Cam Timing

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who_gives_a6 · #1 Post by **who_gives_a6** » Sat Apr 16, 2011 12:26 am

Finally broke down and bought a dial indicator, wheel, dial mount, etc to do cam timing. I have 3 sets of cams, 1 new and 2 lightly used but well in spec according to caliper readings. After doing about 5 checks on each and verifying I was doing it correct, I'm getting 106 on every cam. None of them are off and readings were identical each time with all 3 intake and all 3 exhausts.

I have 450 12.5:1 piston, stock stroke crank, ported head, open intake, HMF exhaust, throttle body ported, and I believe that's it. Two almost identical motors are being done with almost brand new everything.

I plan on doing solely MX, mostly wide open high speed tracks, on them. I've read different things and been told go for 107 intake and 108/109 exhaust. Not quite the 106/106 combo I have now. But here's my issue: I'm living in an apartment for a few more months and have nothing more than basic handtools to do this on hand. Is there really any way to change the pin location on the cams to achieve these without a bench vice with wood/soft blocks? I'm drawing a blank on what I can use to break the gears loose and move the pins, and then retighten later.

Would 106/106 be a waste for what I'm doing or not a big enough issue to even bother with here? I'd like to throw them in and get them going, but don't want to be down on possible free performance increase if it's a big difference. Any ideas/experiences here?

cannondale27 · #2 Post by **cannondale27** » Sat Apr 16, 2011 1:32 am

It is a worthwhile mod but even at 106, odds are you are way better than stock. Only other way to hold that cam would be to cut lobe shape in a piece of wood but it would be no big deal for a guy to take the cams to a vice for first loosening and final torque. When doing the initial pin changes those bolts don't need to be fully torqued.

2000ex · #3 Post by **2000ex** » Mon Apr 18, 2011 12:55 pm

Take two 6 inch sections of pine 2x4 and sandwich the cam between them in a vice. Cheap, effective and all you need is the vice, hex socket, propane and a breaker bar

kdeal · #4 Post by **kdeal** » Mon Apr 18, 2011 3:46 pm

QUOTE (2000ex @ Apr 18 2011, 08:55 AM) <{POST_SNAPBACK}>

Take two 6 inch sections of pine 2x4 and sandwich the cam between them in a vice. Cheap, effective and all you need is the vice, hex socket, propane and a breaker bar

Excellent idea!

peterock · #5 Post by **peterock** » Mon Apr 18, 2011 7:31 pm

I always thought it worked best to just hook a battery up to the starter and crank it over with the smallest ratchet I could find attached to the cam in my tool box.

I swear this is the best way to do it. I would encourage anyone that does it this way to post a video of it just for proof.

who_gives_a6 · #6 Post by **who_gives_a6** » Fri May 06, 2011 7:59 pm

Finally got the cams gears broke off. Had to pay $10 because I couldn't find anyone with a vice anywhere. Now to the confusing part:

I had 106 intake as stock. Figured I'd go to 108 and leave exhaust at 106. Stock positions at 1 and 7. Manual said to add 2 degrees to go to 2 and 8 so I did. That actually lowered it to 103. I then went to 12 and 6 and got 107. Seems opposite the manual.

Is it just a put pins in a location and pray you get what you want or is there a method to the madness? Just curious what it takes to get this to 108. I do the measurements 3 times each time for accuracy.

Rundown:
12-6 = 107
1-7 = 106
2-8 = 103
3-9 = 113
4-10 = 106
5-11 = 104

I figure I have to be doing something wrong but following instructions I found by searching here. Just doesn't seem to make sense how the measurements are coming in for me. I don't understand how these measurements come up varying up/down. Any ideas or tips?

kdeal · #7 Post by **kdeal** » Fri May 06, 2011 10:11 pm

They are opposite in the manual. "+" = less timing numerically and vice-versa.

who_gives_a6 · #8 Post by **who_gives_a6** » Fri May 06, 2011 10:21 pm

Well that makes sense. I'm still a little confused but gives a better understanding.

cannondale27 · #9 Post by **cannondale27** » Sat May 07, 2011 2:42 am

This is why it is beneficial to actual check cam timing. In short no the holes in the cams are not accurate to a T and not guaranteed to give any stated figure in the manual especially newer cams. Old FX cams do seem to be very accurate but old FX cams are rare. That says to me that some cost cutting measure is responsible for the inaccuracy. But ask any Jap motor builder about the cams in there motors. Not accurately timed either. Once again best is to do it yourself so you know.

who_gives_a6 · #10 Post by **who_gives_a6** » Sat May 07, 2011 2:50 am

Thanks guys. Got it to 108.5 intake now. Do you think that a 108.5/106 combo would work well or shoot for the. 5 degree lower for 108 i need? Doing track and desert mostly. Lots of high revving and midrange needed.