I built a 383 stroker about a two years ago. When I built it I took advise from an old guy who builds dodge big block engines and put 5.7 rods in it. He said it would make it rev quicker. BUT soon after that I outran his 1973 440 dodge challenger with my old 350 tuned port vette. I originally built the engine for my 85 vette so the cam was ground specifically for a Tuned Port vette with a stock TPI and stall, but after the engine was completed I got the camaro bug. Now the engine is in my 84 Z28 H.O. with an Edelbrock intake and Holley 750 street evenger. So I'm gonna pull the engine and tranny back out this summer. I wanna change to a roller cam, but while I'm at it I thought about the rods. Most guys I know have put 6 inch rods in theirs. Soooooo........ to make a long story short ........

what are the pros and cons of between 5.7 and 6 inch rods?

 

Pros = insignificant power gains.
cons = significant $ increase.

 

Some thing else as well.... How can 5.7 and 6.0 in a 30 over block both equal 383 cubes?

 

Rod length does not effect displacement.

 

The piston still has to reach the top of the block so the piston compression height has to change to make up for the different rod/crank combination.

 

That makes since, but I still don't understand why some would choose 5.7 or 6.0 rods. What are the pros and cons of each?

 

I did a lot of reading/research before I built my 388.

This is one of many articles I read http://www.stahlheaders.com/Lit_Rod%20Length.htm

 

Nowadays price is not a consideration between the 5.7" rods and the 6.0" rods. Looking through the Scat catalog there is no difference in price. For my 370ci build up I went with the 6.125" rods in order to get the rotating assembly weight as low as possible without the piston pin getting into the oil ring. I went with the longer rod with corresponding piston to get the weight down.

 

The original poster was asking about replacing his rods to 6in which is why I said it would be alot of money for little gain. I should have been clear that if one were building from scratch it would be something to consider. But with rods, pistons, and rebalancing, etc. an upgrade to 6in rods would be low on the bang-for-buck ratio.

 

My old 383 had the 400's 5.56 rods which allows standard 350 pistons to be used.

Using a 5.7" rod needs a different piston which moves the wrist pin up into the oil control rings. A 6" rod moves it up even higher, getting close to the compression rings. The proper piston needs to be matched to the rod length. A longer rod allows more piston dwell. It doesn't change displacement.

Other engines other than a SBC have different deck heights which allow different lengths of rods so ignore what's in a "dodge" engine. Standard BBC rods are 6.135". It's common to use .250" longer rods which are 6.385" in standard 9.8 and 10.2 deck height blocks. Going to an aftermarket super tall deck block, there are BBC rods which are 6.535 and 6.800" long which could never fit into a standard 9.8" deck block. The wrist pin would be in the compression rings.

 

"The original poster was asking about replacing his rods to 6in which is why I said it would be alot of money for little gain. "

I agree.

 

considering he has a good motor with 5.7 rods, replacing the rods and pistons and having it rebalanced would be very little gain for very high cost. so this guy is right, but when building a new motor the added cost is negligable, so so is every one else.
The pros of long rods is most signifigantly less cylinder wall scuffing, as well as the piston spending more time at tdc.The cons are the shorter piston height causes the wrist pin to become very close to the oil ring, but piston manufacturers have long since figured this out. The other con is shorter piston skirts increase piston rock, but this is negligible.
You will not make more any more considerable amount of power with long rods! A nascar motor with 7oo hp and 9000 rpm might make 3 more hp, and this is some difference for them but completely useless in a street strip car. so if you are building a fresh motor, go for it for decreased rod angularity and since it is no more expensive. but if you have a good motor, spend the money somewhere else, just about any other change will make more power per dollar.

 

Thanks guys, that pretty much answers my question. I got another question but I put it in a new post. Thanks again.