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MG Midget and Sprite Technical - 1500 cam timing - calling Debs!

Hello, hopefully someone out there will know the answer to this.

What is the correct timing angle for stock 1500 camshaft - and from which cam should this be measured?

Any tips for checking the timing would not go a miss either.

Thanks
Christian
C L Carter

Christian, I have just put my stock system back together - I just used the stock markings on the cam and gearwheels. I assume you doing something special - as with the std stuff I didn't find any problems following the haynes type instructions on re-assembly....
John Barber

The stock 1500 cam is fairly mild, with a timing of:

18 - 58 - 58 - 18

with a cam lift of 0.340"

Thus the duration is 256 degrees (18+58+180) and the LCA is 110 degrees ([Duration/2] - 18).

Thus, to time the cam 'straight up' (ie no cam advance or retard) you would time it for max lift on no. 1 inlet at 110 degrees AFTER TDC. (No. 1 inlet valve is cam lobe no. 2 when viewed from the front).

The way to do this is to get yourself a dial gauge. Set TDC on No. 1 Piston. Then put a second tappet upside down in No. 1 inlet tappet bore and measure maximum lift with the dial gauge by rotating the camshaft.

Now turn the engine 110 degrees in the normal direction of rotation (clockwise viewed from the front).

Now carefully fit the timing chain and cam sprocket being careful neither to turn the crank nor the camshaft.


Then, as they say, Robert is yer Ma's brother!
Deborah Evans

Debs, out of curiosity, what would be the overall effect of advancing or retarding the std cam by a few degrees?
Bob T

Surprised Deb didn't mention that the cam sprocket is a vernier. The bolt holes are offset a bit, and by using the "other" set gives different timing. Further increments by flipping the sprocket over.

Advancing the cam a couple of degrees tends to give better low/mid range, at slight expense of top end. Effect is faint, and not as much as a couple of degrees retarded loses. For this reason, I time at 2 deg advanced with a new chain, which soon settles in to dead on for the useful life of the chain. Also highly recommended to use the TR6 double row chain/sprockets for increased stable chain life.

FRM
FR Millmore

Thanks Debs and people - very useful.

Quick question on Thrust Washer replacement. I measured my TW as 0.092" uniform on both washers. What is the standard size. I measured 7 - 8 thou end float with these. I've heard different things on what the clearance should be, some have said as little as 2 thou?

So, where do I get replacement and oversize replacement TWs, and do I need oversized ones?

Cheers
Christian
C L Carter

Your TW are standard if not marked for OS, and your measurements confirm.
They come from the same places other engine parts do.
I set the clearance at low limit = .004, as Max. But .002 is OK as long as it is not actually tighter.
I would use one +.005 and one of yours, should give a free .002 or more likely .003.

Check carefully that there are no burrs on the backside of TW.

FRM
FR Millmore

This thread was discussed between 11/05/2012 and 13/05/2012

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