improving VB performance

[brenton.roy]

I've been inspired by a series of events - an ebay sale that didn't work out and an article about Hartley's fast sidevalve - to have a go at building a warm 600.
I emailed with Chris Reynolds in the UK a few years ago, and he gave me quite a bit of info about his Hartley motor.
I was silly enough to pull the bike apart after the sale, thinking I might be better to sell it as a running bike. I found I needed to replace all of the usual parts and so while it is apart and while I am repairing stuff, I may as well do some tuning work.
This motor will be limited by a renewed, but original crank assembly. I also don't want to lose all of the feel of the sidevalve.

I am mostly interested in your ideas around the inlet tract, a cam profile (or at least timings), carburetion, gearing and general tips.
Thanks in advance. Brenton

* I have been able to source a Hartley profile cam and advice that 1 1/16" is a good start for the inlet tract.

[john.nash]

ahem .. just put an OHV top end on it (just a compression plate needed)

[brenton.roy]

Hmm, yes probably easier John - but two issues there. The big one is Finding a 500 top end! The other is the fun of it. I am waiting, not very patiently, for the cam to arrive and have a porting tool at the ready. For motivation - http://www.arielownersmcc.com/members ... /index.htm and http://www.arielownersmcc.com/members ... /index.htm

[tony.barnett]

I guess reducing the weight has got to help - look for some fibreglass or ally mudguards, ditch the tool box and stands, ally rims, smaller fuel tank.

[nevhunter]

Please, Don't be offended by what I am going to say . Side valve engines have a couple of problems if you want to get power out of them. There is a lot of heat around the exhaust port area and a lot of resultant distortion. This causes a lot of blow-by. Also the combustion chamber shape is far from optimum. ( Large surface area to volume) and you just cannot get the compression above about 5 to one without creating a restriction to gas flow. You need a lot of ignition advance if you are going to rev it. ( Not a good idea with a VB)
Having said this, some American 750's (class C) I/2 mile track bikes were turning out above 65 HP. In fact when the OHV twins were introduced it took over three years before they got them better than the Sidevalves, but years of development had gone into the flatheads wheras in england there was little development of the sidevalve, the logic being if you wanted snappy performance, you utilised an OHV. The sidevalve was preferred by some for sidecar work, because of it's simplicity and better reliability, This was a hangover from the earlier days when exhaust valve metal wasn't up to much and a broken valve stem had much less disasterous consequences in a SV compared to what used to happen in an OHV. In the later engines with enclosed and lubricated valves there is little difference in reliability across the types. The SV has it's own appeal though it the smooth slow revving torque it delivers. Tuning them can lose this attribute. Nev

[brenton.roy]

Hi Nev, I'm not that easy to offend. The things you are talking about are the challenge. I was roadracing a few years back and there were a pair of quite fast WLA's running in the classic class. Admittedly twins, but still quick.
I'm sure there is every chance I will stuff up somewhere! I have OHV Ariels, which I love, and which no doubt have stronger motors, but have always wanted to have a go at this.
I've been looking for ideas re modified head design and have found a bit of info, mostly re US and English car heads for racing. I'm not sure how this translates?
This bike is really to learn on and I don't plan to go silly. I have another bike and a later ally head motor to use if this one works out.
I had a chat with Dave Dyson in SA, who (as long as I supply enough money) can build me a stronger crank assembly and steel flywheels and I guess I could alter the stroke at that point. I hadn't considered this as a problem, but you may be right.
For now, what I plan is to clean up the inlet port (it's not really well cast anyway) and guide to 1 1/16", use the Hartley cam (which is a "B" version), mill 25 thou off the head and run a concentric.
I'm replacing (with standard) Mains, Big and small end bearings and piston, and will look for a later or Triumph oil pump. If I can figure out how, I'll do the mod to raise oil level around the cam.
If it gets hot, I'll look into Avgas / a methanol mix / ?
I plan to use 500 gearing and VH jetting as a starting point - but suspect I might need to go bigger? - mostly because I don't have a clue where else to start.
Thanks for your ideas.

[nevhunter]

I have built some fast Ford flatheads but a while back. and I fiddle with Harley flatheads and Pocket valves as well
Ok, Enlarge the inlet valve, use the better cam, and play with the inlet port length. A dome piston would help, ( ALA the Hudson Terraplane and Ford mercury ". Does the later alloy head fit (I thought it had more studs). The long stroke is an advantage performance wise as it breathes better and you can get more compression. It's only the mechanical considerations, (limiting revs). Some engines remove metal fron the cylinder top face between the valves and the cylinder. Radius down into the bore in this area but the top ring may be exposed if it is too close to the top.. Use a 3 comp ring piston if possible. ( I wouldn't run an oil ring).
You may end up with a crack between the exhaust seat and the cylinder but it won't stop it running.
There are two ways of dealing with the gas flow around the valves.
One school of thought puts the valve up almost touching the head and assumes the gas comes out the side, the other one is that some comes around the other side of the valve too and clearance for this is provided in the shape of the head, in that case.
With a SV the cams can be pretty wild as the action is more direct. Some of the Harleys were doing high revs. (Tom Sifton would have had to be up amongst the best tuners in the US).. There was a sports JAP 350 SV, in the late 20's Cotton that turned fast too

[john.nash]

Brenton,

As I changed my VB for a VH, then I have a complete VB top end including a couple of pistons.
I also have two VB crankshafts. One in the OHV and another with big end gone. (I have a OHV crank to go back in at some point - so both cranks are spare really)
I have a spare (early) twin lobe 664 cam an followers

I could be parted from these, probably in exchange for OHV bits, but the problem is one of distance .. adelaide is a long, long and expensive way away ..

[brenton.roy]

Thanks John and Nev,
I'm waiting for bits to arrive (the big end is on back order...) - and have the frame primed - and a week off coming up.
John, thanks for the offer. I'll see how I go with what I have, but I do need some of these bits. I'll write to you direct when I get myself sorted.
regards, Brenton

[barry.swanson]

...an interesting project Brenton...are you going to race this or just get some more go from a road bike? Barry.