Catmaigne

iTrader: (6)

To those running 4032 pistons and boost...
What piston brand are you using and what are the specs?
How many miles have you put on them and how much boost do they see?
Octane? Intercooler? Water?
Was your tune on point?
If it failed, why?

The biggest hurdle I'm trying to get over right now is picking a decent set of pistons. I'm pretty set on the 4032 alloy for longevity being that it's going in a street car with an intercooled 13-15 psi and 9.0:1 to 9.3:1 compression on 93 pump gas. 2618 sounds like it would be overkill if my tune is good, I want this thing to last. I need a shelf piston like this:

- Forged 4032 alloy
- 1.425" compression height
- Thick crown preferred... like around .25-.3"
- 10 to 15cc dish, nothing too deep to compromise top land strength

The closest thing I'm seeing is the Speed Pro LW-2605F30 (4032, 1.425" height, 12cc dish w/reliefs) and another option from Probe FPS. I can't find specs on the crown thickness but I can make a few calls to find out.

I would love to go with a set that's a little bit nicer but I'm just not seeing them out there.

nitrous2fast

iTrader: (2)

my lt isn't boosted but I do own a few boosted vehicles. The 4032 will have a lot tighter clearances and wont rock on you typically at startup. Some food for thought. Nitrous is MUCH harder on pistons (and everything connected to them) than boosting with Turbos. There are nitrous guys running 200 shot on stock pistons. So you do the math IF you think that you are more than doubling the stock hp then maybe you should think about getting the 2618 but for a street car I believe that 4032 is fine. my .02

Catmaigne

iTrader: (6)

That's exactly why I want 4032, this car is going to spend most of it's time being flogged on the street. I figured 10-15 psi wouldn't be too extreme with my setup if the tuner is good. I'm looking at a forged 355 ~9.3:1, Trick Flow 195s, 224/236, FMIC, and a decent blower (D1SC, T trim, etc.).

I noticed SRP and Mahle both have 4032 piston sets for a little bit more than the Speed Pros and they include rings... The dish is a little more than I would prefer @ 16cc but I still need to find out about the crown thickness. I'm leaning towards the Mahles.

Purple Poncho

iTrader: (1)

I ran the SRP at 10-11# for 7 or 8 years. That engine was beat on a lot. Maybe 30 000Km in those years and was my daily driver. Even drove it in the winter up here in the great white north for a few years.
Tune was spot on. No intercooler, pump gas and 9-1cr but was meth dependent. I had alternator failings, over revving..all kinds of crap happened over the years with that engine and it survived it all. I had the deep dish -31cc I think. It finally let go after back to back meth system failures at the track but by that time the engine didn't owe me anything. The pistons got way way to hot and way lean. No pitting at all on the piston face but did warp the ring lands on 2 or 3 pistons.

Catmaigne

iTrader: (6)

That's surprising, don't see many positive experiences with those running SRPs on the forums. I'm wondering if the issue stems from poor piston design, the wrong alloy, or some other factors in the build like ring gap or tune. It's hard to say because there is so much to consider, but it sounds like they can take some abuse.

Does anyone have any experience with 4032s @ 15 psi on 93 pump gas w/o injection? I want to run just an intercooler for simplicity. I know I'm comparing apples to oranges, but I think it's funny that some will tell me 10 psi with 4032 is on the jagged edge when factory LS9 engines run that much boost with 4032 Mahles STOCK. Granted, the dish is only 10 cc and O shaped... but c'mon. How could an OEM setup be that extreme?

What I'm looking at right now, both -16cc:
SRP 139627
Mahle Power Pak SBC425030I16

nitrous2fast

iTrader: (2)

When building a street machine, I prefer a low boost higher compression engine, With fast spool time and great throttle response and typically better MPG. For street driving a typical vehicle can only handle so much power for the traction devices it has on it. With that being said, A Fbody with over 550 at the wheels is the power line I wouldn't typically cross for street only methods. Street winning typically goes to the one with the best traction per power(assuming the vehicles are relatively close in power wise).

So get a lesser dish and run 10-12# on a 10:1 motor, or 8-10 on 10.5:1. If you ever take it to the track some race gas would allow quite a bit more boost and tons of power.

Kevin Blown 95 TA

I built my 383 engine 9:1 with Mahle pistons, 6" rods. I use water/meth injection and no intercooler. It gets over 15# of boost with a medium cam and AFR 200 cc heads. If I had it to do over again, I would probably do a few things differently and I would run a little higher static compression as the guy above me has mentioned. However, the engine is really tough as hell. I found this out at the track when I ran out of fuel pump at the top end of the track a couple of times and saw 14:1 on the meter - it went 126 and 11.1 that day on drag radials. The water injection saved my engine that day, no doubt. Anyway, I rebuilt the whole fuel system after that, so now I have plenty of fuel, but haven't got back to the track to cram the tune in. So it is still rich and retarded until I get around to beating on it again. But the point I am trying to make here is that the pistons really held up well for the past 4000 miles and I think the silicone helps them take the heat. I suppose if you rattle the engine bad enough, you will crack them, but keep it out of det and you'll probably be Ok and have a better street engine to boot. I had second and third thoughts about how I built this engine, but the light pistons revs easily and makes a ton of power, and nothing is more awe inspiring than doing a burnout from a 70 mph roll.

Here's what the pistons look like:

Catmaigne

iTrader: (6)

It's not a dedicated street car, I just want something useable on public roads being that the track is about an hour away and my car is no trailer queen. I want to be able to drive it to the occasional car meet, the track, and other events without feeling guilty about deforming a soft alloy piston from too much cruising. That just seems like wasted potential. On the other hand, my biggest fear by far is picking the inappropriate piston and watching my motor grenade. I'm trying to be a little on the safe side with the compression ratio and the build in general (for what it is) in hopes that it will take the boost I'm gonna throw at it with some grace and won't blow up right away. Longevity is #1 but it's hard to say what is truly safe with boost. No two people have the same setup.

I think I'm gonna go with the Mahle's if I can get some more detailed specs. A light deck, untouched 62cc TF 195 chambers, and the -16cc dish should put me at 9.3:1 which seems about right. My quench distance should be at .044 with the Felpro 1074, a lot better than some of the other LT1 FI builds I've seen on the web.

Catmaigne

iTrader: (6)

A rep from Mahle just got back to me with some specs on the pistons I'm looking at. Top land thickness is .326" and the crown is .197" at the very bottom of the dish. Is this too thin? Everyone recommends .3" for crown thickness but never mentions the thickness below the dish.