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MG MGA - Vlave clearances

Would really appreciate some help please. I have a Mk2 and according to the paperwork the engine was reconditioned in 2007. I thought I would double check the valve clearances.
The drivers handbook and the original workshop manual both say that the clearances should be 0.015 inches when hot (manual also says to add .001 inches when cold). However Haynes says it should be 0.015 inches when cold! I am inclined to assume Haynes has a typo but any ideas where I can find the definite answer please?
Graham M V

Graham -
I've posted this in various forms before but:
"Once at running temp for 10 minutes, shut down, final torque while warm to 45lbft, adjust valves to normal. (I know it says to adjust valves cold. The guy I first worked for was a BMC service manager; he pointed out to the BMC factory chief service rep that they had specified variously hot, cold, and cold running (!), all at the same measurement. They measured, and I have measured - it matters not on this engine.) "
It is very unlikely that you actually can set valves reliably within .001.; it is equally unlikely that your ".001" and mine will agree; and you can't reliably define "cold" or "hot" or "warm" either - are you in Oz in the summer, or Norway in the winter? Get them close and even by your feel, and drive!

FRM
Fletcher R Millmore

I think that in practice there is no significant difference between hot and cold. All the parts are steel or iron with the same coefficient of expansion and by the time you have finished checking, all the parts are the same temp. During actual running, the valve stems will be longer b/c thats where the heat is and thats why you have the clearances
Art Pearse

OK, thanks. That all makes sense. Sorry if it was a dumb question but I am still learning
Graham V

It wasn't a dumb question. You'd be amazed at how some people screw up big time because they didn't want to as a dumb question. Marvin
Marvin Stuart

Note that the valve clearances differ slightly for the MGA. The 1500, 15GB and 15GD, engine is 17 thou (hot). The 1600, 16GA, engine is 15 thou (hot), and the 1622, 16GC, engine is 15 thou (cold), all according to the original workshop manual.
Ceclia at SF has the 2 different brass "firing order" plates for 1500 and 1600/1622.
Definitely not a dumb question (but my answer may be).
Peter.
P. Tilbury

Peter -
That is part of the conflicting data I mentioned above, re actual BMC Factory tech experts c1967. Note that all the engines you mention are exactly the same in construction and applicable parts.

The clearances are in fact not primarily for expansion considerations (that would only take <.005 for an all iron engine), but for cam operating design, and involve cam opening ramp rates with a trade off for noise consideration. Any very precise determination of what is "right" would have to account for changes in valve material, which has changed a lot over time. It is probable that more engines today have "Wrong" valves considering the OE as "Right". It is quite possible that if you dig through all the FSB of the time you might find changing and contradictory recommendations on exact clearances.
You will also note that Graham says his two original books for his MKII (should be 1622) say .015 Hot, one adding .001 if cold, his Haynes says .015 cold; you say that your original manual says .015 Hot for 16GA, .015 Cold for the 16GC, but the plate for 1600/1622 is the same!

Bottom line: Set all of these at .015 hot or cold.

FRM
Fletcher R Millmore

It's strange as I have checked the brass plate (1622cc). It says 0.017 hot! Exactly as in the example in the MGOC catalogue - see pic attached. Although it is of course possible a PO bought the wrong plate.
But I think you are saying the difference between the extremes of .015 cold and .017 hot is not significant for this purpose?







Graham V

Graham

According to Clausager, the 1500 plaque is .017. The 1600 plaque should say .015.

Steve
Steve Gyles

Graham
My MK2 plaque says 17? I tend to set mine at 15 as per the handbook
Graham give me a ring 01707874626 to set up a meeting
Paul
P D Camp

This thread was discussed between 28/02/2010 and 03/03/2010

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