AO

Total bummer! Those cams must have been singing!

Rob Edwards

Yow, total bummer. And brand-new looking chain tensioner pads- Wonder whether there would be any interpretable tell-tales in terms of wear on one pad or the other on this side of the motor vs. the other.

Maybe there's an IWIS racing chain that would be more robust (or at least provide theoretical peace of mind)?

mark kibort

absolutely the way to go... after i lost some teeth off the cams, probably due to the slack and whimpy chains, i changed to the IVIS chains.. they are much more durable looking and beefier. and if you have any stiffer valve springs, more the reason to change!

Sorry to hear Carl!!! Darn, right after qualifying!! UGGGGGg

any video footage????

Carl Fausett

Still looking for the causal point - haven't figured that out yet.

Exhaust cam has 1 broken tooth, the chain tensioner is torn out of the head, the chain is broken. That's just what I can see. Tomorrow I will do a cylinder leak-down test to see if I have bent valves or not.

Mid-Ohio is 30 days away...

mark kibort

that's ugly!

the broken tooth is probably in the pan right now. are you going to change the cam? I used the three cams with one tooth missing each for a while. as soon as there were two teeth missing adjacent, I pulled the cams. I think my problem was due to the chain being worn out and loose. as well as the tensioner being jammed.

Carl Fausett

I wondered if you could run a cam with one tooth missing.... but I wont do it. I have cores, so I am sending off to have a replacement made now. I have a pair of the 951 IWIS racing chains on their way to me now - thanks to Adam Birnbaum. Thanks Adam!

Carl Fausett

Some good news: every cylinder in that bank passed a cylinder-leak-down test at only 7% leakage. That, and the fact we could see no impacts with the bore scope, lead us to think we escaped without any bent valves.

The distributor drive collar is cracked in two places. Wow. That cam stopped abruptly when the chain piled up!

The intake cam is undamaged, and I even found the tooth! Can't believe I found the tooth.

Here are some pics:

bureau13

A little JB Weld, she'll be good as new

dr bob

I've seen sprockets repaired with the right TIG technique and some local heat-treating. The load on an individual tooth isn't that great, and if the rollers in the chain actually roll and the chain isn't stretched, a good repair will last as long as the rest of the sprocket. Just don't warp the cam...

Good that you have spares available. Hate to lose a chain at 220 on the salt. It would ruin your day.

mark kibort

at the time I lost a tooth (or two, or three and then 4-5 etc.. ) I talked to some sprocket and drivetrain engineers that said the increased load was only 7% greater on the adjacent teeth, so I left the cam in until it lost two teeth next to one another.

mark kibort

how were the lap times and do you have some video of qualifying??

I found your times on the nasa site. looks like the track is very close to the times that are run at LAGUNA. (top GTS3 cars are in the 1:36-7s)
http://www.nasamidwest.com/results/?...ventID=1129553

PelicanParts.com

This looks great! What NASA sanction are you running in?

-Luccia

Carl Fausett

I am in NASA Midwest, the GTS series, Unlimited group. So: GTS-U

Mark: I was paying no attention to my lap times whatsoever. Like I said, I had a new differential that I needed to learn with aftermarket ramps and clutches, a new transmission, a new motor that I was still breaking in, and 3-year-old slicks (hard) on a track that had puddles and rivulets across it.

Nope, just trying to get some seat time and sort out the car.

mark kibort

video is good , even though the sorting. (driver and car! )

we want to know how fast down the main straight.

Carl Fausett

I have found a supplier of the IWIS racing camshaft chains, a direct replacement that is heavier and stronger just for performance/racing motors. These were invented because Porsche was experiencing cam chain failures on the 951 (944 Turbo) after they installed stronger valve springs to control the boost. Sound familiar?

If you have high-lift cams or high-strength valve springs, please consider these cheap insurance against a potentially very expensive repair.

I've just put a pair in, and I offer them to you now as well:
http://www.928motorsports.com/parts/...aft_chains.php