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MG Midget and Sprite Technical - Engine number plate

I am thinking of getting my car's original engine back into it, so have dug out the block with a view to getting all the usual machining done. This will include skimming the top deck, so I need to remove the engine number. I have not done this before. The last time, the machine shop did it and gave me the plate afterwards, without ruining it. I find now that the rivets are incredibly hard. I don't have a drill bit that will touch them. The plate is pretty knocked about and may not survive the process. So the questions are:

1. How do I get the rivets out?
2. Can I get a replacement engine number plate? Maybe from British Motor Heritage?

I'm keen to do this because Frogeyes with original engines are quite rare now. No I am not going to swap the engine number to the one in the car, because (a) that's dishonest, and (b) the original block is marked 09C in the casting so you can always tell it's the correct one. BTW I have an almost period log book with the original engine number.

Les
L B Rose

Les. The rivets are a form of screw with a very steeply pitched thread. On the ones I have removed, I have used a cut-off wheel in a Dremel tool to cut a slot in the head, then used a screw driver, turned anti-clockwise, to remove the rivets. You might, depending on the thickness of the cut-off wheel, have to use two or three cut-off wheels stacked on the same mandrel to get the thickness of the slot you are cutting correct.

The other Les
Les Bengtson

They're drive screws and the usual method to remove them is a U shaped chisel to get under the head or plate and lift them out. Do you have a flat bladed screwdriver you can sacrifice to the cause. Another way is tapping the head from side to side which may loosen it up enough to allow removal.
David Billington

Minimail produce the engine plates in the correct under stamped form and supply the rivets.

They took quite a long time to do mine as I think they do them in batches - but they look good.

If you have to shear them off you could probably get away by re- drilling close to the original position, the other old hole being just covered by the new plate.

R.
richard b

I used the other Les’s method but with a hacksaw blade, then hammer and screwdriver to twist them out.

Then to replace them I just used some ally rivets that were a tight fit in the holes. I’ve now got the right plate but on the wrong engine. Or vice versa depending on how you look at it!!
John Payne

I use the claw part of a builder's claw hammer, just lightly/carefully tap it in under the rivet from the end is usually enough to lift the pin a bit, give it a wriggle about then spin the hammer around 1/2 a turn onto a couple of old icecream sticks placed along either side of the stampings and lever the pin out--works for me--they're not very tight just awkward to get hold of

willy
William Revit

Thanks folks. I used the other Les' method and one came out but the other fractured. Half the head is still there so I might get a claw hammer under it. As expected the plate is now even tattier, but at least I can get another one.

Les
L B Rose

Well the remains of the screw head broke off so that's the end of that. Drilling a new hole seems the only other option.

Les
L B Rose

Les. It is possible to drill the center of the rivet and use an "Easy-Out" (broken screw extractor) to get the remains out. If you do not have one, simply drilling the rivet with a slightly undersized drill should allow you to get the remains out. Les
Les Bengtson

I find that a well sharpened wood chisel (not your favorite cabinet makers' one!) will cut through even the hard steel rivets pretty effectively. You can slide it between the alloy engine plate and it won't then do much if any damage to the plate. A few sharp blows with a hammer will slice the top of the rivet off.

You will then still be left with the rivet remains to drill out although it may lift out with the blows from the chisel. But drilling it is easier with the plate out of the way anyway.
GuyW

IIRC drive screws are often a case hardened low carbon steel so you may have luck and be able to drill and possibly tap the core which may enable the removal of the remaining screw section.
David Billington

I tried to drill one in-situ once, I found out as the drill started to wander off that the block was much softer than the remains of the pin.

If the holes are siginificantly deeper than the pins that came out you can also punch the remains in and put a new pin on top. Assuming you are the first person to try this of course!

Otherwise leave to the machine shop, it's a trivial job if you already have the block mounted on a milling machine.
AdrianR

I did manage to drill down the softer middle of the screw, but then the case hardened sides collapsed into the hole and resist drilling out. I have an extractor but it's no use now. I'll probably leave it to the machine shop.

Les
L B Rose

Not being one to give up, I eventually got most of the bits out. The more I tried the further they jammed in, and of course could not be drilled. So the hole ended up a lot bigger, restored by tapping it 5/16" UNF and making an insert from an old bolt.

Les
L B Rose

This thread was discussed between 19/06/2021 and 27/06/2021

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