Cam Timing G3 Cams GS1100

[isleoman]

I'm checking the cam timing on an engine assembled by someone who should know their stuff.

The engine in question has run for about 20 minutes and then I discovered the cases were cracked. Its an 1166 with G3 cams.

I have no experience with cam timing so I thought it would make sense to check the timing on the assembled engine as a form of practice.

i have a hot cam degree wheel kit with piston stops and dial indicator.

The degree wheel is mounted on the ignition end of the crank. As installed now the degree wheel is snug against the advance unit on my Dyna 2000 and I'm wondering if thats the way it should be mounted.

I used the piston stop to set the degree wheel at O Top Dead Center. I then rechecked using the piston stop and I'm an equal amount of 32 degree either side of top dead center

When I check the cam lobe centers on the intake I get 24.5 degrees at 40 ten thousands lift opening and 55 degrees at 40 ten thousands lift on closing.

24.5 + 55 + 180 = 259.5 259.5 / 2 = 129.75 129.75 - 24.5 = 104.25 which seems believable for intake setting although torque oriented .

On the exhaust cam I get 64 degrees at 40 ten thousands lift on opening and 14 degrees at 40 ten thousands on closing. The 64 is BBDc and the 14 is ATDC.

This results in 64 + 14 + 180 = 258 258/2= 129 129 - 14 = 115 for the exhaust. This number seems off to me.

I did find a reference to ignition advance affecting cam lobe numbers. The reference was with respect to cars but got me wondering. Th..e reference said 6 degrees of advance would lead to 104 and 114.

The cams are mounted with slotted sprockets and the the cam chain appears to be at 21 pins counting from the marks on the sprockets.

So should I remove the dyna plate and advance unit from behind the degree wheel or does it not make any difference. Just doesn't seem right that the buler would choose 104 /114 for a GS1166. I was expecting numbers in the 106 /108 range.

[blowerbike]

ignition timing has nothing to do with it.
i also believe cam motions are checked at .040 valve opening's and closing's unlike webs that are checked at .050
at least my G10's was ground that way.

[isleoman]

Thanks Blowerbike.
i must be saying it wrong I did check at .040. Still puzzled by the results.

[blowerbike]

as you should be...
104/114 is goofy.
set your 20 pins and check again.
the more you do it...the more sense it makes.
hell it would take me a while to get warmed up again from not degreeing cams for a couple years.
a cam card is your friend...always check your wheel if it's at or before TDC/BBDC ect.. and compare to the cam card for reference..

[posplayr]

The other recommendation is leave the beer in the fridge till you are sure it is right ....

[isleoman]

as you should be...
104/114 is goofy.
set your 20 pins and check again.
the more you do it...the more sense it makes.
hell it would take me a while to get warmed up again from not degreeing cams for a couple years.
a cam card is your friend...always check your wheel if it's at or before TDC/BBDC ect.. and compare to the cam card for reference..

Here's a pic of the slotted sprockets that also allows you to see the cam marks on the end of the shaft. The exhaust sprocket is hard up against the slot.

I seem to remember in a recent post by Carter Turk that it was mentioned that 21 pins may be required to get to the desired settings. That's a piece of steel flat stock held in place by some sockets and head bolts. Its for the magnetic base.

[rapidray]

Isle, I ALWAYS use .050 as my checking # no matter WHOSE cams I am using. You are only looking to get the lobe center # correct & you can do that so many different ways that it would confuse the crap out of you! LOL!! Like Carter said, sometimes you have to move the cam chain to get one to degree correctly but I have never had that issue on one as small as a G3.
Ray.

[Carter Turk]

I don't recall saying 21 pins. I just couldn't see visually how rotating the cam chain would change where the arrow pointed on the the exhaust cam in relation to the side plates. Mine was pointing straight through a side plate, but when I rotated the cam chain 360 degrees as Ray suggested, with the cams out, the arrow pointed between side plates. I was also off one tooth on each sprocket as Gustov guessed, when the arrow was pointing through a side plate. All this was on stock cams with no slots though. Even when I was off 2 teeth, I had 20 pins between cams. As Blower said- "I see a bent valve thread" for sure if I tried to degree cams and slotted sprockets.

[rapidray]

Hey Isle, call me if you need to at 714--356- five.
Ray.

[madmikeracing]

Yeah listen to Blower.. I saw a guy years ago ,he put a Kit in his 750 and was finishing it up, He was cranking the engine over and said man does it ever have compression with these cams i cant even turn it over as he was going at it like a Monkey with a Johnson Bar, I had to walk over for a look (we were in a large Garage a bunch rented for our stuff to work on) I almost started laughing as the spark plugs werent even it it!!!HA HA anyhow I helped him take it apart and yeah some of the valves were bent, I chucked them in a hardings chucker and straightened them and we redid the head and all was OK again, That thing ran like a scladed cat fast) anyhow moral is dont be rammy if yo ufeel a obstruction dont get the johnson bar out, Take youre time no Joints and beers when doing it ha ha anyhow Giving Ray a call may also be helpful, I used to do my cams at 110 lobe centres worked well, some guiys liked 107 depends what youre cams are and driving styles> Good Luck Mike

[madmikeracing]

This what we use to do our cams up North in the Frozen Tundrah!! Mike

[rapidray]

This is the wheel I use Mike. Moroso, 18 inches in diameter! LOL!! The degree marks are almost 1/4 inch apart!!
Ray.

[trippivot]

I'm checking the cam timing on an engine assembled by someone who should know their stuff.

The engine in question has run for about 20 minutes and then I discovered the cases were cracked. Its an 1166 with G3 cams.

I have no experience with cam timing so I thought it would make sense to check the timing on the assembled engine as a form of practice.

i have a hot cam degree wheel kit with piston stops and dial indicator.

The degree wheel is mounted on the ignition end of the crank. As installed now the degree wheel is snug against the advance unit on my Dyna 2000 and I'm wondering if thats the way it should be mounted.

I used the piston stop to set the degree wheel at O Top Dead Center. I then rechecked using the piston stop and I'm an equal amount of 32 degree either side of top dead center

When I check the cam lobe centers on the intake I get 24.5 degrees at 40 ten thousands lift opening and 55 degrees at 40 ten thousands lift on closing.

24.5 + 55 + 180 = 259.5 259.5 / 2 = 129.75 129.75 - 24.5 = 104.25 which seems believable for intake setting although torque oriented .

On the exhaust cam I get 64 degrees at 40 ten thousands lift on opening and 14 degrees at 40 ten thousands on closing. The 64 is BBDc and the 14 is ATDC.

This results in 64 + 14 + 180 = 258 258/2= 129 129 - 14 = 115 for the exhaust. This number seems off to me.

I did find a reference to ignition advance affecting cam lobe numbers. The reference was with respect to cars but got me wondering. Th..e reference said 6 degrees of advance would lead to 104 and 114.

The cams are mounted with slotted sprockets and the the cam chain appears to be at 21 pins counting from the marks on the sprockets.

So should I remove the dyna plate and advance unit from behind the degree wheel or does it not make any difference. Just doesn't seem right that the buler would choose 104 /114 for a GS1166. I was expecting numbers in the 106 /108 range.

My racing engine I run similar numbers you have -- 102.5 intake and 115 exhaust. I set my cam timing to the mechanical limits of the engine - valve to piston -- to get the most overlap possible. bad ass power from idle to 10K. yes it works - - the 2 valve engines will hit valve to valve at those numbers during overlap -

108 to 110 equal lobe centers will give you a nice sit at a 5 minute red light idle and easy starting - but the classic torque dip in the mid range will appear.