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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 MGA - SU Carb Kits warning (Never assume anything)

I had purchased and installed SU carb kits as I was finishing the restoration of my '57 1500 back in 2003. Recently I changed the air filter elements to K&N, using the original Vokes cans. I had always resisted doing the high speed shutdown test to check the spark plugs (I must have had a latent fear of embarasment as a Triumph might drive by and snicker as I was stopped at the side of the road with the bonnet up pulling the plugs!) I decided maybe I should do it with the K&Ns installed and the result was slightly rich at idle, but SUPER lean at high speed! I mean those plugs were pearly white and clean as a whistle! I thought "wow, I can't believe the K&Ns could do that, it must have been lean before". I ordered some CC needles and when I went to change them I noticed the old needles were "EM". I must admit I knew nothing about SU needles when I restored the car and had "assumed" that the correct needles were in the carb kits -big mistake! I looked up the needle profiles at one of the sites on the net, and EM neeles are way, way leaner that CC or the original GS. In fact at about a little less than midway they taper off to almost a flat line while the correct needles continue to rise in richness at an even rate. I now have settled on the CC needles, but I am thinking that the car has been very lean at high speed all along!
The car has much more power now and the plugs are now a nice tan colour. Its a wonder I didn't do some damage, but it probably explains why the engine temperature rose above about 3800 - 3900 rpm on the freeway, and a quick stop for a traffic jam after those speeds see a sharp spike in the temp gauge reading! The exhaust manifolde were probably glowing. I found the old receipts and I had ordered the proper kits from one of the major suppliers who I wont slam here.
So the moral of the story is "Check those needles that they include in the SU kits"
And the scariest thing? We drove the car to BC and GT32 in Whistler last year, over 6000 miles through searing heat and steep climbs. I guess we got lucky.

Ralph
Ralph

This thread was discussed on 05/07/2008

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