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Holbert Car cam update. Two MORE teeth found after 4 race weeknds after oil change

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Holbert Car cam update. Two MORE teeth found after 4 race weeknds after oil change

 
Old 09-12-2005, 01:13 AM
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mark kibort
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Default Holbert Car cam update. Two MORE teeth found after 4 race weeknds after oil change

Ok folks, looks like I may have to finally retire the Holbert racer after this next race. two more teeth were found on my magnet of the drain plug. it hasnt lost a tooth now in over a year. now, with only one cam potentially, with all its teeth. one or more cams are now missing more than one tooth on its sprocket. I told myself, that two would be the limit, and two next to each other would also retire the car for the season. going to pull the covers and see where it is.

I am thinking about using the 85 cams, as they are probably the same spec as what came in the car. however ,there is a need to modify the driver side exhaust cam, which does just happen to not be missing any teeth!! If i can verify that the cams are essentially the same, i may have to only change 3 cams which some have said are identical to the s4 cams as far as fitting in the engine.

Stan, you still out there?? how did the 85-86 cam conversion to s4 go from your cam grinder?

MK

Last edited by mark kibort; 09-12-2005 at 01:50 AM.
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Old 09-12-2005, 04:09 AM
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Ouch.... best of luck with this... Keep us posted!
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Old 09-12-2005, 08:10 AM
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Amazing that the engine still runs. Don't drive it any more until you replace those cams, OK?
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Old 09-12-2005, 08:31 AM
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Hi Mark,

I haven't finished the project yet, as I acquired different heads with 968 valves. When I replenish my funding I will bring the heads back in (still chasing the honing/lapping process on the bored blocks too).

So many projects, so little time.... not to mention $
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Old 09-12-2005, 12:32 PM
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Tick-tock, tick- tock, tick-tock, tick-tock.........BOOM ! it is not IF only when ! If you swap out the camshafts that is the extent of the "rebuild" but if you bend the valves then the heads must come off then you see the pistons then might as well do bearings then and then ...
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Old 09-12-2005, 12:35 PM
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You are sure pushing it, small fragments arn't always caught by the magnet and the mesh on the pickup is pretty large. When my tensioner pad failed at idle I found a fragment in the oil pump. At speed you would have no chance.

Chris
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Old 09-12-2005, 01:11 PM
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Originally Posted by mark kibort
Ok folks, looks like I may have to finally retire the Holbert racer after this next race. two more teeth were found on my magnet of the drain plug. it hasnt lost a tooth now in over a year. now, with only one cam potentially, with all its teeth. one or more cams are now missing more than one tooth on its sprocket. I told myself, that two would be the limit, and two next to each other would also retire the car for the season. going to pull the covers and see where it is.
<snip>

MK
Mark,
I've seen companies that advertise that they can fix those broken teeth. I don't know the procedure they use. I doubt that the cams you have are '85/'86 grind. Your engine performs better that what those would do. More like a GT. Be careful about replacing 3 cams using a known type and leaving one of xx type. When you take the cam cover off, measure the lift of the intake cam. If 10mm, then they are same lift as GT cams which I think is the most lift for any stock 928 cam. S4 is 9mm, GTS is 9.5mm.

Louis Ott
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Old 09-12-2005, 01:48 PM
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Mark,

With the risks you were taking, I had kinda figured that you were waiting for the engine to blow up so that you would have a reason to do a complete rebuild and maybe pursue a stroker - while you were in there.

It looks like really aren't waiting for Ka-boom and will take care of your issues after all. Had me fooled. Any others as well?

Anyhow, I hope you get your work done quickly and will not miss much track time.
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Old 09-12-2005, 02:54 PM
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He secretly wants an excuse to build a stroker...
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Old 09-12-2005, 03:39 PM
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Thanks louis. yes, there is a 10mm lift and the hp curves are almost the same as rons GT. my hp is a little broader up top, but that could be due to the 85-86 grind that also has a 10mm lift.

im taking the covers off tonight to see what i got in there

thanks

MK
Originally Posted by Louie928
Mark,
I've seen companies that advertise that they can fix those broken teeth. I don't know the procedure they use. I doubt that the cams you have are '85/'86 grind. Your engine performs better that what those would do. More like a GT. Be careful about replacing 3 cams using a known type and leaving one of xx type. When you take the cam cover off, measure the lift of the intake cam. If 10mm, then they are same lift as GT cams which I think is the most lift for any stock 928 cam. S4 is 9mm, GTS is 9.5mm.

Louis Ott
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Old 09-12-2005, 03:57 PM
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nice!!!! great!!! Now what??????
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Old 09-12-2005, 04:48 PM
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Mark
Scary....gotta crack it open and take a look!! Didn't it slip a T-belt a while back?
Brian
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Old 09-12-2005, 05:10 PM
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No, these are the same two teeth as i found them on the plug

mk

Originally Posted by Sterling
is that 2 more in addition to the ones you posted about yesterday?
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Old 09-12-2005, 05:49 PM
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Mark,
take the before you replace the cams take them out and check them. You have a special car and I would not be surprised if these cams were somewhat unique. They could be off the shelf ones, but it would be better to know for sure.
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Old 09-12-2005, 05:57 PM
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knowing mark's luck - he could finish the season w/those things.... if it were me, I'd have the Tbelt wrapped around the torque tube and the pistons sitting next to me in the pass seat, etc...
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