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MG Midget and Sprite Technical - 1275 Camshaft

One big question and a couple of supplementaries.
I'm having to rebuild the engine on my son's car (1972 RWA). The camshaft looks quite worn but not yet through the case hardening. I have been offered a brand new A+ shaft part no. 12g2983 - would this be suitable?
I realise this needs a slot drive oil pump, does this cause any problems in the midget engine (bolt spacings, fitting inside the "tin can" etc)?
Is it worth fitting new cam bearings, visually they don't look worn or scratched?
BTW it's a very long time since I worked on an A series engine, so probably lots more questions to come.
Thanks
Bill
W Dunsmore

With this perticular camshaft thats a defiant yes on replacing cam bearings

The 1275 to my knowledge donst have an issue with worn cam bearings ive only seen one person that i can recall had a cam bearing issue BUT its also a good shop practice to have them replaced when your having the block machined

That said... you didnt provide much info on the camshaft so i googled the part # and came up with an interesting artical...

The cam is known as a rifled cross drilled camshaft...(i have never heard of this) but in a word its like the crankshaft it uses pressurized oil to flow thur rhe core of the camshaft and out thur the sproket

For some reason i thought all cams are like this with oil passing thur the center...i guess not

The problem is it takes specialised camshaft bearings and the A+ oil pump (may need some modifying) and maybe need a special sprocket or modified for the oil to pass thur.and extra machine of the block from my intial read

My gut tells me this free camshaft could be extrmely expensive... but still cool idea

Try looking up swifttune, they got great cams and engine kits at very good pricing... im a customer and a fan

The cam there known for is the Swiftune SW5-07 ... they make there own camshafts in house and are not regrinds so no core charge

Here is one of several articals i found for the code # you posted... the code you show is listed as a cross refersnce # to this rifled cross drilled camshaft

http://www.bpnorthwest.com/camshaft-rifle-drilled-and-cross-drilled-a-series-1275.html

Im in no way an expert but others here will have a better thoufhts then i can provide

Good luck... im interested in what the others have to say

Prop
1 Paper

I did find 1 uk supplier that has 1 in stock, so he may be able to help withthe details and sourse the extra part you will need

I think minispares has one listed on ebay at the moment so you maybe ableto use them also as a sourse of info and parts needed

Also ...it appears the pressurised oil is actually distrubuted thur the lobes and into the lifters... fascinating,??? ... to me that seems like it would create a weak lobe considering the forces agianst it

Also there is other info by adding the capitol letter N to the end of your code number without any spaces or additional digets....sorry i ran out of time and didnt get to search that option

Good luck
Prop

http://www.mgroverpartfinder.com/Distributor-12G2983---CAMSHAFT.aspx
1 Paper

Bill

From what I can see, it is probably a standard A+ camshaft.

What Prop so referring to is something that has been modified.

Some A+ oil pumps will fit under the tin cover, but some high capacity pumps won't. Bolt spacing is the same on the 1275 version.

If the cam bearings look good, I would leave well alone. I would change the followers, though.

If you want a good, used Midget 1275 camshaft, I have one or two.

daveo138 at yahoo co uk
Dave O'Neill 2

What Prop is trying to talk about is a cross drilled billet camshaft.
It picks up pressurised oil from the forward bearing, flows it through its central bore, and passes it out through a hole in the lobe base.
Oil is not passed through the sprocket nor into the cam followers.
It does not need specialist machining nor specialised bearings. It wont require special sprockets either. Fitted one yesterday.
Alan
Alan Anstead

Thanks alan

Like i said, ive never heard of anything like that before and im just passing off what mentioned in the articals i found

Appearantly a rare cam

So what does that mean when it says the pressured oil flows thur thw lobes...does that mean the rifleing is off center so the oil is passed thur (horizontially) thur the length of the cam shaft ?

Prop
1 Paper

The camshaft is drilled end to end and then through the base of the lobes to the central passage. The ends are then blocked off. It picks up pressurised oil, through a bearing in the block, which flows the length of the cam exiting the lobes. I said it gets oil from the the front camshaft bearing but it might actually be the middle one.
Someone will surely correct me.
Most camshaft suppliers supply cross drilled camshafts but they cost a bit more.
The one I fitted on Saturday was an A.C.Dodd designed Road Torque Specification ground by Kent based Newman Cams.
I have another on the shelf, to fit sometime, as this camshaft is seemingly popular with my local group.
Alan


Alan Anstead

Bill, I did my best to get a slot drive oil pump that fitted. The fixings were OK on a Metro pump, but it didn't fit in the tin can (I made it fit, in the end).

What's the type of oil pump drive on your existing cam?
Nick and Cherry Scoop

Nick, was it a high capacity pump you were trying to fit as Dave suggested or is the tolerance so tight that some ordinary pumps fit and some don't? The cam and pump are the originals so star drive.
Dave, the cam I removed has some scoring up the ramps and a number of the lobes have a linear scratch or crack right at the point, detectable by the "fingernail" test. I presume this is a good enough reason not to reuse it. Some of the followers have actually worn through the hardening, new set already acquired.
Bill
W Dunsmore

Thanks for the feedback and offer from Dave. I've decided to go with the NOS cam and keep fingers crossed on the oil pump. I'll be starting the rebuild in a couple of weeks once I get all the bits together and return for refund the new cam thrust plate that arrived this morning with apparently no white metal on either side and looking like it had been filed flat by an O level metalwork student on a bad day.
Cheers
Bill
W Dunsmore

Sorry Bill - missed your reply. I didn't know about high capacity oil pumps, so can't tell you. Ordinary, I expect it was.

Good luck. You're bound to find a pump that fits.
Nick and Cherry Scoop

This thread was discussed between 09/07/2017 and 14/07/2017

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