piston/rod combo
 

Im finishing up my parts list for my 355 build. But I was wondering if anyone had any advice/comments about going with a Manley H-beam 5.7 rod and Wiseco piston combo? And is it nitrous friendly? Thanks.

You shouldnt have a problem spraying those rods or pistons. There are guys spraying on stock bottem emds. You are goin to run flat tops right? Also id run a 6in rod to help save weight. Whats the rest of your build look like?

yes, flat tops. Is there that big of a difference between 5.7 and 6?

yea I'm one of them but I'm getting the spare bottom-end ready now. Just rolled 205k on a 150 shot. I'm gonna try to get away reusing a factory crank, Le2 heads that have been reworked, and I'm not really set on a cam yet

The Manley rods are probably overkill depending on what your setup is like. I think any 4340 rod with good 7/16 bolts in it will do. Whether or not a rod will survive is more about RPM and less about power. There are a number of guys pushing the Scat I beams pretty hard and if the RPM isn't out of this world then they would probably get the job done for less money.

Longer rods are good because piston acceleration at TDC isn't as great (= less prone to detonate), but be aware that running a longer rod shortens the compression height of the piston and pushes the pin up further. Smaller compression height usually means a shorter ring pack, shorter lands (top land thickness is EXTREMELY important with nitrous/FI), thinner crown/general construction, and less surface area (which means less heat dissipation). You have to contact the manufacturer to find out these specs because they're usually not listed.

You also have to watch out with the Wiseco pistons. They don't list the alloy (4032 or 2618) in the catalog, even by their "nitrous ready" pistons. I was certain "nitrous ready" meant the less brittle 2618 alloy (more malleable and less susceptible to damage from detonation) BUT my assumption was wrong, they were actually 4032 and had thinner crowns/top lands than a comparable Mahle which is less than ideal for lots of boost/juice. You'll have to email one of their techs to find out because it's not listed anywhere. It depends how extreme your setup is, but if you plan on running a pretty big shot I'd go with 2618 > 4032. Be aware that 2618 pistons are not street friendly and don't last many miles.

I have a tendency to over-think things and understand that a lot of this doesn't come into play unless you really push the motor... but I don't know the details of your build so it's hard to say if any of this really matters. This is just all of the stuff I considered for the boosted 355 I'm working on and my power goal is pretty high. I wanted my motor to be rock solid so I built the entire thing in my head from the start. The devil's in the details I guess.

awesome info, thanks a lot

Good advice catmainge

Even a 2618 piston won't take a lot of abuse.... proper setup and tuning is the BIGGEST factor in making things last. A 4032 piston can handle a bunch of power. For street I always suggest a 4032 as they are much more street/daily friendly. Typically I have always seen it this way, If you must have a 2618 piston then you probably are not concerned with daily driver/multiple starts kind of stuff. Also a 6" rod does add a bit of dwell time at TDC and BDC which can lessen the stress the piston has to consume when changing direction; but the real add is the less stress/wear on the cylinder walls when driving the piston up to TDC. In reality though there is not much of a difference in our application from the 5.7 to 6".

On a thinner land/ring pack piston with a 6 inch rod, do you think it'll hold up to a 200 shot (max i wanna go)? Or would it be better to just run a 5.7 rod and a thicker land/ring pack? I'm not intending this to be a super extreme build, just a somewhat reliable weekend car.

Sure It will if you keep your timing in check and don't go for broke!! lol A piston isn't decided on by what rod you run. getting a set of pistons specifically made for your application and uses really is affordable for our application. A thick top ring land will handle a bunch on nitrous, and no 200 shot isn't what is considered "big" for large nitrous users. Find a piston manufacturer that you like and just give them a call about custom pistons. Thinner rings give less friction than larger. Top land thickness is important but a dead on tune is worth its weight in gold when you start talking larger nitrous shots and engine variables such as large cams/heads/FI.

I run a 6 inch rod and JE slugs, seems to work just fine.

awesome thanks

A 200 shot isn't crazy so I wouldn't worry about anything I said.

Neither piston alloy will stand up to lots of detonation but the 2618 is much better off. 4032 is much more brittle and prone to breaking into little chunks whereas the 2618 is softer and can form cracks without shattering. 2618 isn't as sensitive because it can take a harder blow but that also makes it have a shorter lifespan on the street.

If you are detonating on nitrous, no piston in the world is going to matter. Just get the cheapest one as you'll be replacing it often.

Despite all the talk about piston materials and rod length, I haven't heard anything about proper piston rings, piston ring gap, thickness from the top ring land to the piston crown, and how close the intake relief in the piston gets to the top ring land groove. A 6" connecting rod will mean a shorter CH on the piston which means you have less room to pack all three rings in there and still have enough material above the top ring land to resist the additional heat you will be putting in the cylinders.

I mean if you get some Hellfire Total Seal rings, you have to finish the cylinder wall to a different finish than if you are running Plasma-Moly (which you should never do on nitrous).