Discussion in 'Norton Commando Classic Motorcycles' started by jseng1, Dec 23, 2017.
Merry Xmas everyone. Enjoy the video.
Very interesting video. Amazing what can be done with basic hand tools combined with a whole lot of knowledge and skill!
I assume bigger valves are being used on engines where the displacement has also been increased, correct?
Thanks for posting Jim.
Bigger valve discussions here all conclude they help low to top rpm flows but some controversy on low rpm benefit and turbulence/velocity listening to likes of Engine Masters. Less heat flow capacity d/t more volume less surface area sometimes a concern. Wonderful ritual to watch and understand Jimmy. May be only way to get more out of Peels big port standard valve head with drag cam. Sometimes too small a bore confines hinders big valve benefits so usually only bigger bores worth doing it on.
What would be the service charge for such attentive work?
Fascinating, Jim. You've always been a master at developing ingenious techniques for machining cool stuff with basic tools. Your technique is one that anyone willing to put in the time can use. The only real machine shop equipment it seems to require is a lathe to make bushings and such, and maybe a decent grinding wheel for shaping tool bits. I've kicked around various tooling designs and procedures in my head to accomplish the same process using a milling machine, which is how most of the big valve conversions I've seen have been done. But I never followed through on any of the ideas. Good on ya for passing the info along to the rest of us.
And here I always thought that what I really needed to work on Nortons was a modern 5-axis CNC mill and thousands of dollars worth of CAD software. Actually, I still think that would be nice, but I'm afraid that train has already left the station.
There was a lot of time involved making some of the tools. I couldn't find any available counterbores that would work and I had to make or modify those. A mill is the common tool used but you still have problems aligning the rocker tip with the valve stem - not all Norton heads are exactly alike and some have been shaved etc. "Neway" valve seat cutting tools and "Goodson" guide lining tools helped inspire a lot of this hand tool technology for me - even if none of their tooling actually fits my application. It would be great if someone picked up on this and offered some tooling similar to that shown in the video above. It seems like there would be a market for it. The main idea was the Heim jts and they work very well with the angular alignment. As with all machine work - you have to be precise and careful setting everything up before pulling the trigger.
The motor in the vid will be a screaming 500cc roadracer.
I haven't decided on offering this service. Right now its just for special motors and customers who go to extremes.
That is a really interesting way of doing that. Thanks for posting it. I know I had one friend that did a lot of work on Vincents and he would do work similar to that by turning the whole cylinder head on the axis of the valves in his lathe. The layout of the Vincent heads makes that a bit suitable for that process. Another guy I know has a Serdi valve seat machine that cost about $60,000.00 and he can do most of that work as well, but the way you do it looks as though it is particularly good for the re angling, It seems a lot less awkward than putting the whole head in the lathe and you don't need a $60,000 machine. I am pretty sure if I wanted to put new valve seats in the Vincent that I could develop a method based on your process that would suit me a lot better than swinging the whole head in the lathe.
Once you have over-ported your cylinder head, there is no way back except by buying another one. If you believe that good results on a flow-bench mean a lot, you might find out you are wrong. What do you do when you find your motor won't pull unless you rev the tits off it ? This is one of the things we discovered from racing 650cc Triumphs. Many of us ported the heads bigger and ran lower gearing. The bikes went slower and blew-up quicker.
Fitting big valves is not the same thing as over porting. Opening up the throat and blending it into the larger seat diameter is also not over porting. One of the best Commando heads I ever used had huge valves with close to stock port diameters. Great flow at all rpm, but still plenty of port velocity for good mid-range power.
This is also a forum about Nortons, not Triumphs as that is comparing apples to tennis balls !!!
Thanks Jim a great post on re angling Vv's
keep up the good work.
Merry Xmas Regards Mike
A lot of work and a possibly compromised port throat via re angling valves. Why not maintain the standard angle, sink the valve and use a nice radius for pressure recovery into the chamber? The exhaust valve can probably be reduced in size for a torque increase as per modern practice.
Momus, it’s good to question the status quo of ‘good practice’ for sure. Especially from someone like you who brings in NASCAR thinking. There’s a lot old good old knowledge in the old bike world, but there’s a lot of old ‘folklore’ too!
The port and valve topic has actually been looked at quite scientifically on this very forum though.
I’d suggest reading the ‘cylinder head flow’ thread and the ‘time for spintron’ thread, both by Comnoz.
His findings show that big valves help with the port throat, and increase power and (contrary to most people’s presumptions) they increase mid range torque as well.
Like most things though, things have to be done as a ‘package’ to get given results.
Comnoz did my own head as a package and the results were astonishing (like a 9bhp increase and an increase everywhere from 3k upwards, measured before and after on the same dyno).
Both of the above threads are long, my advice would be to get in your best comfy arm chair and start from the beginning!
Yes - Good port work can have dramatic results. My 1st Atlas (see below) with 28mm ports was a dog with no top end. After some port work I was getting 2nd gear wheelies (low gearing). It was so fast that I decided to go roadracing.
There is an old article about Ron Woods flat tracker that had sunken intake valves and the valve seat shape that Momus describes. But they did much better later on with bigger re-angled valves and help from Axtell (84 HP short stroke).
For comparison - my friend Chris Scott used an Axtell cam and Axtell ports and got 68 HP on Axtells dyno. You can see the Axtell flow chart in Comnoz tests. The JS1 cam profile (on yours Fast Eddie) is a copy of the Axtell but Chris used 102 lobe centers and stock size valves. The tighter lobe centers make it difficult to avoid valve clash but kicks up the power band. His was a 750 but had open megaphones. I rode that bike on the street with peashooters and was very impressed.
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