Hello all,

I'm in the process of getting the mini on the road and I've hit a bit of a snag. A small one but a snag no the less. After I removed what was left of the coolant bypass pipe that sits in the cylinder head, i've found that the new pipe won't go in. I've had a look at the thread and it looks undamaged, just covered in crud and needs a thread tap put through it. Could someone tell me what sized tap I need please?

Cheers

Simo

If I recall it's a 5/8 16TPI and is a special tap, same as the end of the crank shaft.

Just checked it is 5/8 16n
I would use a small wire brush in a drill, or a pick

Way cheaper than the correct tap as they are exspensive.

I put a 5/8-18 UNF tap in there (it's only got about 4 threads), then machine up a brass fitting. No more rusting...

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DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R.

Excellent idea Doc, then you won't have to replace it every 25 years.

Can't you just blank them ala Rover style? Don't shoot me, just asking.

Haha.
Every head I buy/acquire seems to be 40 years old, nothing much left there to unscrew so I stick a 9/16" drill in it then peel the threads out with the tap. I object to paying $10 or more for new adaptors with built in rust capability, so I make brass ones.

Sure you can plug it, I'd drill one or two 3mm holes in the thermostat to provide a little circulation during warmup.
The Rover heads are plugged but have a sandwich plate under the thermostat instead. I don't know how that is plumbed in the system- there ain't no Rover Minis around here.

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DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R.

Yeah, I think it's still by passes through the manifold heating section. Rover's have the most hiddius hose arrangement.