Lateral-g Forums - Bad day on the dyno...

So this isn't the way I had hoped my first chassis dyno run would go in TOW.

http://i100.photobucket.com/albums/m...pseb0e21ee.jpg

During the first pull, after warming the car up and doing a little idle tuning, the operator starts the pull. There was a little hiccup around 3500, but she kept pulling until around 5500 or so. Then BAM! She just shut down. We tried to restart her, but she wouldn't start, and there were some bad sounds...

The shop owner pulled out tools and we started pulling plugs, then he pulled out a bore scope. Unfortunately we couldn't see much with that, so then he pulled out a compression tester. And guess what? On the LAST cylinder we checked (#5) due to the tri-y headers making that one a bitch, we had no compression.

Next step, we pulled the coil pack and valve cover, and voila: the picture above... Looks like the coil spring broke, dropping the valve which is now bent. That's about all we could do, so we bolted the cover back on and were done...

I have to given this shop their due: they really helped me out trying to find the problem instead of just kicking me out of his shop. Also thankfully, I didn't puke anything on the floor, so that probably helped. ;)

And I need to give some even BIGGER props to Steve (gernon) from here. I texted him about what happened, and he offered to load up his truck and trailer to come get me. Note, the weather yesterday sucked (grey and drizzly and cold), and he was at least 90m away from me. Unfortunately that 90m turned into almost 3 hours with traffic, then an hour to load her up, then 2 hours back. I think he had 7 hours into this pickup, then he met Eric and I today at Eric's shop to unload her. Steve, I still owe you big time!

Anyway, TOW is at Eric's now, and I pulled the head off today. The news is mixed... The valve certainly smacked the piston, which if that were all would be ok. But unfortunately I have 2 small nicks in the cylinder wall that you can almost see in the picture below. I cannot tell if they are deep enough to be fatal yet, but what this does mean is that the engine is coming out. :shakehead:

http://i100.photobucket.com/albums/m...ps9a263ca9.jpg

At the moment, I haven't fully decided what route I'm going to take. The head doesn't look like it took any real abuse, other than the guide since I'm sure it's dorked up with the bent valve. The valve seat looks ok. At a minimum, I'm going to need a bore / hone, a set of pistons, a set of sprints and retainers, and a set of valves. So a full rebuild is in store. Then it becomes a matter of what else I might do while it's all apart. I have a lot of ideas, but I'm not quite ready to turn TOW into a full blown beast. I like the mild-ish street manners yet good power on the track. But I think I can improve on the mid-range torque of my setup, Researching some of the LS sites, it seems that there is a lot of knowledge about designing cams for a single plane intake that didn't exist 5 years ago when I had this one speced. So I think a cam change is going to happen also while this is ongoing...

One other thing I learned. Something is wrong with my wideband sensor. TOW has always smelled as if she was running really rich, but I could tune her in the 13.5 to 14.0 AFR range just fine. Well, the dyno WB sensor was showing numbers in the 12.0 range at cruise speeds. That would explain a lot of my frustration with the gas smell at idle and cruise. I'll be digging into this while doing this project...

So tomorrow, back to Eric's. The engine is coming out, and I'll pull a plan together by early next week. This engine is SUPPOSED to have some nice pieces inside of it, so whatever I do, I will plan to reuse those (if they are actually there). If the block cannot be saved, then I may consider an LS3 block instead.

Weeeeeeee....... :G-Dub: