i was wonderig what kind of power and high rpm reliability i would gain by stepping up to a 6" rod and lightweight piston over stock lt1 stuff? i know the longer rod increases dwell time which makes for better combustion, so im told anyways. it also has a better rod/stroke ratio. thanks for any info anyone can let me know -dave

 

The rod will also not see as much angle, so you will probably see some better reliability and possibly a little more power there, the rod wont get bound up as much.. I know that going from a 5.7 to a 6.0 isnt that much, but sometimes its all that it takes.

Mike

 

I know a longer rod would have greater compressive strength from my materials/solids class (something like 1/12*width*hieght^3 where height was in the direction the load was coming from) but does that include stretching or just compression?

 

I was told by the engine builder at my local machine shop that a 6" rodded engine will rev slower than a 5.7" engine, but will make more peak power. He also said that a 6" rod is a little easier on the crank.

 

A piston that is significantly lighter will be the bigger influence in reliability because the inertia forces trying to pull the rod big end apart will be less. (F=ma). The change from a 5.7 to a 6.0 rod won't be significant in durability/reliability at least over the life of a modified engine, IMO.

Long rods do some of the things pointed out, but unless the engine is specifically designed for the increased "dwell time", which is minute in a 5.7 to 6.0 length change, even measuring the difference in power might be difficult. 6.0 rods are not a "magic bullet" for power or relaibility.

If you are getting new pistons and rods anyway, 6.0 might be a good choice. If I had GOOD 5.7 rods and was just changing pistons, I'd look for a lighter, but strong piston to "unload" those rods.

My $.02

 

i have stock 5.7 rods right now, i figure for the price id just get some eagle sir 6" rods. any lightweight piston reccomendations? im gonna be spinning it up to about 6700 or 6800. thanks

 

Just going to the longer rod is going to get you a lighter piston.

SRP has some pistons that will work, and they come in a few different masses, you are going to spend more money for a ligter piston, but anything is probably lighter than the stock piston and pin.

Bret

 

Exactly. You cannot just put a 6" rod on a piston designed for a 5.7" rod. They have to be matched. A piston for a 6" rod has a shorter skirt, so it will be a bit lighter.

Another pro of a 6" rod is that they are a little easier on the cylinder walls because of the angle.

 

thanks for the info. im gonna get the 6" rods just because i want new rods and every little bit helps right? thanks -dave

 

The six-inch rods also move the wrist pin in your new pistons 0.3 inches closer to the dome of the piston. As a result, your revised piston will have the rings relocated upwards closer to the piston dome. This means your top ring will be subject to slightly more heat. It's more pronounced in a stroker application. In addition, when you look for a lightweight piston, remember that mass helps absorb and conduct heat. Therefore you'll have to pay careful attention to fuel and ignition details, because the lightweight piston may not be as forgiving when it comes to running lean, detonation, or nitrous use. If in doubt, pay extra money for the best piston you can afford.

Oh, and Dave, most rod failures are fastener failures. If you want to spend money, it might not be a bad idea to keep your existing 5.7 inch rods, and spend that extra cash on a really, really good set of pistons, then installing ARP Waveloc Pro rod bolts, followed by having those rods resized and weight matched.

 

so you think ill be alright with stock rods and really good pistons? im going totally n/a with this, so nirtous use means nothing to me at this point. i just want something thats going to be light and be ok with higher rpms. thanks -dave

 

With higher RPMs it's always kind of hard to tell what's going to happen. When you say "higher RPMs" are you talking BEYOND 7000 RPM? I think the PM rods are a fine rod for under 7000 RPM NA useage: They are what GM terms "Pink" rods, except they 100% crack check & magnaflux their Pinks. Other than the extra step, I believe that the LT1 rod is identical to the GM hi-po PINK rod. Thus, with upgraded fasteners, and a resize, your rods should be as good, if not better than GM's new-generation PINK rods.

 

thanks for the info, i meant higher rpms as in 6500 - 6800. i was gonna go with the gm847 but i might end up getting a 230/236 instead. ill definately use the stock rods with new bolts and just buy really nice pistons now. thanks for your help -dave

 

A set of Scat I beams or Eagle I beams is going to give you a stronger cheaper rod when all your prep work is done on the stock rods to make them stronger and have the tolerances right on them along with them being equally balanced.

In todays market saving stock rods is a waste of time when aftermarket rods are stronger and CHEAP ($240-$265 for a set of Eagles)

Bret