bouncedcheque

I read elsewhere an engine builder claiming a 60 hp increase by porting the stock heads on a 496HO and retaining the stock ecm. Does this sound possible?

Tinkerer

He must be increasing the fuel pressure then.
The heads are the key to producing HP but they are only part of the equasion.

Raylar

Its very doubtful that just porting 496 iron heads will add 60HP We developed a new all aluminum head with awesome flowing ports, velocity and 1 point more compression and thats about what we saw in added horsepower from the heads only. Also if you see our cutawys of the stock 496 iron head you would have to be crazy to start porting them. In some locations the port walls are only .060 thick. There are a few who have tried and ended up with water filled motors.
Good Luck!! Hope you got money for a new motor!
Raylar

bradfitz

Rylar
What else would you need to change, if anything, by adding a set of your heads on a 496 ho?

bradfitz

A tech asked me if I wanted to raise the rev limiter on my 496 mag ho to 5450 rpm the last time I was in for service. Would this be ok if the engine has the stock heads?

Raylar

I would not raise the rpm limit on stock 496 with stock heads above 5200 rpms. the stock springs are not the greatest pieces and the valves are on the edge from a heavy weight standpoint.
Sutphen 30: our heads have a completely redesigned intake port. The humps are gone the short side is radiused, the roof is raised, the port floor is raised and that crazy step is gone with a whole new bowl and seat design. Our head flows 360cfm at .600 lift on a 2.19 valve and a 295cc port so you can imagine the velocity numbers we have as well as a lot of swirl and tumble. We could not ever figure out the step, I guess they were trying for swirl, but all they did was screw up the port bowl area.Some times GM engineers get a little carried away with their experiments. Our heads will run on any 496 and improve the power levels, however they flow so well that at about 4000rpm, the factory intake manifold runs out of air, thats why we had to build a new manifold. Then we realized the cam needed a whole new profile and timing change to match the components. this is how we got to our current kit.
If anybody is serious about upgrading their 496, take the iron heads, remove a valve, tie on a rope or chain and use them for a boat anchor, get the idea!
Ray @ Raylar

bradfitz

Raylar,
Knowing the stock springs and valves not being the greatest, when should they be replaced.

FASTERDAMITT

Ray,
Can you run a intercooled 3#'s of boost with your heads inplace of your intake?

Raylar

The stock springs and valves are ok as long as you don't buzz them a lot over 5200rpm. they should last the life of your motor to the first rebuild. they are single springs and they don't get hot and need replacing. The problem is they only have about 90lbs. seat pressure closed and with the factory heavy valves they will start acting up with some valve bounce over 5200rpms for long periods.
With our heads you can run three punds of boost if your ECM has been properly reprogrammed for a supercharger. The only question will be on any supercharged 496 is how long the factory piston will last. When they fail, it tends to be ugly and expensive. Best bet is to replace the factory pistons with forged supercharger pistons and rods, then you can run 5-7lbs of boost and really make some power.

Ray @ Raylar

FASTERDAMITT

Thanks Ray.