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MG Midget and Sprite Technical - Camshaft Locating Plate Locking Up

Hi, I have a 1500 engine which I am slowly rebuilding, I have arrived at the point of reassembling the camshaft, the locking plate has a clearance of between 0.1 & 0.15mm within the camshaft groove. When I "nip" the bolts up the camshaft can rotate freely, however tighten up the locating plate to 28NM (20 ft/lb)and the camshaft cannot rotate.
I can not find any documented torque figures for these bolts.
Any advice/help appreciated.


Kevin Fuller

Have you checked the locking plate against a straight edge. Perhaps it is bowed.
GuyW

Try the locking plate the other way up? Does that help?
Malcolm Le Chevalier

When the plate is placed on the m/c face of the engine block and held down at the bolt hole positions it is not possible to get a 0.05mm feeler gauge between them. Maybe the torque figures is too high, if I torque the screws to 10 ft/lbs the camshaft rotates freely. I seem to remember that the screws were very easy to undo, however as that was some months ago I would prefer to have data to work to and not my memory.
Kevin Fuller

Hi, Malcolm, the result is the same whichever way I fit the plate.
Kevin Fuller

Have you fitted new cam bearings - the cam should not bind on tightening the screws unless there is something binding on the shaft as it is pushed back into the engine.
Chris at Octarine Services

hi kevin
I had same issue. Rebuilding an old engine i had a triumphtune cam and a new plate....cant remember where the plate came from. Same thing happened...After spending several hours timing the valves, no marks on new cam...I finally nipped up plate and all went solid.
No probs with old one though The new plate was not absolutely flat so spent some time on a stone flattening the plate . Eventually ok. 3k later all is still well
rgds tony
tony boyle

I will see if I can find the torque spec and any fitting details in my shop manual and post it on here later.

Clare
Clare Ravenwood

The cam & plate are the "original" units, the cam shows no sign of wear, the plate has a slightly worn rubbing ring. I can get the plate surface ground to ensure that it is flat & still be well within the end float tolerance. There is sufficient end clearance to ensure (without the plate) that it does not bind.
Kevin Fuller

Hi Kevin. Could not find the torque spec anywhere in my books. however, it does not seem to do anything except hold the plate to the engine.

The camshaft end float for the 1500 engine is as follows: 0.0045 to 0.0085 in or in metric, 0.120 to 0.216.

If the end play is excessive, it says to renew the camshaft end plate.

Clare
Clare Ravenwood

20 ft lbs ... thats alot of torque to hold what amounts to a cover holding a ball bearing unit from popping out

Are you sure the spec is not 20 INCH pounds

THAT said i dont know much about 1500s

On a 1275 cly head its 50 foot pounds and thats actually doing something structurally funtional under high pressure and force

So with this plate comming in at just barely under 1/2 the torque of a cly head stud... that just seems odd to me

Id rhink you could get block flex and distrotion with that torque spec.

Prop
1 Paper

This thread was discussed on 18/06/2017

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