid on these.
The P6 carbs are different from the original V8 carbs, so i would need a couple of rather expensive parts to make it a fit.
Since the SU carbs are due to overhaul anyway, i will rather tuck them away for spares on my P6 and buy a new carb which will fit right away for my MGB GT V8.
Seems to be the more economical route to me.

CU Olaf
 
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