[Bullet Whisperer]

Paul - The valve springs you used were competition springs by Hitchcock. I did check them on their site and it says that they work on Iron barrels only. Any idea if any sort of modification is required? or is it just plug and play type?

Regards,
Sanket

Hi Sanket,
 From memory, I think I fitted them using the lower spring seats which came with the spring kit, but retaining the original [AVL] spring caps, even though they had no register for the inner springs as such. I relied on the outer springs to retain the inner springs at the top. Also, Hitchcocks had [at that time], two different types of competition spring - they sent both types and I remember the type I chose being able to fully compress to a shorter overall length, making going coil bound less likely. I have included the one and only photo I took of this - sorry it is of rather poor quality!
 B.W.

[armando_chavez]

so what exactly has to be done to the head in order to fit compitition valves and springs or beehives

[AVL Power!]

Hi Sanket,
 From memory, I think I fitted them using the lower spring seats which came with the spring kit, but retaining the original [AVL] spring caps, even though they had no register for the inner springs as such. I relied on the outer springs to retain the inner springs at the top. Also, Hitchcocks had [at that time], two different types of competition spring - they sent both types and I remember the type I chose being able to fully compress to a shorter overall length, making going coil bound less likely. I have included the one and only photo I took of this - sorry it is of rather poor quality!
 B.W.

I checked recently and could find only one. I guess I will wait and see.

Regards,
Sanket

[Bullet Whisperer]

so what exactly has to be done to the head in order to fit compitition valves and springs or beehives

I can't speak for the 'Beehives', but the types I used were a straight swap, with no modifications to the head required.
 B.W.

[rep_movsd]

so what exactly has to be done to the head in order to fit compitition valves and springs or beehives

The beehives that ACE puts in the ACE Mondello heads are totally custom made for the special valves, it's not something you can plug in.

[armando_chavez]

well what i wanted to know is if the whole Hitchcocks competition set can be made to fit with easy to no mods i can do some stuff.  I feel like if its minor i can do it.  Do the HC valves and springs and everything fit?

[Bullet Whisperer]

well what i wanted to know is if the whole Hitchcocks competition set can be made to fit with easy to no mods i can do some stuff.  I feel like if its minor i can do it.  Do the HC valves and springs and everything fit?

No, they are for the 'Classic' type engines and a totally different type.

[Bullet Whisperer]

It just so happens I am working on 'Asbo' No 12, which is a fairly well known engine already to some of this group, being a hybrid of AVL top end and crank, but fitted on / in 'Classic' type crankcases. The cylinder head for this engine was modified by the fitting of Hitchcock's double competition valve springs some time ago, in my workshop. The work I am currently undertaking meant the valves needed to come out for cleaning and checking etc, so here are some pictures - as can be seen, I have used the springs and lower spring seats from the Hitchcock's kit, but the holes through the centres of the spring seats have been enlarged slightly, to pass over the valve guide seals. The 'stock' AVL spring seat shim has been retained, but an additional spacer, in the form of a suitable washer has been added. The outer spring sits 4.6 mm above the machined recess in the head with the washer, shim and spring seat underneath it. The 'stock' valve spring cap and collets are then fitted as normal, to compress the two springs and retain the valve. Exactly the same was done with both valves 
 B.W.

[AVL Power!]

Paul, I had a doubt. I have few friends who are running their iron barrel motors on high compression pistons and cams with higher lift. They never face any sort of valve bounce and can happily rev past 5500 or 5800rpm barrier. So do you think it's the AVL head which restricts the revs ?

-Sanket

[Bullet Whisperer]

Paul, I had a doubt. I have few friends who are running their iron barrel motors on high compression pistons and cams with higher lift. They never face any sort of valve bounce and can happily rev past 5500 or 5800rpm barrier. So do you think it's the AVL head which restricts the revs ?

-Sanket

Hi Sanket,
 I think the AVL head in its' standard form is pretty efficient, after all I was expressly forbidden to 'play with' the head on the original testbed machine, because everything had to be a 'bolt on' tuning part and as is well known I saw over both 33 BHP and 100 MPH from the end result, which could rev to 7000 RPM in the lower gears, although maximum power occurred at 6000 RPM. I stand by the cams holding the revs back, for whatever reason, as different double valve springs that will work for the huge valves in the 'big Head' types could not control the valve bounce until the 'S' cams went in. The 'Iron' types don't seem to suffer in this way to such a degree.
 B.W.

[ace.cafe]

It's possible that the stock cams have closing ramps that are very fast closing, and this can cause valve bounce. Changing the cam profile can solve that, and maybe those S Cams just have the right profile to do it.

And remember, these RE stock cams vary from one to the next, and it is possible that one set of cams might work okay, but other ones might not.

[Adrian II]

So the Chennai factory might have produced the odd set of "S" cams by accident, due to manufacturing inconsistencies. Excellent! 

I suppose that is just about feasible as the Indian C.I. Bullet cams have broadly similar though not identical profiles.

Valve bounce on stock AVL cams aside, it has always puzzled me as to why a skilled engine tuner, with a good selection of performance cams known to work in classic Bullet engines, could only find one set of cams that would really do the business, and these turn out to be a set of touring cams. There's definitely something about the 500 AVL engine that doesn't seem to want to play by the rules.

I'm at a loss to understand why the head itself should be to blame, so is there perhaps some peculiarity in the rocker design that makes this engine so attuned to one particular cam profile?

Still puzzled.

A.

[ace.cafe]

It also might be the valves. They are very long. This could cause a "springy" behavior when hot, which might lead to bounce.
When we do valve gear, we change out all the stock parts, so we are in control over what happens.

[AVL Power!]

So the Chennai factory might have produced the odd set of "S" cams by accident, due to manufacturing inconsistencies. Excellent! 

I suppose that is just about feasible as the Indian C.I. Bullet cams have broadly similar though not identical profiles.

Valve bounce on stock AVL cams aside, it has always puzzled me as to why a skilled engine tuner, with a good selection of performance cams known to work in classic Bullet engines, could only find one set of cams that would really do the business, and these turn out to be a set of touring cams. There's definitely something about the 500 AVL engine that doesn't seem to want to play by the rules.

I'm at a loss to understand why the head itself should be to blame, so is there perhaps some peculiarity in the rocker design that makes this engine so attuned to one particular cam profile?

Still puzzled.

A.

I am confused because of the same set of reasons. My friend has an AVL with UCE top end and even that one doesn't like to rev past 5500rpm or so. So I was wondering if the top end of Iron Barrels can give us more freedom? I guess it's worth the try 


Regards,
Sanket

[ace.cafe]

I am confused because of the same set of reasons. My friend has an AVL with UCE top end and even that one doesn't like to rev past 5500rpm or so. So I was wondering if the top end of Iron Barrels can give us more freedom? I guess it's worth the try 


Regards,
Sanket

Okay, well the AVL and UCE have very similar internal parts and design. They might even use the same valves/springs. I haven't actually compared those parts side-to-side. The springs on both are single coil with single diameter, and have no damping system.
Also note that the UCE has a rev limiter set at around 5500 rpm. This may be for a reason of valve control issues at rpms higher than that, which in the UCE could cause lifter pump-up problems.
So, we might be seeing a possible similarity of this sort of behavior on both of these models, possibly because they have these internal similarities.

The top end of the iron barrels will rev, as long as you change to performance valves and springs.