Topic: What cam is this? Stock or Hign Performance? P or R11

[Yamahawk]

Seen this cam upstairs at Pat's from a CB750 or perhaps a CB550 engine that was torn down, it has a marking of P11 or R11, not sure which, but is the cam stock? or is it a performance cam that I ought to look at? Thanks!
Charlie

[seanbarney41]

R numbered cams are stock

[BPellerine]

when looking for an aftermarket cam,they are usually stamped under the washer on the end.bill

[Yamahawk]

Thanks, Sean wasn't sure, and ya never know what you will find laying around over there lol... Found a set of HM341's upstairs, but one was pretty Holy. (pray)
And thanks, Bill I will look for that!
Charlie

[Bodi]

A cast-in number (identifies the pattern used to make the sand mold for the cam blank, it tells you nothing about the grind. The pattern numbers may indicate the year the thing was cast? These are raised characters - the number is grooved into the pattern so it sticks up on the casting. I haven't seen punched-in numbers on a cam,
To modify a cam, assuming you want more lift or duration, you either grind down the base circle or hardweld the lobes bigger.
Modified stock cams usually have an ID stamped on one end face. Maybe a brand ID and a grind ID, maybe just a mystery code that hopefully someone will recognize.

[Yamahawk]

A cast-in number (identifies the pattern used to make the sand mold for the cam blank, it tells you nothing about the grind. The pattern numbers may indicate the year the thing was cast? These are raised characters - the number is grooved into the pattern so it sticks up on the casting. I haven't seen punched-in numbers on a cam,
To modify a cam, assuming you want more lift or duration, you either grind down the base circle or hardweld the lobes bigger.
Modified stock cams usually have an ID stamped on one end face. Maybe a brand ID and a grind ID, maybe just a mystery code that hopefully someone will recognize.

OK, thanks for the info. This cam has a stamp of R 11 on it to one side of the cam gear. Not sure what that designates. It looks like pretty radical lift and then drop, but perhaps that is the way the cam was made stock. Still learning about this stuff.
Charlie

[Jerry Rxman Griffin aka MuthaF'er]

R11 really means nothing as far as cam ID.

[Yamahawk]

R11 really means nothing as far as cam ID.

I wonder what it designates then. The cam has no other makings on the ends, or otherwise.The cam gear looks stock also, no slots or extra timing holes, so that must be stock. I guess there may be no way short of measuring lobes to figure out what it is!
Charlie

[Don R]

What Bodi said.

[seanbarney41]

Here is burnt up stocker F3 cam...KIMG0190 by Sean Barney, on Flickr
KIMG0191 by Sean Barney, on Flickr
KIMG0192 by Sean Barney, on Flickr
the only reason I know it is F3 is because I pulled it out of the untouched F3 that burnt it up

[Yamahawk]

Hey thanks, Sean that looks kinda like the cam I saw, except for the L that was cast in. I will look closer at it next time, but the R1 is close to the R11 in the one I saw, which may mean it came out of an F model engine maybe? And that means it might be a better performing cam than a stock K1 cam?
Charlei

[seanbarney41]

no, as stated the R numbers tell you absolutely nothing about which of several slight variations it is.  It just tells you what casting rig they came from at the factory, for quality control purposes.  The only way to identify it, is by measuring.

I am of the opinion that all the different cb750 cams differ so slightly that you will not notice the difference in a running engine.

[Jerry Rxman Griffin aka MuthaF'er]

I think the most conclusive identification of any stock Honda cam (F2/F3) may be that rectangle by the tach gear on Sean's cam. Forget all the others.

[754]

2 measurements with a caliper, and you will know the lift.

[Bodi]

Yes the raised lettering only identifies the (probably wood) pattern used to make the cam blank sand casting molds. They are numbered so if QC notices cams with missing parts they can easily find the pattern that's been damaged.
Any reasonable CB750 cam profile can be ground onto a standard CB750 cam blank, I don't think Honda had specific patterns for specific 750 engine types - the pattern number does not have any correlation to model year or engine type.
Base circle and lobe height are basic specs - should be published but I don't know for sure. Cam chart lift is specified as valve lift, I don't think the rockers are 1:1 so measured lobe height won't equal valve lift.

[754]

It seems to on our bikes, easy to check.
 But in a nutshell, if stock lift is under.300 like on our bikes, and the cam measures .320 or more.. try to grab it.

[Terry in Australia]

The good thing about the resurgence in interest in CB750's is that you can buy relatively cheap performance cams from CycleX and Dynoman etc, I have what is probably an old RC cam here but I wouldn't bother installing it when I can just drop in something new.

[Yamahawk]

It seems to on our bikes, easy to check.
 But in a nutshell, if stock lift is under.300 like on our bikes, and the cam measures .320 or more.. try to grab it.

Frank, what is the best way to measure the lift on a can that is out and on the bench? You mentioned two measurements with a caliper, would that be bottom of lobe to top of shaft, and bottom of lobe to top of cam lobe?

Yes the raised lettering only identifies the (probably wood) pattern used to make the cam blank sand casting molds. They are numbered so if QC notices cams with missing parts they can easily find the pattern that's been damaged.
Any reasonable CB750 cam profile can be ground onto a standard CB750 cam blank, I don't think Honda had specific patterns for specific 750 engine types - the pattern number does not have any correlation to model year or engine type.
Base circle and lobe height are basic specs - should be published but I don't know for sure. Cam chart lift is specified as valve lift, I don't think the rockers are 1:1 so measured lobe height won't equal valve lift.

The R11 isn't raised though it is stamped with a die stamp, it is an 'innie' not an 'outie' lol...
I am thinking to gain more lift, you grind the lower part of the lobe where you check and set valve clearance at, like Bodi mentioned? This, in effect would be like welding a higher lobe up top and then grinding it to contour... as the rocker arm would already be lower from the grinding of the bottom of the cam lobe, correct?

I think the most conclusive identification of any stock Honda cam (F2/F3) may be that rectangle by the tach gear on Sean's cam. Forget all the others.

Jerry, I will look to see if that is present on this cam.

The good thing about the resurgence in interest in CB750's is that you can buy relatively cheap performance cams from CycleX and Dynoman etc, I have what is probably an old RC cam here but I wouldn't bother installing it when I can just drop in something new.

Yeah, but free sure beats $220 for a new cam

Charlie

[Bodi]

Yes, my brain was on vacation. Characters stamped into a sandcasting pattern will be "innie" on the molded part. Some casting methods like "lost wax" make a pattern for each piece that's molded, for these any markings stamped in the "mother" mold will be protruding from the one-use pattern and the cast piece.
I doubt if a simple piece like a cam blank would use a lost pattern casting system, and the cast surface looks rough like sand cast steel.
The R number also looks way too rough to have been stamped into the actual camshaft, more like it was cast in.
Maybe Honda also used a mother to cast a bunch of metal patterns for production casting? My experience has been with low volume castings, where one pattern was sufficient. I've seen videos of casting engine blocks where they must have had a bunch of patterns in order to make one block every few seconds.

[scunny]

My 650 cams have the same numbers R10 and R11. One blank fits all ?

[Yamahawk]

Pretty sure this is a stock cam, there were two of them upstairs and they both had lines under the washer on the end...
Charlie

[Yamahawk]

2 measurements with a caliper, and you will know the lift.

Frank,
  Are those 2 measurements from the blank casting to the bottom of the lobe, and the other side of the blank casting to the top of the lobe?
Then subtract the smaller number from the larger...?
Charlie

[754]

On the lobe, take the biggest measurement, then urn 90 deg, take the smallest measurement, subtract = lift
 Cam looks stock.

[Yamahawk]

Ok.. 90deg or 180? Ah, I think I understand... the side to side measurement on the ground surface and the top and bottom ground surface measurement. Not sure what the 3 and 5 lines on the end mean.
Charlie

[PeWe]

Cam
B-C = Lift
The base circle differs between cams. To increase the lift on a cam, grind the base circle so "A" will be thinner. too thin might cause a too heavy angle for the valve adjuster screw that does not need much additional angle to dig marks into the valve stem, "mushrooming"
Valve lash when rocker arm is resting on base circle.

A hot cam (more lift and duration than stock) might not look that hot. When measure it the lift is around 0.400", base circle smaller. If not making smaller base circle the lobes will be very high and risk to collide with cam holders. Some cams have the instruction, check lobe clearance. (And grind the alu on cam holders for clearance if needed.)

Aftermarket cams usually have markings on cam ends as the photo on ignition side.
Under washer on other side.
On the edge of sprocket "wings" where sprocket is bolted. Web Cam can mark here. (DP cams and CycleX cams made by Web Cam)
Some other mark beside the foundry marks of the cam billet.

Other more special and exotic cams can have "-JMR" engraved after numbers between cyl 1-2. Nice grey surface with additional steel welded on the lobes. I had to visit my garage and have a look, beautiful

It would be nice with a cam thread were CB750 cams are specified with numbers and photos from all angles. Many different cams have been made for the CB750.