Hey guys, I'm new and inexperienced to engine building. I 'm wondering how do intake runner sizes effect engine performance? I have a 98" S&S with 79cc S&S Super Stock heads, S&S single bore tuned induction air cleaner and thinking of going with 52mm S&S single bore throttle body on my 03 Night Train and don't know what the difference would be between intake runner sizes of 1.660, 1.710 and 1.730 or what size would be best? I believe S&S retains the stock size of 1.660 and if so, would it be a good idea to maybe go bigger? I appreciate any and all feedback! Thanks!

 

I'd measure to verify, but most S&S heads are 1.780".
Scott

 

Ok, I thought since with the manifold they recommended ( 410 ) that they used stock size. Stock is 1.660 correct?

 

It really depends on what your heads flow.. But as Scott has mentioned, I would definitely measure the intake port on the heads and match the intake to it...

 

I have a set of S&S 79cc heads on my bench right now. They measure, as Scott said, 1.780"

 

Cool I appreciate that. Now, for a question ( hope not too many make fun of me ) but I don't exactly know what an intake runner is or where? I just assumed that with the manifold they ( S&S ) recommended to use which is " 410 " and that's same as stock that the runner would be stock and I could have swore that S&S told me that they retain the stock size of 1.660. I do appreciate all the help fellas! I'm learning what not to do if I ever do another build lol

 

The 410 means 4.100" center to center of the inlet ports, the width of the stock manifold. The 410 manifold S&S suggested has 1.780" ports to match the heads. https://www.jpcycles.com/product/404...e-manifold-410

 

Cool, thanks man

 

If I decided to go with a HPI throttle body, their runner sizes are 1.760” & 1.800”, how would I go about matching it up to my 1.780” heads? Thanks

 

Any head porter or perhaps, a machine shop, can open it up for you in a heart beat. Or you could do it yourself with a dremel with a burr bit. Obviously, clean the daylights out of it afterward.