350 heads on 400

I have a 400 small block. It is bored 20 over with flat top pistons, I have a magnum cam from comp cams with .490 in and ex lift. I had a set of heads from a 350 that I sent in and had rebuit ( casting # 458624) they shaved the heads 30 over ported polished and 2 angle valve job.I just told them to give me some performance and thats what they did for me..( this engine was built about 7 years back and used for only 3 summers..well I have it im my firebird with a 700R4 and 390 gears...well it hauls ok....but it still doesnt have that extreme power...I have one of those G-tech meters that measures horsepower and 1/4 mile time...well I can pull 13.89 @ 101 mile/hr....I guess thats fast but to me not fast enough if you figure what I put in my engine....my thought is I am lacking in the heads..seeing as they are low performance truck heads....I have been always thinking about getting a set of vortec heads and use them...but I have been told that with my heads shave and the compression I have I may not gain a thing with the vortec heads...my question is should I replace my heads? or what do I need to get holy crap amounts of power....
thanks in advance

The first thing I would recommend is changing out those 624 heads. They are extremely light 76cc castings and make excellent doorstops.

I have Vortecs on my 406, with Comp's XE268 cam. I went with slightly dished pistons to get the static compression down to 10:1 with these 64cc heads. This combination would break the tires free even with the old 2.41 rear gears I had.

yup, you're running with too large of a combustion chamber, even with the heads shaved a little, its just not enough..... a new set of vortecs will give you a big change in power...... you're definately missing something somewhere

if I change to vortec heads ....should I stay with 76cc chambers? because right now I have a hard time running pump gas..I need premium or it pings from low octane.....I was told I had around 10 to 1 or 10.5 to 1 compression with the flat top pistons and shaved heads..Is that true? I am not sure how to calculate it...anyways....what size chambers do you guys recommend I get and still be able to run pump gas

thanks again

well since you wont be using shaved heads going to the vortecs.... get like a 68cc or 64cc, whichever they offer.... that'll keep the compression up and give you more valvetrain performance

The 0.030" cut dropped the cc's from 76 to 74. Assuming 4 cc's of valve relief in the pistons and a 0.039" compressed gasket with zero deck, you're at 10.53:1 right now. A change to 64 cc Vortec heads will put you at 11.77:1, so how do you plan to run on pump gas then? :confused:

techinspector1 thanks for the reply...
I have been reading and am wondering if I hould go with a set of twist wedge instead of vortec...seeing as I wont need to change my intake...the cam will work with everything on the head...basically plug and play rather than vortecs that arnt...now I figured if I went to a lower cc I would be running into a compression problem seeing as I have enough fun finding pump gas now...what do you recommend I get to replace the heads?
thanks for your time everyone

Trick Flow twisted wedge heads were excellent, but Trick Flow doesn't make them any more. They ran into too many problems with dumbass hotrodders who wouldn't check valve to piston clearance and bent valves due to the rolled over valve angles. If you can find a set of 76 cc heads on e-bay or from some other source, go for it. CHECK PISTON TO VALVE CLEARANCE.