pskel350

whats the difference other then the length? does one have the ability to make more power?

which would be better for a 383 street engine?....i want to be able to hit low 12's.

Motor City Mike

As a rule, always use the longest rod whenever possible/feasible. If you're going to put new pistons and rods in no matter what, definately go with the 6" rods. Less piston to cylinder side loading, and it also slows piston velocity at mid-stroke, both of which will free up a little extra power and increase your high rpm reliability.

AJ_92RS

No it doesn't.

Using a longer dwell time at TDC and BDC (which is what happens) gives less time for the piston to move up and down the cylinder.

Just as an example with no merit to precise times....

Let's say you have a piston that uses 5.7" rods. At 6000 RPM the piston has to move up then back down the cylinder 100 times in one second.

Let's say that .2 seconds of that time is used for dwell at TDC and BDC combined. That leaves .8 seconds for the piston to make it's full travel up then down the cylinder 100 times.

You change to 6" rods and increase the dwell time to .25 seconds at TDC and BDC combined. You've just decreased the amount of time the piston has to move up then down the cylinder 100 times to .75 seconds.

It has to travel the same distance in less time. That means it has to move faster.

Again, these are just examples of the actual times, but that's irrelevant at this point.

fireturd350

iTrader: (8)

Another difference is since the rod is longer the piston has to have the pin mount moved up on it. That's why they sell pistons for 6.0 and others for 5.7... the ones with the 6.0 take a ring that keeps the oil ring from coming in contact with the wrist pin.

OMINOUS_87

Either or will be fine, this is something people really tend to get wrapped around the axle for and argue about, dont ask me why. The difference for a low 12 sec application on 5.7" Vs 6" isnt even worth talking about. Get whatever gives you the best deal on the greenbacks.

I am running 5.7"ers in my 383.

EvilCartman

iTrader: (1)

Here's a pic of one of my Wiseco pistons made for a 6 inch rod. Wrist pin comes really close to being into that groove.

fireturd350

iTrader: (8)

I'm going to run 5.7's in my 383 also... balanced 4340 forged bottom with stud girdles and roller solid cam :-)

DTL504

iTrader: (1)

A little more infor on 6" rods
ok first look at this chart

http://www.iskycams.com/ART/techinfo/ncrank1.pdf
what youll notice is the longer rod stays closer to TDC longer, youll notice also that cylinder pressure peaks and starts dropping rapidly after about 24 degrees past TDC.
the piston has moved less than 1/4" from TDC at that point

http://www.chevytalk.org/forums/Foru...ML/009055.html

then read these CAREFULLY

http://www.aros.net/~rbuck/rick/rodstudy.htm

http://www.grapeaperacing.com/GrapeA...rodslength.cfm

http://www.stahlheaders.com/Lit_Rod%20Length.htm

http://victorylibrary.com/mopar/rod-tech-c.htm

http://victorylibrary.com/mopar/cam-tech.htm

http://victorylibrary.com/tech/crod-c.htm

http://victorylibrary.com/mopar/cam-tech-c.htm

fireturd350

iTrader: (8)

Not to take over the thread or anything... but how do you like that 3k ACT stall with the 700-r4? I'm upgrading to 3.73s and a new 383 I'm thinking I'm gonna go bigger... I have 2400 ACT now with the SS 700r4

AJ_92RS

I agree 100%. I wouldn't waste my time nor money unless they were the same price. The benifits aren't worth the money/hassel.

I was talking with a friend and he pointed out that "mid-stroke" to Mike may mean "between strokes", which is correct, just worded in a strange way.

DTL504

iTrader: (1)

This A.C.T. Converter was recommended by Dana and its GREAT, driving normal she shift real smooth and dont have to rev her to get the car moving. I will give it 98% grade as excellent. What 2% missing I dont know! Talk to Dana he will do a free upgrade on them convertors if you had it less than a year.
DTL504

Motor City Mike

Thanx for the correction AJ. I was about ready to get my flame-thrower out.

I will also agree that the actual performance gains are minimal. But if you're putting new aftermarket pistons and rods in (regardless of length), I'd definately go with the longer ones (price should be the same).

DTL504

iTrader: (1)

Do like Smokey Yunicks said and I quote:
Put the biggest rod that you can fit in the engine...

fireturd350

iTrader: (8)

Thanks DTL sounds like your 3k runs a lot like my 2400 with 3.27 gears... just wanting to make sure it wasn't going to be a big change. I got mine from Dana also. So with my new cam and 3.73s it should be fairly good behavior once Dana matches the stall.

Air_Adam

A longer rod will help to decrease sidewall wear on the cylinders and will not be as stressful on the engine at high rpm.

These were the 2 major problems with the 400 small block. The rods were really short, which made for excessive sidewall wear on the bores and the were fairly easy to grenade at high rpm.

92 zzz28

If you are buying a complete assembly, then go for the 6" rods, price is usually the same. If you are thinking about retaining your stock rods to save a few bucks, go ahead...

I run 6" rods in my 385 but I bought a rotating assembly through my machinist years ago and the price was just right...

pskel350

i will be buying a complete forged bottom end, the price is the same for 5.7 or 6.

Thanks for all the info. I have decided to go with the 6 inch rods

Confuzed1

iTrader: (4)

I'm in the middle of buying a 406 ...hope you're prepared to lay out the $$$ for a forged bottom end, but for a 383 it may be cheaper....

DTL504

iTrader: (1)

I wanted to spend $1000.00 on a good bottom end and this is what I got.

EAGLE H-Beam Rods CRS6000B3D $335.09

CLEVITE Main Bearing MS1038P $27.00
Rod Bearing 8-CB663P $27.00

SCAT 9000 Int Ball Crank 400-3750-6000 $222.50

WISECO Pro Tru Forged Pistons PT020H4 (0.040) $419.00

TOTAL Price Including Shipping = 1030.59

Ok I did go over the budget by $30.59, but I have forge pistons, forge rods and a int bal crank.

ME Leigh

The Scat 9000 crank is not forged, but it is a very good crank made out of some good steel.

DTL504

iTrader: (1)

I did not say my crank is forge, but I have forge rods and Pistons. I belive for what I want to do with my engine (RPM) I would not need a forge crank. Crank is usually not the weak point in a SBC bottom end. Its the rods bolt that usually break and tear everything else apart. Thats my reason for not wanting a forge crank. Also the 400 dont need to wind as high as a 350 to get max output out of the engine...

Confuzed1

iTrader: (4)

That's exactly what I've read about them. If you are running a combo that requires a high RPM's, you need to invest in splayed caps for the 2 bolt main blocks. I don't know anyone that has seen a crank break at the track....spun bearings? YES - thrown rod? - YES..... but no broken cranks...