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MG MGA - Drain cock thread size

What is the thread size in engine block for coolant drain cock? I measure it as 1/2IN Whitworth - 19P. That size does not exists. I try 1/2IN 18 and 20 TPI and nether fits. Would be the tap available?
Martin
Martin

It sounds like it might be 1/4 BSP. The 1/4" is internal dimension of pipe.
John DeWolf

1/4 NPT screws into the bottom of the radiator. I think that is the same as the block, but my radiator is a Moss reproduction, and it may not be the same as the original. 1/4 NPT is 1/4" inside dia. national pipe thread. It is a tapered thread and does not rely on a shoulder with a sealing ring to be water-tight.
Ed Bell

Thank you for your coments. I THINK that it is same as radiator drain cock it may be the same as oil drain. It is not pipe thread, I try that, it is straiht thread. It has sealing washer, pipe thread does no need washer to seal.
Martin
Martin

BSP can be either straight or tapered and 1/4" is 19 TPI
John DeWolf

ATT:John DeWolf
You are right on. How do I go about to get the straight tap as oposed the taper. Is there some diferent designation? Will the seller know what I am talking about? Do you have place to recomend? Google does not list anything like it. Any help gratefuly accepted.
Martin
Martin

Moss have them as part number 385-765 (I think they are straight, although not certain). But it's a bit expensive. They often show up on eBay, search for 'BSP taps'. If ordering them you have to specify tapered or straight. They are often sold in sets of one of each.
John DeWolf

Martin - BSP is straight thread, one has to specify only if they want a tapered thread. Taps are available from British Tool Company <http://www.britishtool.com/> and British Tools and Fasteners <http://www.britishfasteners.com/Merchant2/merchant.mvc>
Good luck - Dave
David DuBois

The tapered is often designated BSPT and the straight or parallel as BSP.
John DeWolf

Martin, both types of taps are carried by the industrial supplier McMaster-Carr (mcmaster.com). They will accept a credit card and normally have these in stock.
John H

Thank you all for your help.
Martin
Martin

This thread was discussed between 11/02/2006 and 14/02/2006

MG MGA index

This thread is from the archive. The Live MG MGA BBS is active now.