[Jako]

Can this be really happening ? Hitchcock's 4 valve heads and long stroke crank

[Otto_Ing]

  ....I dig it.

Four valves and a stroker? Kind of contradictory setup.

[Adrian II]

Well, that is their facebook page so I assume it's really happening.

Not sure it needs the long stroke crank but we'll see how this pans out compared with Ace's Billet Head Fireball conversions.

Now why didn't they offer this for the AVL models?

A.

[malky]

I bet you the kit will cost more than what some GT's are selling for in the UK. I have every confidence it'll be good, but I'd make sure the bike was a long term keeper before shelling out.

[Adrian II]

Ace's stuff is not cheap either, people have to cover their costs at least or it's not worth doing commerically, which is why there are no more AVL Fireball heads for the moment.

However I don't think we could ever accuse Mr. H. of under-pricing.

HMC will have to judge the market carefully, I wonder how many of their super special 5 speed boxes are unsold at 6 or 7 times the price of a pefectly adequate Indian 5 speed box. No use getting a batch of 100 4 valve heads made if the price scares the customers off, we know the long-stroke cranks will hurt the wallet enough.

On the other hand, a hybrid kit fitted to a set of C.I. cases might make for a very nice engine...

A.

[malky]

I'd like to get one of these to play with.
Not much chance.

[ace.cafe]

It can be good if they do it right.
It comes down to the 4-valve has more flow area, and needs less lift to reach the necessary flow. The 2-valve has less flow area, and needs more lift to get there.

Bottom line is that both types can service the necessary flow at the rpm ranges involved. Six to one, half-dozen to the other.

The other aspects besides number of valves will be at least as important,  if not more so.

At least I won't be so alone losing money doing this stuff now.
 

[Otto_Ing]

HMC will have to judge the market carefully, I wonder how many of their super special 5 speed boxes are unsold at 6 or 7 times the price of a pefectly adequate Indian 5 speed box. No use getting a batch of 100 4 valve heads made if the price scares the customers off, we know the long-stroke cranks will hurt the wallet enough.
A.

100 would be a number, that could help with the cost substantially, but 100 heads on the RE market...

[ace.cafe]

100 would be a number, that could help with the cost substantially, but 100 heads on the RE market...

Maybe the catch phrases will help.

You know, the general market seems convinced that OHC and/or 4-Valve arrangements are "modern requirements ", even though they rarely understand any of the underlying matters about why, or indeed, if.

A 100+mm stroke is piston speed limited in rpm. Lightweight multiple valve arrangements and/or direct actuating cams are of very limited value in such a platform, and increase cost and complexity. However, they can still be a very good performing package if the application is well designed. So it can be a real good thing in spite of the potential "overkill" nature of the application.

We shall have to wait and see how it comes out. I am as interested as anyone about it.

[Otto_Ing]

Absolutely, it will be exciting see this develop. The market reaction even more so...

[Arizoni]

It's not as though a long stroke, 4 valve head is something new.

In 1911, Indian had a 61 cubic inch, 8 valve, V Twin engine powering some of their racing motorcycles. 

[Adrian II]

That's true, Royal Enfield also had some 4 valve singles in their 1930's model line-up.

If the new 4 valve head is any good (let's hope Hitchcock's have fewer foundry problems than they did with the last batch of big head castings) it will probably work very well with a stock crank as a 535, no need for the 112mm stroke carank, and as such would make an interesting comparison to Ace's high-lift 2 valve billet head.

So to build the hybrid engine we need a set of late C.I. crankcases, a 500 AVL/Electra-X crankshaft modified for the C.I. Bullet big-end oil feed, 500 UCE barrel plus the new head and whatever piston the new kit uses. That means I will have to try and track down ANOTHER Redditch frame, sigh... 

A.

[Adrian II]

Also, regarding the benefits of keeping the stock stroke for these engines, remember our friend da punds ran his big head Fireball as a 612 for a while, but he put it back to 90mm stroke and was happier with it as a 535.

A.

[ace.cafe]

Well, regarding a hybrid package, the pushrod oiling system that we use cannot work with solid tappets. So the CI external oil line to the head would plumb into the oil temp sensor location for oil feed. This is one reason why we retained the UCE oil feed passages in our head. It can do the oil feed lthat way, and we have changeable oil spray jets which allow you to change orifice size to suit the engine oil delivery pressure and volume. So you can use tighter orifices for a lower oil feed like a CI or AVL and still get a suitable squirt velocity to get the oil up on to everything in the top end.

For more general info regarding a hybrid:

The stud pattern is the same, but new stud lengths are needed to make.

The head does not use a spigot like the CI, but a CI barrel could have the spigot milled off, or just use an AVL or UCE type barrel and suitable length con rod.

CGT 535 piston with rings can be used.

Regarding 612 or 535, there are numerous discussion points.

First, I already mentioned piston speeds are significantly higher with the 612. This is good for lower rpm torque, so that is a plus. However,  it gets into the area of too-high piston speeds earlier then too, and that limits safe rpms to a reduced level than the 500/535. So, it would typically be considered as a lower revver than a 500/535.

Also, the bigger displacement draws harder on the intake system at all revs. This is again good for low rpm torque,  but runs out of power earlier than a 500/535 , given the same port size. Again, reinforcing that lower revving character of that long stroke package.

We have found that the long stroke crank just revs up a bit slower too, so it doesn't accelerate as quick.

Now, this is all fine for certain applications, such as making a lot of torque beneath a 5500 rpm rev limiter like we have in a UCE. Or, for use in a sidecar pulling application.

For higher rpm applications, we'would feel happier with the 90mm stroke, or even shorter. The 4-valve system would have more benefit at higher rpms, IMO.

I do think that if Hitchcock can make a good quantity of these as castings, he could bring the price down into a somewhat more affordable range.
I simply cannot do that with the individual billet manufacturing process, and I  cannot afford to make 100 units at a run. I don't have funds anywhere near that amount.

[malky]

It will be most interesting to see the outcome. I have this strange formula which equates to Pounds or Dollars spent, in relation to increase in performance and usability. I am guilty of forgetting that either I or someone I know has the ability to quietly get on with the job and hope for the best. My old 500 Bullet would go "off the clock" but realistically it was probably doing in the region of low to mid 90's on standard gearing (it had a steel rod). Left with standard gearing meant it was tractable from around 30mph to flat out in top, which made it ideal for the type of roads I ride, and my riding style. My mate threw a shed load of money at his bike, built close to the spec of Hitchcock's "end to end" Bullet. OK it probably had a 20mph+ advantage on mine in a straight line, but on a twisty road it was a pig. It wasn't overgeared in respect of straight line top end speed, but where my bike made up, was as result of better midrange power (for which it was intentionally set up for and not having to "play tunes" on the gearbox. So for a difference of over £2000, is 20 - 25 mph extra, worth it. OK I spent a lot of time and got a lot of work done FOC but still ?

Finally, a question.
Somewhere in my collection of notes, which I can't find, I have a letter I got pre internet days, from a guy in the States who successfully raced a flat track bike with a Fury motor. He was using modified Chevy con rod blanks (i.e. before they were split and machined ) anyone know what they were ?