[ace.cafe]

Well, I just happen to have the flow bench information on the AVL head right here, so we can discuss.

The AVL rockers do have about 10% lift multiplier ratio built in, and the cams have .300" lift on the intake, and .280" on the exhaust. So, we have max lifts in the vicinity of .330" on the intake, and .308" on the exhaust.

These flow figures that I have do NOT include the manifold stub or carb attached to the head. These are bare head numbers.
We are looking at a peak intake flow of about 157 cfm, and 123 cfm for the exhaust. This is very very similar to the stock intake flow of the Iron Barrel head at similar lifts, except the Iron Barrel exhaust port flows about 10 cfm more because it is a bigger exhaust port and valve. So, we find it no surprise that it also gives about the same power as an Iron Barrel engine which had its compression raised to a similar figure. Apples-to-apples, very similar indeed.

However, we find that if the lifts are increased, the stock AVL intake port does have some ability to flow beyond the stock Iron Barrel intake port, but the exhaust port has a problem at .400" lift and begins to "back up" and lose flow at that lift, which is an indication of a problem in the exhaust port. So, the exhaust port has some problems.

The AVL responds to a larger intake valve and to some porting of both ports. With a 1.8" intake valve and a 1.57" exhaust, things definitely seem to look up. Without any additional lift over stock we got up to 183 cfm after making these mods on the intake side, and got rid of the exhaust back-up issues at all lifts. So, a 26 cfm improvement on the intake side is getting us pretty close to the Iron Barrel Fireball flow rate. Not quite there, but getting close. Pretty good, especially for not having any change to the stock cams or rockers. With the Iron Barrel Fireball, we have higher lift cams to get our lift up to get the 195 cfm flow rate we have with that head.

But, if we add lift height, by cams or rockers, we can get a lot more out of this porting job. By adding Ace cams and the roller rocker package with 1.45:1 ratio, we can bring that lift at the intake valve up to .510" lift. And at that lift with this AVL ported big-valve head, it will flow 208 cfm at peak lift. That is a significant increase of 51 cfm(33% more) over stock, and in fact that is enough to support a peak hp rpm near 7000 rpm, with a carb of sufficient size, like 36mm.

Additionally, the combustion chamber improvement with the  new compact shape is more compact and efficient, which allows faster and more complete burn, which in turn allows us to use a higher compression ratio without detonation. So, we get more out of it on the combustion efficiency end of things too.

This is what is going to give that elusive 40+hp figure that was alluded to when the bike was introduced. We pull more torque out of it with more flow, more compression, better combustion, increase the lift and duration to increase the rpm capacity, and push it to 7000 rpm, and you'll get your 40hp at the rear wheel, which will be around 47hp at the crank.
Essentially, right about the same specs as a Norton Manx 500.

[motorman2whel]

47HP , that's impressive !  . Is it just me or does the AVL head resemble the old Fury head?  .

[DanB]

Wow, that sounds very cool ace.

This is what is going to give that elusive 40+hp figure that was alluded to when the bike was introduced. We pull more torque out of it with more flow, more compression, better combustion, increase the lift and duration to increase the rpm capacity, and push it to 7000 rpm, and you'll get your 40hp at the rear wheel, which will be around 47hp at the crank.
Essentially, right about the same specs as a Norton Manx 500.

Do you think the AVL or UCE bottom end can handle that?

[ace.cafe]

47HP , that's impressive !  . Is it just me or does the AVL head resemble the old Fury head?  .

Yes, it was intended to be a "new version" of the Fury Big Head. And there are some similarities, but it is updated with some changes for pollution control.

After having the opportunity to work on an AVL head, I think it is a pretty good head that we are able to do a lot with.

[ace.cafe]

Wow, that sounds very cool ace.

Do you think the AVL or UCE bottom end can handle that?

For a certain length of time, the length of which is yet untried and unknown. If it were mine, I would put new high quality bearings in it. The rest of it should probably hold up, except the stock clutch would not hold the power.

[Bullet Whisperer]

At least the AVL engines have a steel conrod with roller big end as standard, so in theory, the bottom end should be stronger than on the 'Classic' Bullets. The oiling system has much greater flow, too, but early engine failures still appear to be possible in some cases, going by what I have read on some forums. I have yet to have one in with a worn out or broken bottom end, though, but I have repaired countless 'Classic' types, but to be fair, there are more of them around.
 B.W.

[ace.cafe]

I agree with B.W. on this, and I think it is the general consensus.
While the parts may not be "racing grade" they are serviceable for reasonable duty, and 'should' handle some power increases okay.
I am leery of the bearings. RE likes to use cheap low-grade bearings in everything, for cost savings.

Owners can try out the longevity with power mods to see how it goes.

Like I said, if it were mine, I would upgrade all the engine bearings, including putting a fully-raced new roller bearing in the big end. I simply do not trust the factory parts or assembly in those areas particularly.

I recognize that people don't want to do that. I have been facing that since I started doing Enfield mods for people. But reliability and longevity are part of our goals at Ace, so we try to promote good practices to achieve that. In the end, each owner decides the extent of the work and expense in his bike. Different owners may have different goals, and expectations. The more power output and rpms, the higher the stress on the engine.

[armando_chavez]

are the ace cams better than the S cams in this application?  I've already made the decision to keep my avl enfield for ever, which means im definitely going to dump excess money into it in the very near future.  Nothing in life would make me happier than a 40 hp custom cafe enfield.

[ace.cafe]

are the ace cams better than the S cams in this application?  I've already made the decision to keep my avl enfield for ever, which means im definitely going to dump excess money into it in the very near future.  Nothing in life would make me happier than a 40 hp custom cafe enfield.

The Ace cams would require the Ace head mods and special valve gear. The S Cams are suited to the stock valve springs, which no other sports cams seem to suit.
So, it is a matter of application.

[Adrian II]

I think some of the talk of 40BHP for the 500 AVL stems from the previous UK importer's claim that the engine had been redesigned to be able to SURVIVE up to 44BHP output (if anyone were to develop it that far) rather than actually PRODUCE 44 BHP! 

[TejK]

This is what is going to give that elusive 40+hp figure that was alluded to when the bike was introduced. We pull more torque out of it with more flow, more compression, better combustion, increase the lift and duration to increase the rpm capacity, and push it to 7000 rpm, and you'll get your 40hp at the rear wheel, which will be around 47hp at the crank.
Essentially, right about the same specs as a Norton Manx 500.

All this with the stock Ignition timing ? or any changes to the stock TCI?

[ace.cafe]

All this with the stock Ignition timing ? or any changes to the stock TCI?

I'm sure that spending some time working on optimizing ignition timing adjustments would give best results.
However, so far we have not seen problems arising from stock timing with the higher compression and our chamber mods. Perhaps it might be a little better with a few degrees retarded from stock, because of the faster burn. It would be up to the owner to experiment with it to find the best timing.

The further the engine is modded away from the stock conditions, the more specialized tuning will be required. This is typical with all performance engines.

B.W.'s adjustable TCI box might be a good idea, along with some offset Woodruff keys, to give plenty of timing options.

[AVL Power!]

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

[1 Thump]

I'm sure that spending some time working on optimizing ignition timing adjustments would give best results.
However, so far we have not seen problems arising from stock timing with the higher compression and our chamber mods. Perhaps it might be a little better with a few degrees retarded from stock, because of the faster burn. It would be up to the owner to experiment with it to find the best timing.

The further the engine is modded away from the stock conditions, the more specialized tuning will be required. This is typical with all performance engines.

B.W.'s adjustable TCI box might be a good idea, along with some offset Woodruff keys, to give plenty of timing options.

Hi Tom
I have heard a lot about the woodruff keys. Are these installed on the crank?

[ace.cafe]

Hi Tom
I have heard a lot about the woodruff keys. Are these installed on the crank?

Yes, they are the key that holds the gear in the location on the crank that is desired. It indexes the timing gear. Offset keys can be used to adjust the timing by the amount set in the amount of offset in the key. These offset keys are fairly readily available, but I do not know the offset increments off the top of my head. On the Iron Barrel engines, we really don't need them.