landonew

If I was looking to build a forged shortblock (w/ intent to spray 200-300 N2O), how big could i go before running out of head. At some point the AFR205s will begin to choke it out at high RPM. I was thinking 402/403 ls2, but would rather bump it up to a 416/418 ls3. Would the ls3 like the smaller heads?

Super Speed

iTrader: (8)

From what I understand its better to sell them if you plan on going bigger cubes...
You leave ALOT on the table with such a small runner!

Patrick G

iTrader: (14)

You're more hp limited than cubic inch limited. The port can only flow so much air. Some people have made in the 525rwhp range with AFR 205s, but that seems to be around the limit (naturally aspirated of course). That means you could make that much power with a 346 or a 440. The biggest difference is that the smaller motors will need more rpm to make the same power and they'll have lots less torque than the strokers. Don't expect to make more than around 525rwhp regardless of how big your shortblock is (unless you run solid roller, add a sheet metal intake, and run 8000 rpm).

Nitrous is a completely different animal and the AFR 205s have an outstanding exhaust port capable of supporting over 800 rwhp on the spray. The question is, is the rest of your combo set up to evacuate that kind of exhaust volume?

landonew

I believe so. I have kooks LT 1&7/8" headers and 3" TD over the axle.

Patrick, would you suggest that i upgrade my heads when going to a 418? Aside from the cost, what benifits (if any) would i derive from sticking with the smaller cubes?

Patrick G

iTrader: (14)

If you stick with the AFR 205s, at least have the combustion chamber opened up to 4" bore. This will enhance your low lift airflow by unshrouding the valves more and giving them a better funnel. If you're going to run a 300 shot, you may want to port the exhaust a little more too.

Your cam timing, especially on the exhaust lobe better be up to evacuating 800 rwhp. You'll want to open the exhaust valve much earlier than you would NA.

landonew

Assuming I take your advice and send the heads to tony for freshening up, and have you custom spec the cam..... How much am i leaving on the table by not upgrading to the AFR 225/235s?


I think that i could maybe sell my heads and buy the 235s for around $1000 out the door all said and done. The AFRs keep their value, but at the end of the day they are still slightly used.

Patrick G

iTrader: (14)

Talk to Tony. For the price difference of upgrading to AFR 225s, you may be able to have him massage the 205s to give you the airflow your stroker needs.