Bummer about burning the piston, but that’s the joy of junkyard motors. Throw another one in. The air entering the intake in the front caused higher air velocities in rear cylinders and they tend to run leaner due to it. If you can flow your injectors I suggest putting the higher flowing ones in the rear or if running full sequential standalone like I do to ritchen up the rear cylinders. 243/799 heads do flow a bit more on a bench but with boost its negligible. Just compensate with more boost. Lol. I ended up running bonestock lm7 with dished pistons and 243 heads for a lower compression. Seems to run good.
I broke number 7 and 5 my rings touched from to much heat! Main thing I learned is I should have been data logging every run or most! Then you could see what voltage/ fuel/ timing did when it blew!!! And I got 799 heads when I rebuilt mine but I have read gm specs and they say it’s exactly the same head as the 862 but maybe we will pick up power. Mine goes back on the dyno soon!
There’s an odd issue with cylinder #7 on the LS. Tuners have been addressing this issue for a long time now. If you haven’t already, do a google search, you’ll get more than enough information. We learned about #7 on our first Turbo build GT45 5.3, blew the ring lands out on low boost. Hence my familiarity. Sorry to see your damage! JD
I think most people have decided it's the way the coolant is routed through the block. I've seen some rock crawlers that were mid engine LS stuff, with the intake flipped around backwards. And they still melt #7. If it was an air flow deal, flipping the intake should flip the problem to #2. No sweat on the damage, nature of the beast man!
Gained 15 whp on dyno from switching to flattops and 799 heads over dished and 862’s. Not worth the expense in my eyes. That’s like 1/2 a pound of more boost. Good luck with new motor tho. 👍
The 862's I had were the ones with the notch cut out of the deck. That always made me nervous, so when the motor had to come apart I decided I'd swap them for something without that notch. I was hoping to pick up a little more than 15 by swapping the heads, but if it doesn't make enough power... Like you said, I can turn the boost up!
