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MG MGB Technical - Carbs - rebuild, recon or new?

Hi,

I've got a lot of play between the throttle shaft and the carb bodies on my '66 GT - the carbs are HS4 AUD135's. I guess I have 3 options - get my old carbs rebuilt, replace with new carbs or replace with recon carbs. What are the pros and cons of each option? I have seen replacements from £100 to £250 - what is the likely difference between these to explain the prices? Finally, does anyone know roughly how much I should expect to pay for my old carbs to be rebuilt (to compare cost with replacement)?

Thanks,
Tim
Tim Jenner

New carbs would be the best...but costly. If you can find a rebuilder who really knows his stuff, having our units rebuilt or perchasing some reconditioned units from him would probably be the best from a cost effectiveness standpoint. Get recommendations from your local car club, or other enthusiasts in your area.
R. L Carleen

I am not sure that you will pay substantially more for new carbs than you will to have somebody knowledgable recondition your existing carbs. The source for new SU carbs is not all that far from you at Burlen Fuel in Salsbury. Their web site is: http://www.burlen.co.uk/
Good luck - Dave
David DuBois

Tim. Over here, there are only a few people who are truly competent to do a quality rebuild on SU carbs. Hence, the price of the rebuilds are somewhat high. In answer to someone else's question, I noted that the cost of a major carb overhaul kit is about $100 with new throttle shafts an additional $30. If you need new throttle discs, they are extra. So, a competent rebuild might cost in the neighborhood of $300 in the US. It may be less in the UK, but competent, experienced rebuilders will expect to be paid a fair price for top quality work. So, properly rebuilt carbs are not going to be inexpensive. I agree completely with David on this and, personally, do not factor cost into the decision. It will be expensive if done professionally and correctly.

Non-professional or do it yourself rebuild. This is an option and many of us have done it before and will continue to do it. However, many of the carbs on today's cars are either old and well worn or they have been rebuilt in the past. You do not know exactly what you are dealing with and, for the first time rebuilder, results can be rather erratic. Nothing mechanical can be rebuilt an infinite number of times successfully. The first rebuild can, often, bring the parts back to as new condition. The second rebuild probably will not and subsequent rebuilds become less and less effective. This is true of any mechanical system.

New carbs cost somewhat more than a quality rebuilt set. However, you are starting with new carbs which will provide many years of quality service. Then, they can be rebuilt as good as new sometime later. In fact, they are much easier for the novice to rebuild because you are starting from new and know the history of the carbs in question. A new set of carbs, purchased now, should have a usable life of 20 years or more. This cannot be said about a set of rebuilt or reconditioned cars. Thus, the least expensive alternative, in the long run, is new carbs now (or early in one's period of ownership). Les
Les Bengtson

Tim,

£100 rebuilds reuse many parts like adjusting nuts and linkages, they just get sandblasted to clean them up.

£200 rebuilds use new parts and instead of sandblasting, the bodies are vapour blasted which deoesn't remove metal and doesn't leave grit in the fine pasages of the carb!

Go to a show like Silverstone tomorrow or Kempton Park or the Classic Car Show at the NEC later on in the year and you can buy good quality rebuilds at around £150 outright.
Chris Betson

Thanks for the replies everyone. The next show I'm going to is the Bromley Pageant and I suspect I'll be able to find some carbs there. Question is, how do you tell a good quality rebuild from a poor one?

Thanks again,
Tim.
Tim Jenner

Hi..

If your carbs have the little valves on the butterflies, you might like to consider changing them for plain ones, or soldering them up.

Don
Don

My two cents would be to bite the bullet and go for new cargs. In truth, you're probably taking the difference of two hundred dollars between rebuilt and new.

I purchased new HIF carbs for my 1980 MGB earlier this year and have been very happy with the results. The piece of mind is worth it. I drive my MGB as much as possible (barring rain) and the difference in price is nothing compared to the difference I have seen between old and new carbs.

Regards,
Kevin
Kevin

Tim - someone gave you the Burlen web data. They also do restoration and rebuilds - super high quality. They come back looking like new and working like new - I think base price is about a hundred and eighty quid plus replacement parts. Good honest service and workmanship. Brian
brian pollard

Besides guys, a hundred dollar bill is just about the same as a fiver whenst we was kids. Vic PS Just bought a new set of HS6 with lean needles installed, plus shipping for AUD$644 at Midel, OZ ( sumidel.com)
vem myers

Thanks for the replies everyone. Hopefully I'll be able to pick up a set from the Bromley Pageant on Sunday. So, I'm standing in a field holding a nice shiney set of AUD135s - what should I be looking for to see if it's a quality rebiuld?

Thanks,
Tim.
Tim Jenner

Tim. There is not a great deal you can inspect. However, these are very simple items. One Brit book referred to them as "bloody primative". Check for movement of the throttle shaft. It should move easily, but have no side to side movement (back and forth movement? it should be tight and when moved from the engine side outwards or up and down). Then, check to see that the pistons drop freely. The jets should lower without excessive pressure and return to the full upwards position without problems. This does not indicate that they will be "as new", but does indicate that they are functional. Les
Les Bengtson

Why do people seem to expeeriance such diffculty rebuilding SUs i rebuild my first SU when i was 16 admitadly it caught fire and burnt my bonet felt and bulkhead plastic ,wiring break servo all things thingas that melt actually resulting in the car being scraped out conecting pipe perished but thats just part of the process. Where is the compliacated part or rebuilding or is it just the seting up part afterwards?
mr mr

I'm not a mechanis but I refuse to believe that I cannot do most jobs on my '77B. I did a ZS to SU conversion recently which involved rebuilding a pair of HIFs. I got the video from Moss Motors and the manual from Brooklnads and off I went. Didn't burn a thing. I followed the fellow in the video, read the book, bought a pair of Su rebuild kits and Robert's your father's brother. If you get the video, believe the fellow when he says that everything else in the engine must be right for the SUs to work correctly. Try it, you'll save yourself a bundle of money.
Bob Anderson

Thanks for the replies. I don't mind most rebuild jobs, the reason I'm erring towards replacing the carbs is that I believe rebushing the throttle spindles requires a specialist machine shop? The rest of the carbs were treated to a refurb kit (new valves, needles, floats etc) a couple of years ago but ultimately they're a bit of an unknown quantity when it comes to wear and age. If I can pick up a pair of new or recon carbs for £150-£200 at least I will know that the carbs are in good condition and won't be able to blame sloppy tuning on the car instead of me! ;)

Cheers,
Tim.
Tim Jenner

Hi

Iv'e read with interest all the comments on carbs in this thread and thought I would toss in my two penny worth. When I got my gt it was running poorly, poor economy, poor power, and useless balance. I fiddled with things to make it better but I hadn't a clue what i was doing. I bought Peter Burgess book on tuning B engines and as a consequence then began to use logic. Checked the tuning and the dizzy found the springs worn resulting in 10 degrees max mechanical advance instead of 20. Modified it improvement. Looked at the carbs and discovered that the previous owner had piped the vacuum instead of from the carb but from the manifold and left the take off point underneath on my carbs open, no wonder I couldn't balance them! As recommended in the book I changed the butterfly plates to those without valves (which leak and restrict flow) changed the filters to K&N's changed the needles to AAA's bought a coloutuner and a carb balancer, set them up. It ticks over well pulls great, and I'm very pleased. The point is in the begining everyone said it's those lousy carbs giving you trouble because they are all worn out. If I had bought new then there would have been little improvement and I would have spent money uneccessary. The moral is be sure of your problem before changing, there are many checks you can make to check the extent of wear, how do they balance, how do they tune, piston drop tests etc. Be sure before you make any move.

gary
G Roberts

This thread was discussed between 21/06/2003 and 28/06/2003

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