Ah heck, I guess I'll put my 2 cents in. For sure the engine builder guys know way more than I do, but I just can't keep my mouth shut.
![Roll Eyes ::)](http://fepower.net/simplemachinesforum/Smileys/default/rolleyes.gif)
I would leave the short block alone. Is it as good and strong as a new 4.25" stroker assembly? Definitely not. BUT, the short block is not why you haven't met your power goals. In my opinion it is the heads, intake, cam, and carbs. I would replace that stuff and keep your shortblock. I will admit that I am partial to unusual combinations like you have in your short block, so I am bit biased. Plus it's all American made which is also cool.
So get better heads and intake. Well done Proports may be the best choice. Survival heads would be awesome as well (Okay, BBM, too
![Tongue :P](http://fepower.net/simplemachinesforum/Smileys/default/tongue.gif)
) . Or even expertly ported plain ole' Edelbrocks would get you there.
The intake is a little harder choice at the 600 hp level in my opinion. Lots of ways to get there. Considering the gearing and vehicle weight a ported Victor would work. But at 600 hp there are "lesser" intakes that can get you there, too. Even an Edelbrock RPM could do it, though you'd likely lose some top end power. I think the Blue Thunder 2x4 intake would be fantastic. And since you could use new carbs, you could move to some nice Holley 750's.
I'd put about 6-8 degrees more cam duration and a little more lift, maybe 0.600-0.625". The hydraulic cam is a real bottle neck in my opinion. You want more duration to make more power, but then you'll need to run more rpm, and that gets harder and harder with a hydraulic roller. You can science-out your valve train with light weight retainers and valves and such and probably get to 6500 rpm or slightly more. That would probably be enough. Plus I'm not sure if you have a pump or accumulator for your power brakes?
I feel like the hydraulic roller is really the focal point of all this. I realize this contradicts almost everything I've said up to this point, but max cubes from a stroker kit is really your friend if you want to stay with a hydraulic roller cam. The more cubes you have the lower your rpm will be for a certain power level and the easier it'll be on your valvetrain. Having a hydraulic roller cam really accentuates this characteristic.
Ah hell, let me put it this way.
Option 1) If
I owned this motor I would get some good Proport or Survival heads, a BT 2x4 intake, and two Holley 750 carbs. Then I would ditch the power brakes and put in a solid roller with about 252 to 258 degrees duration. I'd spin it in the 6500-6800 rpm range and hope the rods didn't let go.
Option 2) For someone who wants to keep the power brakes AND the hydraulic roller, a big motor just makes sense. So you might as well get a stroker kit. 4.25" or even 4.375". Then put a slightly bigger hydraulic roller cam in and some Holley 750's. Then I'd see how that does with your current heads and intake and go from there. Things is, if you end up replacing the heads and intake, well now you have almost a whole new motor. Only the block is remaining.
Option 3) Keep the shortblock, get the good heads and intake, and get a better hydraulic roller cam, but not one with a lot (or any) more duration. Maybe one specifically picked by one of the engine builder guys. It might have more lift and just the right duration and other spec's to get you some more power without raising your rpm much. With good valvetrain parts you might take it to 6500 rpm or less and still make over 600 hp.
semi-coherent ramble officially over!
JMO,
paulie