Topic: DP315 cam: Valve lash 0.25-0.30mm reduced to 0.10/0.15mm - less comp. Cam tests

[PeWe]

I had another 160km ride today and had time to think about the 295 behaviour vs the 315.
Cam descriptions does not match my engine

"RC295 Racer Cam - Smooth, good idle and torque with lots of the top end. Quiet operation. Exceptional for smaller motor. Ideal for 900cc motors." 
- Idle is fair, not smooth, 1400-1600 rpm. Louder engine than 315. 295 comes more from low than 315

Update: Fuel screws were too lean. Opened them today in 1/4 increments from 3/4 turns out to 1 1/4 where idle is stable around 1200 rpm. Carbs acted like bad synchronized.

"RC315 Hot Racer Cam - Strong torque curve from the ground up. Comes on low and never quits. This one makes lots of horsepower. Very good for heavy street and altered race bikes. Our favorite in the Street Class. Has flowed us to many national records. Very tractable. Fair idle - quiet. Ideal for 900cc and larger motors."
Idle is really smooth in my engine, no problem with stable 1000-1200 rpm. Good street and touring cam. Engine not that nervous and explosive as with the 295.
I still like the 315. Max power is not everything. The smooth way the power applies is positive. 315 soft rounded lobes with the lower lift must be easy on the valve train. Only double lash that might hammer a little but give longer cooling times for the valves and more lubrication under the rocker pads

How the power was applied out of the corners was how Ducati 916 could win over the 4 cylinders back in the 90's right?
Sudden too much will loose the grip...

My ride stile is opposite what can be seen on the race tracks    Twist on the straights, easy in the corners. I see sand, dirt, cow dung, tractors and frost damaged road behind every corner.

The engine combo now will stay.
1000cc  JE 10.5:1 to match the head by Dynoman in JMR porting block
Cam RC295 profile
Ported head with 34mm IN, 28 EX (5mm stems). Rather large ports, chambers opened for 65mm back in the 80's.
Mikuni TMR32 carbs that reacts really quick, a little bit too quick on 1:st gear. Less than 1/4 turn is full throttle.
APE lightened and balanced crank with Carillo rods.
Alternator lightened.
Exhaust Yamiya Lotus root 4-4 that work and sounds right.
I had plans to mount a Hindle 4-2-1 to get max power. I'll wait with that. Find a 3:rd bike to sneak in to the garage?

[Don R]

 We got a new cam for our 567" race engine, (by the engine builder during a refresh job)  it was for reduced lash according to the card. from .020/.018 cold to .012/.010 cold it was  supposed to be worth more 30 hp on a thousand hp engine. It ran well but was instantly a spring and rocker arm killer. We broke enough springs to cause a redesign of the valvetrain and spring upgrade.  All told the new cam used up about $6K in carnage with two rocker arms failing , stud girdle bolt getting loose in the motor and one new roller lifter spewing needles into two billet oil pumps.
 This was .830's intake lift and .790's exhaust. I suspect it is nearly the same cam only the lash was changed to protect the innocent parts. The car runs the same ET and MPH.

 Just some crazy cam info that may relate to this thread or not. My cb836 has a ported head and a Kenny Harmon F cam in it. After this hard learned lesson on cams I plan to swap it back out to a Honda F1 cam and call it good.  There is an RC327 in the tool box though. lol.

[dragracer]

We got a new cam for our 567" race engine, (by the engine builder during a refresh job)  it was for reduced lash according to the card. from .020/.018 cold to .012/.010 cold it was  supposed to be worth more 30 hp on a thousand hp engine. It ran well but was instantly a spring and rocker arm killer. We broke enough springs to cause a redesign of the valvetrain and spring upgrade.  All told the new cam used up about $6K in carnage with two rocker arms failing , stud girdle bolt getting loose in the motor and one new roller lifter spewing needles into two billet oil pumps.
 This was .830's intake lift and .790's exhaust. I suspect it is nearly the same cam only the lash was changed to protect the innocent parts. The car runs the same ET and MPH.

 Just some crazy cam info that may relate to this thread or not. My cb836 has a ported head and a Kenny Harmon F cam in it. After this hard learned lesson on cams I plan to swap it back out to a Honda F1 cam and call it good.  There is an RC327 in the tool box though. lol.

How about send that RC 327 cam my way?? Sounds like you aren't a fan of .012 lash. Lol

[livefast_dieold]

I was checking satanic mechanic website, and I came across this document:



Those are the same degrees of the DP315, but they need to be checked at 0.044 (.04+.004), while DP315 should be checked at 0.062 (.05+0.012)

[PeWe]

My DP315 at 0.04" (1mm) lift and 0.3 mm lash
IN 28,5°/56,5°   
EX 60°/26°

The yoshi numbers closer to the 295 cam I have in now, lift is same too .392/.360, my 295 in my engine at 0 lash .391/.361.  If I should timed it with less ex lash the duration numbers should be closer.
lash 0.1/0.15mm (.004"/.006") and 0.04" lift
IN:  22.5°/52°
EX:  53°/18° 

The shapes of the lobes might differ despite same numbers of lift and open/closing.

I have an update that can explain my earlier experience with 295 cam's bad idle. The fuel screws were too lean. The idle is much better now. 315 cam was not that sensitive on the lean fuel screws, only hypersensitive idle screw and struggling take offs on low rpm.

Fuel screws were opened 3/4 turn. 1 turn made idle and low lift better and 1 1/4 turns out engine idles really well.
I was worried about a carb synch which is boring with tank off again.

Adjusters on the TMR carbs 1,3,4 have a strange concentric nut with a lock screw.
Even if carbs have acc pump, it must run a little bit rich to idle correct and have a stable take off. Something to verify together with correct and equal ignition before eventual carb synch.

I'll update my comments about bad idle with 295 cam.

It is very interesting to discuss about different cams and experiences.

I like the 295 cam since it work really well, street and road use does not need to rev more than 6000 rpm since it is strong. That match my breather systems too, revving much during longer period the hoses will spray oil.  I have an extra clutch cover that will get a spigot and hose to relive some of the pressure. Valve cover might need some extra ventilation too since its hose drips good expensive oil after inspired riding.

[PeWe]

Interesting detail about ignition timing, 3° adv from stock.
My advancer has a play that I have to handle correct when time cam and set ignition.
'T' match real TDC when advancer is in its counterclockwise position. If I set it max clockwise case mark must sit 3° later to match. If I then set ignition at stock case mark, ignition will be advanced 3°.

Same with 2 different crankshafts but same advancer.

[Ilja]

Road test of the RC295 today. Cam is approved by the butt method!
Nice raw power with less need of gearing down when passing cars. Thought that 3:rd was in when twisting the throttle but tacho revealed that 4:th was in.
Again need to watch out when twisting and release in time since 180 kph happen really quick.

DP 315 is also a good cam but must have lash around 0.25-0.3mm to get the power.
Why not a RC315 with 0.15mm shaved off the lobes? Same cam with half lash than original with 0.3mm lash, right?

Both these cams work fine with 4-4 pipes. The overpriced early CB750 design, Yamiya Lotus Root with less restrictive junk inside work fine with both RC cam profiles.  I have drilled diffusers in the pipes, not that loud and the old CB750 look.
HM300 replica pipes No numbers work too but no diffusers is a must.

I'll check a day for a dyno to get the power printed.
Photos of the cams, DP 315 and cam with RC295 lightly engraved on the washer side. Maybe an old one?

I'm sure most of you have seen them many times. Same with nude women...seen many but always very interesting...still..

Hey Pewe!

I had that cam (295) in my turbo bike for half an hour, but it took away my bottom end torque completely and the turbo spinned up 1000rpm later.

So I sold it again..... but now I wish I didn't as I will remove the turbo kit and install 4-4 pipes, and weld up the F2 head for higher compression (battub shape) so it gets a nice squishband with the flattop 836 pistons.
Do you have a source for CB cams inside Europe?

The last one I ordered via a friend in the U.S... so it skipped some customs.. ;-) But it was expensive with shipping...

[PeWe]

Hi Ilja,
Cams will cost since the shipping and customs add a lot.  Dynoman use quick shipping, but expensive
My 295 was found on eBay, seller did not know which cam it was except a tune cam. I later found RC295 scratched on the washer side if looking in a specific angle.
German guys might have or get. Price might not be cheaper
https://classic-bikes.bikeside.de/      (Bought my carbs Mikuni TMR32 here)
http://www.fourever-classic-parts.de/  (They have restored prim hubs for me, new rubbers inside)

[bear]

The setup I use on my 1200cc motors work for our application.
We use high lift short duration cams and run 5 deg extra advance with our timing.
This pulls the top of the torque and HP curves down the rev range.
It's my experience that these motors can handle lots of cylinder pressure but aren't keen on high RPM.
Works for us.

[Ilja]

The setup I use on my 1200cc motors work for our application.
We use high lift short duration cams and run 5 deg extra advance with our timing.
This pulls the top of the torque and HP curves down the rev range.
It's my experience that these motors can handle lots of cylinder pressure but aren't keen on high RPM.
Works for us.

1200cc!!! wow..

The engine handles the cylinder pressure fine but mine with the turbo pinged fairly quick though.. torque at lower revs is a bit more prone to detonation as torque at higher revs but with a few degrees less (27) advance and 8:1 compression with good squish it was fine.
But indeed, nice torque down low and most smooth power from 5500-8000rpm.

The engine has a 63mm stroke, so thats quite long for a 750cc 4-inline which makes it more of a midrange engine.

[PeWe]

The setup I use on my 1200cc motors work for our application.
We use high lift short duration cams and run 5 deg extra advance with our timing.
This pulls the top of the torque and HP curves down the rev range.
It's my experience that these motors can handle lots of cylinder pressure but aren't keen on high RPM.
Works for us.

Good experience. 
- Megacycle 125-70/75 cam? Or another with grinded base circle?
I have seen similar with my current setup. 5:th gear and full speed, same on a road as on the dyno. It does not like to rev much more than 8000 rpm. I blame the 4-4 pipes, Lotus root open pipes that sings loud and very nice. (I have a new 4-2-1 waiting)
I like the torque. More for the clutch and gearbox to handle, though. Rear tire disappear...

More power earlier match the breather system that is not enough at higher revs. Added a hose from clutch cover to release the pressure.
- Advance ignition... Advance curve you can tune?

I tried more advance at the dyno by turning plate 2mm counterclockwise rel F mark at 1200-1400 rpm, 1-2 hp less, moved plate 2mm clockwise from my setting and got 2 hp more than first. stock mechanical advancer, cut springs.

There are a lot of cams, but different needs too. I have started to think that different race tracks need different cams It might not exists a best cam for all.

[Cb750 Racer]

I think bear meant cam timing 

The setup I use on my 1200cc motors work for our application.
We use high lift short duration cams and run 5 deg extra advance with our timing.
This pulls the top of the torque and HP curves down the rev range.
It's my experience that these motors can handle lots of cylinder pressure but aren't keen on high RPM.
Works for us.

Good experience. 
- Megacycle 125-70/75 cam? Or another with grinded base circle?
I have seen similar with my current setup. 5:th gear and full speed, same on a road as on the dyno. It does not like to rev much more than 8000 rpm. I blame the 4-4 pipes, Lotus root open pipes that sings loud and very nice. (I have a new 4-2-1 waiting)
I like the torque. More for the clutch and gearbox to handle, though. Rear tire disappear...

More power earlier match the breather system that is not enough at higher revs. Added a hose from clutch cover to release the pressure.
- Advance ignition... Advance curve you can tune?

I tried more advance at the dyno by turning plate 2mm counterclockwise rel F mark at 1200-1400 rpm, 1-2 hp less, moved plate 2mm clockwise from my setting and got 2 hp more than first. stock mechanical advancer, cut springs.

There are a lot of cams, but different needs too. I have started to think that different race tracks need different cams It might not exists a best cam for all.

[PeWe]

I think bear meant cam timing 

The setup I use on my 1200cc motors work for our application.
We use high lift short duration cams and run 5 deg extra advance with our timing.
This pulls the top of the torque and HP curves down the rev range.
It's my experience that these motors can handle lots of cylinder pressure but aren't keen on high RPM.
Works for us.

Good experience. 
- Megacycle 125-70/75 cam? Or another with grinded base circle?
I have seen similar with my current setup. 5:th gear and full speed, same on a road as on the dyno. It does not like to rev much more than 8000 rpm. I blame the 4-4 pipes, Lotus root open pipes that sings loud and very nice. (I have a new 4-2-1 waiting)
I like the torque. More for the clutch and gearbox to handle, though. Rear tire disappear...

More power earlier match the breather system that is not enough at higher revs. Added a hose from clutch cover to release the pressure.
- Advance ignition... Advance curve you can tune?

I tried more advance at the dyno by turning plate 2mm counterclockwise rel F mark at 1200-1400 rpm, 1-2 hp less, moved plate 2mm clockwise from my setting and got 2 hp more than first. stock mechanical advancer, cut springs.

There are a lot of cams, but different needs too. I have started to think that different race tracks need different cams It might not exists a best cam for all.

Yes, I see that now!   5 degrees is rather much. I have so far limited it to 3-4. These tested cam experiences are good info.
I should have thought about it since I usually advance the cam too. Last cam might be advanced 2 degrees.
The real numbers visible with running lash. If cam timing is "balanced" at 0 lash, a lash of 0.1/0.15mm will change that.