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Newman Cams
#1
 
Newman have provided me with a list of their standard cam profiles. It looks as if the first 3 would be suitable for road and light competition use on a light car with C/R gearbox and strong engine. Does anyone have experience of them?
 
I assume that 260° duration is about the limit for a road engine? It is interesting that they offer a cam with higher lift and shorter duration (A7/256/308) and one with lower lift but longer duration (A7/260/270). Any thoughts on how these would differ in performance?
                                                                      
Part Number     Duration @ 0.010"         Camshaft Lift     Lobe Centre Angle                      
A7/256/308       256°                                    0.308"                    110°                   
A7/260/270       260°                                    0.270"                    110°                   
A7/260/325       260°                                    0.325"                    110°                   
A7/268/310SC  268°                                     0.310"                    110°      Super Charge Camshaft
A7/284/320       284°                                    0.320"                    107.8°   Race Cam          
A7/284/325       284°                                    0.320"                    107.8°   Race Cam          
A7/252/314       252°                                    0.314"                    110°      Trials Cam         
 
From what I understand a cam with 0.308" lift will fit through the centre bearing hole on a standard crank case but not one with 0.325", is that correct?  I have a ten stud block so not too worried about it lifting from the crank case, but noise and wear of the cam followers are also a factor.
 
Will these cams generally fit out of the box or do they need they need keys and gears to be modified to get the correct timing?
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PS, sorry about the small font, can't seem to make it any bigger!
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#2
I have a cam with 330 inlet lift and 300 exhaust and it fits through a standard centre bearing, but it wouldn't if both were 330.
I'd personally use an adjustable (aka "vernier") cam gear. It's not a massive mod.


Charles
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#3
If the maximum lift figure is 'off' when you install any new cam, it's almost certainly going to be because the keyway isn't accurately placed in your timing gears. The cam grinder references all the lobes from the camshaft keyway. Although I've had to make an offset key for a number of motors to get the timing right when testing the usual number one inlet, all the other lobes have been spot on once the right key is in place.

@Charles P did you turn up a steel hub for the timing wheel to create the adjustable gear using a re-machined factory outer?
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#4
Newman 'road' cam in my Nippy - sorry I have no data, it wasn't slow though.
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#5
New EN24 hub and the outer of an existing steel one. I hate machining short tapers and made a dummy centre to prove the taper was correct.  The construction uses slotted holes in the "outer" part and button head cap screws. As a failsafe once timed I removed one cap screw and filed a pair of "lozenges" to fit into the residual oval slots to avoid the potential for movement. They are retained by the washer under the cap screw. 
Dave Dye makes very nice ones. 

Charles
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#6
(12-11-2020, 01:14 PM)Charles P Wrote: Dave Dye makes very nice ones. 

Charles

Certainly does.

   

Steve
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#7
Thanks all, I have a stepped key on my current gear which allows for adjustment by half tooth. Depending on how it fitted I might have to try something more sophisticated, in which case I'll get in touch with Dave. Does he need the original outer part of the gear to start with?

Any thoughts on the profiles themselves? What is the max duration/lift you would live with on a car being used on the road? Not intending to do many hill starts but don't want to be burning the clutch out every few months!
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#8
(12-11-2020, 02:08 PM)Tom Coates Wrote: Thanks all, I have a stepped key on my current gear which allows for adjustment by half tooth. Depending on how it fitted I might have to try something more sophisticated, in which case I'll get in touch with Dave. Does he need the original outer part of the gear to start with?

Any thoughts on the profiles themselves? What is the max duration/lift you would live with on a car being used on the road? Not intending to do many hill starts but don't want to be burning the clutch out every few months!

Dave's are new steel gears. If it's a mag engine I'd replace the original gear - they do break.
I reckon 260 degrees will be fine in a lightweight road car and you probably don't want/need much over 270 lift. It really depends what you want the car to be. Until the development of variable valve timing technology camshafts were always an exercise in compromise. 
If you're worried about the clutch then fit cast iron linings (as per the works). Makes a very nice clutch, long lived and no nasty smell if you do slip it.  

Charles
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#9
Dave's gears are a complete new set, Tom, and for what they are, not expensive (although I'll let him quote you direct). As always with Dave's items, properly made and of excellent quality. As to clutches, think about Kevlar based linings. I stripped down my previous Ulster engine a couple of months ago that has a Borg & Beck driven plate with Kevlar based linings. As well as normal road use, we've worked out that it's done over 300 hill climb and sprint starts since 2014 (surprising how they add up with a shared car!) and the linings show no sign of wear indeed they're not even fully polished 'shiny' yet.

   

Steve
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#10
(12-11-2020, 02:17 PM)Charles P Wrote:
(12-11-2020, 02:08 PM)Tom Coates Wrote: Thanks all, I have a stepped key on my current gear which allows for adjustment by half tooth. Depending on how it fitted I might have to try something more sophisticated, in which case I'll get in touch with Dave. Does he need the original outer part of the gear to start with?

Any thoughts on the profiles themselves? What is the max duration/lift you would live with on a car being used on the road? Not intending to do many hill starts but don't want to be burning the clutch out every few months!

Dave's are new steel gears. If it's a mag engine I'd replace the original gear - they do break.
I reckon 260 degrees will be fine in a lightweight road car and you probably don't want/need much over 270 lift. It really depends what you want the car to be. Until the development of variable valve timing technology camshafts were always an exercise in compromise. 
If you're worried about the clutch then fit cast iron linings (as per the works). Makes a very nice clutch, long lived and no nasty smell if you do slip it.  

Charles

My understanding is that extra lift beyond the point of maximum flow is still useful as it increases the amount of time the valve is open at the peak flow level.

What is the downside of extra lift? Is it just wear on the valve train and noise or are there other factors that I am missing?
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