MG-Cars.info

Welcome to our Site for MG, Triumph and Austin-Healey 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 TD TF 1500 - Moss SU H4 Gasket and seal set

Very disappointed with what Moss calls a gasket set #298-208. All it had was cork jet seals, lower cork O-ring for the jet bushing retaining nut, bowl lid gaskets, and the manifold and air cleaner gaskets. No gaskets for the lid banjo bolt or the fuel inlet banjo or the float bowl mounting to the main body. Really? I would have thought a gasket set meant a complete set for both carbs.

Using Dave Braun's tech sheet I put one of them back together. while performing the drop test I noticed that my pistons are different. One has a bleed hole in the piston the other doesn't and neither top nut had a hole in it. Obviously I have mismatched parts. as they were set up neither had a 5-7 sec drop. Switched housings and I now have a 5 sec drop on the piston that has the bleed hole. Yes, I plugged it with white grease for the test. checked the upper and lower jet bearing washers and they check in at .015" and .016". I've set the jet at .070" and it is centered so I think this one is ready to go back on and hopefully wont leak out the bottom bowl mount but not holding out much hope since this is why they came apart and I still don't have replacements. I did away with the MGA mounting bolts that I had switched out and put what I thought were the originals back in place It would appear these are not right either as I tried installing Moss #370-700 and 370-260 and the banjo bolts bottom out before the bowl is snug. Back to the rubber isolators on the banjo bolts again, which is what was on them when I bought them.

I have to ask this question though. Why is the drop test so important? When the dampers are filled with oil, the pistons can't rise or fall speedily anyway.

Dave Braun, care to comment?

Cheers

Bill Chasser jr
TD4834



W. A. Chasser Jr

Hi Bill -

The drop test is made to determine if the pistons and domes have the proper clearance and action - the test is made to check for a mismatched pair. The piston's response to suction is based on a proper clearance between the piston edge and the interior of the dome.

Hope you are able to obtain a good matched set for use on your car.
DLD

Bill, I posted the answer below to your same question over on Facebook.... but I'll repeat it here for anyone else it may help...

"The drop is important because it is the engine's vacuum that lifts the piston... if there is a vacuum leak it won't raise the piston as high, meaning there will be a smaller area under the piston (where the air comes into the engine) and thus a higher vacuum over the fuel jet, which in turn will lead to a richer mixture throughout the range of acceleration (but particularly noticeable on idle)."
kmclemore

Dont know if it was mentioned, but also each piston should weigh the same.
mog

Seems to me it's possible to install the cork upside down. I did and leak got worse. On a TF this is not a fun project. Removed and refitted the cork and no leaks for 4 years.
Peter Dahlquist

In the old Moss paper catalog it was clearly marked via different symbols what was included with each kit, While not very clear on the web site, the info is in there as to what is included with each kit. Yes the pistons have to drop at the same rate or carbs will not function the same and running will be compromised. George
George Butz

This thread was discussed on 15/05/2015

MG TD TF 1500 index

This thread is from the archives. Join the live MG TD TF 1500 BBS now