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I happened to be rereading the " Head Flow Testing" thread today and came across the following
Ex member Caustic Carbon fibre questioned the value of flow testing for an old Dinosaur like the Commando.
Jim responded with 13 things he had learned from flow bench testing Commando heads.
Number 7 relates to the discussion above.
From that post-

7. Bigger valves are nice. Re-angled valves are not.

I happened to be rereading the " Head Flow Testing" thread today and came across the following
Ex member Caustic Carbon fibre questioned the value of flow testing for an old Dinosaur like the Commando.
Jim responded with 13 things he had learned from flow bench testing Commando heads.
Number 7 relates to the discussion above.
From that post-

7. Bigger valves are nice. Re-angled valves are not.
Of course if you could stagger the entire valve over without reangling it - that would be more ideal. But then you would have to move the rocker arm with it along with the pushrods (or make longer rocker arms) and that would be great - but too much work. No one has moved or elongated the rocker arms to my knowlege but Herb Becker and myself (there may be others).

So everyone re-angles the guides to make room for larger valves.

The proof of high HP Nortons with bigger re-angled valves starts all the way back in the 1970s when Ron Wood was getting 84 HP from his big valve short stroke 750. Then there is Steve Maneys claim of approx 100 hp with a 1000cc big valve. Herb Becker has seen over 95 HP with the big valve 920 he built for Andy. Etc etc.
 

Fast Eddie

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If you have a mild cam it is possible to go a little bigger on the valves without clash. But if you want a serious performance cam ‘package’ that means a bigger cam and bigger valves and it just isn’t possible to to so without re-angling.

But perhaps it is not ideal as Glen pointed out, therefore John is probably right to sell normal heads with normal angles.
 
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Of course if you could stagger the entire valve over without reangling it - that would be more ideal. But then you would have to move the rocker arm with it along with the pushrods (or make longer rocker arms) and that would be great - but too much work. No one has moved or elongated the rocker arms to my knowlege but Herb Becker and myself (there may be others).

So everyone re-angles the guides to make room for larger valves.

The proof of high HP Nortons with bigger re-angled valves starts all the way back in the 1970s when Ron Wood was getting 84 HP from his big valve short stroke 750. Then there is Steve Maneys claim of approx 100 hp with a 1000cc big valve. Herb Becker has seen over 95 HP with the big valve 920 he built for Andy. Etc etc.
Are these figures at the crank or rear wheel?
 
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If you have a mild cam it is possible to go a little bigger on the valves without clash. But if you want a serious performance cam ‘package’ that means a bigger cam and bigger valves and it just isn’t possible to to so without re-angling.

But perhaps it is not ideal as Glen pointed out, therefore John is probably right to sell normal heads with normal angles.
Nigel, what size intake valve does your Comnoz modified RH10 use? I recall that you ran a JS sporty cam of some sort with that, and got a very good result, not 85 or 95 rwhp, but enough to destroy the stock trans over time.
Most aren't looking to spend $6k on a TTI trans, but might spend for a new head.
The stock Fullauto head on a stock motor gives 10% more torque at 5500 rpm. The transmission might hold up to that.
That's a pretty good bolt on.

Glen
 

Fast Eddie

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Glen: 3mm oversize inlet and 1.5mm oversize exhaust. JS#1 cam but with the lifters ground to 7/8” radius rather than 1 1/8”. IIRC.

That, along with other work, resulted in 65rwhp with a very linear power curve and fat, flat torque curve.

The gearbox held up fine to that to be honest. I’d be happy to run that engine / gearbox combo again. But, it did have a stronger AN shell and I was running a belt with alloy basket and Barnet plates, which takes a lot of weight (thus stress and flex) off of the gearbox mainshaft.

Where did you get the “10% more torque at 5,500rpm” info from out of interest ?
 
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lcrken

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Are these figures at the crank or rear wheel?
The Ron Wood numbers are at the rear wheel on Axtell's Heenan & Froude brake dyno, corrected to standard temperature and pressure. Steve Maney's 100hp for the 1007 cc engine is crankshaft hp, obtained by using a correction factor on the measured rear wheel hp. Measured rear wheel hp, corrected to standard temperature and pressure, was 86 hp at 5056 rpm. I don't know which Herb Becker's numbers are.

Edit: Herb Becker's 920 engine numbers are 95 hp at 7500 rpm at the rear wheel.

Ken
 
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Fast Eddie

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The Ron Wood numbers are at the rear wheel on Axtell's Heenan & Froude brake dyno, corrected to standard temperature and pressure. Steve Maney's 100hp for the 1007 cc engine is crankshaft hp, obtained by using a correction factor on the measured rear wheel hp. Measured rear wheel hp, corrected to standard temperature and pressure, was 86 hp at 5056 rpm. I don't know which Herb Becker's numbers are.

Ken
86rwhp at 5056rpm ?

Strewth !
 
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Are these figures at the crank or rear wheel?
Are these figures at the crank or rear wheel?
Ron Woods 84 HP 750 short stroke was a rear wheel output number on Axtell's dyno. Ron and Axtell worked together to perfect that motor. Herb Beckers 95 HP figure is also on a rear wheel dyno. As Ken mentioned - Steve Maney's was a crank HP number.

Ron told me that the Norton people didn't believe his numbers. So he flew to England with the motor and showed them. It revved to 8000 and would barely make it through a dirt track race. One problem was pulling the through bolts out of the cases because everything was milled - The cases, the cylinders, the head, even the copper head gasket because he was using stock aluminum rods with the short stroke crank to keep down the reciprocating weight.
 

lcrken

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Update, I just hunted up Eldo's post on the Herb Becker 920 engine. He said the 95 hp at 7500 rpm was at the rear wheel.

Ken
 
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Nigel, what size intake valve does your Comnoz modified RH10 use? I recall that you ran a JS sporty cam of some sort with that, and got a very good result, not 85 or 95 rwhp, but enough to destroy the stock trans over time.
Most aren't looking to spend $6k on a TTI trans, but might spend for a new head.
The stock Fullauto head on a stock motor gives 10% more torque at 5500 rpm. The transmission might hold up to that.
That's a pretty good bolt on.

Glen
So they will drop $20k on the engine and then can't spend anything else to make sure the power gets to the rear wheel?
 

Fast Eddie

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So they will drop $20k on the engine and then can't spend anything else to make sure the power gets to the rear wheel?
Pretty sure Glen isn’t planning to spend $20k on his motor Swoosh. He’s already got most of it, he’ll struggle to spend $2k I reckon !
 
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Pretty sure Glen isn’t planning to spend $20k on his motor Swoosh. He’s already got most of it, he’ll struggle to spend $2k I reckon !
A 100hp engine is going to cost at least $20k.

You can barely rebuild a stock engine for $2k. You'll have more than that into the head for a flow and rebuild.
 

Fast Eddie

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A 100hp engine is going to cost at least $20k.

You can barely rebuild a stock engine for $2k. You'll have more than that into the head for a flow and rebuild.
Yeah... you‘ve lost me!

Glen isn’t building a 100bhp engine.

Pretty sure (most of) those that do, also fit suitable gearboxes.
 
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For the Special I'm building, so far it's been quite inexpensive. I would like to see how much performance can be had with a reasonable outlay of cash combined with an unreasonable amount of free labour.

My comment on the transmission is based on the idea that most Full Auto head customers are not also planning to purchase a TTI trans to go with it. This is something that is generally done with full race type Commando engines.
I really have no idea or experience regarding the valve re-angle question, however the designer of the Full Auto head says it's not a good idea. So perhaps G81 has it right by leaving that area alone. It doesn't need to be redesigned for the 100 HP crowd. It might be a crowd of 2!
For the rest of us, a bolt on 10% is quite nice. There's a bit more available with slightly larger valves, if you are flush. Go much beyond that and it's time to put the stock motor under a bench, now you are building a complete new one off engine from aftermarket uprated parts.
I could be wrong, but I don't think this is the main market for new heads.
My guess is the number of people building an extreme high performance Commando engine would be very small, tiny even. Those people can generally figure out a way to do such things as valve re-angling, if it is a must have.

Glen
 
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Glen - the "designer of the Full Auto head" installed big valves all the time. He installed them in Fast Eddies and he did it to increase performance. The small valves in the Norton are a hold over from the SS 650 and they are undersize for a 750 and bigger. My original post was not to suggest that John make heads with bigger valves but to reangle the stock size valves and the OD of the seats so anyone could install bigger valves if they wanted to. Its better to have the option to go to bigger valves than to be restricted in your choices. If you simply move the entire port a couple millimeters towards the manifold along with re-angled valves then you lose nothing - you have the same flow as stock. Its a win win situation and you get the best of everything. This is really about increasing the efficiency of the Norton motor - not going to extremes. And it wouldn't have to cost a cent more if John offered his heads that way.
 
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"Glen - the "designer of the Full Auto head" installed big valves all the time. He installed them in Fast Eddies and he did it to increase performance."

Yes, this is the point I was making. Bigger valves can already be installed in the Full auto head for those who want them.


Comnoz did this without re-angling the valves and also recommends against re-angling.
I'm not sure why, but he must have his reasons, otherwise you can bet that re-angling would have been part of the Full Auto design.
I see your point that it would be good to allow for large valves and high lift if nothing else is lost, but there's that recommendation against re-angling.
Perhaps Jim will explain why.
 
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"The small valves in the Norton are a hold over from the SS 650 and they are undersize for a 750 and bigger. "
I believe this is incorrect.
From my reading, the 650ss intake valves are 1.406" for all versions of the 650ss head.
The Commando intake valves are 1.5"
Norton did increase the valve size with displacement, for the 750 at least.



Glen
 
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In the interview of an old guy from the Norton factory who died last year he mentioned a law in the UK that limited 750 twins to a 1.5" intake valve.
 
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