mark kibort

got the passenger side off before dinner and back together right after. What did i find??? still 1 tooth missing on each cam sprocket. Interesting. I would have bet at least one tooth would come from that pair, as the driver side is only missing 1 on the intake cam. Pretty cool it has lasted this long. one would think the adjacent teeth, with more load would cause a failure. the tensioner was kind of weak, but i wonder if that is due to it not being pumped up with oil after a 24 hour rest.

Now, the other side will have to come apart tomorrow. wonder what ill find. one of the cams will have a total of two teeth missing. will it be an adjacent tooth to the one missing on the intake cam, or will it be two missing on the exhaust cam. or worse yet, will it be 3 missing on the intake cam!!!!

any bets?

mk

mark kibort

Does anyone know if you can take off a single INTAKE cam (the one not driven by the cam belt and pulley)? It looks like you could slowely remove the bering caps and raise the cam, then, it looks like you could then just feed it through the chain and tighten everything slowely to replace. Im just preparing myself for contingency plan B if the Intake cam on the driver side is missing both of the teeth next to its original missing tooth. (ie missing 3 in a row!). this would mean the exhaust cam sprocket is still unmolested

it sure looks like it can be done. should be easy to align the cam due to there not being any alignment. Just match the 1/20 tooth position and all stays the same.

thoughts?

MK

Ketchmi

Jesus Mark, just fix it right and put the baseball bat away!

We can have the gears replaced on the cams but they do cost about $400 a pair. Depending on what you find when investigating your cams, it might be worth it. It's usually reserved for cams that there are no easy replacements for.

whall

I still find Marks some of the most amusing posts in this forum. Everyone is so **** about doing everything "by the book" and then some and then there is Mark.... "just a few broken teeth" I can still race it.

I recall a post by Jim Bailey a few months back where he talks about how this car should be enshrined in a museum, not beat down until it was within a inch of it's life. I fell over laughing - way too funny.

BTW: Sorry if I misquoted you Jim if my memory is off... and as always no offense meant to you Mark.

Jim bailey - 928 International

Mark has been extremely lucky with this S-4 (he did however total the former race car). It was a HANDBUILT preproduction S-4 made from an 86 chassis with a special no one knows how special preproduction engine. In Italy at a track near sea level it exceeded 180 mph ! It set the official production land speed record at Bonneville with Holbert. It was then used as a race safety car, IMSA ? eventually Porsche gave it to a high school shop class to be used as a teaching aid example(destroyed). The car was never to be sold ,registered ,driven on the US highways as are ALL preproduction prototypes... After Mark bought it he simply registered it in California no problem ! He pulled out the unusual one of a kind upholstered seats and turned it into a race car. So yes I do think it is a special car and really wonder what if any modifications were done to the engine oiling system since Kibort does not run an accusump or dry sump and nearly every other 928 especially GT cars run hard on a race track with decent tires in just a few hours blows out the #2 ,#6 rod bearings.

mark kibort

Its UGLY, and ill post pics on my next post.

by the way, i was able to see a very faint hand engraved number for the cams on the Holbert car. only at night, with the right light and a light film of oil, can you read it. most of it is clear, until the last 3 digits.

928 093 105 87M found this on the exhaust driver side cam. (in addition to the casting numbers)

make any sense?

MK

mark kibort

Pulled the final cover tonight, only to find a disaster!! not only is it my worse case expectations, (2 teeth missing together on a sprocket) the two teeth mission on a sprocket are addition to one tooth being missing already!! Now, if that wasnt bad enough, out of the corner of my eye, the only cam prevoiusly to not have teeth missing, is now missing TWO teeth as well, and right next to each other!!! so, the driver side now has 5 teeth total missing and the passenger side has 2 teeth still missing.

should i run the grand finale triple race weekend?

funnything is, im trying to justify it. but, the exhaust cam dual tooth missing, i think , tossed me over the edge.

NOW WHAT??? since i only have 2.5 weeks, maybe i should just poney up for a set of GT cams. otherwise, i have to modify the 85 cams and put in an unknown entity.

thoughts??

I think im yanking the cams out tomorrow night. manual, and some of the sites of information is kind of confusing, but i wonder if i get the new cams in, how important is it to fine tune the cam timing. maybe when i get to that point, ill be able to rig something up to test. But, first things first. CAMS, i need some GT cams! Any help would be appreciated?

MK

mark kibort

just found the old picture of the one tooth missing on the driver side intake. its now part of the dual tooth missing. who knows when the 3rd single tooth broke off. maybe all at the same time.

Do i buy entire tensioner system or just the chains

MK

FlyingDog

Can you throw in a set of S4 cams for the last race then worry about the GT vs 85 vs Holbert/custom cams later? I think the first thing to do is yank the cams and find out if they are special.

SharkSkin

Mark, whatever cams you use, I would say that getting the timing as precise as you can is worth doing. With everything already apart it won't take you long. Also, I agree with Joe & Dave above, that you really ought to get the specs on those cams... If it were me I'd do so before committing to any replacement cams. You may find that it doesn't match any production cams, in which case you might want to slap in the 85 cams short term while you investigate restoring to original spec. Also, if the cams in that car are different from production it will be of great interest to the community at large to find out the details...

SharkSkin

Dang, Matt, I didn't see your post.... had to do a plumbing check between loading the page & replying.

mark kibort

Thanks Dave. wonder how much it would cost to get that thrust bearing surface installed on the 85 cams? i think thats all it needs and then the ends need to be cut off (thats not a big deal at all obviously)

question is, who to take it to?? need some analysis pretty quick to make the decision.

I know Devek has a good cam guy.

MK

poc62

Mark with your luck, I sure you can run another 7 races without any issue!

Joseph

H2

If you run without a few cam teeth, I'd suggest you also buy a lottery ticket to help pay for the repairs. You may need the money.

Harvey

IcemanG17

Mark
You gotta pull those cams and get them measured...inquiring minds want to know...I think its safe to say they are not run of the mill GT cams...probably closer to the Devek B1 cams! Either way the differences will be very telling to the Holberts cars secrets!
Brian