Don Terrill’s Speed-Talk

My 400 sbc is bone stock except for a 252-425 lift comp cam. I think its 206 at 50 deg 110 lobe sep. It runs good for the stock heads part #441-I guess there stock 74 cc. I bought a new pair of 906 Vortecs from the dealership. I changed the valve springs to a little stronger Comp spring , I will also drill the steam holes.. I also have a 268 comp extreme. Must be a daily driver. Just rpm intake and headers. Just changing over to vortecs what HP gain should I get-there 64 cc also .

A big worth while boost in torque and hp both.

On mine I did not drill steam holes. Just re routed the heater hose to the additional rear water port on the back of the manifold by the diz (drivers side) This aids cooling and thermostat function. Stops thermostat surging and keeps the 400 sbc cool with vortec heads (which cool better anyway). Many most of the perf vortec manifolds have these rear water ports.

If it is a low rpm pure torque application where mpg is important just use the 206-206 cam u got and put 1.6 or 1.65 rockers on the intakes only.
It will have lots of power.

The vortec head swap on 400's rocks.

If using a comp extreme cam be sure to use a Moly additive in your oil or use a oil with it in it.
www.molyslip.com. these hyd cams are normally a bit noisey at idle..... 15w-40 shell rotella helps minimize this.
Do not use fast bleed or "high perf" hyd lifters. Not needed. Use Normal GM hyd lifters.

Again if its a truck use the small cam.
If the small .425" lift cam and just stock GM L31 vortec motor rockers the stock L31 valve springs are fine.
You don't need to rev the piss out of it with that cam, +vortecs on a 400. 5000 rpm shifts are just right.
It will be all about TORQUE.

Because of the net increase in the compression ratio your 400 may now need to use premimum unleaded gasoline. 87 octane may/probabily won't be enough.

Your 441(X)(?) Or 487(X) 400 heads have resale value to those that want a budget big chamber head for a low CR budget street roots supercharged 305-307-327-350 sbc project, if they are in good condition.