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MG TD TF 1500 - Carburetter Damper Top Nut.

My carburetters have a difference in the damper tops. The back carb top cap has a hole in it about 1/32 of an inch in diameter, the front carb has no hole. Is this normal or do I have a miss match of dampers? PJ
Paul Jennings

I've the same setup! I have no idea why-it just came that way. I've been told to drill a hole in one but it's still on the back burner. Seems to make no difference I can see but I've not tried the hole yet.
efh Haskell

You both have a mismatch. They should both be the same.
Hole or no hole depends on version of the carburettor and how the top side of the piston is vented, either thru the inlet flange (has 4 holes) and from the ait filter (NO HOLEIN DAMPER TOP) or thru the hole in the damper top.
The purpose of both is to provide a reference atmospheric pressure vrs manifold vacuum which lifts the piston.

Check with Joe Curto to see which you should have
Don Harmer

It makes a huge difference- Don's explanation is exactly right. Generally 4 holes unvented, 2 holes vented top. George
George Butz

Am I to assume that the carburettors on my car are different? The front carb, the one without the hole in the damper, has a link that hooks up to the primer/choke, the back carb, the one with the hole, doesn't. Is this normal? Where are the numbers on these carbs and what model/s are they? I know all the MGB carbs, but these are different, or so they appear. PJ
Paul Jennings

The carbs will work OK as long as you have the vented cap on the unvented carb.

Dallas
Dallas C Congleton

Paul,

Here's the link to a youtube video by John Twist that explains and shows you what is correct.

http://www.youtube.com/watch?v=GHNlT5yHDxk

Dave
Dave Runnings

You could luck out and each need one that the other has?
gblawson(gordon)

i believe you have different production run caps. joe curto would have the answer. i have an early 1951 car and both caps have vent holes. regards, tom
tom peterson

Paul - please send a photo of your carbs so we can identify what you have - that way we can advise you about the proper cap. Both carbs should have a link for enrichening the mixture, connected by a horizontal bar at the bottom. Do you perchance mean the fast idle arm?

The numbers are cast into the carb bodies, but a picture is worth a thousand words.

Tom
t lange

Tom, I'll take photos today, but in the mean time I found the numbers on the carbs and their both the same, AUC-6020.
Paul Jennings

That's the carb body number for an H4 (most T-Series except for the TF and TD/C have H2. The TF and TD/C carbs are not interchangeable. The H4 body would be combined with other parts (such as the suction chamber) to create specific carburetors.

The carb number is usually found on a tag at the float bowl banjo bolt, usually long discarded.

warmly,
dave
Dave Braun

Dave,

Your link to John Twist on Utube was very informative.may explain why my '51 TD is running too rich.
Going to check it out first chance I get.

Ron.
R Bowden

Here's about the best photo I can of the carbs in such a small area. The air cleaners are a joke and are headed for the junk pile, as their full of holes in the back that don't belong. PJ


Paul Jennings

The rear float chamber does not seem to be vertical. Could it be the wrong chamber? The correct ones have a funny little twist between the chamber and the carb body.
Cheers,
Bob
Bob Jeffers

Paul,

The front float chamber is not visible in your picture, but if it has the same angle as the rear, then the front and rear float chambers are reversed.

John
J Scragg

Hard to tell from the picture about the chamber, but as said above it should be verticle. Definitely not original TD carb- from the one you can see, it looks like the position for three suction chamber screw chambers (TD carbs had 2), and the 'strut' going foreward from the damper top not there either on the H2's.
George Butz

Paul,

I think Bob Jeffers has caught one problem you have, and John Scragg may have given you the answer. When the correct bowls are attached to the carb body, the connecting arm should be at a 90 degree angle to the carb boby. In this position, the top of the float bowl should be level. If not, you either have the bowls reversed, or you have the wrong bowls.

George Raham
George Raham

the carbs should definitely be linked by a horizontal bar between them connecting to the choke linkage.
Geoff Baker

Paul - In addition to the incorrect float bowl angle, the rear carb appears to have the damper cap with the hole in it, but the vacuum chamber may will have a vent hole it is through the where I have a yellow arrow pointing (you will have to look inside the the chamber just below the damper cap to see if there is a hole there). If this is the case, the piston will not operate correctly. Check the carb for the same hole through the web. If it has no hole there, then the vented cap should be on that carb. Also, the vacuum chamber is either not installed correctly or you have an incorrect vacuum chamber - see the tab at the red arrow, there should be a corresponding tab on the vacuum chamber and a screw at that point. It is beginning to look like somebody cobbled together a pair of carburetors with left over parts. Cheers - Dave


David DuBois

I'll pull the air cleaners off and take more pictures. Eventually the carbs will be sent out, but for my benefit, the information you guys are giving is well received. I sure do like this forum!
There are a lot of issues with this car. As I said before, I never saw such a miss match of bolts and screws. I can not believe just how many are totally missing. The wiring looks mostly original, but is a night mare with connectors, hanging ends not connected to anything, extra added wires that don't belong. The amazing thing though, is that all the outside lights work! headlights, tail lights, turn signals, even the tag light. Good thing I didn't buy this car to drive, but bought it to restore and since half the bolts are already missing that should save me a lot of work. (Grin).
Paul Jennings

I'll agree with most of what has been offered here on the carburetors, however, I don't necessarily agree that the float bowls are mismatched or incorrectly mounted. I think it is a function of the photo angle. Here is an image that corrects the slant of the carburetors.

I think Dave D hit it on the head when he said "It is beginning to look like somebody cobbled together a pair of carburetors with left over parts."

Because of the constraints of the body depth of the H4 on the TF and the side panels, along with the correct suction chambers, you may want to start looking for a set of TF carburetors. It would be easier to rebuild even a very worn set of TF carburetors than try to find the correct parts scattered to the winds.

warmly,
dave


Dave Braun

The float bowls are level, it's the photo angle that makes them look funny. Had a guy from a local club look at them last week and he said my carbs are the proper ones for my engine, late TD-MKII & TF. When I get the fenders and side panels off, I'll take more photos. Also, the Shop manual shows that my carbs are correct. We'll see. PJ
Paul Jennings

To stand with the Originality Police for a moment of precision, Mark II carbs are quite different from TF carbs in terms of the length of the body and other details. Both are 1-1/2" carbs and both types will fit either car, but aren't necessarily correct.

Tom
t lange

I don't know for sure Tom, but I have a tendency to lean toward the photo in the shop manual, page B15, as that carb is identical to my rear one with vac chamber position and all. Like I said before, when I get the side panels off, which will be soon, I'll get better info. I think these cars were named midgets because you need to be a midget,(oops, little person), to get to some of the parts on them. (Grin). PJ
Paul Jennings

Paul, somehow I thought you had a TD- duh. Those look like correct TF carbs to me-but not for a TD MkII. You sure do need small midget hands to work in the front TF carb in place. George
George Butz

Here's a set of new TF carbs a guy just bought. Mine are the same with the exception of the vent boss on top. Mine are on the front and these are on the side. The base screw tabs are in the same position though. Everything else on my carbs seem to be correct, it's the position of the vent bosses that are different. Do you think the vac chambers are from another pair of carbs? If so, anyone have a clue where their from? Incidentally, the engine runs great! PJ




Paul Jennings

haha...nope..those are MKII carbs.....(what a nice room)
gblawson(gordon)

This thread was discussed between 14/05/2010 and 24/05/2010

MG TD TF 1500 index

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