stock piston question

sootie · Dec 4, 2014

its a crap shoot

strokin08 · Dec 4, 2014

Well tonight I ran my guages to see my back pressure on tune I run almost all the time and on a wot run from 45 when tc is locked to 85 never got over 48. Thats using a dash daq using absolute pressure.

strokin08 · Dec 4, 2014

And the number I gave is subtracting barometric pressure.

k2xp · Dec 5, 2014

Is it always the same piston that cracks ? Number 7 or 8 im not to sure.

madman1234509 · Dec 5, 2014

I think people see the rear cylinders crack quite a bit, or even melt. But a lot of times its just a crap shoot. And the rear cylinders probably get hot due to the intake manifold design.

If you think of the intake manifold and its volume, looking at it, on the top it tapers downward in towards the center of the valley, and at the back it tapers downward to the back. Its obvious when looking at it cut apart, the front cylinders have a huge advantage at receiving airflow than over the back cylinder on each bank. With the back of the manifold tapering in the rear it really restricts the volume allowed to reach the rear cylinders. What a real improvement would be, is an intake manifold that is slightly taller, creating more volume, and is square, or in MPDs custom manifold round, all the way to the back, creating more volume, and an equal volume all the way to the rear. Only downside with this is that you most likely can not use factory appearing turbos in the valley due to the manifold not being tapered towards the valley creating the room for the turbos to fit.

sootie · Dec 11, 2014

also the 7 & 8 are the cylinders that do the regen. lots of extra heat and fuel washdown

stroker221 · Dec 11, 2014

I know a guy last summer his truck cracked a piston and scrapped the block. It only hooked to a sled a few times. Only had H&S and the normal stuff. Seems like H&S has the most kills for the 6.4. Coincidence?

powerstroked08 · Dec 11, 2014

stroker221 said:
I know a guy last summer his truck cracked a piston and scrapped the block. It only hooked to a sled a few times. Only had H&S and the normal stuff. Seems like H&S has the most kills for the 6.4. Coincidence?

There is also a TON of people running h&s. It really boils down to the factory pistons are a crap shoot. Either there wasn't great quality control or something. Because some of these pistons hold up to 1K+ horse power and get beat on, while others crack at stock levels being pu$$y footed around.

sootie · Dec 12, 2014

stroker221 said:
I know a guy last summer his truck cracked a piston and scrapped the block. It only hooked to a sled a few times. Only had H&S and the normal stuff. Seems like H&S has the most kills for the 6.4. Coincidence?

nothing to do with H&S. there are faaar more of those tuners around than any other so of course more trucks that fail will have their tuners on it. i have seen stock trucks crack pistons also...

stroker221 · Dec 12, 2014

Ya I didn't believe they are the culprit. But ya it would make more sense if there's alot more h&s tuners on these trucks than anything else. I wonder if h&s and sct state how many tuners for the 6.4 they've sold just to compare whats being ran more? Probably not relevant, just curious. Like you guys said, it comes down to poor quality hit n miss. But I definitely believe if funds are available to get aftermarket pistons asap to avoid scrapping a 6k block.