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MG Midget and Sprite Technical - Core plug straps

I've just started the rebuild of my spare 1380, i'll be replacing the core plugs as part of the rebuild but do i really need to strap them in place?
Brad (Sprite IV 1380)

I never have. The 1275 core plug has quite a lot of surface area around the periphery, where it is in contact with the block, compared with the earlier versions.
Dave O'Neill 2

If you plan on racing the car I'd say go ahead. It's not the protection of the engine, but rather the possibility that if one pops and spills water all over the track you could write off the whole car. For a road car I wouldn't worry about it.
Bill Young

Hi Brad

We do not strap the A series core plugs as they are 'proper' ones, the MGB ones are rubbish and need strapping ( apart from the odd block which was fitted with A series style core plugs).I smear blue hylomar around each plug before drifting it into place.


peter burgess

What is strapping?

strapping is what my head master used to do, it hurts, the first time is the worst.

it's a road engine, blown & going to have a hard life as i almost have my own hill climb circuit next to me.
If you say it's ok not to strap the cores then thats good for me, I will plug the other oilways NPT as usual.
The pulley is a rather nice MED one & the VP bracket just visable is a beautiful Tom Fenton design.

Brad (Sprite IV 1380)

The one thing I would suggest is swapping the oil filter head for the earlier style spin-on version - the one with the long bolts. They are much more robust and less prone to fracturing.

I had one of the thin-flange versions crack on my racing A35 and I have seen several others fail on race cars.

They are probably fine for a normal road car, but you say your engine is going to have a hard life!
Dave O'Neill 2

I'll check what i have, though i'm sure the spare engine oil filter take off is different to the one in the car.
Brad (Sprite IV 1380)

Nick, strapping a core plug is either adding a metal strap across the plug secured with two small machine screws into the block on either side of the hole or in some cases just the screws which have heads that are large enough to overlap the edge of the plug and keep it from coming out.

Bill Young

Im sure Nick and I are the only ones on the BBS that have never heard the term "Straping" Most likely because Im an idiot and Nick is what you might refer to as ... "Special" LOL

But Im sure the "special" guy is thinking the same thing as the idiot guy...."Dosnt the strap defeat the whole purpose of a core plug to begin with, seems like a redundent odd Idea to me.

Prop...At least nick can spell better then me

Prop, you're thinking that because you are thinking that they are to protect the engine from cracks if the coolant freezes, but that isn't really accurate. They are merely left over from how an engine is cast. Those holes are where the sand comes out of. The plugs just keep the coolant in (until they rust or leak).

Modern engines use styrofoam cores that melt and "wash away" and so they don't need those holes (or as many, anyway).

Norm Kerr


Being that Im a blonde, My favorite color is clear, and I love the flavor water...but really, Not even I can be tricked into beliveing that.


Prop...intersting idea

Thanks Bill. Now, I don't expect a helpful answer from Brad, but can somebody else tell me what NPT and VP bracket are?

I agree wholeheartedly with Prop. Norm's sick fantasies aren't going to fool the likes of us.

NPT is the the thread used when instead of simply using interference fit plugs for the oil ways, they're tapped and plugs are screwed in. So they cab easily removed for cleaning and less prone to blowing out under the oil pressure.

VP - Not immediatelys sure what VP is. I've normally seen them referred to as VR (Variable reluctance)sensors. Essentially the sensor used for the likes of megajolt/EDIS etc to determine crank position by detecting the missing tooth on a toothed wheel. In Brad's pic it looks like the damper has an integral toothed wheel. The bracket that will hold the sensor is just behind the damper. The sensor is the small black plastic stubby "thing".
Dean Smith ('73 RWA)

NPT stands for 'National Pipe Thread' (often referred to as NPTF - 'National Pipe Thread Fine') and is an American Standard for tapered thread fittings with a 60 degree thread angle.

Quintessentially it is similar to BSP(T) which stands for 'British Standard Pipe (Tapered)'.

This is often incorrectly referred to as purely 'BSP' since there is also a BSP(P)- 'British Standard Pipe (Parallel)'. BSP fittings have Whitworth threads with a 55 degree thread angle.

With regard to core plug strapping on hard worked engines, I have seen it done on some engines but, as Peter Burgess stated, it SHOULDN'T be a requirement on A-Series motors where the core plug is designed with a flanged edge that helps it seat nicely into the block.

Indeed in over 25+ years of racing I'd NEVER seen a core plug blow out, that is up until the debut of our race midget at Silverstone in 200,7 when the centre right plug blew out. I heard it bounce along the underside of the car whilst passing the pits and several witnesses saw a fine mist of pink OAT coolant behind the car.

Fortunately the engine wasn't 'cooked' and a replacement plug sourced and fitted with a smear of Red Hermatite.

Since then there have been no problems, so I assume the original plug was not up to spec.
Deborah Evans

Deb -
NPT and NPTF are slightly different. NPT is the basic form, the derivative NPTF is also known as "dryseal". NPT can leave a spiral clearance along the thread crests when tightened, hence leaks, hence sealants. The NPTF thread form is such that there is mechanical contact over the entire surface, thus requiring no sealant. (good theory!)
Despite reading a million descriptions over the years, I never knew where the "F" came from, until I looked it up just now and found maybe the only known description that actually tells you: F = Fuel! See:

FR Millmore

your right, i use VP at work, i should have said VR sensor.
i thought it was quite funny, but Deans explanation covers it well.

I got the engine apart this afternoon, it's in very good condition despite the poor external paint making it look rather rough. Got a bit of home chemistry on the go this evening with a battery charger, some lead flashing & a large bucket of washing powder solution, maybe it will work.
Brad (Sprite IV 1380)

This thread was discussed between 15/01/2010 and 16/01/2010

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