May have cam sprocket problem
10-08-2013, 04:20 PM
#31
Wow, didn't quite expect anybody to respond that quickly to a more than a year old thread. :thumb up:
Like rgs944 it is the drivers side (left side of car from direction of travel)
The issue actually looks very much like what is shown in the video.
As i said, I have had the sprocket/gear checked…including two old sprockets. All had approx the same tolerances.
We mounted them in a turning lathe. We mounted them using a custom peg to fit the center hole. All three sprockets showed about 1/10 of a millimeter in variation measured on the side of the gear right below the "teeth". I know this is a bit tricky to explain, so let me know if I need to clarify how we checked the gears. (perhaps a figure would be nice?)
Anyhow, in my opinion, this is not crucial, especially since all the gears showed the same. Furthermore the offset/movement seem on my car (and on the video by rgs044) seems to be definitely more than 1/10 of a mm.
We also checked the small steel bracket, which mounts to the back of the cam sprocket. Nothing to mention here.
Just after my post here (earlier today) I spend some time messing with it in the car. I realized, that the cam sprocket actually has a little play on the cam itself when not bolted down. This is definitely now much, but it actually becomes visual at the gear perimeter (at the teeth). This could actually make out, at least for my problem, the wobble of the gear. This play is of course supposed to go away once the big center bolt is tightened. However, IF for some reason the gear was NOT bolted down straight, it would sit a bit "skew" and do the wobble.
Can't really see how this could happen, since the big center bolt would force the gear and the steel bracket against the "neg" on the cam itself. I can only think of a few possible ways this can happen:
1) The cam "neg" or the bolt is not completely "straight"
2) some dirt or other material has been trapped in between on install due to poor cleaning.
What do you guys think? Could the problem lie in the "mounting" of the sprocket?
As I have also transitioned to a Porken Tensioner while at it, I am actually considering assembling it all again in order to see if the issue is still there.…
Otherwise it must be something else…. Could it be the cam itself, which is "skew"???
And, am I correct that the cam can actually be rotated while the engine is at 45 deg before TDC without interference with the valves?? so I could rotate the cam to check it??
Inputs are most appreciated…
Like rgs944 it is the drivers side (left side of car from direction of travel)
The issue actually looks very much like what is shown in the video.
As i said, I have had the sprocket/gear checked…including two old sprockets. All had approx the same tolerances.
We mounted them in a turning lathe. We mounted them using a custom peg to fit the center hole. All three sprockets showed about 1/10 of a millimeter in variation measured on the side of the gear right below the "teeth". I know this is a bit tricky to explain, so let me know if I need to clarify how we checked the gears. (perhaps a figure would be nice?)
Anyhow, in my opinion, this is not crucial, especially since all the gears showed the same. Furthermore the offset/movement seem on my car (and on the video by rgs044) seems to be definitely more than 1/10 of a mm.
We also checked the small steel bracket, which mounts to the back of the cam sprocket. Nothing to mention here.
Just after my post here (earlier today) I spend some time messing with it in the car. I realized, that the cam sprocket actually has a little play on the cam itself when not bolted down. This is definitely now much, but it actually becomes visual at the gear perimeter (at the teeth). This could actually make out, at least for my problem, the wobble of the gear. This play is of course supposed to go away once the big center bolt is tightened. However, IF for some reason the gear was NOT bolted down straight, it would sit a bit "skew" and do the wobble.
Can't really see how this could happen, since the big center bolt would force the gear and the steel bracket against the "neg" on the cam itself. I can only think of a few possible ways this can happen:
1) The cam "neg" or the bolt is not completely "straight"
2) some dirt or other material has been trapped in between on install due to poor cleaning.
What do you guys think? Could the problem lie in the "mounting" of the sprocket?
As I have also transitioned to a Porken Tensioner while at it, I am actually considering assembling it all again in order to see if the issue is still there.…
Otherwise it must be something else…. Could it be the cam itself, which is "skew"???
And, am I correct that the cam can actually be rotated while the engine is at 45 deg before TDC without interference with the valves?? so I could rotate the cam to check it??
Inputs are most appreciated…
Last edited by cschou; 10-08-2013 at 04:35 PM. Reason: more info….
I admit, a little out of my league. I've only been in there twice myself, but curious to what is going on.
10-08-2013, 04:57 PM
#33
Addict
Lifetime Rennlist
Member
Lifetime Rennlist
Member
Yes but lock the crank to be safe.
10-08-2013, 05:09 PM
#34
Leon, great response… I guess I never figured the steel bracket is called a spider gear. 
I agree, that the spider gear do fit very tight against the cam, and that this does significantly reduce the play of the sprocket, but not eliminate it completely. However, I agree that the mounting of the sprocket and spider gear is unlikely to be the cause…unless some dirt or similar has made its way in between during assembly?
Regarding cracks, I am not at the car right now (and won't be until Thursday), but I didn't notice any cracks in the cam nose. But then again, I didn't particularly search them for cracks… would a crack be easily visible?
I had all the cams out less than a year ago, and I didn't notice any cracks back then either.…
My next attempt might be to rotate the cam itself and check it with a gauge… Hopefully I can do that Thursday…
I agree, that the spider gear do fit very tight against the cam, and that this does significantly reduce the play of the sprocket, but not eliminate it completely. However, I agree that the mounting of the sprocket and spider gear is unlikely to be the cause…unless some dirt or similar has made its way in between during assembly?
Regarding cracks, I am not at the car right now (and won't be until Thursday), but I didn't notice any cracks in the cam nose. But then again, I didn't particularly search them for cracks… would a crack be easily visible?
I had all the cams out less than a year ago, and I didn't notice any cracks back then either.…
My next attempt might be to rotate the cam itself and check it with a gauge… Hopefully I can do that Thursday…
10-09-2013, 03:26 PM
#35
Addict
Lifetime Rennlist
Member
Lifetime Rennlist
Member
A crack in the cam can be spotted pretty easily, it usually starts at the rear of the key slot. Since you measured and found some deviation in cam gear thickness (I assume, rather then being completely skewed) a wobble could be an optical illusion (?)
10-09-2013, 05:32 PM
#36
We didn't actually measure thickness. We measured how the outer rim of the wheel tracks according to the center hole.. we measured only 1/10 of a millimeter, but the wobble is visible with the eye. But it could be a visual illusion. I wouldn't be able to tell at the moment since it is disassembled and not running...
