Norris cam Magnum 70

Classic Norton Commando Motorcycles.

Norris cam Magnum 70

Postby Chris » Sun Dec 02, 2012 2:11 pm

Hi

Just been given a cam by a friend from a proddie racer. Its a Norris Cycle Magnum 70.
Never heard of this one! Its not in Daves list. I have not measured it yet.
Any ideas? Performance mid range etc

Thanks Chris
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Re: Norris cam Magnum 70

Postby lcrken » Sun Dec 02, 2012 2:25 pm

The Magnum 70 was the grind used for their #1516E cam. Duration is 318/310 degrees, and lift is .438/.413". Norris catalog describes it as "Drag, Roadrace (750cc+), Flatttrack (750cc), Street (850cc) (COMPLETE Vave Train recommended)".

Ken
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Re: Norris cam Magnum 70

Postby Chris » Sun Dec 02, 2012 2:57 pm

Hi Ken

Wow! thankyou. Looks like one to use. It is very clean, no real wear marks at all.
750? Ikren ie revvy engine?

Thanks once again

Chris :D well chuffed
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Re: Norris cam Magnum 70

Postby lcrken » Sun Dec 02, 2012 3:30 pm

It's a pretty serious cam for a 750. The intake lobe is basically the same as their 750D all-out racing cam, but the exhaust is a milder profile from their Super Street cam. It's still a lot of lift and a lot of duration. Probably has great top end power in properly built engine. Might be a bit fussy in a street 750 for around town putting. Milder exhaust profile also helps reduce risk of valve interference in big valve heads. With that much lift and duration you'll definitely have to check for piston-valve clearance, valve-valve interference, and valve spring bind when you set it up. Should make a good race bike cam, though.

Ken
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Re: Norris cam Magnum 70

Postby SteveA » Mon Dec 03, 2012 5:55 am

lcrken wrote:It's a pretty serious cam for a 750. The intake lobe is basically the same as their 750D all-out racing cam, but the exhaust is a milder profile from their Super Street cam. It's still a lot of lift and a lot of duration. Probably has great top end power in properly built engine. Might be a bit fussy in a street 750 for around town putting. Milder exhaust profile also helps reduce risk of valve interference in big valve heads. With that much lift and duration you'll definitely have to check for piston-valve clearance, valve-valve interference, and valve spring bind when you set it up. Should make a good race bike cam, though.

Ken


What about in a 750 short stroke Ken?

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Re: Norris cam Magnum 70

Postby hobot » Mon Dec 03, 2012 8:06 am

Was just lurking until Ken stated this Mag-70 cam is on similar scale as Norris D [D= drag race?] and may not be desirable for timid civilized use. This confuses me as I see the hottest vintage engines idle reasonably on cold starts and easy control rolling through crowed pits areas. My '68 Ranger P!! drag only wonder went BLATT! not varrRROOOM on short throttle blips yet was a short shifting HD like treat for low end torque to waddle through school lots or deep sand lanes no problemo even in top gear no throttle even climbing grade. It was extra fun with soft steady kettle drum like 600 rpm at lights - so the hot rods of the era, 2 & 4 stroke triples would glare down at me on 50cc size bike and go varrRRoOOMM and let out clutch still on throttle for a short lerch forward to invite a contest, which generally I cut short with just a BLATT! with slight clutch release w/o throttle to whiplash head to tires blur too fast to focus on til 2 bike lengths later in less that a blink. I'd bet this Magnum 70 might work a treat to live with if valve train and CR to handle it. Drive train and tire wear may be the real issue to consider in traffic to pass - not bogging stalling easing around. May tame it to taste by advancing cam degree some too.

BTW DynoDave Comeau has CNC set up to profile cams fast w/o much tedium so might be good to alert him to send cam to add to his reference base.
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Re: Norris cam Magnum 70

Postby dynodave » Mon Dec 03, 2012 8:16 am

lcrken wrote:The Magnum 70 was the grind used for their #1516E cam. Duration is 318/310 degrees, and lift is .438/.413". Norris catalog describes it as "Drag, Roadrace (750cc+), Flatttrack (750cc), Street (850cc) (COMPLETE Vave Train recommended)".

Ken


Assuming Ken's lift # are at the valve.... then it looks very close if not identical to this web cam: http://atlanticgreen.com/images/cam930.gif

A local roadracer uses it and it is very strong especially with a rather "free flow" exhaust. ... a touch hotter than a combat

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Re: Norris cam Magnum 70

Postby Chris » Mon Dec 03, 2012 1:50 pm

Hi Dave

Thank you

Everytime I find a cam I look at your site! Thanks for all your help.

You may notice that Steve A has chimed in about his short stroke?
He called in Sunday & appears not to have a cam for his engine yet :D

Might give it a bash in my 850

Thanks Ikren Thanks Hobot.

Time to get my roadbike back on the road

all the best Chris
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Re: Norris cam Magnum 70

Postby lcrken » Mon Dec 03, 2012 1:51 pm

Dave, as you assumed, the lift figures I gave are what Norris specified for lift at the valve.

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Re: Norris cam Magnum 70

Postby lcrken » Mon Dec 03, 2012 2:04 pm

SteveA wrote:What about in a 750 short stroke Ken?


Should work well in a short stroke 750 race engine. Same warning applies about checking for valve-valve interference with big valve heads.

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Re: Norris cam Magnum 70

Postby SteveA » Tue Dec 04, 2012 12:41 am

Chris wrote:Hi Dave

Thank you

Everytime I find a cam I look at your site! Thanks for all your help.

You may notice that Steve A has chimed in about his short stroke?
He called in Sunday & appears not to have a cam for his engine yet :D

Might give it a bash in my 850

Thanks Ikren Thanks Hobot.

Time to get my roadbike back on the road

all the best Chris


Chris, you have too many projects.... :wink:

750 long stroke, 960, 850! Nah, it needs to be tried in a 750 short stroke first....

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Re: Norris cam Magnum 70

Postby SteveA » Tue Dec 04, 2012 3:40 am

lcrken wrote:The Magnum 70 was the grind used for their #1516E cam. Duration is 318/310 degrees, and lift is .438/.413". Norris catalog describes it as "Drag, Roadrace (750cc+), Flatttrack (750cc), Street (850cc) (COMPLETE Vave Train recommended)".

Ken


BTW Ken, what do you interpret Norris meant by 'COMPLETE Vave Train recommended'

Followers? (Radiusing?)
Pushrods?
Valve Springs?
Rockers?

Steve

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Re: Norris cam Magnum 70

Postby hobot » Tue Dec 04, 2012 7:57 am

I've a Norris D which needs heavier-longer springs and lighter valves- retainers not to coil bind,float or clash with the lift- rpms the cam was intended to breath at. I think my ole P!! had similar, idled nice and low 600 rpm and would cough-stumble if throttle snapped - for ~.5 sec till ~1000 rpm for BLATT! response, clutch in free wheeling or fully engaged going nowhere in street tire smoke cloud w/0 any front brake applied. Magnum770 reported installed in Production Racer so might look up what their details were but there's better valve kit available nowadays like Beehive springs and 6 mm stems. Might also look up the mass of proddie flywheel as both P!! and Peel had about 5 lb less which helped avoid the sluggish varrRROOMMM response for more of BLATTTT! If you can snap throttle to WOT and back fast as ya can from 1000ish rpm and not shoot tach needle right past 7000 into upper redzone, then ya ain't experienced what's possible in Norton push rod clunker. Fast rising torque curve allows reversed controls delight, extra throttle slows ya down and backing off thrusts harder hooking up unless short shifting to mimic a touring Harley.
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Re: Norris cam Magnum 70

Postby SteveA » Tue Dec 04, 2012 10:57 am

Steve, I had some thin stem inlet vales in '75/'76, in cast iron guides they didn't last long!....they came from Thruxton....

So who is doing them now? and I hope they supply them with the right collets....see above.... :(

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Re: Norris cam Magnum 70

Postby lcrken » Tue Dec 04, 2012 1:13 pm

SteveA wrote:BTW Ken, what do you interpret Norris meant by 'COMPLETE Vave Train recommended'

Followers? (Radiusing?)
Pushrods?
Valve Springs?
Rockers?

Steve


Steve, I think they were primarily referring to using their high performance spring kits, which included springs, titanium retainers, and spring seats, as opposed to using stock springs. That was what cam grinders back then typically specified as necessary for their higher performance cam grinds. The other common warnings were to check for spring bind, retainer-to-guide clearance at full lift, and valve-to-piston clearance.

Other mods like rocker lightening, aftermarket pushrods, bronze guides, bigger valves, and so on were not things cam grinders normally required for their cams to work. They did sometimes include recommendations for mods like high compression pistons and free flowing exhausts to get maximum benefit from hotter cams, but not as a condition for using them.

This particular cam profile is for flat tappets, so no follower radiusing required, unless you wanted to do so to make the valve lift profile a little milder.

Ken
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