One other thing that had to be taken care off while I was in Tennessee was a little tweaking on the EFI tune. I noticed that the car would heat up some while making a long uphill pull.

Considering that a stock LS1 wasn’t considered to be overheating until it got over 230, I wasn’t technically overheated. It would hit 225 and the high speed fans would come on. Then the temp would drop back to 218, hit the low speed fans and go right back to 225. This extra temp would cause a little timing rattle under load, so I had to go really easy with the throttle so as to not hurt the engine. I had reprogramed the fan override switch before we left (long story), so I couldn’t turn them on by hand. This would have solved most of the issues since the high speed fans kept the car plenty cool.

I had my tuning laptop with me at the hotel and corrected all this ASAP. First, I reprogrammed to fan override so that it was actually a fan override. High speed fan is now just a flip of a switch away. Anytime the engine was under load, and I saw the temp getting over 210 or so, I would start the fans and have it under 200 in under a minute most of the time.

Next, I pulled 2 degrees of timing out of the complete timing table. Probably a little drastic, but I didn’t want to rattle a ring land off, either. Also, I knew that the Holley software had some timing modifiers built in. One is a temperature modifier. This allowed me to start pulling a little timing at 220 to ward off any temp induced rattle.

The other thing I played with was the knock retard. I hadn’t activated this before because I had read that some aftermarket cams can create noise that fools the knock sensors into thinking they are hearing detonation. This cam seems quiet as far as I can hear (for what that’s worth), but I also had never had any issues with detonation.

After these changes, I never heard any more rattle. It is possible that some of the issue was related to altitude, but the Holley ECU is supposed to have a barometric pressure sensor built in to compensate for that. I may feed some of the timing back in now that I’m back at sea level, but honestly, I haven’t noticed any lose in power through the butt dyno (also for what that’s worth).

I have talked with someone that owns a chassis dyno and while he says he doesn't know anything about Holley ECU’s, he will rent me his dyno by time for as many pulls as I want to make. He says his machine will allow you to load the engine as if it was at a steady state cruise, too. Way more valuable info to me than just doing full throttle pulls for bragging rights.