Big Bend Open Road Race 2017

This year's race went only slightly better for us.

After trashing the LS7 last year, we stuffed in a more budget friendly LS1.

Motor was fresh from a reputable shop with a stock lower end. Tuned on a rolling Dyno after it was in the car.

Motor lasted through about 15 Dyno pulls, a 20 mile qualifying run (My 17yo made his rookie run), about 140 miles of around town and highway the week of the race - cop stopped us once (no plates/reg/ins) but let us go on our way.

Then 12 minutes at 6,100 RPM. Which was 11 minutes short....

At least we have pictures this time. Fire system put the flames out.

Could have been worse. A camaro went up in flames during practice (blown motor melted the car diwn to a hulk and closed the road for hours), and a newer Porsche went off in the race, took out a telephone pole about 40 yards from the road - car totaled, Town of Sanderson without power for hours, race red flagged while Texas New Mexico Power fixed it...

I'm contemplating motor options...

TWMm8f


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Not sure why my flicker pics are not showing up...

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That vett had a 60 second Head Start on us and was running the same speed class. We stayed 13 mph below our tech speed, just made most of the corners at 155. Did slow to 130 or so for a couple.
 

PeteB

GT40s Supporter
Wow, that's a bummer. I'll admit I was a bit worried about hurting my new engine when I took mine to the track. Are you running an oil cooler? My oil got hot enough just running 15 minute track sessions that I had to quit early.
 
Rev limiter was set at 6800 rpm. We had a target speed of 135 and tech speed of 168 (not to exceed). The last 1/3 of the run is much more challenging, so our plan was to run 155mph up to the challenging part, then average 110 through the twistys.

6100 rpm is about 155 with the Graz.

So the 6100 was pretty much constant. My son was driving that leg, he did back off to about 5500 rpm twice. The car has a bit of push at corner entry at those speeds (which we will address).
 
So, do you 'breathe' the engine RPM, run it say from 5900/6300,
not lifting off the throttle completely, just ease off to 5900 then run it up to 6300 rather than simply maintaining 6100, this helps reduce the chances of harmonics building up in the valve train or rotating assy which might be the root cause of engine failures. Valve train in particular as this could cause a 'rich' mixture signal which when compensated for would then create a high speed lean out.... boom!
 
Not intentionally, but there is always some drift. Last engine (LS7) was definitely a rod bearing (which led to rod bolt failure). The tops of all the pistons looked great - including the one beat to shit by the rod/crank.

This engine won't get an autopsy until the weekend at the earliest. But there are chunks of piston laying on the frame rails and water/oil/aluminum coming out the exhaust on both sides. So it could be a piston let go first.

Toying with the idea of going turbo'd 1UZ/2UZ.

Would like to run a faster class next year with the intention of running unlimited in 2020.
 
BTW, we are not the only one that keeps grenading LS engines. There are two unlimited cars with LS engines. One is a C5 that seems to usually finish w/o engine issues. One is a Camaro that regularly has engine issues. The Camaro pulled out last year the night before the race with a rod knock. Then this year, blew the bottom end out of the motor - the resulting fire totaled the car.

The cars running SBCs seem to have fewer serious engine issues.

Not implying an LS can't be reliable, but these constant high RPMs are tough on a motor.
 
It would appear that the LS3 can/might have an issue around 6000,
I remember some guys talking on the Homebuilt Aircraft forums engine page and an x GM Performance engineer posting about engine failures in that RPM zone and claiming they 'GM' had experienced wrist pin/piston failures. I also noted in some pics of a members build here on GT40's where spacer washers were being fitted between rod small end and pin boss in piston and wonder if it was intended to address this problem. Only guessing on my part, but it would appear that there must be some flexing taking place in the crank/block structure that these mods were reqd.
 
Dan Frank. Sorry to hear about the luck, but glad your son is ok. Are any of the races in Houston? MSR Houston? Interested in coming out to watch a race.
 
Rev limiter was set at 6800 rpm. We had a target speed of 135 and tech speed of 168 (not to exceed). The last 1/3 of the run is much more challenging, so our plan was to run 155mph up to the challenging part, then average 110 through the twistys.

6100 rpm is about 155 with the Graz.

So the 6100 was pretty much constant. My son was driving that leg, he did back off to about 5500 rpm twice. The car has a bit of push at corner entry at those speeds (which we will address).

How will you address this?

I understand there are some small sensors you can place at the front and back suspension so that you can measure if the front end is getting light at high speeds?
 
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