Tim's 944LS1 track car build!

I decided to get creative, I taped a 1/8" piece of alum to the pan where it was hitting the rod bolt. Heated the pan up a bit and bolted it on. Left it to cool. Removed pan, and alum strip. Bolted it back on and all is well.

There is definitely a difference in the bottom end. Things stick out much further than on the LS1. For most pans I'm guessing that this is not a problem, my pan is a one off alum pan with a very low profile on the very front. I'll post pics later.

Crafty!

Long weekend working on the car, new engine is in, now it needs a tune or two. Have to get that done before the weekend, will be at Barber with Chin.

Got the car on the dyno mid-afternoon on Friday. Car made 468 rwhp and 461 ft-lbs, that was on a very mild tune. After leaving the dyno I dropped the car off at Barber. Car ran great all weekend, pulled like a freight train, scary fast! Temps were in the high 90's, lots of sun and humidity, yet no issue with cooling, water temps never exceeded 220 on track.

Is this an LS3 6.2. very nice power is the motor stock our is there upgrades?

That's a ton of HP and torque! What cam are you running?

6.2L LSA block mated with AFR LS1 heads, 11:1 compression.  Cam info below

Lap times were not very good, due both to track temp and me getting used to this beast of an engine.  I was just comparing acceleration and speeds and the differences are substantial compared to my old engine.

Cam #3310118 XA246
Installed at 109 degrees
Intake lobe lift: 0.364 (0.618 at Valve)
Exhaust lobe lift: 0.3688 (0.625 at Valve)
250/254 duration at 0.050

Ah, that's why. Your cam is much more aggressive than mine, I have the same baby cam I had in my first LS1.

The power must feel nice!

Snapped the rear lower coilover adapter bolt (to trailing arm) coming out of T3 at Barber yesterday, definitely a code brown moment. Managed to keep the car on the track! Talked with Karl and racers edge and he has only had two failures out of thousands sold. Suggested that the bolt may have come loose, but I'm not sure that is the case.

No real damage other than a good Hancock.

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Wow, those bolts are super expensive too. I'm just running the stock bolts on mine for now, I was told those Racers Edge bolts wouldn't work on my Escort Cup coilovers...

Whoa! That's a scary failure. Glad you came out relatively unscathed. I have those RE lower mounts on my car too. Hmm...

Rich

Make sure that the bolts are tight in the trailing arm (150 ft lbs). My new ones will be here today, while i was in there I pulled my 900 lb springs and am going back to 600 all around.

I didn't see any damage to the car other than the tire and bolt, so I got lucky.

Glad to hear you made it out of that incident unscathed... loosing a wheel anywhere, be it track or street would be very scary.

Ive searched around in the past reading about those adapter bolts and only came across one other incident where the bolt sheared off like that. The common consensus was that the bolt wasnt fully seated in the arm with both faces in contact. As you know those bolts rely on face to face contact for the extra strength in "shear".

The thread I read with the other that broke the owner figured his were were vibrating loose over time and or were never fully seated due to trash in the A-Arm threads. He chased the threads, tightened them up... threw on some loctite I believe and re torqued them. He also stated that he just checks them often now to make sure they are staying tight at that 150 ft lbs rating.

I am actually about to buy a set of those... and this doesnt deter me at all, because I would bet money a similar situation as described above lead to yours breaking.

Although it does have me thinking about a way to ensure they are "locked" into the A-Arm. Some sort of locking, ring/washer with a matching Hex pattern that goes around the base of that adapter after its properly seated in the A-Arm. A couple small dowel pins or tapped holes on that face or maybe fingers that extended around to a beefier area on the A-Arm that could be drilled/tapped safely. Essentially a "lock" for the adapter much lock a locking header bolt... but with tight tolerances so it couldnt vibrate loose/spin back out slowly over time.

Its just a thought though and my main concern with it is compromising the strength of the A-Arm or doing anything that could lead to fractures around holes drilled/tapped into the aluminum Arm. Considering how rare the failures are on these adapters... its probably not worth the time or risk... but on the flip side, if it could be pulled off safely and easily... it might prevent any chance of one breaking like this again.

I know that the bolts were put on correctly, but I can't say that I have torqued them since they were installed; I will in the future.  I did have the outer coilover bolt safety wired to the coilover.  I would think that would keep the inner bolt from turning as well.  

Those bolts were old, they were purchased when I installed Leda's on my 924S in 2005.

Lemming wrote:I know that the bolts were put on correctly, but I can't say that I have torqued them since they were installed; I will in the future.  I did have the outer coilover bolt safety wired to the coilover.  I would think that would keep the inner bolt from turning as well.  

Those bolts were old, they purchased when I installed Leda's on my 924S in 2005.  

Well the fact they lasted 10 years is great, especially when youre beating them harder than most people ever will. Its unfortunate it happened, but nice to hear they lasted that long.

My setup is just for street and the occasional auto cross outing... so hopefully theyl last as long as yours did too.

Lemming wrote:

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I’m not sure I’m qualified to practice failure analysis from a forum picture, but…..I don’t think the bolt was loose at all, there is no fretting on the seat. The dark/smooth 1/3 in the upper middle of the stud looks like a hairline crack/fracture that has been like that for a long time (dull/dirty/smooth). The course, shiny, lower halve and upper edge is the fresh break from last weekend. I think the mount had a defect from the beginning and the failure was from fatigue around the defect.

Glad the failure was uneventful.

Car is back together and ready for the weekend. Still need to send the broken support back to Karl for analysis, will do that soon.

Not a good weekend, cold and wet on Saturday, spent most of the time doing my CDI duties.  Sunday was much better weather wise.  Went out in the first instructor group only to have my left half shaft fail.  I pulled the unit and installed another during the lunch break, the inner CV cage was damaged, likely from the failure two weeks ago.  

First session of the afternoon, it's starts to mist heavily right as we are about to get on track, it was slick and I was not able to put the power down and really test the car.  

Middle afternoon session is dry, tires are gripping well, time to really push this thing given I have a race at the end of the month.  Coming out of T8 I went hard to power, there was a loud pop and I was bouncing off the rev limiter.  Push in the clutch and coasted to the black flag station, had to be pulled into the pits.  Started the car and left out the clutch, noise coming from the rear, but not way back. I'm hoping that I stripped or broke the torsion tube couple, but that may be wishful thinking.

The good news, the engine is a real beast, the bad news, maybe too much of a beast for the transaxle (turboS unit).

I have a spare complete torque tube from an S2 if you need one...

Got the car on the lift and got lucky, killed the brand new EMPI inboard CV joint, not the trans.


EDIT:
Upon further inspection, it appears that I'm missing one bolt and the other is loose on the drivers side of the trans hanger.  I'm guessing that this is allowing to trans to twist/move and breaking the CVs under hard cornering and acceleration.  Just hit Rob up for new bolts and poly spacers.

Sent the bolt back to Karl at Racer's Edge.  Here is his response

"I looked at the failed bolt head under a magnifying glass,.. it shows the classic signs of a fatigue failure for the first 70%-80% and then sudden fracture.   The shiny edges at the lower outer edges of the head do imply that there was some bending going on before final fracture due to the bolt not being tight.  I also asked Harry King who I work with here what his thoughts were on it,  Harry has a Masters in Material Science and he agrees that it looks like a fatigue failure due to the bolt not being torqued tightly enough."

Well okay. I feel like it's not surprising they see it as somebody else's fault. But assuming what Karl says is true, it either backed out or never tightened all the way down in the hole to begin with. Do you feel like either of those is a possibility?

And bummer about the trans hanger issue causing a CV to fail. All of this on the same corner of the car? Could the suspension collapse have over-angled the CV, damaging it and tweaking the mount? You use the van axles right? They don't have the same range of motion as the 944 axles.

Rich

I respect Karl's opinion.  The bolt was put in when I built this chassis many years ago (supercharged 968 engine at the time) and it is not one of the bolts that I routinely check, so it is possible.  Karl said that he checks that bolt a few times a year on his race car, I'll start doing the same.


Cannot be sure which issue caused the failure.  When the suspension collapsed, the increased angle might well cause the issue, on the other hand.  If the trans mount was already broken, then movement of the trans could have been the issue both times.  

And yes, I use the Empi vanagon CVs, which are now sold under the Empire brand name from what I can tell.  I did quite a bit of research and found other sources saying that these had the same range of motion as the 944.  Regardless, there is plenty of range under normal motion.  I posted that data on RL long ago.

As a precaution, I've added a trans brace on the drivers side.  I had one on there in the past but removed it when I went to xchops mount.

I'll find out this weekend if all is well as I'm racing with NASA at Barber. Was going to detune the engine to run ST2, but am very busy with work so that's not going to happen. Guess I'll be running ST1 this weekend, might supersize to TT1 as well (I need another track record since my TTB record with my 968 powered 924s, of many many years finally fell). Currently hold the TT2 record at Barber, even though it was a slow lap.