Topic: Cam Swap question...

[MAX1MVS]

OK, I have tried the search engine, but either I have a search engine handicap or it isn't working at this time...as such I have not been able to find any info on what kind of performance gains dropping a 650 cam into a 550 engine one should expect.

I apologize if this is a subject covered in great detail, I just haven't been able to find much on it.

Thanks in advance!!!

[iron_worker]

I'm not much help regarding the cam info but the search on the right hand side is indeed not working at this time. If you use the google search on the left hand side you can still pull up some good info.

IW

[PeWe]

Like this?
Search: 650 cam into a 550

http://www.google.com/cse?cx=partner-pub-9323359806520211%3A1305160748&ie=UTF-8&q=650+cam+into+a+550&siteurl=forums.sohc4.net%2Findex.php%3Ftopic%3D109842.0&ref=forums.sohc4.net%2Findex.php%3Fboard%3D2.0&ss=5141j1649583j18#gsc.tab=0&gsc.q=650%20cam%20into%20a%20550&gsc.page=1

[MAX1MVS]

Awesome!!!  Thanks, that will help my searching...I was getting uber frustrated with it.

[phil71]

I've always been suspicious that the extra low-mid rpm snappyness was from putting a new cam chain in when installing the 650 cam. basic combustion engine theory would tell you that a cam from a bigger engine would not be likely to make an improvement in a smaller one. How about some figures. Is there a chart that shows lift/duration/lobe centerline on the two?

[Bailgang]

I've always been suspicious that the extra low-mid rpm snappyness was from putting a new cam chain in when installing the 650 cam. basic combustion engine theory would tell you that a cam from a bigger engine would not be likely to make an improvement in a smaller one. How about some figures. Is there a chart that shows lift/duration/lobe centerline on the two?

I follow what you're saying however at best the 650 cam is mild. My memory sucks so I can't give you any actual #'s or specs but when I did my research when I did my cam swap on my 550 I know that the specs on the 650 cam are very close to that of say a mild street performance 550 cam offered by webcams. In my case my budget wouldn't allow for a new timing chain but even with the original timing chain I still noticed a snappier throttle response, stronger midrange and a stronger top end charge that really turns on at around 6,000 or 7,000 rpm. It also idles just as smoothly as it did with the original 550 cam.

[dave500]

I've always been suspicious that the extra low-mid rpm snappyness was from putting a new cam chain in when installing the 650 cam. basic combustion engine theory would tell you that a cam from a bigger engine would not be likely to make an improvement in a smaller one. How about some figures. Is there a chart that shows lift/duration/lobe centerline on the two?
[/quote


you dont understand cam timing phill,,the engine size dosent matter,,you can have two vastly different cubic sized engines with the same cam timing.

[Lostboy Steve]

The only reason I didnt go for a cam (650 or other) is because I figured the improvement still wouldnt be anything enormous. I am fairly happy with the factory esk performance after a good port. I am completely satisfied with the reliability of the factory components.

[Greggo]

I've always been suspicious that the extra low-mid rpm snappyness was from putting a new cam chain in when installing the 650 cam. basic combustion engine theory would tell you that a cam from a bigger engine would not be likely to make an improvement in a smaller one. How about some figures. Is there a chart that shows lift/duration/lobe centerline on the two?

I follow what you're saying however at best the 650 cam is mild. My memory sucks so I can't give you any actual #'s or specs but when I did my research when I did my cam swap on my 550 I know that the specs on the 650 cam are very close to that of say a mild street performance 550 cam offered by webcams. In my case my budget wouldn't allow for a new timing chain but even with the original timing chain I still noticed a snappier throttle response, stronger midrange and a stronger top end charge that really turns on at around 6,000 or 7,000 rpm. It also idles just as smoothly as it did with the original 550 cam.

That's a BIG +1 from me on that one.  No new cam chain, and I noticed a dramatic difference in the midrange with just the 650 cam...no other changes. 

The only reason I didnt go for a cam (650 or other) is because I figured the improvement still wouldnt be anything enormous. I am fairly happy with the factory esk performance after a good port. I am completely satisfied with the reliability of the factory components.

The 650's cam is a factory component, so I'm not sure what you're referring to in terms of reliability.  The combo of a good port, and the 650 cam reportedly give a much more dramatic performance boost.  If there is a downside to having a good 650 cam in a 500 or 550, I don't think anyone's found it yet.

[Bailgang]

The only reason I didnt go for a cam (650 or other) is because I figured the improvement still wouldnt be anything enormous. I am fairly happy with the factory esk performance after a good port. I am completely satisfied with the reliability of the factory components.

My 550 ran sweet even with the original came but I can't help messing with stuff looking for an improvement, it's just my nature. The only "issue" I had in the swap was finding a suitable tach because part of the swap involves using the 650 tach drive gear and using a 650 or 750 tach. I got lucky and spotted a 750 tach from someone local that was literally a drop in replacement to the 550 tach.

[phil71]

I understand cam timing just fine, thank you.. that's what I was saying about the new cam chain. And still, no one has evem attempted to put any real data behind what the 650 cam might be doing. Has anyone MEASURED anthing? Lets say, for the sake of argument, that you come to find that all its geometry is the same, but that the mount for the gear is 2degrees advanced, that would mean that you all could degree your stock 550 cams and have the same gain without hunting for cams. 
   Or, just keep guessing.

[Greggo]

There was a thread a while back that covered this stuff, but it's pretty much impossible to find now. IIRC, someone measured the cam, and as previously stated, it was very close to what Web Cam sells as a mild street upgrade, not just a very slight difference from the 500/550 cams. I don't really understand your skepticism...it's been tried and true, and it's a cheap upgrade.

[Bailgang]

  Or, just keep guessing.

All I can say to that is whoever first came up with the idea of swapping the 650 cam into the 550 must've been a pretty good guesser however you're skepticism is understandable being none of us so far has posted any specs yet. I would post the specs except I'm too lazy to look it up again.

The bottom line is if you're pleased with how your bike performs just the way it is then by all means leave it the way it is and let us guessers knock ourselves out while we keep guessing. As you probably already know trying to get substantial HP gains out of these small engines isn't easy nor is it cheap which can make one question the practicality of it all.

[dave500]

sorry phil i didnt mean to sound condescending,the analagy of a cam from a larger displacement engine not suiting a smaller one dosent hold true,im sure you understand cam timing.

[phil71]

I wasn't offended,  I just think that cam timing is not what this is about anyway. In 1971 Chevy made 396's (though they were all 402s) and they made 454s. If you took the cam from a 454 and shoved it into your 402, it would run like dog$#!t. Sure there were things that would make that work.. better heads, more compression etc.. but it all comes down to volumetric efficiency as it relates to the displacement of the engine.
   Let me put it another way..  a cb 650 with 9.0:1 compression made 63hp@ 9000rpm the CB 550 w 9.00:1 made 50hp at 8500 rpm. So an 18.19% bump in CCs yields a 26% gain in HP. The fact that both engines have the same compression ratio is a lucky thing, because, if for instance, the 650 was a 10:1 engine, that cam would make a pig out of that 550 and you'd have less compression.
    Lastly, I only brought it up because the 550s cam chains stretch pretty badly, and I wondered if the first person to try this might have seen a performance boost from a new chain, but attributed it to the cam swap.
   I'm not doubting that it works, but I was curious to know if there were real numbers to explain why it works.

[dave500]

the 500/550 dont have a bad reputation for cam chain stretching,your guessing now with the hyperthetical 10:1 650 engine on what cam it would have run.

[phil71]

quoted from hondaman "
Also: if the cam chain slipper tensioner and the chain are pretty worn, the cam timing goes late by almost 4 degrees. This pushes the power peak up to start at 650 RPM instead of the original 4500 RPM, making it a long time before the power seems to appear. New parts are the best solution, here."

so, yeah.. not the stretch, but the resetting of the cam chain tensioner from resetting everything. Man, if it works it works, I just want to know why.

[dave500]

the 650 cam is a different grind.

[Bailgang]

I am trying to dig up some data for you Phil but at the moment I'm coming up with some crazy stuff. I'll try to post something later.

[dave500]

its around here somewhere,slightly more lift and a little more overall duration,,you gotta be sure you dont mix and match those 454 and 396 cams,dont shove a peanut cam into an early engine,be sure to check you have the correct sprocket to suit aswell,,youll lose power badly.

[trueblue]

Here is some specs on the 550 and 650 cams, if you see the cams side by side you don't need to measure them, there is a significant difference between the two.  Figuring out that the 650 cam fitted the 550 wouldn't have been hard considering the 650 was built on the same tooling as the 550 to save on production costs, it was basically a factory hotroded 550.

Some good info a fellow forum member sent me in a PM. Thanks Kemp!

Here's the info I have on the CB550/650 cams. Unfortunately I do not know the rocker arm ratio and have not seen that info published. Would like the answer to that question also. The text below is cut and paste from articles and notes from others on the forum.

OK I found specs for Yosh cams.

Street special part# YH500-121-00

IN opens 20 BTDC, closes 50 ABDC  .278 lift
EX opens 50 BBDC, closes 20 ATDC  .307 lift


TT Special race cam  #YH600-122-00

IN opens 27 BTDC, closes 57 ABDC  .324 lift
EX opens 56 BBDC, closes 27 ATDC  . 336 lift


From another post, the lift on stock cams is:

CB650    IN .280 
            EX .293

CB550    IN .252
            EX .272

It looks like the 650 isn't too far the Yosh street cam as far as lift, not sure about timing?
In corresponding with hymodyne I guessed the 650 cam would have about .020 more lift than the 550 cam. Kayaker's #'s say I was close. I also guessed about 10 degrees more duration at least on the intake.
think .030 or so more lift would have a miniscule effect on ramp angle, but more duration would add to it. No matter what, lift is good, but its the timing that matters. The most important timing event as far as "feel" is intake closing. Closing later moves power up the rev range because it gives more time to fill at high revs.

I've searched and searched and just can't find all the cam specs for these cams.

Here's what I HAVE found:

SPECS:
 
 Stock (1974) CB550 cam
 
1.36 exh.       lobe              1.38 in.
1.110           base circle       1.110
0.252              lift              0.272
 
CB650 cam
 
1.39 exh.       lobe               1.40 in.
1.110            base circle       1.110
0.280             lift                0.293
 
 Can anyone give me the duration?
 What ratio are the rocker arms?
 Are the CB550 and CB650 durations the same?

[dave500]

the actual opening and closings still seem to be a secret?you drink rum true blue?(ILL GET THE NEEDED INFO)

[trueblue]

I try to avoid the old "Queensland Diesel", makes the head hurt too much  , I used to drink a lot of it in my teenage years but I learnt pretty quickly that Gold doesn't hurt as much in the morning, but my favourite drink is scotch, neat .  I have to check my valves in the next month or so, if I get keen I might get the dial gauge and degree wheel out at the same time.