A British hole in the head.... what to do?

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Sam_Fear

Brother Rat
Joined
Oct 11, 2008
Messages
12,478
Location
Dixon, IA
We've been working on a rebuild for my wife's MG Midget motor that had about 120,000 on the odometer and #2 cylinder rings finally gave it up. (She just wouldn't quit driving it) At least the rings were my diagnosis - squirted oil in #2 and it brought the compression reading back up. Only other thing on teardown I found was #3 piston had some scoring on the skirt.

Anyhow, the PO had the head rebuilt about 15-20,000 miles ago. The machinist had also told the PO the bores looked good so don't rebuild the block end. I left the head alone beside just a quick look. It's got little double valve springs I didn't want to mess with and besides, it'd been rebuilt not that long ago so I figure I'll do a good clean and check later.

We get the block back and the wife gets to work wiping it down, so I decide it's later and time to get the head cleaned up - lots of carbon from burnt oil, etc.

Found something odd. From the factory there was a brass plug in the block between #2 and #3. The brilliant part is, the plug tends to extend into the cylinder chamber!? And apparently they tend to sink a bit over time, so the best fix is to thread the hole and put a steel plug in before surfacing the head.

It seems that is what the PO's machinist did. BUT they left gaps on the sides of the plug past the crush ring of #3 so it didn't seal 100%. Obvious by the burn in the gasket. It didn't leak anywhere beyond the plug area.

So, I decided to take it apart and see if my shop can't do a better job of it. While taking the valves out, I find intake of #3 is sticking and the guide is moving too, and there is a gouge in the valve base, but it still sealed. All others seemed OK.

Unless someone says otherwise, I think I'm just gonna have the whole head redone. Disregarding the valve guide problem, IMO that head shouldn't have left shop with that gap around the threaded plug. So what else did they not do diligently?

Am I right in that thinking?
 

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I've done better work under the influence.

I would definitely have that head rebuilt and the plug fit/machined perfectly flush!

.
 
Thanks Doc. Just needed a second voice. I was wanting a cheaper and faster way out of this, but know there isn't.
 
Don't let the valves and guides ride.
Have the shop replace and hone them correctly. You'll regret not doing this.
 
what size motor is it?

my dad has a rwd 1275 motor

he got the motor when he wanted to upgrade the 998 in the classic mini
but rwd and fwd A series motors are different because of the gearbox set up

so the motor has sat in the garage ever since

it would probably make a sweet motor for a go-cart with like a t-5 or something like that, lol
 
I told the shop to do the whole thing. Its the time more than money that bugs me.

It's a 1275. Heck, it's not that hard to find a non-running MG Midget for 5-700$.
 

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