Carbureted LSX forum - 317's vs 853's

need some feed back thinking of changing from the worked 853's I have to a set of worked and milled 317's...

Who worked them? The 317 starts out as a better casting and can flow over 300 cfm with stock valves, the 853 and 241 is not happening without bigger valves.

The 317 share same intake and exhaust port as 243/799
Take the 317 and run

What does the 317's flow stock?

245ish, depending on the flow bench, like 243/799 castings.

The 853's had stock valves in them. I have one witha pin hole instead of trying to have it fixed I picked up 2 sets of 317's and am going to have them milled, bowl blended and what not. I am hoping to pick up some more power with them but not sure if I would.

You probably will. They flow about 20 extra CFM over the 853/241 stock.

That's good news man Thanks! I am so worried I'm going to lose power. I am going to have them cut enough to bump the compression up some more.

I see allot of folks going .040 with no issues if that helps.

I see allot of folks going .040 with no issues if that helps.

my 853's were cut that much.

245ish, depending on the flow bench, like 243/799 castings.

The numbers I have see for the 317s have ranged from 255 to 265 cfm. The regular 862 - LS1 head test I have seen have been closer to 240 cfm.

Depends on who flows them, this is where i get my info(some):

http://users.erols.com/srweiss/tablehdc.htm#Chevy

853@.600: 227/180

5.3 castings: 223/187

806: 231/173

LS6 on SF600 flow bench: 257/183

Than another advan ind flowbench: 260/183

Then another rating the 243 and 317 casting:236/185 (rather low)

317: 253/184

L92: 322/214


So many variables, but there is tons of data in there, several shops port jobs, stock and aftermarket, great site.

So many variables, but there is tons of data in there, several shops port jobs, stock and aftermarket, great site.

There really is. Way back in the day when flow benches started to become affordable, I was working on some turbo v-6 heads and the guy I brought them to for the "after" testing said to me: "what do you want them to flow?" LOL. That was an eye opener.

Man, some shops, i think you can tell which ones, dont have a spark plug or plug of any type in the head when flowing, makes them look like they flow more than they do.

this is some good info. I hope with some work they will make a really nice increase

One guy i know that owns a shop says he has got 300 cfm from a 243 casting with very little work before, but the 317 and 243/799 are supposed to be identical, they are a very popular head for this reason and are cheap, just the bigger chambers people bitch about, but if you have 400+ cubes, they really work.

My friend that is a SAM graduate got a 243 flowing 310cfm with stock intake valve. He also got a l92 around 368cfm and even shrunk the port. Hes pretty good at grinding. But he work in medical field. Make mo $$

Oh yea, 243/799/317 can all hit over 300 with stock valves, it is the other cathedral ports that need the larger pieces.