I am considering a set of the dart 308's for next year on my little 525sc's (454's =.03). or maybe the Jegg's aluminum heads. Has anyone switched from stock cyclinder heads to after market with any noticable results without changing nything else. The motors are in a 1990 42 fountain .

You will want to find out the runner volumn on your stock heads. If you increase the runner size or increase your air flow, through better designed heads, you will need to increase your boost to offset the loss of boost. I had a pair of 500 hp's stock heads, whippled them ran them for a year, at 7 psi of boost on the gauge. Changed the heads to AFR cnced heads and with everything else the same could only make 5 psi of boost because of the lower restrictions. Had to put smaller pulley's on blower to get the boost back to 7psi.

what kind of mph did you pick up with the head change?

I replaced my stock GM heads with Dart Pro Ones on stock 502 mpi's. Didn't do any good, but glad I had them once I upgraded my engines.

I couldnt tell you exactly what the heads did, I changed cam shaft also. Ran a 741 Crane Hyd. roller. If your exhaust is restrictive, then a head change wont net much h.p. Doesnt do any good to get all that air and fuel in if you cant get it out. Its hard to change just one thing because Exhaust, cam, heads, all work together to make h.p.

well what kind of gains did you get when you did that before you changed the pully?

well what kind of gains did you get when you did that before you changed the pulley? I have the cmi headers on it

I just blew one of my 525sc's , I am going to put a keith Eickert motor package in both motors will let you know how they run when I get them running.

Thanks. What kind of rpm did the 525's want to turn? I am only running 4950 with the 29 three blades and was considering going to 27's for more rpm.