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Saturday Night Racer >> RACE TECH >> Rod Length
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Message started by hookdup on 04/10/10 at 4:09am

Title: Rod Length
Post by hookdup on 04/10/10 at 4:09am

In a 23 degree steel head limited late model engine with a 50 lb. 3.500 max stroke crank and flat top pistons, would you use a 6 inch (or longer) rod or stick with stock length (5.7) rod? And why?

I am having a debate with a friend of mine and need ammo..... Thanks!

Title: Re: Rod Length
Post by TIM_BEWLEY on 04/10/10 at 8:25am

well you will probally get some different opions but i have always liked the 6" rod. less rod angle on the cyl. walls, stays around tdc & bdc longer. i'm not a pro engine builder it just what i like. check out this like

http://www.chevymania.com/tech/rod.htm

Title: Re: Rod Length
Post by Andrew on 04/10/10 at 8:52am

I agree with Tim, I like 6" rods(that just doesn't sound right though). I'm no pro builder either. I can't get technical, but the benefit of the 6" rod is based on the relationship between the bore and stroke. There are engines, that are built right from the factory, and they have a long enough rod(mostly imports). If I were building a small block, I'd want the 6"ers.

Title: Re: Rod Length
Post by OLD SCHOOL#6 on 04/10/10 at 9:06am

Oh-Geeez, I guess I will have to agree with Tim also. My knowledge is that long rods will not gain much more HP than 1 - 3% but there are some gains there to be had. The big gains are in the stress areas on your motor. Short rod exerts more force to the crank pin at any crank angle that counts (ie.20-deg ATDC to 70-deg ATDC). Also short rods will side load cylinder walls more than long rods (this one is the big one to me). Using short rods will make piston design selection and cylinder wall rigidity more important. There is a lot more to the subject than this, but it's about all I know ................... Tim's link is pretty good................

Title: Re: Rod Length
Post by Andrew on 04/10/10 at 12:08pm

Cyl wall load = heat. The one long rod motor I build(4 cyl) had a real hard time getting hot. I had to use a 195* thermostat and drain some water from the radiator to keep the engine from running too cool on those cold spring nights. Kind of a good problem to have though.

Title: Re: Rod Length
Post by hogracer3d on 04/10/10 at 1:25pm

Smokey Yunick and Randy Dorton say, put the longest rod in that will fit.
lighter piston, likes more rpm, but becomes very cam dependant.

A good long rod camshaft, will make the difference between a rocket and a turd

A limited late is the perfect application for a 6.200+ rod package, especially if on a 2-bbl

Title: Re: Rod Length
Post by hookdup on 04/24/10 at 4:31am

Thanks y'all!!!