line bored cases?

lwmcd1 · Oct 30, 2019

I have to rebuild. I blew the engine.
I going to have to replace the RH case.
I heard that the earlier Nortons were "line Bored"?
If true is that also true of the later ones?
Mine is a 1974.
Will I be able to use a case half from another '74?
Thanks,
Larry

comnoz · Oct 30, 2019

They were all matched at the factory -so they shouldn't be replaced one half at a time.
But I have seen it done successfully.

lwmcd1 · Oct 30, 2019

Well I guess I'll give it a shot then.
I have a machinist friend, Dave Carter of Carter Brother's Garage
maybe I'll stop by his place to see what he thinks.
It will give me an excuse to stop in for a visit.

Torontonian · Oct 30, 2019

Dare I ask what caused the blow up ?
Maybe fitting one of those stoopid valves in the feed line ?
That's what munched my 76 motor by the previous owner.
So when I bought it there was a welded up scar on the right side case upper rear. That's where the rod hit. Plus crank journals ground to the next undersize . Other scrapes internally to the crank and cases where the rod nut bounced around.
Good luck to ya. It's only money.

Hortons Norton · Oct 30, 2019

They still make them.

https://andover-norton.co.uk/en/home/

concours · Oct 30, 2019

lwmcd1 said:
Well I guess I'll give it a shot then.
I have a machinist friend, Dave Carter of Carter Brother's Garage
maybe I'll stop by his place to see what he thinks.
It will give me an excuse to stop in for a visit.

Dave can do it.

acotrel · Oct 30, 2019

Superblend bearings are designed to allow for flex in the crankshaft. If you are using those, a slight bit of misalignment might not be a big problem

kommando · Oct 30, 2019

On BSA Unit single took 2 B40 cases from different engines and had to do nothing, took a set of matching B44 cases and found dowels missing, replaced dowels and the crank would not spin so had to take them back out. You might be lucky.

bill · Oct 30, 2019

dave is not doing any work at the moment. if you need more info you can call me @ 4074843388.

lwmcd1 said:
Well I guess I'll give it a shot then.
I have a machinist friend, Dave Carter of Carter Brother's Garage
maybe I'll stop by his place to see what he thinks.
It will give me an excuse to stop in for a visit.

jseng1 · Oct 31, 2019

If the crank and cam turn freely you're probably OK. But you'll have to mill the deck surface for the cylinder base - or take a few thou off with a surface plate and abrasive. I did that once long ago with a plate of glass and coarse valve grinding compound when I was racing and dirt poor.

Danno · Oct 31, 2019

"Aye, where's me stick?"

lwmcd1 · Nov 1, 2019

Torontonian said:
Dare I ask what caused the blow up ?
Maybe fitting one of those stoopid valves in the feed line ?
That's what munched my 76 motor by the previous owner.
So when I bought it there was a welded up scar on the right side case upper rear. That's where the rod hit. Plus crank journals ground to the next undersize . Other scrapes internally to the crank and cases where the rod nut bounced around.
Good luck to ya. It's only money.

And oil line came loose from the oil filter.
I would never use a check valve.
I just resurface the oil pump when needed.

lwmcd1 · Nov 1, 2019

acotrel said:
Superblend bearings are designed to allow for flex in the crankshaft. If you are using those, a slight bit of misalignment might not be a big problem

That makes sense.
i only use SuperBlends anyway.

bill said:
dave is not doing any work at the moment. if you need more info you can call me @ 4074843388.

Is he ok?
I'll have to call or drop by to see him.
Good friend and doesn't live far from me.

Torontonian · Nov 1, 2019

lwmcd1 said:
And oil line came loose from the oil filter.
I would never use a check valve.
I just resurface the oil pump when needed.

Good. Thanks for the reply.

Matchless · Nov 2, 2019

The so called Superblends are NOT designed to allow for misalignment. Don't confuse them with self aligning spherical roller bearings. Any more than 0.0003" out of line would be unacceptable in my opinion.

Martyn.

comnoz · Nov 2, 2019

Matchless said:
The so called Superblends are NOT designed to allow for misalignment. Don't confuse them with self aligning spherical roller bearings. Any more than 0.0003" out of line would be unacceptable in my opinion.

Martyn.

Martyn is correct. Jim

jseng1 · Nov 2, 2019

Matchless said:
The so called Superblends are NOT designed to allow for misalignment. Don't confuse them with self aligning spherical roller bearings. Any more than 0.0003" out of line would be unacceptable in my opinion.

Martyn.

I think anyone would agree that a stock Norton crank is going to flex a lot more than .0003" when revved. My crank flexed so much at racing RPM that the big end sides of the rods were showing wear from misalignment and the pistons were hitting the squish band (starting with .050+" clearance). The superblends managed to survive. At Willow Springs (desert temp) racing heat I don't think the superblend outer races were all that tight in the cases. After all - they fall right out of the cases when heated in an oven.

cliffa · Nov 2, 2019

jseng1 said:
I think anyone would agree that a stock Norton crank is going to flex a lot more than .0003" when revved. My crank flexed so much at racing RPM that the big end sides of the rods were showing wear from misalignment and the pistons were hitting the squish band (starting with .050+" clearance). The superblends managed to survive. At Willow Springs (desert temp) racing heat I don't think the superblend outer races were all that tight in the cases. After all - they fall right out of the cases when heated in an oven.

That may be so, but the combination of misalignment and flex would only end in tears ( or worse).

no750 · Nov 4, 2019

jseng1 said:
If the crank and cam turn freely you're probably OK. But you'll have to mill the deck surface for the cylinder base - or take a few thou off with a surface plate and abrasive. I did that once long ago with a plate of glass and coarse valve grinding compound when I was racing and dirt poor.

comnoz said:
They were all matched at the factory -so they shouldn't be replaced one half at a time.
But I have seen it done successfully.

my crankcase is from two different motors. i aquired the needed drive side case from a very helpful norton enthusiast for low money together with the infomation about former norton twins had different spare-numbers for each case half and i should check for alignment and eventually mill the cylinder base. i found someone done this properly for me. doing good.

line bored cases?

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