For head work i suggest goodwinn cmpetition in WI

I have 14-71's on 572's, and they are not working very hard to make 1000 hp (6-7 psi). This is 9:1 compression with chillers though.

I think getting to 850 hp without chillers on a 509 block is pushing your luck. 10-71 would probably be the best blower for it, if you can make it fit.

If you haven't torn down the motors yet, maybe don't drop the CR all the way down to 8:1. What block do you have? Can you punch it out for more cubes? If you could build a 540 or 572, you'd stand a better chance of getting 850 hp sans chiller. Like others said before, definitely aluminum heads.

Have you looked at using a Whipple intake manifold/cooler. I'm not sure if you can bolt a regular roots up to it, but it might be low profile enough. If the bolt pattern isn't the same, there are NC shops everywhere that can make anything.

buy a 3.3L whipple with carb set up and intercooler and set your comp ratio at 8.5:1......run 7 lbs boost(steel heads) or 8-9lbs(alum heads)

With the chillers could I run 8-9 pounds boost and keep the steel heads, and make the 800-850 range? If I did run the chillers, I will be able to fit the 10-71's, and given the choice to run either 8-71's or 10-71's is the 10-71 the one to run with?

if the chillers wil fit under the hatch,run them,my 548,s with 8.71 and chillers at8 lbs boost made 950 hp on dyno,if i didn,t have chillers,id run them at 7 lbs boost.hope this helps.also.i had a 509 with ported iorn heads,8.1 comp,8.71 with no chiller,made 770 hp at 7 lbs boost.

That does help, thanks Mike. Look at that, my post counter does not seem to be working!

Rob , there is a set of 10-71's with everthing you need in the swap shop form at not a bad price . Jeff

Did some 509's with 8.5:1 comp, Canfield aluminum 350 cc runner out of the box head, not a real agressive solid roller, 8:71's, 4150 carbs, 7# and made 848 hp at 6000 on Zul's dyno for what it's worth. Never had any detonation issues.

The 10-71's with chillers should get you the numbers your looking at, and also be very reliable with low heat build up, and not spinning the blowers very hard.
My motors started life as 600SC's. They had cams installed, chillers, PFM blower drives, and 10 lbs of boost on 91 octane(only junk we have in Socal.) The motors make 800hp and i have put over 200hrs on them. The 10-71's will be able to do this with even less heat produced.



Darrell.

my 509 recipe was fairly simple. 8.2 to 1, 741 grind but double firing order swap roller cam, box stock edlebrock 6155 heads, chiller and a 420 blower at 8% overdrive. 902hp at 6000 after Crocket put a tune in the mefi.