Mine was 6.0 AFR 225 headed LS6 intake and it pushed water on #4 and I didn't feel the surge but saw it on the AFR in the log on the root cause investigation and autopsy. It didn't like 19#s and was pushing the IATs up to 167 at the end of the runs. Went 140 at 3950 lbs with me in it before it pushed the water on the last run. Popped the upper radiator hose off and cooked number 7's Diamond Piston from the instant heat. With my AFRs my ported 19# was probably decent air flow just speculating. 775 to 822 on the HPF the two times I had it there.

I thought it might have been trash in the injector but Eric Derr found pretty much nothing wrong with any of them. Both 525s are still pumping so I feel pretty confident that the head gasket on #4 caused the issue with #7.

If the 4.8 rolls out and lives then I'll leave it alone for a while. Next phase will be to put my Callies and Howard rods in an aluminum 5.3 or I might replace the one piston in the 6.0 and go again with that in the future with a S400. The 4.8 was supposed to be a get me by engine but if it makes the power then I'll keep my wrenches off that black bitch for a while.

I just lit it off a couple of hours ago and I'm letting it cool all the way off for a few hours so I can try to get the vapor out of the block before the dyno.

The original questions answer to me is that the 6.0 would have been plenty happy if I had not pushed the boost to 19. Even at 17 I think it wouldn't have caused enough back pressure to hurt my 6.0. Same same if it had been at 19 with 1/8th mile runs. I just gave it too much opportunity to stack up the heat especially in my heavy pig and 3" DP

 

What is your timing strategy per rpm and IAT as you push boost? Any adjustments when running 1/4 vs 1/8? Sounds like too much timing for fuel, combo and run duration at 19#s.

 

It was max of 16 and dropping to 10 as the IAT climbed. Sunoco Race Fuel (Fresh) E85. I really don't plan on dwelling it because it quit gaining on the Dyno at 17-18 with a 19 in the boost controller. I left it there at 19 instead of being smarter and moving it to 17. I believe it developed too high of a cylinder pressure from the back pressure and pushed the head gasket/water. It was moving well so I didn't realize it was hurting itself until after the 1000' marker.

On the data log I can see I should have lifted sooner but the difference between the 137 hurt pass and the 140mph first pass wasn't readily felt on the butt dyno.

 

Thanks for the reply. I agree, the additional back pressure impacted chamber dynamics and increased temperatures that caused it to detonate. Detonation will cause CC pressure spikes to push head gaskets, bend rods, break pistons, etc. Do you pull timing around peak tq to minimize pressure spikes?

 

The rods and pistons seem well received. Any thoughts on providing forged cranks as well?

 

I hear this alot about dome VS manifold pressures lately. Should really get a back pressure reading... Dome VS manifold isn't always accurate. There all kinds of different factors acting on the WG valve face that determine boost pressure VS dome. The smaller the diaphragm chamber and the larger the valve face, the more dome pressure will be needed. This doesn't mean system back pressure is high. Yours may be very close as well, they often are. But i've seen 40psi of dome pressure required to make 25 at the manifold and back pressure was below 1.2:1. Just throwing it out there!

 

Just to clear this up as I've been asked a few times by people now. Do the summit PRO LS pistons require an overbore for piston expansion? Or are they a drop in affair on a STD bore?

 

I honed mine with a ball hone, dropped in. Mine was on the way looser side so I get a small amount of piston rattle until the engine is 140-150 degrees. My car is pretty quiet so I head everything. An engine builder I know told me just run it that way because with a turbo, things get real hot and it better than it seizing in the bore.

 

CHECK THIS OUT FELLAS......I really like this...you can get the crank and rod kit https://www.summitracing.com/parts/sum-cr4024125 and then pick your pistons. Pistons are $499 and the crank and rod kit is (4"stroker) $1080! $1600 for a QUALITY rotation assembly. Holy sheet!

 

Yes except I don't tune the engine on my Turbo Car. I mess with the transmission and stuff like that but I leave the fuel and timing to Cesar (HPF).

This afternoon. 4.8 Precision 76/75 CEA Huron V3 AC Kit 4L80 unlocked & MWC 9"

I just got home from Tune. We didn't max it out and it's conservative on the timing. He asked me if I wanted to add two more lbs to the AMS and I said that's a good place for this SBE. We started off at 10# (Spring only) and worked it up to 20#. My long term plan is an aluminum 4.8 or 5.3 depending on what I decide about my 6.0. Cheapest thing is a new 4.005 Diamond piston and go again. Right now I'm thinking a set of Summit Pistons on my 6.0s Callies and Howard Rods is a pretty reasonable bad *** 5.3 and gets 100#s off the nose.

Time will tell as I'm sick of working on it right now.

 

If you guys look on Summit's Home Page Nosy Book videos there is a Austin and Cesar video discussing the Summit Rods and Pistons from about a month ago or a little more.

Well if the link isn't there, someone else can link it.

 

As Kfxguy mentioned we do offer Pro LS forged cranks. We also offer a variety of rotating component combos. Pistons and rods, crank and rods, or whole rotating assemblies.

Thanks for the question Forcefed86. The pistons were designed with expansion in mind. Our standard bore pistons can be run on a brand new block without the need for an overbore. We have .005" over and other plus sizes for people willing to hone and bore.

Pro LS Pistons are designed to be run at .004" clearance as measured at the gauge point in the skirt coating 90* to the wrist pin. Extra clearance will result in piston slap. If an aftermarket block has thick ductile sleeves and/or a partial block fill, increase clearance to .005".

 

I'm probably going with Summit Racing rods and pistons, might source a crank from them too. Their LS guys come out of companies like Wiseco and have been around these kinds of parts, specifically LS since the early days of the scene.

Probably going with set of their H beam rods, and pistons that support 1400 HP. Block has been dropped off at Fast Times Racing to get it started.

 

John,

I think I’ll be doing the same in the future. Good stuff at fair price.

 

I did a cheap build, Summits budget forged pistons, gen 4 rods, balanced. Its not a max. effort deal, so should be fine for the street. I saw where you were able to buy just a single Summit LS piston if the need be, like nicking one, with the right #.