ogkevin13

i blew 2 motors both #7 but they were only the rings i have one that am building and piston 7 was fine just the rings gave out. i blew both due to too much timing and leaned out. be carefull one motor lasted me 2 and half months and the other one lasted me 1 week. i would stay out of boost in lean conditions!!

kbracing96

iTrader: (26)

Lean??? Ha,ha and I have your logs to prove it

Most of the pics I've seen of broken ringlands on 5.3's, it breaks between the land and the bottom of the dish. The 4.8 have a flat top piston, I think they might be a little resistant to braking. It only a theory, but makes since to me.

Wilde Racing

iTrader: (26)

KR. do to being lean, I heard it too late....

ogkevin13

will the rings give out for that same reason?

vanillagorilla

iTrader: (1)

It looks like they fail where the material is thin from the radius of the dish to the outer edge. It could be a combination of that and the higher stress concentration at the radius. Hmmm...

Hey Wilde, that doesn't look like your #7 piston, why do you think your #5 went and not #7.

edit:Nevermind, I saw your previous post, so you broke both pistons!

I think you guys should start looking into Vic. Jr. intakes or at least and LS1/6 intake or something.

Whippled 496

iTrader: (4)

i wonder if the 8.1L intakes are prone to setting up #7 piston failure like the small blocks?

FlaBouy

Two things...42-44# injectors will take you further than me because my fuel system is a returnless, constant pressure flow on demand in my 2004. With the earlier fuel systems running a return line and FPR, the pressure is not constant so you are going to see about 65 psi under boost where I only see 55 at best....I was seeing 130% duty cycles at 5800 rpm on the GM 8.1L marines (42#) at 10 psi... I now see about 69% at 5800 rpm with the 60# at 12 psi (185 kPA on my 2 bar map). That is also seeing a 65.4 lb/min airflow with the new heads, TB, and exhaust...

Valvesprings on my 5.3L were seeing float at about 5200-5800 under about 10 ps... that was at 45,000 miles....even with the snow meth kit.... fixed that with the Ferrea valves and patriot golds...

I keep my AFR in the 11.8 to 12.2 range and have had no issues with the 5.3L handling 12 psi on a stock bottom.... boosted since september of 2005..

Hope this helps

Wilde Racing

iTrader: (26)

Ya that is what I want, hopfully I'll have a vic set-up this winter....
I did brake both 5 & 7, #5 was the one that a chunk of the pistion broke off. #7 pistion is cracked in almost the same place as #5....

I should say that I never spun mine up past 5,500 rpm, and at the time I was just going off my boost gauge not the map......

ogkevin13

5,800 rpm thats kinda high i think the highest i will be about 5,200 at 12 psi running meth and i/c what is the averge duty cycle for #44 injectors

GMC_DUDE

Mine does 5900 on WOT, at times have hit limiter at 6100. All at 10 psi. OK so far.