Author Topic: Anyone know what these cams are?  (Read 24596 times)

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ace.cafe

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Reply #30 on: February 06, 2016, 09:48:11 pm
518cc, not sure on the other details, and I am not sure it is fair to guess or put a tuners head details on a forum.
Generally speaking, the more the head can flow, the less cam you need.
IMO,  36mm is a bit large for a 518cc application, unless it will be revving pretty high.
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Bullet Whisperer

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Reply #31 on: February 06, 2016, 10:20:00 pm
518cc, not sure on the other details, and I am not sure it is fair to guess or put a tuners head details on a forum.
Hi Ace,
 It is one of mine and pencilled in for 'Asbo' No 19. Presently, we have a rebuilt bottom end with my trademark lightened crank, which is fitted with a forged steel conrod and roller big end. The cams I asked about at the beginning of this thread are fitted at present.
 The cylinder head has been ported [by me] to a nominal 34mm inlet, flaring out at the manifold flange to 36mm, to give a margin should a carb of that size be required. The head was ported before I had the rest of the engine and taken off the shelf to contribute to this project. This engine is one for which I have slowly been working on isolated components, resulting in a more or less complete engine to assemble, short of a decent piston and alloy barrel at present. It was to be built as a complete engine before being made available, but I was asked if I had anything.
 I intend to offer the so-called 9:1 American made piston from Hitchcocks, in a +0.060" oversize if available, although I rate them at 7.75:1 and will shorten the barrel by 2mm, to get closer to a true [by my calculations] 9:1 compression ratio.
 It is not intended to build a revvy engine, similar units I have built in the past give around 30bhp @ rear wheel at around 5600 rpm or thereabouts, with good power from low engine speeds and a sharp torque rise.
 I think we will be using standard valves, with competition springs, although any number of changes could be made to many of the specifications at this point, should they be requested. This engine build is aimed at lively acceleration from relatively low engine speeds, thanks to the lightened crank and getting quickly into its' torque zone, with the capability to rev to around 6000 rpm at times.
 I have suggested an 18t gearbox sprocket, to aid a higher cruising speed, while not detracting too much from acceleration by going any larger, but the final decision will not be mine.
 I also suggested a 32 - 34mm carb for this application.
 B.W.
« Last Edit: February 06, 2016, 10:52:44 pm by Bullet Whisperer »


ace.cafe

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Reply #32 on: February 06, 2016, 11:23:24 pm
Well B.W., it sounds like you have it well in hand.

Dave, just let B.W. give it what he wants to do to it. It's in skilled hands.

I like the choice of 18T sprocket too.
 :)
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Dave1

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Reply #33 on: February 06, 2016, 11:48:25 pm
Already have Ace, I am very pleased, even getting excited, I am still very new to this, and we spoke a lot today on the phone, so I may of got a little confused!


dginfw

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Reply #34 on: February 07, 2016, 10:31:06 pm
Sounds like you will have a well thought out, sweet running bike Dave.
Enjoy it !
Dave in TX:   '01  W650- keeper
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Dave1

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Reply #35 on: February 08, 2016, 06:38:11 pm
Thanks dginfw, I am looking very forward to this. Been wanting an engine like this for 6 years. Finally is happening.


cafeman

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Reply #36 on: February 09, 2016, 04:11:18 pm

 I intend to offer the so-called 9:1 American made piston from Hitchcocks, in a +0.060" oversize if available, although I rate them at 7.75:1 and will shorten the barrel by 2mm, to get closer to a true [by my calculations] 9:1 compression ratio.

 B.W.

B.W.,

Do you have that piston now? I believe I've read in past posts that you have experience with these Robbins pistons on various builds you've done. What brand and size rings have you been using with them? These pistons require 1/16" 1st and 2nd compression rings and a 5/32" oil control ring as I'm sure you are aware of. Not very easily sourced these days in the sizes we need for these engines. Just wondering what you have come up with in the past. The rings on the Robbins .040 over piston I bought from Hitchcocks came with Caber brand rings, but with the correct piston/bore clearance the end gaps were at the max on all when checked. No allowance for file to fit as I'd hoped so I'm in the process of sourcing correct rings from either Total Seal or Hastings here in the states. Awaiting info from both as to "wall" dimensions on their rings that fit "Axtell" 3-5/16" (std 3.312"/84.12mm with required oversize options) which fit old Harley Knuckleheads.
  Update, just got off phone with Total seal. They don't have any rings to fit these pistons. They can modify the piston to accept bigger rings though. Not an ideal option IMO. Talked to Hastings,  they have the ring sets still available and/or can package a set to fit the Robbins.
« Last Edit: February 09, 2016, 07:33:40 pm by cafeman »


devon john

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Reply #37 on: February 09, 2016, 05:00:55 pm
i run a R cam in my bike ,,, 535 ported big valve head omega piston  amal carb  roller bearing and carero rod bottom end etc ,19t sprocket
it pulls very well and i have not found it over geared,,,
i will see Henry Price the weekend ,,nice man

john
harley hydra glide FL (1950)
harley FLH 80
535 Royal Enfield bullet


Bullet Whisperer

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Reply #38 on: February 09, 2016, 09:14:02 pm
B.W.,

Do you have that piston now? I believe I've read in past posts that you have experience with these Robbins pistons on various builds you've done. What brand and size rings have you been using with them? These pistons require 1/16" 1st and 2nd compression rings and a 5/32" oil control ring as I'm sure you are aware of. Not very easily sourced these days in the sizes we need for these engines. Just wondering what you have come up with in the past. The rings on the Robbins .040 over piston I bought from Hitchcocks came with Caber brand rings, but with the correct piston/bore clearance the end gaps were at the max on all when checked. No allowance for file to fit as I'd hoped so I'm in the process of sourcing correct rings from either Total Seal or Hastings here in the states. Awaiting info from both as to "wall" dimensions on their rings that fit "Axtell" 3-5/16" (std 3.312"/84.12mm with required oversize options) which fit old Harley Knuckleheads.
  Update, just got off phone with Total seal. They don't have any rings to fit these pistons. They can modify the piston to accept bigger rings though. Not an ideal option IMO. Talked to Hastings,  they have the ring sets still available and/or can package a set to fit the Robbins.
Hi Cafeman,
 I have fitted a good number of these pistons to date and all has been well so far. I would assume Hitchcocks would be able to supply replacement rings, if required, as that's where my pistons came from, but if not, I have bought oddball piston rings for old Panther and AJS machines from these people in the U.K.
http://www.coxandturner.co.uk/holding.php
 B.W.


cafeman

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Reply #39 on: February 12, 2016, 03:03:19 am
Ace, you happen to know what the in/ex duration @.050" lift on those "R" cams are? Just wondering for wonderings sake, by an old Mopar B/RB V-8 enthusiast where those numbers are used in making cam choices. But "I" would be interested in knowing what "all" the cams @.050" specs are, especially the Hitchcocks cams, being they are more race oriented. It would be very interesting to see these numbers ;)


ace.cafe

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Reply #40 on: February 12, 2016, 02:47:14 pm
Ace, you happen to know what the in/ex duration @.050" lift on those "R" cams are? Just wondering for wonderings sake, by an old Mopar B/RB V-8 enthusiast where those numbers are used in making cam choices. But "I" would be interested in knowing what "all" the cams @.050" specs are, especially the Hitchcocks cams, being they are more race oriented. It would be very interesting to see these numbers ;)
Yes, of course.
They are about 240° duration between the .050" points.

The Hitchcock "fast road cams" give data at the 1mm lift points, and I don't have that sheet here in front of me. However,  the big issue which affects them is a narrow lobe center and very wide overlap period of about 100 degrees. 50 before and 50 after. As you might expect, that essentially guarantees a loss of low rpm torque in comparison to the other cams which have about 60 degrees of overlap and wider lobe centers. Long overlap is good for high rpms, less good for lower rpms. Short overlap is better for low rpms and activities such as towing where high torque at lower rpms is important,  but can run out of power at high rpms. The decision of how much overlap to use is important for the targeted application. As most decisions in engine modding, it comes down to the compromise that you feel is best, and pick an overlap period to suit.

It's a matter of cam philosophy,  and what the goals are. We like the later intake closing and shorter overlap from wider lobe centers.

« Last Edit: February 12, 2016, 03:31:16 pm by ace.cafe »
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cafeman

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Reply #41 on: February 13, 2016, 05:32:26 pm
Ace, thanks for the additional info on the "R" cams, which just arrived from England...couldn't help myself I suppose! Those were what I wanted to use when I did my build in 2014 but Price was out of stock at the time, plus $$ was tight so I went with re-phasing. With what I've done to my bike and how I use it I'm looking forward to that "little bit more".....sorta like going from "10" to "11" ;D
Anyway, regarding cam philosophy, I'm in the middle of working out details and choices for a  360 V-8 small block build for a 67 Dodge van, a little hot rodded, but with good street manners for the real world. I've been looking at cams for these engines and the latest rage for the Mopars is cam makers offering cams with correct lobes to take advantage of the larger Mopar sized lifters vs. cams that have Chevy sized lobes (which use a smaller lifter diameter) and also "area under the curve".
I know you know this, larger lifter diameter offers the ability for more aggressive designed lobes, faster lift etc.. A couple of cam makers now have various grinds that in fact make more hp/torque with the larger lifter type lobes than comparable cams with the smaller lifter type lobes. Have read much of your writings here and elsewhere, as well as reacquainting myself with these V-8 engines and what cams are best. Seems the same theories apply, generally speaking of course. Could really get in deep with this stuff (reminds me of Hi-Fi equipment) Another wondering: with the mushroom style lifters in the Bullet engine, what are your thoughts of roller lifters and cams for our engines? From what I see it could be possible but.......Just ponderings ;)
« Last Edit: February 15, 2016, 02:34:24 am by cafeman »


ace.cafe

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Reply #42 on: February 13, 2016, 06:54:49 pm
The extra lift will really wake up your engine with the porting you have.
 :)

You could put in solid roller lifters, but they are very very heavy. I didn't consider it a good compromise, especially considering that special cam profiles would be needed for the roller lifters which were outside the available blank size, and would be very costly in small quantities.

Our mushroom tappets have plenty of foot, st over an inch, but the narrow stems prevent using it fully,  due weak stems combined with high side thrust.
« Last Edit: February 14, 2016, 05:36:07 pm by ace.cafe »
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Dave1

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Reply #43 on: February 14, 2016, 11:44:31 am
Be interested to hear your thoughts on the R cams Cafeman after you have fitted them.


cafeman

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Reply #44 on: February 25, 2016, 01:41:59 am
Be interested to hear your thoughts on the R cams Cafeman after you have fitted them.
Got them installed, everything checked out good, total timing reset and running. So much rain lately still haven't gotten it out on the road. Hope by this weekend  ;)
« Last Edit: February 25, 2016, 01:46:53 am by cafeman »