Topic: DP315 vs RC315 cam : excatly the same?

[PeWe]

Is the new  DP315 exactly as the old RC315?
I have seen different numbers of RC315 so I'm not sure. Maybe only different ways of measure. Data at various lift or total open/close degrees.
- Someone that has compared both side by side or measured both when timing?

A DP315 is coming my way from Dynoman... I have to know! :-) I have read several posts of how fun this cam was on the streets back in the days.

I'll publish the numbers when installed, dyno when done too :-)  My not yet installed Ultra crank need a cam that deliver a fun rpm range.
"Strong torque curve from the ground up. Comes on low and never quits"   This sounds like a horny cam!!

[gschuld]

I don't have the hard data that you would prefer, but I have some background info.

From everything I have researched, the RC cams went through one complete revision.  EVERY one of those cb750 cams, save perhaps the huge 454 cam, were tweaked. 

The first photo is from the 1976 RC catalog. The second from the 1978 RC catalog, last is the Dynoman specs.
The early 80s RC catalog kept the same specs as the 78 catalog.  And the 1972 RC catalog cam specs are the same as the 1976 catalog specs.  So it appears that the one and only published revisions were across the board and done between 1976 and 1978.

Just looking at changes to the lift numbers:

The 240 cam went from .335/.335 to .327/.330.  Nearly the same
The 295 cam went from .345/.345 to .390/.360.   Got a LOT taller
The 315 cam went from .375/.375 to .365/.365.   A little shorter
The 327 cam went from ..373/.385 to .369/.368   A bit shorter

Dynoman used the 2nd generation cam specs for the DP cams as far as I know.  I would guess that there were/are far more RC cams out there made to the later specs than the original specs.  My RC cams match the later version specs.

George

[PeWe]

Thanks for all data. This explains the different cam values I have seen.
The specs do not say if lift is at 0 lash or at the specified lash. In that case will the later 315 lift be more than .365 when lash is 0.012

I have a custom made cam that has RC295 scratched into it, under the washer at #1. The lift I measured was 0.393/0.363" at 0 lash.

I'll see what data the cam will have in my engine.  I'll use 0.006" (0.15mm) lash and get more lift and duration than  specified 0.012.

An RC collector must look for an early 315 with higher lift  :-)

[BPellerine]

my 315 is old the timing sheet that came with it is on early rc stationary with the specs handwritten in
lift inlet and exhaust 358
234 duration..012 lash
billp

[754]

Is it a cardboard card ? .mine said 310 degrees open ..yours must start at .040 or .050 lift.
 Myself I am surprised at how hard it can pull at 4,000rpm.... So was the guy on a Ducati Monster as we both pulled out of a gas station.  . Might be the big squirters in the Webers make the difference. ..
. Keep in mind though, unported head so maybe low end would be better than on a ported motor.

[Bill/BentON Racing]

RC measured at .050 with valves set at lash specified.

[PeWe]

All these cams timed and measured in an engine at .04 and .05 lift, total lift at 0 lash would be a fine reference list to compare with other cams.

[Sam Green Racing]

"Strong torque curve from the ground up. Comes on low and never quits"   This sounds like a horny cam!!

that sounds like the http://www.dynoman.net/images/engine/cams/DP/DP295Cam.jpg

[BPellerine]

Is it a cardboard card ? .mine said 310 degrees open ..yours must start at .040 or .050 lift.
 Myself I am surprised at how hard it can pull at 4,000rpm.... So was the guy on a Ducati Monster as we both pulled out of a gas station.  . Might be the big squirters in the Webers make the difference. ...

frank,my specs are on a sheet of paper,I don't know when it starts.40 or .50 ,is from the period when they had worlds quickest and fastest fours in their logo.
be nice if cam makers gave a better description of what low means to them ie 4000?6000,and what compression requirements were advised.posted a pic here before,search my 315 and timing card.billp

[gschuld]

Found it.  I had in my files already.

George

[MRieck]

Found it.  I had in my files already.

George

.080 is a lot on the exhaust side but if you are using those Golden Rods...............

[BPellerine]

here are a couple of pics of my specs,see what you make of it,was installed straight up in an 836 with webers circa 1976


billp

[PeWe]

Found it.  I had in my files already.

George

Same data as the DP315.  23/53  53/23 @ .05" lift, total lift.365.  Might be something like 27/57  57/27 @ .04". I got 4 degrees difference on another cam I timed last summer, RC295 look a like cam. I'm very curious about the lift when installed.
Time to pull engine and start work. I have to clean the garage from all junk that has invaded...

[PeWe]

"Strong torque curve from the ground up. Comes on low and never quits"   This sounds like a horny cam!!

that sounds like the http://www.dynoman.net/images/engine/cams/DP/DP295Cam.jpg

295 described like this:
Street cam, smooth with good idle and torque. Plenty of top end, quiet operation; exceptional for street or touring.
The cam in is a 295. It has good ground torque with very good idle. I do not need to gear down in 80kmh on 5th gear when touring around, just twist. 2 steps down and I'll pass the slow cars even quicker
But I like to get more after 9000 rpm, wild responce up  to 10000 would be fine   Fun to try different cams. Strange that so small differences in numbers do that much on the engine characteristics!

[Sam Green Racing]

PeWe, I really do like how you said it's fun to try different cams, please let me know how much fun it is to try different crankcases.
Our other Moderator Mark liked to rev the nuts off his motor till it went bang and we've never seen him since.
I really hope to God that he is OK and just ashamed to show his face after being told so many times.
9000 is pushing these old girls, 10,000 was where I changed gear and then crossed the line making peak power but safe in the knowledge that the motor was protected by a set of Carrillo rods.  Is your's ?


Sam.

[Medyo Bastos]

i have that problem too, i like to rev to the point where i just about start to smell sh1t


...Save a tree, eat a beaver...

[Sam Green Racing]

If you are racing these old bikes, stick it on a dyno and find out where it makes power.
It's no good taking it any further, yes, you will be going faster but you won't be getting there as quick.
Change up when you reach peak power, a shift light is a good idea.
If your peak power is higher than it's recomended to rev it, get a rev limiter or a set of Carrillo rods that won't go bang if you push it that little to much.

[gschuld]

Sam,

If I recall correctly, Pewe has an APE lightened and balanced crank, but also set of Carrillo rods and an NOS set of RC 836 pistons.  Sounds like some of the ideal parts for an 836 to handle 10,000 rpm.

George

[754]

I was reving my stock rod 836 to 10, 500 or higher constantly.. , then ran mostly without a tach for a long time..
 One day racing a Ducati Monster I could not hear when to shift, think I went a bit high.. Seemed off a bit after that..

[teebee67]

Sam, do what I do - rev it 'til the road goes blurred, then stick another gear in !!!   

[Sam Green Racing]

Sam,

If I recall correctly, Pewe has an APE lightened and balanced crank, but also set of Carrillo rods and an NOS set of RC 836 pistons.  Sounds like some of the ideal parts for an 836 to handle 10,000 rpm.

George

Don't forget George, I'm having big problems recalling anything full stop, let alone correctly.

Sam.

[PeWe]

Sam,

If I recall correctly, Pewe has an APE lightened and balanced crank, but also set of Carrillo rods and an NOS set of RC 836 pistons.  Sounds like some of the ideal parts for an 836 to handle 10,000 rpm.

George

I have to rev a lot whith the Ape crank with Carillos Undercutted trans 2,3,4, HD primary chains since before, primary hub with new rubbers going in too. Head and cyl block need to be decked for true flatness, a little bit more compression.

I'll not stay at 10000 for long, just a good shifting point. I have a Megacycle cam 125-20 that is very fun from 7000- around 10 000 rpm, I had to shift. Maybe cam want more It looked like  the tacho was tuned when it ran wild so easy:) I had problem at 4000-6500, way to rich. Maybe the acc pump.  Cams Action Fours SS1 and RC 295 have no problem, needed even richer pilots.

125-20 has very special exhaust data. This might work  with my old smoothbore 29's without acc pump.

[PeWe]

Quick shipping! Got the DP315 today. Measured the lobes with a caliper. Lift might be 0.373" or a little bit more.
Base center "stickout" 2.5mm,
total lobe height all around 36,25mm
Base circle radius: (22/2)+2,5=13.5   
Total lift:36.25-13.5=22.75  22.75-13.5=9.25mm -->0.36417"  (look like specified 0.365")
 
I compare with other cams I have measured and timed, caliper data usually lower than real in engine when I have checked so far.

I look forward to the real test. I have some work to do before the fun timing.
Photos below with other cams as reference. RC295 copy is still in engine.

Lets see if the DP315 is hotter than the "RC295" that has lift .393/.363. Duration and overlap to be measured when assembly the engine not yet taken apart

[BPellerine]

that is some collection pewe.bill

[PeWe]

Yes, I get more ideas more I visit this forum with the race guys and normal CB750 part horders
Looking for the perfect cam!

It is one thing to read about specified cam behavior, something else to test it
Today  5 "power" cams.

It would be fine with a web based cam order site where I can order a cam I shape on site.
Start with a cam that can be adjusted in lift and opening/closing times. The order will go direct to a machine that will shape it and in the end ship it to me.