Cams (2012)

hobot said:

What is split lobe point? Don't ya have to do each lobe to know for sure?

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That is the point during overlap when both valves are at the same lift -if the intake and exhaust lobes are symmetrical and identical. If this point is set to occur at TDC then the cam is considered to be timed "straight up".

Finding it using a big lifter that contacts both lobes is only accurate if the cam has the same symmetrical lobe for both intake and exhaust. [most cams]
With different lobes such as used on a 2S or 4S cam I would have to find the centers of each lobe and split the difference. Jim

Thanks some more for bothering with us. Must admit I was a bit underwhelmed by the tedium of that antique and in this 'puter age thought it was over and done when ya first hit the motor centering stage and it spung a bit then stopped, 'wow no wonder he's ready for more cames', then ya told us that was just the initatiating stage of the process. Neat way to get a radius which interestes me for detuning proposes, whould a bit of radius dull down a radial flat tappet grind or chew up the works? Could ya bias a systemic lobe cam with radius lifters?

hobot said:

whould a bit of radius dull down a radial flat tappet grind or chew up the works? Could ya bias a systemic lobe cam with radius lifters?

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Yes, a radius cut on the lifter will shorten the effective duration without reducing the lift. It will broaden the powerband at the expense of peak power.
You have to be careful though because the valve acceleration around the nose increases as the radius gets smaller, too small a radius will make a short lived valve train.

Evenin' all complete newbie here. Just bought my first Norton, a Commando basket case. This cam is in amongst the "treasure" . A quick google search doesn't provide much info; would anyone have any ideas?

I'm sure one of our veterans will chime in here soon and explain where the Norris 380 fits into the Norton cam pecking order. If I were to guess I'd bet it will be very similar to Johnson Cams 380.

http://www.johnsoncams.com/jc_n_cams.html

I'm curious, your cam looks like a hardweld that still has the molycoat spray on it and has not been used. Is that possible or are my eyes failing me and it's just a another dirty old camshaft? Below are a couple vintage pictures for you to savor while you reflect on what the Norris 380-8 grind might be. Maybe the black color of your cam is because it's smoking hot, straight from the devils hand!

snail said:

Evenin' all complete newbie here. Just bought my first Norton, a Commando basket case. This cam is in amongst the "treasure" . A quick google search doesn't provide much info; would anyone have any ideas?

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Snail, that looks like a pretty hot cam to me. Can you provide us the camlift data (lob centre minus base circle).

Norris generally numbered their cams with the lift.
IE, it should be .380 lift at the valve. Jim

I love the Norris cam logo and may paste it on Peel somewhere. Norris D has .438" lift listed for pecking order.
MegaCam has listing of their range of Norris cam to check your cam spec's.

I believe it is a brand spanking new cam.
I can't actually measure it as its hopefully in a shipping container in the middle of the Pacific, along with the rest of the treasure! Its coming from the US to Oz. Once it arrives (couple of months?) I'll jury rig a rotary table and dial gauge to do a manual version of that rather nice 4th axis set up.

Expect to hear a lot more questions in the future!

hobot said:

I love the Norris cam logo and may paste it on Peel somewhere. Norris D has .438" lift listed for pecking order.
MegaCam has listing of their range of Norris cam to check your cam spec's.

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Was there a Norris D and D+? Always assumed they were one and the same. I see the D+ listed as 0.405 cam lift in the Megacycle catalog, or 0.458" valve lift (1.13 rocker ratio * 0.405" cam lift = 0.458" valve lift).

I see it both as D and D+ but ain't expert on it just heard old bored selling out shop Norton drag racer go bonkers like a slug of moonshine jumping around knee slapping yelling again and again at least a minute...
THEM NORTONS JUST LOVE THAT NORRIS D+ CAM THEM NORTONS JUST LOVE NORRIS D+ CAMS ...
Called Duncan Campbell in Joplin MO a few months later and happened to ask cams again, he dropped the phone and I heard him doing his knee slapping dance yelling like a little kid on & on...
THEM NORTONS JUST LOVE THEM NORRIS D+ CAMS THEM NORTONS JUST LOVE NORRIS D+ CAMS ...
Boy howdy I wanted some of what he had. Had two photos of Hogslayer level single engine dragster, one natural inspired the other blown - both with Harley tannys.

For Peel to exist on pump gas with over 10:1 CR and maybe 1 BAR of boost needed online calculations for a late closing int valve and when Norris D popped to top of the list I too felt like excited kid about to lit a rocket fuse.

Peel's cam came via Jim Schmidt as MegaCycle current 560-NDP, old label 560-N-D+, lift .405", Int & ext close 73" ABC, opens 43' ATC. diration 296', lobe center 105', lash .15" ugh, but gives Dynamic ~7.5 CR for kick offs, I hope. I have adjustable pop off valve to prevent Peel exceeding 17 effective diesel CR.

comnoz with all your wizebang back ground and gizmos do ya think ya could develop a cam tailered to a particular extremist engine, out of say an unused Norris D core?

Hey Jim. Any interest in a Dunstall cam. The markings are PD/04, so I assume it's the MK4 Street. It came out of a 810 part out on ebay last year. I'd like to know the specs on it anyway. I'm not even sure what to set clearances at, as I lack the installation instructions. I'm thinking it's similar to a 2S, as it precedes '72.

Deckard said:

Hey Jim. Any interest in a Dunstall cam. The markings are PD/04, so I assume it's the MK4 Street. It came out of a 810 part out on ebay last year. I'd like to know the specs on it anyway. I'm not even sure what to set clearances at, as I lack the installation instructions. I'm thinking it's similar to a 2S, as it precedes '72.

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You bet, send it out and I will post the results. Jim

hobot said:

comnoz with all your wizebang back ground and gizmos do ya think ya could develop a cam tailered to a particular extremist engine, out of say an unused Norris D core?

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I don't grind cams but there are a lot of different lobe profiles and timing specs that can be ground onto a Norton shaft. I have done that with a few builds using my engine analyzer program. It can take a lot of time. Jim

The comment made earlier about using lash of 0.016 thou (0.4 mm) for the 4S cam may be causing some to wonder why so much lash.
The illustration shows the opening ramp of a 4S exhaust lobe, and a vertical blue line indicates where the lash takeup pont occurs on the ramp. Clearly the ramp is being used to load up the valve train before the big opening push commences.



This leaves a question begging an answer - what happens to this lash as the engine warms up to eventually reach it's working temperature.
Does the lash clearance close up, or does it increase ?

Snotzo said:

The comment made earlier about using lash of 0.016 thou (0.4 mm) for the 4S cam may be causing some to wonder why so much lash.
The illustration shows the opening ramp of a 4S exhaust lobe, and a vertical blue line indicates where the lash takeup pont occurs on the ramp. Clearly the ramp is being used to load up the valve train before the big opening push commences.

This leaves a question begging an answer - what happens to this lash as the engine warms up to eventually reach it's working temperature.
Does the lash clearance close up, or does it increase ?

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With a cast iron barrel and aluminum pushrods the lash decreases as the engine warms up. About .0035 to .004 in with a 300 F. change. Jim

Deckard said:

Hey Jim. Any interest in a Dunstall cam. The markings are PD/04, so I assume it's the MK4 Street. It came out of a 810 part out on ebay last year. I'd like to know the specs on it anyway. I'm not even sure what to set clearances at, as I lack the installation instructions. I'm thinking it's similar to a 2S, as it precedes '72.

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If this PD/04 cam came from New England area, it may be this cam:
http://atlanticgreen.com/images/cam210.gif
after profiling it, I returned it to the owner probably before 2000.


If it came from a 810 Dunstall basket case with no head, then this may be the 810 big valve head...
http://atlanticgreen.com/images/dnstllg.jpg
This head sits on an engine (among many others) on a display table in my store front window: :mrgreen:

Getting a bit behind in the engine building dept, are we ?? !!

Rohan said:

Getting a bit behind in the engine building dept, are we ?? !!

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Not really. Every 1st and 3rd Saturday, NENO club members come by for tech sessions. These are mostly engineering research and training samples from 1949-1975 with almost every norton heavy twin variant except a 650SS (deal made to soon get one of these too). Also a warehouse full of heads, barrels, gearboxes, carbs, electrics, suspensions etc..sorry none for sale.

garage, machine shop, warehouse, and home