longer connecting rod

[Bar50]

A guy here had a '66 Nova with a 400 SBC block and a 327 crank to sorta' do the same style of combo. Like the DZ 302 motors.

 

[UMI Sales]

Smokey Yunick said to put as long a rod as possible in any engine you ever work on...

6.00 inch rod SBC 350's on oval tracks are popular, maybe just because it's the in-thing.

The longer piston dwell time usually benefits from a change in cam.

I've always wanted to build a destroked 400 with super long rods just because Smokey said to.

 

[StreetBu]

There was a magazine article many years ago, (probably 10-15) with a destroked 400, 3" stroke, made 350ci or so using Ford 300 6cyl rods, they are 6.248 long IIRC. Thing spun to the moon and actually made a lot of power!

 

[80malibucoup]

I'm going to jump in towards the end of this topic. Mnay years ago there was a build up of a sbc in on the car mags. It was a 400 block .030 over, with a 283 crank-only 3" stroke. Makes for a VERY high revving small block with unshrouded valves because of the large bore diameter. The catch was they used Ford straight 6 connectiong rods which are 6.209" long. This made for a good ratio, I believe almost 2.1. The compression ratio with the custom pistons and steel heads was almost 13-1 and they were able to run 87 octane, not by retading the timing but because of the rod ratio and dwell time at TDC. The engine made alot of horsepower at a very high rpm, but was very street friendly. I'll try to find the article.

**edit** the rods werent the reason the HP was made, but rather a good combination of parts that when totaled when a good package, like any strong running engine.

I think you hit the nail on the head. I built a 11.1 406sbc with stock rods and crank,I can't run nothing under 93oct,but there are some people on here that can run 87-92oct, I could never understand how or why.Has anyone done any reserch on that?I really would love to know,they don't sell 93oct every where in Cali. I hate octaine boost and where I live there is only one station that sells 100oct at $7.56 a gallon.

 

[MalibuMan1979]

Re:

I used 5.7's in my 413. My understanding is that a longer rod remains at a closer to parallel angle to the bore/piston, therefore power is delivered to the crank better versus at a greater angle. Also I thought it decreased side loading the piston into the outside wall of the bore on the compression and exhaust stroke. However longer rods at a certain point bring the wrist pin into the ring area and requires design changes in the piston that may not be beneficial. Again, this is knowledge picked up from god knows where over the years but makes sense to me.

EDIT: oops, I didn't read all the posts carefully, I could have saved time and just said I agree with Squire Racing above.

x2