[mgarblik]

There seems to be enough interest in our car and good or bad luck on the track to post up this thread. I have taken the transmission apart and we are confident we know what happened and how to fix it. Turns out the idiot who rebuilt the transmission didn't make an important measurement and shim properly. (That was me!) Once the situation was explained to LENCO it became clear right away what happened. This is a little technical mostly for the LENCO guys. When setting up for an air shifter after an overhaul, when new forks, roller plates, or clutch drums are installed, the stacked-up tolerance needs to be checked and adjusted with shims. With a manual shifted LENCO this can be accounted for by simply adjusting the tower pressure, a common adjustment. With an air shifter, this stacked-up tolerance must be adjusted with shims between the sprag support and roller plates. If not correct, the air shifter will apply the plunger and fork but even at full travel, it won't compress the clutches tight enough and those of you who saw the car run know what happened.
I knew something was up when the car did a very weak burnnout. That was because the clutches were already slipping. The car ran almost 1/8 mile fine because clutches are not used in 1st gear. When Eric made the shift, the clutches just burned-up because of not enough clamp force. The heat was just tremendous. In one of the pics you will see a wave plate that is MELTED. That is a steel plate! So well over 2000 degrees in that area.
The biggest issue for us now is getting the engine fixed in just a few weeks. If the oil pump belt would have stayed on, the damage would have been minimal. Unfortunately, that was not the case. I will have the engine apart this weekend and will up-date and post some more pics. Keep in mind, Pontiac faithful, this iron block Pontiac with a standard weight crankshaft ran to 10,200 RPM and all rotating components stayed attached with the exception of 1 broken push rod.

[Elarson]

I've given the driver an ass-chewing and he promises to lift sooner next time.

Eric

[goatless]

I am just amazed at how well you guys handle the setbacks! Hats off to you!
Can't wait to see her back on the track.

[stevep]

I have never been inside a Lenco, but the clutch plates look like Fordomatic!

[Tom Vaught]

Thanks for the great info, Mike and Eric.

yep, you guys build a tough engine.

Tom V.

[Dragncar]

I believe the clutches are based on the Ford C6.

[PAUL K]

Thanks for sharing. Good luck with the repairs; looking forward to watching you run at GLD.

[J.C.you]

Hang in there guys, all the effort will pay off when you start making clean passes.

[67GTO4SPEED]

Good luck to you guys getting it back together. I've always loved the Boss Bird and I hope to see you guys at top of Pontiac list one day! I agree with others that it is really cool that you guys share the story (good and bad) of the build. It makes us guys sitting in the cheap seats kinda feel like part of the team in some strange way! -lol

I do have a dumb question. I've wondered this since the original post about the damage this weekend, but I didn't have the nerve to post right after it happened.

What is the reason that there is no rev limiter on the engine to keep it from spinning that high? I figure there's got to be a reason, I just don't know what it is. Thinking out loud, I've wondered if maybe a rev limiter would cause just as much damage on nitro engine as not having one or something like that?

[mechanickeith]

"What is the reason that there is no rev limiter on the engine to keep it from spinning that high? I figure there's got to be a reason, I just don't know what it is. Thinking out loud, I've wondered if maybe a rev limiter would cause just as much damage on nitro engine as not having one or something like that?"



Cant shut it off. Burns so hot the spark plugs are like a welding rod. Once its going, only way to shut it off is to cut off the fuel or air. Cant shut off air, so that leaves fuel. Even if fuel is cut off, there is enough left in the lines & injectors for it to continue running for several seconds. The mag is there to get the plugs firing & away you go!

[Jack Gifford]

Originally Posted by mgarblik

... I knew something was up when the car did a very weak burnnout. That was because the clutches were already slipping...

Burnout in top gear?

So... the "idiot" in post#1 "... knew something was up..." and didn't try to abort the run? (Just trying to understand, Mike- I wasn't there)

In "olden times" we considered belts too vulnerable; that's why we drove drysump pumps off the front of the cam.

What a bummer. Best of luck getting back out.

[mgarblik]

Lenco always wants the burnout done in high gear to avoid damage to the sprag which is holding in low gear. The potential uneven loading can be absorbed through the clutches I guess. As far as aborting the run. 1. Things are happening pretty fast up there. 2. People expect us to make our runs and some travel a distance to see the car. We feel strongly that we "owe" the people who are in the seats the best run we can give them. 3. With the 36" Goodyear tires, the car often will not do a big burnnout, certainly nothing like the Grocery Getter with the Hoosiers. 4. Still trying to get the throttle stop just right for a good burnnout and not too much RPM. 5. The track was SUPER sticky, national event sticky. At the time I remember thinking the burnnout sucked and attributed it to not enough water not realizing some of the problem was the clutches slipping in the transmission. 6. The transmission was fresh at the time and I didn't consider a transmission issue until the run was over. So, yea, mistakes were made.
This is one of the reasons I applaud when a Pontiac powered car DOES make a tremendous run at Norwalk or anywhere else. So many things have to go right, lots of possibilities for problems. The engine has to be just right with the right tune, the traction has to be good, the driveline and chassis have to work right, the wind and weather have to be just right, and finally the driver has to do everything just perfectly to run the big number. When Rodney Butler ran his 6.27, the stars were just aligned perfectly for that instant. When Steve Dale ran his 6.13, same thing. It's really hard to repeat those numbers, and that's why we have all struggled to various degrees. The Kauffman dragster is probably closest to being consistent and reliable, but even they had some issues. I think they have run 3 5 second passes, but their final 2 at Norwalk were aborted for various reasons. We knew it would be very tough to run in these circles, but this car definitely doesn't give any freebies. It makes you earn every .10 of a second and every MPH. This is the most difficult car related project I have ever tackled in my life.


Jack, concerning the belt drive, I HATE IT!! We had several long conversations about what to do with the oil pump. This is why we ran the in pan pump for several years, trying to make it work. Our current pump flows 43GPM, measured and verified. We also ran 241 PSI straight and true on the data graph. Finally have it perfect and the damn belt gets knocked off. We have the fuel pump and a big 44 amp mag driving off the cam. We were concerned about putting even more load on the front cam drive. We may take another look at this in the off season. I agree completely, if there is any other way to drive the pump other than a belt, do it. I have seen far too many beautiful high dollar engines ruined by an oil pump belt flying off. Our pump mount is super robust with 1/2" fasteners and a very thick aluminum plate mounting it to a 3/4" thick steel plate. But the belt is still hanging out there in harms way.

[mechanickeith]

" But the belt is still hanging out there in harms way. "

Any way to put some kind of guard around it?

[BruceWilkie]

Sorry for your misfortunes.

If you are "stuck" with belt drive on the oil pump then you need some basic detection to kill the motor. More than just lost pressure sensing. Probably some type of circuit that clocks motion of pump itself and compares it to "clocking" of the crank shaft. Basically 2 encoders with a comparator circuit. Probably need a "missing pulse" circuit to allow a predetermined amount of clock pulses lost before shutting down motor.(allows for x amount of lost clock pulses that could occur like belt jumping 1 tooth or a lost clock pulse due to electronics "magic" or minor synchronization of pulses due to belt stretch.)

On the other hand would driving fuel pump from the crank and oil pump from the cam solve anything? Seems that would allow oil pressure even with fuel shutdown but engine still turning from being connected to driveline.(if cam isnt turning chances are motor is broke bad enough to not matter)

Good luck on next outing.

[67GTO4SPEED]

Originally Posted by mechanickeith

"What is the reason that there is no rev limiter on the engine to keep it from spinning that high? I figure there's got to be a reason, I just don't know what it is. Thinking out loud, I've wondered if maybe a rev limiter would cause just as much damage on nitro engine as not having one or something like that?"



Cant shut it off. Burns so hot the spark plugs are like a welding rod. Once its going, only way to shut it off is to cut off the fuel or air. Cant shut off air, so that leaves fuel. Even if fuel is cut off, there is enough left in the lines & injectors for it to continue running for several seconds. The mag is there to get the plugs firing & away you go!

Thanks for that! I knew there was something I didn't know about it and I was just curious.

[PMD1969]

Originally Posted by mechanickeith

"What is the reason that there is no rev limiter on the engine to keep it from spinning that high? I figure there's got to be a reason, I just don't know what it is. Thinking out loud, I've wondered if maybe a rev limiter would cause just as much damage on nitro engine as not having one or something like that?"



Cant shut it off. Burns so hot the spark plugs are like a welding rod. Once its going, only way to shut it off is to cut off the fuel or air. Cant shut off air, so that leaves fuel. Even if fuel is cut off, there is enough left in the lines & injectors for it to continue running for several seconds. The mag is there to get the plugs firing & away you go!

holy crap! grenade! I too do not know how you guys are able to handle those type of set backs. I wouldn't last under the pressure lol. Hope you are able to get it back together and make improvements. Unreal that a standard assembly held together so well to over 10k rpms

[Elarson]

Originally Posted by BruceWilkie

Sorry for your misfortunes.

If you are "stuck" with belt drive on the oil pump then you need some basic detection to kill the motor. More than just lost pressure sensing. Probably some type of circuit that clocks motion of pump itself and compares it to "clocking" of the crank shaft. Basically 2 encoders with a comparator circuit. Probably need a "missing pulse" circuit to allow a predetermined amount of clock pulses lost before shutting down motor.(allows for x amount of lost clock pulses that could occur like belt jumping 1 tooth or a lost clock pulse due to electronics "magic" or minor synchronization of pulses due to belt stretch.)

On the other hand would driving fuel pump from the crank and oil pump from the cam solve anything? Seems that would allow oil pressure even with fuel shutdown but engine still turning from being connected to driveline.(if cam isnt turning chances are motor is broke bad enough to not matter)

Good luck on next outing.

We're looking at all options. But the fuel pump is tuned to run at half engine speed and the oil pump runs at 57% engine speed.

Our problem this time....the Crowerglide centrifugal clutch doesn't disengage until the car slows down. So even though the engine isn't running, the car is still turning it.

Eric

[warriors revenge]

sorry to hear about your misfortune. speaking for myself and hopefully for most others, nobody would be mad if you aborted the run because of something you thought was unsafe or going to end in catastrophic failure.... i know and understand that hindsight is always 20/20 and when you are in race mode you just want to get to the line, and make a good clean fast pass, especially when you are guys like yourselves and do not want to disappoint your fans.. mark this one down in the **** happens column and keep pushing forward.... i was just happy to see the car there... you guys are awesome and have a handle on things... best of luck
kal

[Region Warrior]

Wow, just the difference between setting up the clutch pack for air vs manual shifter.
So easy to miss, yet so costly....

[mgarblik]

Yea, the guys at LENCO think a single shim between .015 and .030" was the difference between a possible record run and this mess. That's the part that twists my stomach and keeps me up at night.