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MG TD TF 1500 - Camshaft lift

My engine is at a machine shop, I was given the following information about my cam and asked to check the specifications. With the cam between centers the "cam lift" for each lobe is: .235, .231,.234,.230,.233,.228,.231 & .229. All I can find in the WSM is that the valve lift is supposed to be .315. I have looked through the archives, learned a few things and have a lot more things confusing me.
My car is a 53TD, engine # 27048 with the rocker cover stating to use .012 for the valve setting. Rocker ratio is related, most comments seem to indicate it is 1.5:1, There are other comments about the a different amount of valve lift but my book states .315. I am curious about how to use this information. Do you take the cam lift .235 and subtract the valve clearance .012 - equaling .233 and multiply it by 1.5 for .349? .349 is not near .315 for valve lift.
Would someone explain how this calculation is done and advise whether or not my camshaft is servicable?
R. E. Lee

For each lobe, subtract the narrowest diameter from the largest diameter. That is the cam lift. Multiply the cam lift by the rocker ratio (1.5) and that gives the valve lift, The valve clearance has nothing to do with the calculations as that is only a factor when the valve is NOT operated.
Lew Palmer

Lew thanks for your answer, however I am not sure that I understand correctly. Is the narrowest diameter the small round part, basically the diameter of the nominal shaft itself and the largest diameter the diameter of a circle made by the narrow tip of the cam lobe?
R. E. Lee

Rob
There are differing opinions on what the actual rocker ration of an XPAG actually is--
1.5 - 1.46 - 1.38 are all talked about but I believe rightly or wrongly that it's 1.38

Lew mentioned measuring the diameters of the lobes and you appeared a bit lost in that ---
Measure the base circle diameter(accross the base of the lobe) then the overall max dia. ---the difference between these two measurements is the lift at the lobe-
If your guy has measured it mounted on centres I'd imagine he's used a dial indicator on each lobe, zero'd on the base circle diameter and then rotated to get the lift----100% acurate method, take his word for the measurements

If the WSM is saying .315" valve lift then that is saying you have .327" gross lift (.315"+.012")
.327" devided by 1.38 (estimated rocker ratio) gives a lift at the lobe of .237"
There would be a small amount of loss with rocker gear flex so I imagine your best lobe at .235 isn't far off the mark, your worst one at .229 is .006" down, BUT these engines are quite old and possibly never were spot on specs
My opinion would be to leave it to your engine man, It sounds like he knows what he's doing--If the lobes don't have any visible signs of wear/damage I'd be tempted to run it but if you're spending heaps on a full rebuild then a new or reground cam won't break the budget in comparison to what you would have spent already

willy
William Revit

Here is a video, not MG, but the theory is the same:

https://www.youtube.com/watch?v=FEeXtDnWy8w

Peter
P G Gilvarry

R.E.: .235" cam lift = .352" valve lift. The rocker ratio is 1.5:! As such it seems that you may have a Crane Cam 340-002 blue printed stock cam =.357" lift.Valve lash .016 I .020" E.
Len Fanelli
Abingdon Performance Ltd.
Abingdon Performance on Face Book
914 420 8699
Len Fanelli

This thread was discussed between 27/02/2020 and 28/02/2020

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