Predator 420 6000 RPM?

[SquidBonez]

Just wondering what's the easiest way to get 6000 RPM out of a big block. I know they don't rev as high as the small blocks. Not looking for a balls to the wall crazy engine build (maybe around 20 or so horsepower), so performance wise I plan on just doing your standard stage 1 kit (air filter, carb jet, header pipe, muffler, 50lb valve springs), thinner head gasket, 6° timing advance, and billet rod/flywheel to keep things from blowing apart. Would these mods be enough to get me to 6000 RPM? Am I going to need a cam/chromoly pushrods?

 

[mike97760]

Yes. Cam and a serious carb. And dont buy springs until you know which ones work best with whatever cam you buy.

 

[SquidBonez]

Yes. Cam and a serious carb. And dont buy springs until you know which ones work best with whatever cam you buy.

I'm trying to keep the stock cam if I can. I want to stay close to the power rating of a 40 series torque converter (which is 18 horsepower, but they can be run a bit past that before you start shredding belts). Honestly 5,500 RPM is the goal, 6k would be ideal. I know people have gotten 5200 out of a GX390 with the governor removed and with stock springs. Since I'll be bumping up the power with the Stage 1 kit and beefing up the valve springs, I'm guessing I'll get more than that. Ultimately, the goal is 55mph (6:1 gear ratio, 22" tires).

 

[mike97760]

I'm trying to keep the stock cam if I can. I want to stay close to the power rating of a 40 series torque converter (which is 18 horsepower, but they can be run a bit past that before you start shredding belts). Honestly 5,500 RPM is the goal, 6k would be ideal. I know people have gotten 5200 out of a GX390 with the governor removed and with stock springs. Since I'll be bumping up the power with the Stage 1 kit and beefing up the valve springs, I'm guessing I'll get more than that. Ultimately, the goal is 55mph (6:1 gear ratio, 22" tires).

It takes energy to compress the springs, and they don't actually do anything to make more power. And more power usually comes from being able to burn more fuel which the stock cam limits by not allowing very much air/fuel into the cylinder.

 

[Skidude]

That will give you 65mph at 6000rpm, or 59mph at 5500rpm. I’d try to find some ratio rockers. That should give you a bit more power and move the powerband up a bit.