Road coursing and our motors.

fturner

Registered User
I had my first engine mechanical failure and of all things to break, it was the timing chain that let go :eek: ....

I was running the car on the Mosport DDT track at an advanced driving school, and I was out on the last run of the day and was coming out of a 90 degree corner in second gear when the motor just up and died. Had to get towed home, which was a 3-1/2 hour trip :cool:.

Now before everyone starts panicking and figues the stock chain is crap, I'm going to explain some circumstances that happened leading up to the failure. The stock chain setup is more than adequate for the majority of folks around here.

1. When I did the cam swap last year, I checked the chain and the tensioner and while the tensioner was showing some wear, everything was well within spec.

2. I'm running a short duration cam with a lot of lift with sufficient spring pressures to run the motor to about 6200 or so. During the day yesterday my average shift rpm was around 5400 or so, with only a couple of runs out to 6000. The ramp rates on this cam are fairly aggressive, but I don't think its killer aggressive... but hey I could be wrong.

3. I was running 10% OD on the MPX blower, mainly to keep temperatures down since I couldn't run with alcohol injection, and I don't have enough capacity with the existing setup to lap for 20 minutes anyways. I also adjusted my tune to back timing off to 22 degrees at WOT. The 10% OD also saved me from wiping the car out because the track is short and had a lot of aggressive turns in it. Suffice to say, I still managed to lap quite a few cars on the track anyway :D.

4. Because of the FMIC I have on the car, the car never bogged down with heat issues which was a good test of it. I am pleased with the style of IC that Dave picked out for my car and yesterday was proof of it. Its not a bar-n-plate setup.

5. Pushing the car on the skid pad, I was told to stop cheating and not use the car's torque to drift through the circle :rolleyes: and actually swerve the car hard to break out the backend and "spin" the car.... it was rather unnerving to actually force yourself to wipe out the car. The secret is to bring it back under control though, anyways. The first time I used the steering to break the car loose, 2 360's was the result and that happened so fast (I barely blinked) I was unable to get the clutch in on time and the car rolled backwards in second gear. It was a hard start but she fired up eventually and off to the races.

6. The car performed beautifully all day, even when the temps got up over 30F. Fortunately it wasn't too humid out. On some of the straighter sections I was able to get the car to about 100mph or so before I had to slow to corner.

The result is, I need to pull the front and top of the motor apart because no doubt I have bent valves and I will need to check for bent rods and so on.

Now, I'm throwing this out there because I am curious as to what your thoughts are in this situation ie, what caused the failure and what can be done to prevent a failure like this again other than not driving the car on a road course which is NOT an option for me :D.

A timing chain failure is rare, and I'm not exactly considered a hi-powered car since I only have an MPX. I also am maticulous with maintenance and checking the car out and monitoring how it is running etc so neglect is not an issue here.

Fraser
 
I had my first engine mechanical failure and of all things to break, it was the timing chain that let go :eek: ....

I was running the car on the Mosport DDT track at an advanced driving school, and I was out on the last run of the day and was coming out of a 90 degree corner in second gear when the motor just up and died. Had to get towed home, which was a 3-1/2 hour trip :cool:.

Now before everyone starts panicking and figues the stock chain is crap, I'm going to explain some circumstances that happened leading up to the failure. The stock chain setup is more than adequate for the majority of folks around here.

1. When I did the cam swap last year, I checked the chain and the tensioner and while the tensioner was showing some wear, everything was well within spec.

2. I'm running a short duration cam with a lot of lift with sufficient spring pressures to run the motor to about 6200 or so. During the day yesterday my average shift rpm was around 5400 or so, with only a couple of runs out to 6000. The ramp rates on this cam are fairly aggressive, but I don't think its killer aggressive... but hey I could be wrong.

3. I was running 10% OD on the MPX blower, mainly to keep temperatures down since I couldn't run with alcohol injection, and I don't have enough capacity with the existing setup to lap for 20 minutes anyways. I also adjusted my tune to back timing off to 22 degrees at WOT. The 10% OD also saved me from wiping the car out because the track is short and had a lot of aggressive turns in it. Suffice to say, I still managed to lap quite a few cars on the track anyway :D.

4. Because of the FMIC I have on the car, the car never bogged down with heat issues which was a good test of it. I am pleased with the style of IC that Dave picked out for my car and yesterday was proof of it. Its not a bar-n-plate setup.

5. Pushing the car on the skid pad, I was told to stop cheating and not use the car's torque to drift through the circle :rolleyes: and actually swerve the car hard to break out the backend and "spin" the car.... it was rather unnerving to actually force yourself to wipe out the car. The secret is to bring it back under control though, anyways. The first time I used the steering to break the car loose, 2 360's was the result and that happened so fast (I barely blinked) I was unable to get the clutch in on time and the car rolled backwards in second gear. It was a hard start but she fired up eventually and off to the races.

6. The car performed beautifully all day, even when the temps got up over 30F. Fortunately it wasn't too humid out. On some of the straighter sections I was able to get the car to about 100mph or so before I had to slow to corner.

The result is, I need to pull the front and top of the motor apart because no doubt I have bent valves and I will need to check for bent rods and so on.

Now, I'm throwing this out there because I am curious as to what your thoughts are in this situation ie, what caused the failure and what can be done to prevent a failure like this again other than not driving the car on a road course which is NOT an option for me :D.

A timing chain failure is rare, and I'm not exactly considered a hi-powered car since I only have an MPX. I also am maticulous with maintenance and checking the car out and monitoring how it is running etc so neglect is not an issue here.

Fraser


slightly more common than you think... i had one fail with 8000 miles on it. not sure of brand, came with an entire overhaul kit from dave d...... it ate a set of heads and made love to piston #1
 
>Now before everyone starts panicking and figues the stock chain is crap, I'm going to explain some circumstances that happened leading up to the failure.

I think it's common knowledge that the 3.8's timing chain isn't a weak link...stuf happens, especially w/used parts in an over-revved motor :)
 
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My first time on an auto cross course I ended up with the car moving backwards in 2nd. Hard start as well afterwards. No evidence of an issue after, nor the rest of the runs, or 2 more times I coursed later in the season after that. I'm sure the timing chain doesn't appreciate that, but it shouldn't snap.

I think it's hard to guess until you get the cover off and can see where the failure occurred and how it looks. Could always be a different failure in the valve train that then led to the chain breaking.

Did it die on a shift, or just after a shift? Stock oil pans with the stock pickup location are not particularly suited to auto cross running, nor road course. I'd check the oil and the oil filter for bearing material. A worn thrust bearing allowing excess crank movement could contribute.

Again, just guessing. There have been enough other cars running them hard with the stock chain and not having a failure. So I have no reason to think that is a big problem.
 
>Now before everyone starts panicking and figues the stock chain is crap, I'm going to explain some circumstances that happened leading up to the failure.

I think it's common knowledge that the 3.8's timing chain isn't a weak link...stuf happens, especially w/used parts in an over-revved motor :)

Out of curiosity, why would you think I was over-revved?

Fraser
 
Going backwards in second probably did something. But there are lots of variables at here. Our motors are not intefering motors as far as I know. Do you have different tolerances that affect this?

This stinks regardless. Sorry to hear about your failure. Maybe you can now move to a 4.2l motor.
 
My first time on an auto cross course I ended up with the car moving backwards in 2nd. Hard start as well afterwards. No evidence of an issue after, nor the rest of the runs, or 2 more times I coursed later in the season after that. I'm sure the timing chain doesn't appreciate that, but it shouldn't snap.

I think it's hard to guess until you get the cover off and can see where the failure occurred and how it looks. Could always be a different failure in the valve train that then led to the chain breaking.

Did it die on a shift, or just after a shift? Stock oil pans with the stock pickup location are not particularly suited to auto cross running, nor road course. I'd check the oil and the oil filter for bearing material. A worn thrust bearing allowing excess crank movement could contribute.

Again, just guessing. There have been enough other cars running them hard with the stock chain and not having a failure. So I have no reason to think that is a big problem.

The shift down to second had already been done going into the corner, and it died as I was accelerating out of the corner.

Fraser
 
6. The car performed beautifully all day, even when the temps got up over 30F. Fortunately it wasn't too humid out. On some of the straighter sections I was able to get the car to about 100mph or so before I had to slow to corner.

I know you're in Canada.. but really, it only got to 30 degrees yesterday? (yes, out of you're entire post - that's what stuck out to me haha) Although I am curious about the IC design you've got.
 
I know you're in Canada.. but really, it only got to 30 degrees yesterday? (yes, out of you're entire post - that's what stuck out to me haha) Although I am curious about the IC design you've got.

Maybe he ment celcius? That would be 86f.
 
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I meant deg C.... I'm of the age where I was half way through school when the switch was made so half the time I don't know what unit I'm working with....

Fraser
 
...stuf happens...

Agreed. I just dealt with all of this carnage due to a timing chain failure in the 5.0L in my F150. Bone-stock engine, 210K miles, just cruising down the interstate at 2K rpm....then BAM!

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Didn't you just change to the 5-speed setup? Maybe your driving style + the 5 speed broke the car? :p

Let's see those datalogs. ;)
 
OUCH!!!!!!!

Yup, just went to a 5 spd, but I'm no nube to stick as I grew up with them. Unfortunately, due to the pedal arrangement in the earlier cars I could't do heel toe so I was having to shift down right after braking just before the corner to minimize drive line shock.

I had Fasted check the pedals out and he noticed how far away the gas pedal was from the brake pedal. I'll be "fixing" that issue shortly.

As for datalogs, I didn't get any :( as they wouldn't let me run the laptop in the car. I wanted to, trust me.... I think though I can rig something up for next time, but I'll need to switch the laptop over to using an SSD drive cause I have a feeling the cornering etc will cause the hard drive to park itself in my laptop.... its an Lenovo, and it has that "airbag" feature in it to protect the hardrive so it has built in accelerometers. I've seen it kick in a couple of times when I accelerated really hard.

Fraser
 
While on topic, what timing chain brand does everyone recommend? Is cloyes the OEM?

My old '94 had some sort of a reman'd SC engine in it, and it developed what we thought was rod knock.. turned out to be a SEVERELY stretched timing chain that was making all the noise... The damper looked fairly new, not sure what the hell happened.. Ended up putting a totally different motor in it (already aquired before we knew it was a simple fix..)

Jeramie
 
The shift down to second had already been done going into the corner, and it died as I was accelerating out of the corner.

Fraser

My previous motor died on the road course. Coming out of corner, very similiar to your situation although the time chain didn't break. It's seized one of the cam shaft bearings and threw a rod. Very spectacular, flames and all. Big hole in the bottom end. (If you're gonna go, go big :D)

After looking over the motor (pieces that were left :rolleyes:) in detail with an race engine builder I know and trust we determined that it was oil starvation due to lost of oil pickup in the corners. That's why my road racer now has an Accusump oil accumulator. Have had no issues since.

Just a thought. :)
 
Update.... the carnage so to speak.

The timing chain broke cleanly... no pieces floating around, no damage to the gears or tensioner. with the result of bent valves and knicks on the piston tops. I wouldn't be surprised considering how bent the one valve was that I may have a bent rod or 2 as well.

I think the oil pump kept being starved because of the high speed cornering etc, and the thought is it may have caused cavitation which would create shock loading on the pump shaft and timing chain. With the chain being the original factory and already stretched over the years, and then add that shock loading to it, it broke.

Now I need to somehow get an oil pan with baffles etc and more capacity. I'm talking with Dave on what to build engine wise :D. Dave will be fixing up the heads for me as he did the original work on them, meanwhile I've dropped in a spare stock motor from a 94 just so I can run the car.

I also have some ideas of my own I'm going to work on as well ;).

Fraser
 
My previous motor died on the road course. Coming out of corner, very similiar to your situation although the time chain didn't break. It's seized one of the cam shaft bearings and threw a rod. Very spectacular, flames and all. Big hole in the bottom end. (If you're gonna go, go big :D)

After looking over the motor (pieces that were left :rolleyes:) in detail with an race engine builder I know and trust we determined that it was oil starvation due to lost of oil pickup in the corners. That's why my road racer now has an Accusump oil accumulator. Have had no issues since.

Just a thought. :)
Cornering is also a problem with power steering pumps. Although i havent had a failure yet, my poor-mans (OK,, cheapskate's) solution is to run 1qt more oil in the engine, and keep the ps fluid level higher to help reduce the cavitation.

And also if you take those slicks off there and run squealy road tires, you won't pull so much side force through the turns.. :rolleyes::D and experience oil starvation. ;) Also reduces the wear on the suspension.
 
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