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MG TD TF 1500 - Done with the 4.3 Conversion

Well, our 4.3 conversion is complete and (knocking-wood / crossing-fingers) everything appears to be working great. The differential is a whole lot quieter, (mostly because the carrier bearings were shot), and I can now travel with traffic and not think that the engine will explode. Really couldn’t be happier.
I want to thank all of the brethren out there who offered advice and guidance. A special thanks to Don Harmer and the Atlanta group who have de-mystified the process. We ended up taking a lot of pictures, and we will be offering to lend our jigs and tools to the next local guy who wants to try the conversion.
I did want to suggest one thing that we came across that might help that next guy. The pinion shaft bearing has to be pre-loaded to an inch-pound specification. We have an inch-pound torque wrench, but the resolution was not very good and it wasn’t working for us at the low end. We had used a bed frame rail attached to the flange to lock the pinion shaft in order to torque and remove the bolt. It was balanced on the flange. By taking a pint can of beverage and sliding it along the rail until it started to fall, we were able to use a tape measure to determine exactly when we had achieved the correct inch-pounds: so many inches away from the center, so many inch-pounds. (That “pint is a pound the world around” quote works for those of us in the land of 16 ounce pints. Our former oppressors with their 20 ounce imperial pints would have to do some algebra.)
So everything is good except now I have to learn how to double-clutch, since I no longer come to a rolling stop and take off in a synchronized second gear. I am using first gear for the first time, and third a lot more than before. But whatever gear I’m in, I’m grinning.
Safety? Fast?
Scott Ashworth – ’54 TF (with a wee bit of MGA)

S. R. Ashworth

Thanks for the update and glad to read of your success. I am just at the starting point of doing the 4.3 conversion and would appreciate your posting the photos of the process that you referred to, to my e-mail: beemers2up at yshoo dot com. in addition to any you may post on this BB, as I find I can get better prints from e-mail attachments.

Thanks and good riding -- John
John Brickell

Oops, that's "yahoo" dot com. of course.

John Brickell

Scott, congradulations! Wish I had the tools/skills to do this. Now that you are done, would you recommend the 4.3 to someone who lives at 9,600' in the Rockies? I use 2nd gear starts all the time and kind of like it but 4 mile upgrades are a reality for me, but 4,000 rpm on the road is a bear as you know (knew-past tense)!

'50 TD
efh Haskell

Ed, I think the 4.3 would work for you. You may have to downshift somewhat but the highway would be nice. I know that my 4:1 can be a bear on long grades. I definatley shift down more on grades but man can I cruise with it..
Tom Maine


If you're at 9,600 feet, irrespective of your cwp, what your engine needs more than anything, is to get more air into the engine.

Stary by cleaning up the head including matching the inlet ports. If you have a TD (you didn't specify) get rid of that convoluted air intake and 1¼" SUs, and replace it with a TF-like system.

Finally Ed, there's absolutely nothing better than using an external pump to force more air into your engine, and the best one I know of, is a supercharger.

Once you've done all this, only then, can you think about a 4.3 cwp.

Gord Clark
Rockburn, Qué.
Gordon A Clark

Honestly Ed, if I didn't go on the main roads, the old ratio would have been great (4.9 I believe). I could put it into fourth and not have to do much shifting. I will keep the old ring and pinion just in case someone (hopefully a great-great grandson) wants to return it to original, but it sure does cruise nicely on the bigger roads now.
Safety? Fast?
Scott Ashworth - '54 TF
S. R. Ashworth

Scott, I don't want to be the wet blanket or smart alec here, but the 16 ounces of energy drink is based on a liquid volume system, not the dry weight avoirdupois system of 16 ounces to the pound.
It may be a coincidence that the can weighed a pound , depending upon what the weight of the particular liquid was- was this the case ?

Probably as close as one normally gets to "one inch pound" anyway.
Dallas C Congleton

Dallas, Knowing the level of sticklerliness on this site, I consulted the highest authority (no, not Dave DuBois but rather, Wikipedia) to fact check before posting - From that fine source:

In the United States, 1 pint is 16 fluid ounces which is equal to one pound (also 16 ounces).

In the rest of the english speaking world, an Imperial Pint (which is 20 Imperal Ounces) will weigh one and a quarter pounds.

Note that a pint is 16 ounces of volume, while a pound is 16 ounces of weight. The popular rhyme "A pint's a pound, the world around" can help you remember this, but keep in mind that they're not really equivalent, and that this is not true "the world around", but only in the U.S.
Safety? Fast?
Scott Ashworth - '54 TF

S. R. Ashworth

Gord, I've not delved into the inlet ports but I installed lean needles long ago and those shiney Stelling & Hellings air filters. I've ridden in Lavernes blown TF and I agree, but it ain't in the budget as we speak:( It runs great, but it's crying for 4.3 freedom on long straight roads...sigh.

(Sorry to rob this thread)
efh Haskell

That whole ounce thing gets ya thinkin. If a sixteen ounce container was filled with salt water would it weight the same as fresh and what if the sixteen ounce container was filled with lead would it still weigh sixteen ounces or just a pound. Seems like liquid measurement and weight measurement is two different measurements of course I only took chemistry one day and decided it wasn't the place for me:)
Richard Taylor

Soon someone is going to ask the question, which is the heavier, a pound of feathers or a pound of lead?
G.E. Love

Folks, I'm looking for a 4.3 CWP set for my TF1500....anyone know a source. Moss N/A
Terry Sanders

Hi guys
I was planning to make a post about my 4.3 conversion like Scott, but his will do it. I finished my job a week ago also. I have about 70 miles on the TF since. I am soooooooo happy with the result. Like Scott, I too agree that the car is much quieter and smoother. I especially like the performance in town (where I have driven most). First and second gears are USEFUL now!!
Cruising at speed it much much better.
My diff was done by Dave Clark in Arizona. He delivered a fantastic end product. I highly recommend him. As part of the job, I rebuilt my rear brakes and bead blasted and painted everything south of the tranny.
For those of you just thinking about it, I recommend you do it.

Tom Norby

Terry....don't rule out a 4.1 or a 3.9 ... the 1500 should be good with either.

Scott, if you'd like to put something together about you experience I'd be happy to set it up as an adjunct page to the Rear End Conversion page on my web site, Bud
Bud Krueger

Scott, I am anxiously awaiting your write up and photo's as I'm think of attempting this conversion myself...I have a spare TD axle that I can put under the TF while I'm learning/doing it. Local expert quoted $1000+ labor ..
Terry Sanders

Scott, the 16 inch / pounds is a bit too much, unless you had the seal installed. Without the seal it should be 8-10,inch / pounds; 12 inch / pounds maximum.
Len Fanelli

Len, The picture shows about 9, but was just to show process. We aimed for six inch pounds, +/-2 per the SEMGTR write-up. I believe we ended up at 7, which was the average distance measuring to the left and right of center.
Safety? Fast?
Scott Ashworth '54 TF
S. R. Ashworth

This thread was discussed between 21/05/2010 and 23/05/2010

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