Author Topic: Ace GT Head Project  (Read 147208 times)

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Guaire

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Reply #645 on: December 02, 2019, 06:12:22 pm
That might be worth the short drive over to see...!

How short is it?
Bill
ACE Motors - sales & administration


Guaire

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Reply #646 on: December 17, 2019, 07:36:03 pm
These are the cams that will be installed.
ACE Motors - sales & administration


Guaire

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Reply #647 on: December 19, 2019, 12:14:38 am
I put the Conti GT on the 'lift' today to get things prepped for pulling the stock head. I couldn't help but note the difference between the stock rockers and the design of the Fireball rockers.
  A short video on getting started...
https://www.youtube.com/watch?v=pkaHQlS6Pjw&feature=youtu.be
« Last Edit: December 19, 2019, 01:09:35 am by Guaire »
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ace.cafe

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Reply #648 on: December 20, 2019, 02:24:59 pm
These are the cams that will be installed.

Lobe specs are .345" lift and 254 duration @.050" .

Rocker ratio changes things.
With stock RE rockers, estimating ~1.2 ratio, max lift would be about .414".
With the Ace head that has about 1.45 effective ratio, max lift would be about .500".

Rocker ratio will also extend the duration @.050" for more area under the lift curve, but the actual seat-to-seat timing will still be the same.

Stronger valve springs required with these cams.
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gizzo

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Reply #649 on: December 20, 2019, 05:34:27 pm
Those rocker arms make the stock setup look like a pathetic lash up. Nice.
simon from south Australia
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ace.cafe

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Reply #650 on: December 20, 2019, 10:10:43 pm
Those rocker arms make the stock setup look like a pathetic lash up. Nice.
Thanks!
 ;)

The rest of the head is also just as far above the factory product.
 8)
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jez

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Reply #651 on: December 21, 2019, 09:59:53 am
Just looking at your cams they have a lot more duration than the Hitchcock set, quite apart from the rocker ratio enhancing the lift. Hitchcock cams are not so much 'performance' cams. Rather they are what should have been fitted by the factory to match their own head.
 I suspect the original cams came about as a longevity feature to  compensate for the variable build quality. Something that seems to have been addressed with the twins. The twin was a British clean sheet of paper project. The unit single is just an evolutionary tweak of the old Bullet
 Oddly enough Triumph produced a similar cam for the 900, seemingly using the restriction to differentiate that engine's output from the 1200.


ace.cafe

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Reply #652 on: December 21, 2019, 01:57:48 pm
Just looking at your cams they have a lot more duration than the Hitchcock set, quite apart from the rocker ratio enhancing the lift. Hitchcock cams are not so much 'performance' cams. Rather they are what should have been fitted by the factory to match their own head.
 I suspect the original cams came about as a longevity feature to  compensate for the variable build quality. Something that seems to have been addressed with the twins. The twin was a British clean sheet of paper project. The unit single is just an evolutionary tweak of the old Bullet
 Oddly enough Triumph produced a similar cam for the 900, seemingly using the restriction to differentiate that engine's output from the 1200.
Yes, we aim to put the hp peak right at the 6500  maximum rpm limit that Dynojet will permit on the Power Commander. This shifts the torque curve up a bit higher, so we aren't putting as much emphasis on the very low rpms as the factory cams do. Our inlet valve closes much later than factory cams. We make up the low rpm torque with a compression increase gained by our smaller 50cc combustion chamber, and bringing the piston up to zero deck height with the "squish mod". That brings the low rpm torque back to reasonable levels, even without a piston change. We use the factory piston and still achieved about 185 psi cold cranking compression test with no perceptible pinking  during full load operation.

I got the impression that the factory cams were designed to produce a lot of low rpm torque for the India riding style of low rpm "thumping".  Probably also for emission control. They run out of breath very early in the rpm range.
Factory cams are like what we in the States call a "towing" cam profile for heavy pulling. Short duration and very small overlap period.
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JerryGT

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Reply #653 on: January 17, 2020, 12:06:42 pm
The same cams should work on non-Fireball UCE too. But, it will need the better valve springs added. No decent cams will be able to run on those stock UCE valve springs anyway, so better springs are a given with any performance cams on the UCE.

Sounds good.
My Problem is, I installed the HMC Performance-Kit, and I thought at the time when installing, that the supplied valve springs are too strong, but there was no alternative, HMC or stock, so I installed them. The pressure of the springs was enough to rotate the engine even in gear.

And after 2000 miles it turned out that the cam wheels and bearing shafts are trashed because of the brutal forces in the valve train, resulting in extreme wear.

I don't need that brutal spring force for the HMC-Cams and a set maximum of 6000 revs. But what do I need and where to get?

By the way: Does anyone know the spring strength of these HMC springs?


Regards,

Jerry
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ace.cafe

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Reply #654 on: January 17, 2020, 02:19:55 pm
Sounds good.
My Problem is, I installed the HMC Performance-Kit, and I thought at the time when installing, that the supplied valve springs are too strong, but there was no alternative, HMC or stock, so I installed them. The pressure of the springs was enough to rotate the engine even in gear.

And after 2000 miles it turned out that the cam wheels and bearing shafts are trashed because of the brutal forces in the valve train, resulting in extreme wear.

I don't need that brutal spring force for the HMC-Cams and a set maximum of 6000 revs. But what do I need and where to get?

By the way: Does anyone know the spring strength of these HMC springs?


Regards,

Jerry
I don't know the spring force of the HMC valve spring set.
However, the force can be adjusted by changing the installed height of the springs. Depending on the hardware involved, the upper or lower retainers might be changed or modified, and/or the valve collets(keepers) can be changed with (typically) +/- up to .050" effect on spring installed height.
You would need to take the valve and collets to a qualified automotive technician(or ask HMC) what the specs for the collets are, I.e. the valve groove type, width, and degree of taper. Then you can search the web for a source of suitable collets. For example, if you just want to increase the installed height by .050", you order the collet type in +.050" configuration. This will decrease your spring pressure all across the entire range. I would caution to not go less than about 95 pounds pressure on the seat. If you don't know the current setting, you can take the head to a qualified automotive machinist and ask him to measure it using his gauge.

Since I don't ever use the stock hardware in my typical Fireball applications, I don't have the answers for the above unknown s on the factory valve spring stack parts.

On the other situation of the cam bushing wear, we have seen it before, and you can install harder bushings or install custom made spindles and roller bearings instead(expensive).

Regarding using the Ace cams with your stock rockers, the max lift would be about .414" with a presumed stock rocker ratio of 1.2:1.

Hope that helps.
« Last Edit: January 17, 2020, 02:23:35 pm by ace.cafe »
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gizzo

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Reply #655 on: January 17, 2020, 11:20:30 pm
Do the cams need stronger springs to accommodate higher rpm or are the to keep the valve train following the new more aggressive profile? If it's only for rpm and you're content to keep the stock rev limit, you could keep the original soft springs? Just thinking aloud, here. I got no cams.
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gashousegorilla

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Reply #656 on: January 18, 2020, 12:07:00 am
Sounds good.
My Problem is, I installed the HMC Performance-Kit, and I thought at the time when installing, that the supplied valve springs are too strong, but there was no alternative, HMC or stock, so I installed them. The pressure of the springs was enough to rotate the engine even in gear.

And after 2000 miles it turned out that the cam wheels and bearing shafts are trashed because of the brutal forces in the valve train, resulting in extreme wear.

I don't need that brutal spring force for the HMC-Cams and a set maximum of 6000 revs. But what do I need and where to get?

By the way: Does anyone know the spring strength of these HMC springs?


Regards,

Jerry

   Compare those new cams you got , to the stock cams.     Look at the bushings pressed into the center the cams gears .... the bushing that rides on the Cam spindles.    I believe you will find the stock cam gear bushing will have holes in it, to retain oil as it goes round the spindle .  And those new ones you have, do not.      This plays a roll in what happened to yours I believe.....

  I was sent a set of those cams to check out from a friend.    Stock valve gear and springs, good up to at least 6200 rpms with a .030 "  spring shim....  This is on a 500 UCE  .    Coil bind not an issue.    You may find something different in a GT   head though...


 
Just looking at your cams they have a lot more duration than the Hitchcock set, quite apart from the rocker ratio enhancing the lift. Hitchcock cams are not so much 'performance' cams. Rather they are what should have been fitted by the factory to match their own head.
 I suspect the original cams came about as a longevity feature to  compensate for the variable build quality. Something that seems to have been addressed with the twins. The twin was a British clean sheet of paper project. The unit single is just an evolutionary tweak of the old Bullet
 Oddly enough Triumph produced a similar cam for the 900, seemingly using the restriction to differentiate that engine's output from the 1200.

    Odd longer duration on the intake then on the exhaust with those HC Cams ?    Decent bottom end power... good mid range ... hits a brick wall in the top end I've found with the shorter exhaust duration.  WIDE lobe separation  as well.

  The stock cams , with the wide lobe separation are good for emissions and they play nicer with the Stock ECU as far a tuning.... a  more steady vacuum signal in that intake.      Short duration , NO lift ... for modest bottom end power.
« Last Edit: January 18, 2020, 12:39:40 am by gashousegorilla »
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ace.cafe

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Reply #657 on: January 18, 2020, 03:19:26 am
Do the cams need stronger springs to accommodate higher rpm or are the to keep the valve train following the new more aggressive profile? If it's only for rpm and you're content to keep the stock rev limit, you could keep the original soft springs? Just thinking aloud, here. I got no cams.
Technically, it would be for both.
For a higher lift to occur in a similar duration, the acceleration is greater, and needs more spring pressure to keep the valve under control. Even with a longer duration, the profile is often ground with steeper flanks to get as much time at higher lifts as possible. Add to that, the fact that most performance cams aim to get more hp, and hp is a product of tq and rpm, the generally aim to increase the peaks of both tq and hp rpms.
So yes, in many/most cases with performance cams, new stronger springs are a necessary part of the program. Pretty much any cam maker will tell you that.
The amount of spring pressure needed depends on the cam profile, the moving masses, and the rpms targeted. Beehive type springs can control the valve at lower pressures than conventional springs, due to their inherent design benefits, but there are limits.
If accelerations and mass and rpms are not changed, but the cam timing is different, then the same springs should be able to be used. For example, if you re-phased the factory cams in either direction, you could keep the factory springs because the cam lobes are still the same as before even though the timing is changed.
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Jako

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Reply #658 on: January 19, 2020, 12:56:53 am
JerryGT
I have  over 23,000 km's on my Hitchcock cams and valve kit  now, (500cc engine) and everything seems fine, I inspected the cams after 10k km's with no signs of wear. Still no unusual sounds coming from that area after 23k.  Did yours get noisy ?
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jez

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Reply #659 on: January 19, 2020, 09:13:38 am
From what I've gleaned, setting up the backlash on these cams is critical. I suspect that's the main cause of wear/breakage when fitting aftermarket cams.