New ACR loses motor at COTA Details?

[Special Ed]

I was told a ACR with heads, cam and 100 miles on the clock hung a rod out of the block. Any e have more details?

[swexlin]

I was told a ACR with heads, cam and 100 miles on the clock hung a rod out of the block. Any e have more details?

Not good. Wonder if it is anyone on here, it is a small group of ACR folks, hopefully someone has some information.

[VENOM V]

Someone was tracking a heads and cam motor with only 100 miles on the clock? No break in? Sounds like a bad idea to me.

[Malu59RT]

SW was at COTA in his Comp Blue ACR, and I don't believe he had a break-in per se, but nothing I heard made it sound like he hurt the car? Sounded like he really enjoyed the car and planned to track it a lot. Then again, I don't know if he's the car in question, I don't think he had H/C on the car.

[ACR Steve]

track a car with 100 miles on it????? hate to say it but sometimes in life you get what you deserve

[Dman]

Holy crap, hope the mileage is an exaggeration, who would track any car with 100 miles on it. I'd think even if VE did the car they'd not warranty it with year warranty with 100 miles on and tracking, although, throwing a rod, wow, that's, wow.

[Coder]

Anytime you see someone ignoring break in because "they know engines" it makes me sad.

Break in matters. If for nothing else, your differential needs it. Gilles himself has said this multiple times.

I hope buddy isn't now on the hook for a new ACR engine because if you ignore break in.. not sure warranty covers you?

[Rapidrezults]

I HIGHLY doubt this car, if the rumor is even true, had 100 miles. Anyone with enough money and hopefully sense to drop cash on a HC package has to know better. Or at least you would hope so anyway.

[kverges]

Speedventures posts results, for example here:

http://www.speedventures.com/results/Default.aspx

One listed car is an ACR with 750 hp, consistent with having heads & cam.

FWIW, I've never trusted cam work on tracked cars; my belief is that the cam developers do not have the resources to endurance test the engines the way an OEM does with stock components. I've worked with OEM engineers and the endurance tests they do on engines are unbelievably extensive. Some tests are specifically intended to anticipate extreme abuse. For example, there is a test that takes a brand new engine, cold starts and within seconds goes to WOT max RPM for an extended period of time. Unless a cam developer can show me test procedures and results for endurance, I worry that the extra lift and duration and higher RPMs typical of an higher performance cam can really be hard on the valvetrain and reciprocating components. A dropped valve can easily cause a rod to part, as the valve head can penetrate the cylinder wall, piston skirt hang and then rod parts on the intake stroke.

As for the break-in, I'd defer to specifics from the engine design engineers for this engine, but I know from other modern engines that break-in is not that big a deal, as production tolerances are so good these days that parts don't have to "wear in" nearly as much as they used to. For example, bearing tolerances better be right to begin with and they don't really wear in to one another anyway, cams are roller so no need for tappets and lobes to wear in, and rings seal very well to begin with and actually seal better, to a point, with more combustion chamber pressure. I'd want to know the specific failure mode attributable to lack of "break-in" that would cause a thrown rod, as to me the cause could just as likely be an assembly error in rod bolt torque or improper bearing clearances or materials.

Bottom line, I'd like to know actual facts and the speculation and willingness to throw the unknown owner under the bus is not what I'd expect out of fellow Viper enthusiasts. WTF, guys?

[kdaviper]

Speedventures posts results, for example here:

http://www.speedventures.com/results/Default.aspx

One listed car is an ACR with 750 hp, consistent with having heads & cam.

FWIW, I've never trusted cam work on tracked cars; my belief is that the cam developers do not have the resources to endurance test the engines the way an OEM does with stock components. I've worked with OEM engineers and the endurance tests they do on engines are unbelievably extensive. Some tests are specifically intended to anticipate extreme abuse. For example, there is a test that takes a brand new engine, cold starts and within seconds goes to WOT max RPM for an extended period of time. Unless a cam developer can show me test procedures and results for endurance, I worry that the extra lift and duration and higher RPMs typical of an higher performance cam can really be hard on the valvetrain and reciprocating components. A dropped valve can easily cause a rod to part, as the valve head can penetrate the cylinder wall, piston skirt hang and then rod parts on the intake stroke.

As for the break-in, I'd defer to specifics from the engine design engineers for this engine, but I know from other modern engines that break-in is not that big a deal, as production tolerances are so good these days that parts don't have to "wear in" nearly as much as they used to. For example, bearing tolerances better be right to begin with and they don't really wear in to one another anyway, cams are roller so no need for tappets and lobes to wear in, and rings seal very well to begin with and actually seal better, to a point, with more combustion chamber pressure. I'd want to know the specific failure mode attributable to lack of "break-in" that would cause a thrown rod, as to me the cause could just as likely be an assembly error in rod bolt torque or improper bearing clearances or materials.

Bottom line, I'd like to know actual facts and the speculation and willingness to throw the unknown owner under the bus is not what I'd expect out of fellow Viper enthusiasts. WTF, guys?

The VE/Arrow cam is as close to OEM as you will ever get. Especially given the amount of work Dick Winkles (who has been elbows-deep in Viper engine development since the Gen I was still a pipe dream) has put into the package.

[Simms]

The VE/Arrow cam is as close to OEM as you will ever get. Especially given the amount of work Dick Winkles (who has been elbows-deep in Viper engine development since the Gen I was still a pipe dream) has put into the package.

I believe Dick was also involved with the recent ALMS GTS-R program as well.

[kverges]

I know Dick; I raced Viper Cup 2010. I am not saying the cam package is bad, but I am saying that I am too conservative to do it on a car I want to get more hours out of than a race engine. I think you will find race engines are intended to have overhauls at under 100 hours, often shorter. I hope to get more hours than that from my ACR and unless I saw data to the contrary I don't believe you can expect OEM durability from aftermarket cam; at the very least doesn't the cam package involve more RPM?

In any event, I'd like to know what happened and would not point blame at engine, cam or driver at this point. It could just be a bad day, as no matter what you do to prevent it, stuff breaks sometimes.

[VENOM V]

I know Dick; I raced Viper Cup 2010. I am not saying the cam package is bad, but I am saying that I am too conservative to do it on a car I want to get more hours out of than a race engine. I think you will find race engines are intended to have overhauls at under 100 hours, often shorter. I hope to get more hours than that from my ACR and unless I saw data to the contrary I don't believe you can expect OEM durability from aftermarket cam; at the very least doesn't the cam package involve more RPM?

In any event, I'd like to know what happened and would not point blame at engine, cam or driver at this point. It could just be a bad day, as no matter what you do to prevent it, stuff breaks sometimes.

Agree on all points, good perspective.

I'm happy with my measly 645 HP and 7 year extended warranty, haha. In the last two years, I've had two engines blow up in track cars (neither of them Vipers), so I'm done modding engines. Just making any drivetrain withstand the abuse we throw at them at the road course is an accomplishment.

[Antonio@CalvoMotorsports]

From what a little birdie told me......7k rpm limiter that someone was standing on around the track then pop went the weasel.

[AZTVR]

Bottom line, I'd like to know actual facts and the speculation and willingness to throw the unknown owner under the bus is not what I'd expect out of fellow Viper enthusiasts. WTF, guys?

[FLATOUT]

Throwing a rod has nothing to do with the top end package, the real possibility is oiling and G loads that the ACRs are able to achieve. Might be dry sump time to be honest.

[FLATOUT]

Oiling.

I know Dick; I raced Viper Cup 2010. I am not saying the cam package is bad, but I am saying that I am too conservative to do it on a car I want to get more hours out of than a race engine. I think you will find race engines are intended to have overhauls at under 100 hours, often shorter. I hope to get more hours than that from my ACR and unless I saw data to the contrary I don't believe you can expect OEM durability from aftermarket cam; at the very least doesn't the cam package involve more RPM?

In any event, I'd like to know what happened and would not point blame at engine, cam or driver at this point. It could just be a bad day, as no matter what you do to prevent it, stuff breaks sometimes.

[FLATOUT]

SW was at COTA in his Comp Blue ACR, and I don't believe he had a break-in per se, but nothing I heard made it sound like he hurt the car? Sounded like he really enjoyed the car and planned to track it a lot. Then again, I don't know if he's the car in question, I don't think he had H/C on the car.

Wasn't SW.

[TrackAire]

From what a little birdie told me......7k rpm limiter that someone was standing on around the track then pop went the weasel.

Antonio,
What is your opinion on what would let go first on a stock Gen 5 at 7000 rpm, the top end (valves, valve springs, rockers, etc) or the bottom end?

[FLATOUT]

Stock valve train is nothing like what the heads cam cars have.

[05Commemorative]

If not SW blue car, then I know the other car and had full break-in process done. what was the comment on 7k rpms though? isn't rev limiter 6600 with arrow pcm?

[FLATOUT]

If not SW blue car, then I know the other car and had full break-in process done. what was the comment on 7k rpms though? isn't rev limiter 6600 with arrow pcm?

Heads and cam motors have an upgraded valve train. My car has been set to 7000rpm for drag and roll racing ONLY, on the road course I shift the car at 6500. Not sure why this one was set to run that high (if it was it may not have been), the valve train can handle it but you don't make much power up there.

[Eachey51]

Speedventures posts results, for example here:

http://www.speedventures.com/results/Default.aspx

One listed car is an ACR with 750 hp, consistent with having heads & cam.

FWIW, I've never trusted cam work on tracked cars; my belief is that the cam developers do not have the resources to endurance test the engines the way an OEM does with stock components. I've worked with OEM engineers and the endurance tests they do on engines are unbelievably extensive. Some tests are specifically intended to anticipate extreme abuse. For example, there is a test that takes a brand new engine, cold starts and within seconds goes to WOT max RPM for an extended period of time. Unless a cam developer can show me test procedures and results for endurance, I worry that the extra lift and duration and higher RPMs typical of an higher performance cam can really be hard on the valvetrain and reciprocating components. A dropped valve can easily cause a rod to part, as the valve head can penetrate the cylinder wall, piston skirt hang and then rod parts on the intake stroke.

As for the break-in, I'd defer to specifics from the engine design engineers for this engine, but I know from other modern engines that break-in is not that big a deal, as production tolerances are so good these days that parts don't have to "wear in" nearly as much as they used to. For example, bearing tolerances better be right to begin with and they don't really wear in to one another anyway, cams are roller so no need for tappets and lobes to wear in, and rings seal very well to begin with and actually seal better, to a point, with more combustion chamber pressure. I'd want to know the specific failure mode attributable to lack of "break-in" that would cause a thrown rod, as to me the cause could just as likely be an assembly error in rod bolt torque or improper bearing clearances or materials.

Bottom line, I'd like to know actual facts and the speculation and willingness to throw the unknown owner under the bus is not what I'd expect out of fellow Viper enthusiasts. WTF, guys?

I believe the heads cam package uses the same cam that is run in Ben's GT3-R so i think this cam has been theough plenty of testing.

[kverges]

I have personal experience with a dropped valve also causing a thrown rod. Years ago in my Pantera the builder had a bad combination of springs, cam and pushrods. Valve head came off the stem, obviously rattled around and beat the cylinder enough the piston skirt hung in the cylinder. Rod parted next.

Lots of things can cause a rod to part, from materials, to assembly to lack of lubrication. On the latter point I'd expect a spun bearing first and you'd have to ignore a lot of clatter or have sure loud exhaust not to hear the spun bearing.

But it is still all speculation at this point and I'd love to hear what happened and an engine postmortem.

[kverges]

If these cars need dry sump to live on track with the OEM tires and aero and setup per the supplement that is a really bad situation. I'll keep my slower GT3.

FWIW I doubt that, as the cup car did fine with slicks and wet sump.