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 - AEG122 Camshaft

Hi,

Does anybody have the original factory info for the AEG122 half race camshaft. I have seen various tappet settings reported but I would like to see what the factory originally said.

Bernie
B W Wood

See attached. For the stage TF3 (1250) tuning, it is recommended that the cylinder head is reduced in thickness to 73.575mm, giving 9.3:1 compression ratio - the tuning instructions state this is the absolute maximum to remove.
The cylinder heads are different, but both would have the round water holes and would be fitted with the larger valves.
Valve lift is 8mm, less tappet clearance.



R WILSON

From Syd Enever's factory tuning notes, TIM1:

"A special camshaft (tappet setting .012" Inlet, .019" Exhaust) is fitted with high overlap, but this will only work when used in conjunction with an extracter type exhaust system."

Sincere thanks to Chris Pamplin for this information.

Tom Lange
MGT Repair
t lange

On reflection, I think my above post and Syd Enever's tuning note applies to the factory full-race 168551 cam, NOT the AEG122 cam. Sorry for the confusion.

Tom Lange
MGT Repair
t lange

Tom do you have the specs for the 168551 cam? Or have one of these in your collection? I would like to find one of these.

Bill Chasser
TD/c/8151

W A Chasser

Bernie, Bill,

You can find information on these camshafts in the XPAG engine tuning book by WKF Wood.

Here is the link. page III - 15

http://www.ttalk.info/WKF-Wood-XPAG-Engine-Book.pdf


John
J Scragg

See attached. Interesting that the 168551 camshaft is only recommended for the 1500cc engine, with an extractor exhaust essential. Valve lift 8mm as before.
The previous Stage TF4 part A is about fitting an extractor exhaust to both 1250cc and 1500cc engines.

R WILSON

Thank you John for the Woods reference but it doesn’t give me all the specs I’m looking for ie, duration, lobe centers and overlap. I am planning for a purpose built spare MKII engine I have acquired for track use. Would like to find this cam or be able to replicate it to make dyno comparisons.

It’s interesting that the Woods info says for XPEG as I always thought anything with a 168xxx was originally a XPAG MK II item.

Bill Chasser
TD/c/8151
W A Chasser

The only information I have is that the Inlet opens 32 degrees BTDC, and closes 58 degrees ABDC. Exhaust opens 60 degrees BBDC, closes 30 degrees ATDC, with a valve lift of 8.3mm.

Do you really want this cam? Seems to me there are plenty of more modern commercially-available cams that are much more suitable to the street/track.

Tom Lange
MGT Repair
t lange

And I have seen many references that state, the valve lash checking clearance for checking the valve timing is .021"
Len Fanelli
Abingdon Performance
Len Fanelli

Hi Guys,

According to my old notes, RW's, Tom's and John's data is correct. The AEG122 timing was only slightly "wilder" than the standard TC timing. Was it 3 degrees extra inlet opening and two degrees extra on the other three readings? 19 thou valve clearance .... down to 15 thou for quietness.

I have included an image of the four factory camshafts. Wolseley/TF, Std TC, AEG122 and 168551 for your amusement.

I agree with Tom that there must be better cams available nowadays. I know that the modern fuel burn rates have changed etc. A field I have not yet explored!

I have factory 168551 cams in my road and race cars. I think next time (if ever) I rebuild the road car engine I will go with the AEG 122 ( because I have a new one in the shed). The 168551 is great but the revs have to be "up there" to get the benefit. I know the standard TC cam is great and something with slightly more overlap, but less than the 168551, sounds perfect.

The 168551 goes well in the race car (supercharged) although I have always thought that slightly more lift might be an advantage. Youtube "MGTC at Phillip Island 2013" if you would like to hear a 1366cc XPAG with a 168551 revving at 6500rpm.

I am always amused at the diagram for the extractor exhaust system suggested by the factory. How could it be the best design if the pipe lengths are not all the same? All pipe lengths should be the same and that length depends on the engine capacity, cam timing, port/pipe diameter etc. It is about 50 years since I built my exhaust system but I think I remember using a formula from a book by Phillip Smith.

Bob Schapel


R L Schapel

This link has some info on page 306 of the appendix:

https://link.springer.com/content/pdf/bbm%3A978-1-4899-7204-0%2F1.pdf

Gene Gillam

Bob - I believe it was you who, some time ago, pointed out the identifying rings on the end of the cam (based on your picture, above). I recently had a chance to look through some factory MOWOG blueprints, and you are quite correct: different cams have different markings on the ends.

Best, Tom Lange
MGT Repair
t lange

Thanks Tom. That is good to know. I made the observation in the early 70s but have never seen any documentation about it. I have learnt more about cams from this forum including the fact that I still have a lot to learn! The only marking which I am still pretty sure about is the "two rings" on the back of original TC cams. I think the "one ring" cam was probably a Morris 10. It is only recently that I have seen photos of numbers stamped on AEG122s but my factory AEG122 and 168557s don't have any numbers on them. I wonder if the numbers only appeared late in production or even later on repro cams.

Bob

R L Schapel

Bill,

The information you require can be calculated from the data given in the WKF Wood manual. I have done this for 168551 cam and found the following:

Inlet lobe centre 103° ATDC
Exhaust lobe centre 105° BTDC
Lobe separation angle 152°
Duration 270° (given in table)

Overlap 62° and 118°


John



J Scragg

I don’t mean to hijack this thread from the OP but in response I have a few more comments.

Bob Schapel. Thank you for displaying the cams side by side in profile. Interesting is the lobes ramp profile of the 168551 cam. It almost looks like a roller cam.

Tom, yes I’d like to find one of the 168551 cams. You made a comment to Bob that the cams can be identified by the rings. The 168551 cam end seems to look the same as the Wolsley cam pictured by Bob Schapel. Am I to understand that the cams may or may not have a part number cast / stamped / etched onto the stick?

Gene, thank you for the additional link.

John Scraggs thank you for doing the calculations for me it was late and my mind wasn’t quite engaged.

I guess my final question would be regarding advertised lift. Is the 8.3mm measurement at the lobe or at the valve. 8.3 mm = ~ .327”. .327” x 1.5 (rocker ratio) = .498”. The .498” seems a bit tall to me for an early cam and doesn’t fit Bob’s comment saying he wished it had more lift on his SC race engine.

Bill Chasser
TD/c-8151
W A Chasser

Bill it is 8.3 MM at the cam lobe = .327" at the valve gross, ( 0 valve lash).
Bob,I have Crane cams in stock, including the NEW (not in their catalogue) full race cam that beats the B&G 102 cam. As well as roller cams.
Len
Len Fanelli

Hi Bill,

The 8.3mm is measured at the valve. You got me into my shed with the vernier caliper! I measured an almost new 168551 cam :(which had sheared off its oil pump drive teeth:( It measured 23.8mm across the base circle and 29.4mm across the highest lift point. That is 5.6mm lift at the cam and equates to about 8.4mm lift at the valve. I guess valve clearance and slight inaccuracy of my measuring accounts for the slight discrepancy from 8.3mm.

Re the rings .... I have only noted the correlation of "two rings" to the TC cam and possibly "one ring" to a Morris 10 cam. The Wolseley/TF cam, the 168551 cam and the AEG122 cam seem to have no "rings". I note that the AEG122 cam in my image has a slight recess in the centre but it is the only AEG122 I have seen in the flesh so can not say that the recess means anything.

Re "numbers on the stick" .... I have seen photos and heard of AEG122 stamped on a couple of cams but my AEG122 has no numbers. None of the 168551 cams, or Wolseley/TF cams I have seen have numbers. They have had plain flat back faces with the centre hole.


Cheers, Bob
R L Schapel

Thank you Len and Bob. I figured it must have been at the valve but thanks for verifying it for me.

Bill Chasser
TD/c-8151
W A Chasser

Thanks Len,

I know I could get the race car to go faster but it is scary enough as it is for an old bloke like me. I built the current engine in 1995 so it has had 23 years of competition without being out of the chassis or separated from the gearbox. (Yes, it still has the same clutch!) The head has been off four times for various reasons. If it had more power it might go "BANG".

Bob
R L Schapel

This thread was discussed between 10/04/2018 and 13/04/2018

MG TD TF 1500 index

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