Topic: Dialling in camshaft, need some tech info?

[Terry in Australia]

Ok guys, I'm re-dialling in my Megacycle 125/75 cam, after "muffing" the timing by a few degrees, it seems.

Now either Mike Rieck (top bloke) or Sean Condon (another top bloke) sent me an article out of a bike book a while ago, but it's a little "vague" (to a thick-head like me, anyway) and appears to be missing at least one page, so I'm wondering if any of you guys have a good article out of a magazine or a book regarding the method of "dialling in" a cam for an SOHC4 engine?

Any help will of course, be appreciated! Cheers, Terry.

[ofreen]

This may help -

http://www.starracing.com/Cam%20Lobe%20Center%20Explained.htm

Also down toward the bottom of the page -

http://www.satanicmechanic.org/cams.shtml

[MRieck]

Terry
 You will just about never hit the exact timing marks on the cam card. This is especially true with a single cam. I always time cams with the running clearances...in your case .005. Knowing this if, for example the intake is suppose to open @ 26 degrees BTDC at .040 lift. With the running lash in place the valve will open LATER...@ 21 degrees. When it closes it will close 5 degrees EARLIER at 51 instead if 56.  51 - 21= 30. 180 + 30 =210 210/5 = 105 LC. Just the same as if the numbers were 26 and 56 on the timing card. Just make sure you lobe centers are correct AND you are positively at TDC when setting your degree wheel. As I said in the past, 2 cam engines offer a lot more latitude in regard to cam timing. We are stuck with a set lobe separation because of the single cam design. Hope this helps.
  Mike

[scondon]

 C'mon Terry, you can do it. Don't let all those numbers confuse ya

  Anything I could tell ya is just repeating what Mike told me and what's in that article I sent ya(which was copied from a book Mike loaned me). After you get past all the numbers and equations the process of timing the cam is pretty simple.

Find true TDC using piston stop and set your degree wheel marker at "0"

  Spin the motor in direction of normal run,watch the intake valve you're measuring come all the way up and sloooowly spin the engine 'til it starts going back down and your dial indicator reads .040 lift(or whatever lift it says to measure from on your card)

  Loosen the cam sprocket bolts and turn the engine, while holding the cam firmly in place, until your degree wheel reads the desired number and retighten the sprocket bolts. Double check that your dial indicator has not moved from .040. If it has then spin the motor all the way around until it comes back to .040 and repeat procedure. Do not back up the motor as cam chain slack will change the readings.

    Come to think of it there might be some help in these old posts. If there's a specific area that's not making sense then ask away. We're here for ya, ya poor bastard

http://www.sohc4.us/forums/index.php?topic=2988.0

http://www.sohc4.us/forums/index.php?topic=3148.0

[Terry in Australia]

Ha ha, thanks guys, I must have sounded a little depressed in my original post, and I do understand the timing  method ok, but your replies have re-assured me that I know what I'm doing, and I must admit that I was almost questioning my own ability there, which is silly, because of course, I am a mechanical super-hero, no doubt!

What I'm gonna do before I put the engine back in the bike is secure it to my hydraulic bench, hook up a truck battery to the starter, and spin the engine over so's I can do a compression test first. Before I did the top end rebuild this engine was giving me 175 psi in cylinders 1,2 and 4, and 150 in #3 (but that's another story) so if it doesn't return those sort of figures, I'll know before I re-install it. Thanks again guys, Cheers, Terry.

[Hockers Choppers]

OK, I understand everything up too the part of moving the cam. After you find your lobe center, what do you do?

[MRieck]

OK, I understand everything up too the part of moving the cam. After you find your lobe center, what do you do?

Put it in the bike and ride it.

[MRieck]

Ha ha, thanks guys, I must have sounded a little depressed in my original post, and I do understand the timing  method ok, but your replies have re-assured me that I know what I'm doing, and I must admit that I was almost questioning my own ability there, which is silly, because of course, I am a mechanical super-hero, no doubt!

What I'm gonna do before I put the engine back in the bike is secure it to my hydraulic bench, hook up a truck battery to the starter, and spin the engine over so's I can do a compression test first. Before I did the top end rebuild this engine was giving me 175 psi in cylinders 1,2 and 4, and 150 in #3 (but that's another story) so if it doesn't return those sort of figures, I'll know before I re-install it. Thanks again guys, Cheers, Terry.

After 3,588 posts I thought you'd be all set. Get the hell off the internet and turn some wrenches.

[Hockers Choppers]

So, what do you set the cam too? I have no card for the cam I'm running. Webcam 63a. What does finding the lobe center do? Other than finding out what degree the lobes are centered? What do you do with this info? What am I missing? Thanks for the help.

[ofreen]

So, what do you set the cam too? I have no card for the cam I'm running. Webcam 63a. What does finding the lobe center do? Other than finding out what degree the lobes are centered? What do you do with this info? What am I missing? Thanks for the help.

The links I put up explain it.

[GroovieGhoulie]

So installing the cam is not as simple as lining up the timing marks and putting the whole works together?  I've built some car engines and that's usually it.

I'm planning my engine build and this is a new wrinkle.  How difficult is this, really?

[Hockers Choppers]

Yes, I just read them again. I don't have the cam info card, so I guess you set the cam lobe centers  on intake and exhaust to match the same degree??

[paulages]

if i understand correctly, with the SOHC it's just a matter of using this method to find true TDC. adjustment from that point is relative to the intended advance or retard of the cam, as required by the cam profile, or to the desired change in power band.

[Terry in Australia]

Well it's worse than I thought initially, I actually had the valve timing spot on, but when I connected my truck battery to the starter, the compression was still down (125 +/- 2 psi in each cylinder) so I had to consider that I may have bent some valves.....................

I took the Megacycle cam off and replaced it with the stock cam and sprocket just in case I'd really screwed the timing up, and spun the engine again, but no, it was still 125. Crap.

I then took the head off expecting to see some bent valves, but the head looked fine, the valves appeared to be seating ok, I looked into the ports to see if the guides were damaged or the stems were bent, but couldn't see any damage whatsoever? I turned the head upside down and filled the combustion chambers with turpentine (cos it was handy) and none escaped past the valves? Hmmmnnnn..............

I looked at the pistons though, and there was some marks where the inlet valves had been "kissing" them, so there you go. The pistons (stock Honda 2nd oversize) were otherwise ok, so as the bike is booked in for registration in a couple of weeks, I decided to return that engine back to standard.

I cleaned up the old head,(it had been "reconditoned sometime between 1972 and it's last known registration in 1983, but like the pistons and bores, it appears to be in "as new" condition) removed (and later replaced) the RC Engineering studs, and replaced the M3 cam chain tensioner with a good used OEM item.

By the time I came in for the night, I had fitted a new head gasket (good old Ebay, I bought half a dozen a few years ago for a couple of bucks each) and torqued down the cylinder studs.(I'd intended to re-use the OEM items, but a couple were badly rusted, so I decided to refit the RC items, as I've still got a new APE set for my racer engine, plus I like to torque the studs down to 24 ft lbs, it makes for a leak free head.

Tomorrow I'll refit the stock cam and set about reinstalling the engine back in the frame (after I do another cold compression test) and I suppose I should pull the (possibly bent) valves from Mike Rieck's beautiful head. Hopefully they're not bent, but I'm not terribly confidant......................   

[MRieck]

That would be bad if the valves are bent...nice Kibblewhite pieces. I could have told you that cam would be too much for stock pistons. You need the deep valve reliefs,

[Hockers Choppers]

damn Terry, thats a real bummer!!

[Hockers Choppers]

 Do I NEED to get the cam card from webcam, or just center in on the lobe centers? Advance, retard or center? Sorry I'm sounding like a dumb a$$ on this. I understand how to set this up, I just don't know what to set my cam at.
Thanks.

[scondon]

Do I NEED to get the cam card from webcam, or just center in on the lobe centers? Advance, retard or center? Sorry I'm sounding like a dumb a$$ on this. I understand how to set this up, I just don't know what to set my cam at.
Thanks.

   Hocker, just sent ya the 63A timing card info. I just set the intake valve open to the # on the card, tighten the cam sprocket bolts and then check that the close and lobe center #'s match the card. When I did my Megacycle cam I found that the valve close #'s were 2 degrees off(54 instead of 52) when the valve open #'s were spot on. Couldn't do anything about that without regrinding the cam, but it was plenty good enough so I buttoned up the motor and called it good. Engine runs great.

  All you're doing when "timing" the cam is to make sure that it is opening and closing the valves at the point it is designed to do. You can get into advancing or retarding the cam a few degrees if you understand that stuff.

Well it's worse than I thought initially, I actually had the valve timing spot on, but when I connected my truck battery to the starter, the compression was still down (125 +/- 2 psi in each cylinder) so I had to consider that I may have bent some valves.....................

  Well damn, mate   Glad you inspected the head and pistons and found the "kiss" spots now instead of later. I thought that 125psi was a pretty good # to get on a cold compression test though. It's been a while and the memory's foggy but wouldn't you expect a 50-60psi increase once the motor's warmed up?

[Hockers Choppers]

Did you try a leak down test? I wouldn't think that the valves just kissing the pistons would accually bend them? At least I hope they didn't! CycleX has some new big bore kits that look badass!! I should have mine this week, I'll let you know.

[Hockers Choppers]

Oh, I forgot to say YOUR THE MAN, SEAN!!! THANKS AGAIN!!

[MRieck]

Did you try a leak down test? I wouldn't think that the valves just kissing the pistons would actually bend them? At least I hope they didn't! CycleX has some new big bore kits that look badass!! I should have mine this week, I'll let you know.

Yes ...the leakdown would be the absolute best test. I don't even do compression checks except to see initial cranking compression.

[ofreen]

Did you try a leak down test? I wouldn't think that the valves just kissing the pistons would actually bend them? At least I hope they didn't! CycleX has some new big bore kits that look badass!! I should have mine this week, I'll let you know.

Yes ...the leakdown would be the absolute best test. I don't even do compression checks except to see initial cranking compression.

I agree about the leakdown test, of course.  He'll be able to hear where the air is going.  It will be interesting to see what he comes up with, since he said the turpentine didn't pass the valves.

[MRieck]

This is a good lesson for anybody building any engine using aftermarket parts. ASSUME NOTHING>>>MEASURE EVERYTHING!!!!!!. You can measure piston to valve 10 degrees BTDC and 10 degrees ATDC by putting a dial indicator on the retainer and prying down on the rocker. I made a tool out of an old tappet cover to help do this. I'll post a pic in a day or 2.

[Terry in Australia]

This is a good lesson for anybody building any engine using aftermarket parts. ASSUME NOTHING>>>MEASURE EVERYTHING!!!!!!. You can measure piston to valve 10 degrees BTDC and 10 degrees ATDC by putting a dial indicator on the retainer and prying down on the rocker. I made a tool out of an old tappet cover to help do this. I'll post a pic in a day or 2.

Well it's a lesson Mike, but I'm not sure how "good" it is, ha ha! Problem of course was a time constraint that I wasn't expecting, you see my intent was to put my bike with the stock engine on the road, then build the engine at my liesure. The trouble was that the only number that the Aussie version of the DMV recognised (and were prepared to register) was the engine number for the "race" engine in bits on the bench, so I had to quickly button it up and get it installed in the bike, so as to get it on the road.

Now I've got several big bore kits in boxes, and I had a good set of 836cc sleeves to go into a cylinder block, which would have saved me a full days work on my boring bar, as I only had 3 days to get the engine together, finish putting the bike together, fit new tires, fix electrics etc etc, but I foolishly left the sleeves in my phosphoric acid tank, which pretty much dissolved them. Without thinking (because valve to piston clearances had never been an issue with the 836cc Wiseco pistons that I was gonna use, I didn't think to measure the clearances with the stock pistons.

A "leak down" test wouldn't have made much difference yesterday, even if I actually owned a leak down tester. You see, by the time I'd figured that my cam timing technique was actually sound, the 125 psi compression pressure was a sure sign of some valve or piston damage, the head had to come off anyway, so it made no difference in reality.

I will pull the inlet valves out of Mike's beautiful head to satisfy my curiosity once I get the engine back together (tonight) and back in the frame, (tomorrow night) it's too late now to ride my 750 down to Phillip Island this Sunday for the classic races, so I'll have to "slum it" on either my Suzuki GS1000S or the BMW K1100LT, not ideal I know, but such is life, ha ha! Cheers, Terry.    

[scondon]

   I still think 125psi is a pretty good # to get on a cold compression test with stock pistons, or am I thinking wrong here It's been a while since I did a cold compression check on a stock motor but I seem to recall getting between 100-115 on a used motor. Also, the fact that they're all even (+/- 2psi) to each other I'd be inclined to rule out valve damage unless each valve was damaged in exactly the same way. By all means, inspect for damage while you have it off. Just holding the good thought that everything is OK Terry

  Let me know if you need another stock bore headgasket rushed over. I've got several leftovers.