Big valve heads - Steve Maney or Mick Hemmings? (2016)

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SteveBorland

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Just wondering if one had to choose between these two suppliers for the same work (larger inlet valves, all new guides, seats and valves plus necessary blending), which to go for?
Is Steve Maney more consistent because of his CNC setup or does this not make much difference? I must admit that I'm leaning rather towards Mick, but I really don't know. Steve does suggest going to a Stage 2 (which includes bigger exhaust valves) but I suspect that's a bit overkill for my purpose (which is to get a fast and fun road bike which is also fun for a trackday).

The bike has a PW3 cam and I'm planning on splurging on a set of the lovely JS pistons & rods, aiming for around 10 or 10.5:1 CR.

Comments? I really don't want to send the head across the pond although I have a very high regard for the various US tuners.

Cheers,
Steve.
 
johntickle said:
On an 850 I would go for the Stage 2 conversion.
Click to expand...

Interesting - what's the basis for this? I would be concerned that enlarging both the inlet and exhaust valves would move the torque curve further up the RPM range, which is not really what I want.

Do you have personal experience of this? I'm very interested in hearing as much as possible before committing my head.
 
Well my Comnoz reworked head has +3mm intakes and +1.5mm exhaust and shows more power throughout the entire range Steve.
 
Doesn't your rev limit and cam profile determine what mass valves you can safely use ?
 
Steve,
I have a 750 with a Maney crank, cam , & stage 1 head. Steve's Norton parts are top notch, but I think that 34mm diameter inlet ports & 3mm oversize valves are too big for a road going 750 Norton unless you ride everywhere at 4000rpm plus.
My 920 has a PW3 camshaft, Maney crank, barrels, & cases with JS rods & pistons. This engine however has a Fullauto head reworked by Jim Comstock. It has the same size valves as the 750 but 32mm inlet ports & smaller exhaust ports. It is a truly lovely engine for any type of road use.
If it was my head it would be going to Jim Comstock.

Martyn.
 
Matchless said:
Steve,
I have a 750 with a Maney crank, cam , & stage 1 head. Steve's Norton parts are top notch, but I think that 34mm diameter inlet ports & 3mm oversize valves are too big for a road going 750 Norton unless you ride everywhere at 4000rpm plus.
My 920 has a PW3 camshaft, Maney crank, barrels, & cases with JS rods & pistons. This engine however has a Fullauto head reworked by Jim Comstock. It has the same size valves as the 750 but 32mm inlet ports & smaller exhaust ports. It is a truly lovely engine for any type of road use.
If it was my head it would be going to Jim Comstock.

Martyn.
Click to expand...

Absolutely!
 
If it was a race built engine then maybe bigger valves but for a road going bike even with a hot motor you don't really need bigger valve, but if you want to spend a lot of money on a head then I like the Fullauto heads, just wish I could afford one.

In 1980 I build my hot Norton but am still running my orginal head and even to this day I still running with the stock valves that came with my Norton when I brought it new, but I have had the ports reworked twice in the last 35 years, getting the fuel and air flow right will make a big diffrents in how your bike will perform, I was lucky I worked at a Tec college for 31 years and the motorcycle teachers, there was 2 of them that were British bike crazy like myself and they knew their stuff and working in the maintenance fitting workshop for 15 years I did a lot of my own machining, shaved head, grinding of worn lifters etc, I had access to some nice well maintain machinery.

But it's not all about just the head, crank balance, pistons, cam, head work, carbies and ignition all work together, get it right and no need for bigger valves.

Ashley
 
If I was fitting larger valves, I'd also fit Jim Schmidt's BSA lifters and I'd lighten and polish the rockers. If you increase the weight of the valve train you probably get valve float more easily, particularly if you also fit a hotter cam. If you tangle the valves with the pistons, that is pretty much the end of the story. I don't do anything to my motor which might move the usable rev range upwards. Because that is where the valve train and bottom end approach their limits. If you increase the diameter of the inlet port much above standard, you will move the torque band upwards. From everything I've read and heard, revs kill Commando motors. I suggest you need to consider the loads due to the accelerations of all the internal components of the motor, they increase as the square of the increase in their velocities.
If you fit larger valves to a road bike without enlarging the inlet ports, you might get a bit more torque across your usable rev range but effectively lower the top of the usable rev range. - Probably won't matter if you never rev your bike to the limit or unless your valve springs start to collapse, and that is a problem anyway.
 
An 850 head (RH4 or RH10) is not ideal for a big valve conversion because it already has the large diameter valve guides.
Steve Maney has reasonably priced donor heads. He changes the bolt pattern from 750 to 850 and the combustion chamber squish area from 73mm to 77 mm if required.
I believe you can also specify 32 mm inlet ports for a Stage 2 conversion because the conversion on the inlet side is the same as Stage 1.
 
You might factor into your comparison actual turn around times on the rework. It can take some time for Steve to get around to things for various reasons! It is not his only business. Mick probably scores better here, particularly now he only does the work he wants, having moved away from general retail of Norton spares.

Include cost of ancilliary repair work and replacement parts, you just might be told that your RH4 has problems you didn't notice.

And you might be surprised that you might even have a Fullauto in your hands for closer to the options than you think.

And after all of that you might find that standard sized valves were perfectly suited to your usage!

Hint, I am happy with a standard Fullauto on my race bike! I love how it makes power, which is as important to me as what power it makes.

Even if it is eventually big valved that won't be because I see the standard valves as the big limitation. (actually, the biggest limitation is probably me!)
 
I suggest the major strength of the Commando engine is it's torque. Increasing horsepower by moving the usable rev-range upwards is an expensive way to go and once you have increased the size of the inlet ports, there is no easy way back. Fitting larger valves might increase torque, however it might come at a cost to reliability if the valves are heavier. I think that many guys subscribe to the idea that 'bigger is always better'. A good bike is not only the sum of it's component parts.
 
I've eventually managed to pull the head and strip it. The reason for the smoke cloud was quite clear - the DS exhaust valve guide fell out of the head together with the valve after removing the valve springs. I did find half a circle lying inside the valve spring pocket when I first stripped the head, now I know where it came from :-(

So now I also need an oversize exhaust guide. Here, I've two options - either get an oversize guide made up and inserted to leave the exhaust valves standard size, or see this as a hint from the Gods of Speed telling me that Steve Maney was right in saying that his Stage 2 (3mm larger inlet and exhaust valves) is the way to go.

Always assuming of course that the bloody head is not cracked anywhere that is.

Problem is that I keep on reading stuff that says that leaving the exhaust valve standard is perhaps better for a road bike, but then again, Steve knows his stuff.

Hmm.

/Steve in Denmark, feeling a draught blowing through his wallet...
 
Both 750 and 850 bronze guides are available from KPM (Kibblewhite Precision Machining) here in the US in .002", .004", and .006" oversizes. I presume stock iron guides are also available in similar oversize, but I've never looked for them. Probably a lot cheaper than having one made. If you have trouble finding them, I have all the KPM ones in stock except the 750 +.006" exhaust, and could ship one or more to you. If you need more than .006" oversize, you will probably have to have one made.

Did you ever mention whether you are working with a 750 or an 850?

Ken
 
Thanks Ken. I knew oversize guides are available, but thanks for the details. Its an 850 by the way
 
I once used iron guides in my short stroke Triton. It went off-tune at a race meeting and I could not fathom why. A few meetings later I had the head off and noticed a mark on a piston. A small piece of guide had come off and dinged an exhaust valve, so I was losing compression.
 
Well, based only on my experience I'd be confident in using your current head. Personally I would no go for re-angling the exhaust valves.
 
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