MG-Cars.info

Welcome to our Site for MG, Triumph and Austin-Healey Car Information.

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 - Cam Shaft Identification

This is related to a recent posting of mine but I have started a new thread to assist in any future archive search. Regular readers may have noted I am having real problems with the TF backfiring and spitting through the carbs. I have partially stripped the engine and found a cracked valve guide so the head is away being reconditioned. In the meantime I have been checking the valve timing and am totally bewildered. I have made up a jig to hold my DTI squarely to the tappets and have drafted out a protractor for the front pulley marked off in 10 degree segments. I have come up with the following results:-
Inlet Opens at 60deg BTDC
Inlet Closes at 50deg BTDC

Exhaust Opens at 70deg ATDC
Exhausts Closes at 80deg ATDC

The average lift of a tappet is 5.6m/m

The engine was running albeit with the spitting and backfiring and I can see that the late valve closing could cause this. But what sort of a cam do I have fitted? The opening of the valves is so much greater than that specified in the manual something must be wrong. Is it possible the peaks of the lobes have worn causing a greater opening. If I have put the bright links in the timing chain to the wrong side of the sprockets this wouldn't cause the long opening duration. Before ordering a new cam I am seeking advice since they are quite costly.

Cheers

Jan T
J Targosz

With a tappet lift of 5.6mm and a rocker ratio of 1.5:1, the valve lift will be 8.4mm. There was only one camshaft with that valve lift, actually 8.3mm, and that was the late TD and TF 5/45/45/5 camshaft. It had rather pointed lobes, if that is any help.
R A WILSON

Maybe I should have added that the engine in my car was reconditioned and tuned by a firm called Mangoletsi in the 1960s. The rebuild, however, was never completed and when I bought the car a couple of years ago the engine was in pieces with unopened boxes of Hepolite pistons and Vandervell bearings. The block and crank were covered in thick protective grease. The polished cylinder head and and manifold were wrapped in greased paper and boxed. I assumed the head was in perfect condition but it wasn't. I have already had to skim it to correct distortion and one of the valve guides was cracked. I now suspect an over the top cam has been fitted. It is essential to double check every bit of previously carried out work!

Jan T

J Targosz

Hardly over the top - the valves are only open for 10 degrees !
R A WILSON

I suggest having someone that does this a lot, such as a machine shop/engine builder check your results. RA is right with his 10 degrees comment. Possibly something is not right with your method? Hard to tell without being there in person, but results make no sense. Or your cam is totally worn and round, but that doesn't fit the decent lift measurement. Also, many replacement chains have bright links which are randomly placed unlike the originals, and you have to count pins/links, etc. George
George Butz

Hi Jan,

It sounds like the camshaft is timed wrongly. I suspect you mean EXHAUST closes 50 BTDC and INLET closes 180 ATDC (same as 180 BTDC) then the camshaft readings roughly match each other ... BUT installed 55 degrees too far ADVANCED.

Bob Schapel
R L Schapel

I never box an engine up without taking this photo and the engine is not fitted before I do a double check.
Jan,
If your engine was running OK before your present trouble, then your timing must be OK.
The only way your timing could now be out is if one of the woodruff keys rotated and fell out during assembly.
I Know it is PIA on our TF's but if you remove the chaincase you can check it.
You may have to turn the engine over a few times to get the bright link to align with the timing marks.(chain link numbers and cog teeth are not dividable)
I had to do this on a friends car as the engine shop had had put the chain on wrong.
Ray TF 2884

Ray Lee

Check lifter rise @ .014" = .021" valve lash, as noted on the earlier post this should be the Camshaft timing checking clearance.
What readings do you get @ .050" lifter rise?
I have new camshafts in stock.
Len Fanelli

Hi Len,

I am uncertain what you are suggesting I do. I have now taken the head, sump and timing chain cover off. I have made up a 360 deg protractor which is fitted over the nose of the crank and a pointer is attached to a vacant screw hole. I have clamped my dial test indicator to the face of the block, making certain it does not touch a rising piston, and positioned the indicator probe on the second tappet in from the front. I have set No 1 piston to TDC and also the protractor to 0 degs. As I turn the crank over tappet No 1 rises along with the piston pushing the exhaust out. When the protractor reaches 300 degs the DTI shows tappet No 2 to start to rise. I thus reason that the inlet vale starts to open at 360-300 i.e. 60 degs BTDC. I carry on turning the crank and the DTI spins clockwise, stalls and then turns anti clock until stopping. The protractor now shows 310 degs so I calculate the valve has closed at 50 degs BTDC. There are 13 links to the left of the bright links and 15 to the right.

I am resigned to buying a new cam. What is your price for a standard one for a TF. What would the postage be to Scotland, how long would it take and how could I pay.

Cheers

Jan T
J Targosz

Jan, Please E mail me.
laf48@aol.com

or
abingdonperforma@aol.com
Len Fanelli

Jan,
your cam is opening the inlet far too early.
The cams are symmetric and the nullpoint (full open inlet valve)is at approx 115 Deg after TDC.
This will give you a better idea of your valve timing.
As I said earlier, if it ran OK at first then the timing has slipped. It is not unknown for Woodruff keys to rotate out on assembly.
Ray TF 2884
Ray Lee

Correction 110 Deg after TDC. must learn to check mental arithmetic.
Ray
Ray Lee

Hi Jan

If you’re thinking about buying a new camshaft, can I recommend B&G’s fast road cam -
Product code AAA3096XD

It’s unusual in that the inlet and exhaust gap is 18 thou and 20 thou respectively so it’s a bit noisy but it transformed my TF 1500.

Alternatively Newman Cams probably make by far the majority of the aftermarket camshafts in the UK - David Newman gave a talk at this year’s T Register Rebuild event and was very informative and gave lots of sensible and practical advice. Here’s the link to his T Type camshafts
http://www.newman-cams.com/wp-content/uploads/2016/03/newman-cams_priceData_Catalogue2016_Vintage-MG-TB-TF-XPAG.pdf

He makes and sells cam followers as well.

David
David Wardell

Also, Len Fanelli's roller cams are a great group, with virtually no tappet or cam wear. For the more traditional among us, he also sells a flat-tappet cam that is probably the best around - better than the B&G cam even!

Tom Lange
MGT Repair
t lange

This thread was discussed between 29/08/2016 and 31/08/2016

MG TD TF 1500 index

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