Well to start off I dont really know to much about tuning. I was just wondering what most people ran for timing? My car broke 2 pistons when dyno tuning and the guy had 33 degrees of timing total. The setup is as follows:

Patriot stage 2 LS6 heads with oversized valves
6.0L iron block stock bore
238/240 comp cam with just over 600 lift
fast 90/90 setup
full bolt ons

I ended up dynoing 412wrhp and 398wrtq. Which seemed kinda low to me since people are making way more power with smaller cams. I have a M6 car if it was an auto maybe I would except it. But the tune was adjusted to 13:1 by scaling the maf and then the guy bumped up the timing to try and raise power I believe. I've heard that a lot of the tune would be set in the P/E tables and maybe that would increase power. I'm gonna do some reading and try and learn something about tuning.

 

33 degrees = too high in my opinion, especially if you have raised your compression any. Alot of the time a good H/C setup will allow you to back off timing as the headflow and valve events provide better aircharge and thus negates the necessity for more aggressive set ignition timing. Usually if your A/F is dialed in, changing timing does not have a drastic effect on the dyno either unless you move it in a big way. Most H/C LSXs I've messed with end up anywhere b/w 25-30 degrees, and out of those, the bigger H/C have been closer to the 25 range.

 

Any other thoughts on the subject? Anyone have a similair setup as me? Could adding to much timing mess with your piston to valve clearance?

 

33 degrees is a lot of timing, you might have been getting low numbers because of the timing being so high. It may have been high enough to be causing major knock retard by the knock sensors, which will kill power. I would go back to arounf 27-28 degrees and try again.

 

At the very same time, it may not knock whatsoever. PTV isn't an issue here (unless you've put together a wrong combination mechanically). That was up to you or your builder. But, with such aggressive ignition timing, you are essentially lighting off the cylinder before a complete compression stroke (basically fighting the tail end of the compression stroke) and probably lighting it for too long for the quality of aircharge. This does not create ideal combustive conditions, which could be a reason for your lack of power. Then again, dynos can be fishy as well. You can tell if timing is affecting power production on a dyno graph, it usually shows up a "seismic activity" in the rpm range affected (typically at high rpms). I like Brad's idea stated here, go back to a good range of timing, 33 degrees is definitely outside the usual sweet spot.

 

Yeah, well i think this next time im gonna go with a different tuner. It just cost so much and the engine I just built fell apart on the dyno. The pistons broke right around the piston ring? So i need to rebuild and try again. Maybe forged this time. But im definetly gonna try to educate myself and pay way more attention to what the guy is doing with my tables.

 

You may just want to learn to tune yourself. Its one of the best mods you can do. I will never let someone tune my ride, its too easy to do yourself once you figure out what all the different tables do. And I use old *** LS1 Edit.

 

Well, just poking around on the internet and checking some of the boards, I run across this thread that sounds just like a car that blew up on my dyno. So let me give everyone the rundown. Customer comes in for a tune on a head and cam 6.0. Says him and a buddy built it. Should have a cam "a little over .600 lift", CNC heads, fast intake. Injectors are FMS size XX. Also says him and his buddy "tuned" it as far as displacement, injector size, yada, yada. So we run it and it puts down 390 and about 366ish(photos and graph should be up in a little while). We squeezed 412 and 398 out of it, but something wasnt quite right. Now, let me back up a little. The displacement WASNT reset, nor was the injector size, so i put them in on the initial tune and we went from there. After thinking about it all weekend (sound familiar stocker?) I called the customer back to come in for a redo, again I knew something wasnt right. On the second go 'round, she started knocking. Upon disassembly we found EVERY VALVE WAS HITTING THE PISTONS. Not just one ALL OF THEM. Pictures coming. Brought customer in and showed him. He said his buddy fly cut them. Told him what the cam was,PN XER281HR-12. Specs are as follows:232/234@.050,.595,.598, 112LSA. Heads were patriots with 2.055 intake valves and I dont remember the ex size. Now keep in mind we're tuning something someone else built. So now even after I tell this guy what cam he has, he's on here telling ya'll something different. And after building an engine, he wants to know if a tune could reduce the PTV clearance. WTF? And how does the tuner get blamed? A "better" tuner could have popped the motor just the same. We tune some of the sickest **** in our area. LT1s, LS1s, SC, NA, blown big blocks, Accel DFI, FAST,SCT(mustangs) with SCs, turbos, etc. I'm more than capable of tuning this thing. This is the problem with tuning stuff that other people have built. And nothing worse than being blamed for someone else's incompetence. I guess we found out why its not making any power. Bangin 16 valves onto 8 pistons has to hurt the output just a little. Will be posting pictures soon.

 

Yes this is one of the reasons I knew something wasnt right. It should run the best at less than 30 deg. It seemed to want more timing the more I gave it the more power it made. I stopped at 33 deg. It may have made more power with more timing. It was very strange. Again i'll be posting some pics of the pistons. Trying to get a close enough photo to show the burrs where its been hitting

 

Please show me where you found this....PM sent!

 

Well up until now, Stocker was being relatively private about the issue, by not naming the said "tuner". Does it sound like he could more educated on the subject? Sure. However, there was nothing said here to discredit a specific source. EDCMat-I1, I understand your frustration, but I don't believe you were mentioned once in this thread and thus have no reason to prove any fault otherwise. That is b/w you and Stocker, please keep this in PMs, thanks