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MG Midget and Sprite Technical - rocker adjustment nut size


Could one of you folk tell me what size are the rocker adjustment nuts on my 1275 midget???
tom crause

Thread size or spanner size?

The latter could be either 7/16" or 1/2" depending on which version of rockers are fitted.
Dave O'Neill2

I am looking for the thread size... I lost a nut and am attempting to replace it locally..


tom crause

Tom, take one with you to a "big box" hardware store lik Home Depot, Loews or any place that sell bulk fastners. Try the bolts until you find one that fits, locate the corresponding nut and away you go. Nothing special about the thread I can recall.
Clive Reddin

I measured one off a pressed steel rocker and it looks like 9/32" x26tpi, which makes it BSC. Not sure how common BSC bolts are in big box hardware stores, but I wouldn't be able to find one here in little old NZ.
Growler

Hi, found one of mine had threaded. The nut thread was 5/16 BSF when measured, however the spanner sizes may differ.
regards, Tony
Tony G

Tony, was that from a pressed steel rocker or a cast one? The one I measures could be 5/16" (dodgy calipers I think), but the thread was definitely 26TPI not the 22tpi you'd expect for a BSF bolt.

Then again, who knows what rocker gear has been installed in my engine..
Growler

It's 5/16" UNF no BSFs on the Midget
Cheers John
HALL JOHN

Measured a forged rocker - Growler wins.
Not clear that it IS BSF/CEI - could be a UNS, I have not measured precisely, but they are .270/,275 OD.
Pressed rockers = Exactly the same.

FRM
FR Millmore

Or how about M7? 0.275" = 6.99mm, 1mm pitch = 25.4 TPI, it's close. OK, it's odd, and so is M7, but BMC had some odd things, and some of them metric where you least expect it.
Paul Walbran

Hi, sorry for the delay, away in sunny Spain at the mo.
My rocker shaft was defo. BSF 5/16 on pressed rockers. I tried all sorts of threads UNF, UNC, Metric etc. Maybe mine is a different thread, I was surprised a BSF fitted. My local fixings man searched through his stock until one fitted and got me out of a spot, did not want to drive the car to a meet with a loose rocker! OK with a loose woman though!

Regards, Tony
Tony G

This thread was discussed between 08/09/2012 and 17/09/2012

MG Midget and Sprite Technical index

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