MG-Cars.net

Welcome to our resource for MG Car Information.

Recommendations

Parts

MG parts spares and accessories are available for MG T Series (TA, MG TB, MG TC, MG TD, MG TF), Magnette, MGA, Twin cam, MGB, MGBGT, MGC, MGC GT, MG Midget, Sprite and other MG models from British car spares company LBCarCo.

MG MGB Technical - Fuel System Questions

Okay, replaced the SU pump with an aftermarket Holley I had in my garage (was having problems with my 73 GT losing fuel and cutting out). I have run a regulator in-line (the Holley pumps 7psi, and I put a regulator to drop it to 2psi). Now I am having problems with fuel coming out of the evaporation lines and a dump valve over by the charcoal canister. I have cleaned and rebuilt the carbs, what else could be the problem?

On a similar note, are there availability problems with the Weber carb conversion kits? I see Proper MG says that it isn't available, but Moss Motors shows the kits for sale with no disclaimer. Anyone know? Thanks all.
D. T. Barnes

D.T. - The Holley pumps are a centrifical pump and as such may needed a regulator that bleeds fuel back into the tank to regulat the pressure properly (I don't know this for sure, just an educated guess at this point, but something to check). The other possibility is that eh regulator just isn't doing its job or you have a float/needle valve problem. If asked, I would recommend a replacement SU fuel pump (one of the all electronic pumps), or one of the after market impulse pumps such as the Carter or Facet that pur out a maximum of 4 PSI. I am sending you a fuel delivery troubleshooting guide that has a list of people that can repair your old pump for you as another possible route to investigate. Good luck - Dave
David DuBois

D.T. -
When you say you installed a Holley pump "I had in my garage", how do you know whether the pump was functioning properly? Also, the regulator could be dysfunctional. I understand that SUs do require about 2psi, while Webers need about 3. I have a Holley pump and regulator on my car. I was having over-fueling problems last year - it turned out to be the Holley regulator, which can be rebuilt for about $5 in parts.
I don't know about the availability of Weber conversion kits from Moss. Weber ceased manufacturing a few years ago, however, I believe they recently began again. If the carb is not available new, you may find a used one on ebay or something like that.

Safety Fast,
Martin
Martin Connolly

Thanks for the responses, I will double check the pump. I know it is good (along with the regulator) because I bought them brand new for another project and they were still in the box they were shipped to me in, never used (used a different pump setup on the other project). I am going to try a conversion to Weber and see if I can get the Holley Red pump and regulator to work. I will also make sure I plumb in a better fuel pressure gauge (my current one has to big of a range for me to feel comfortable onthe reading). Any other suggestions?
D. T. Barnes

Don't right off the SUs yet! A rule of MGs goes something like "new part is not the same as good part". I'm thinking that if the pump is pushing past both needle valves you are either very unlucky and have two faulty needles or leaky/maladjusted floats, or the regulator isn't doing its job. You could test quickly by seeing how much it pumps in in one minute. It should be about two pints for the SU's requirements.
Steve Postins

New doesn't necessarily mean good. I've had parts bad straight out of the box! Not saying yours are, but it's best to verify everything so you don't waste time chasing ghosts.

Don't know which Weber you're considering, but a downdraught Weber isn't necessarily a step up from SUs. It might be better than worn out SUs, but fresh SUs would be better still! ;-)
Rob Edwards

Steve, looks like you were posting as I as typing. As they say, great minds think alike.....
Rob Edwards

D.T. I would add to the group which favors rebuilding or replacing the SU carbs. I have a 68GT with twin SUs and three RB cars with the Weber DGV. Would swap the DGVs for SUs in a heartbeat if it were allowed under our emissions testing standards. The basic source for all the Weber conversions is Redline in California. Redline offers very impressive customer service--but only as an example of how not to do it.

If you should decide to have your SU carbs rebuilt, both Joe Curto (who has a website under his name) and John Twist (University Motors Ltd) can do the job in a highly competent manner.

If you decide to go with the Weber conversion, I would get it from Bob Ford, at Brit-Tek, because of the quality of his customer service. The Weber intake manifold is not a proper match to the thickness of either factory exhaust manifold, nor to any of the aftermarket header systems. You will have to make shims so that the large washers will draw the intake/exhaust manifolds up in a proper manner and allow a good seal to the gasket.

Les
Les Bengtson

Thanks for the info from everyone. I have ordered a Weber from Brittek and am pursuing a rebuild kit for my SU's, then once I have both, I will decide on a performance/reliability standpoint. Thanks again.
D. T. Barnes

This thread was discussed between 09/05/2006 and 15/05/2006

MG MGB Technical index

This thread is from the archive. The Live MG MGB Technical BBS is active now.