Built Predator 420cc Horsepower?

[SquidBonez]

I'm building a ground-up go kart/mini-buggy, and I plan on running a "Stage 2" Predator 420. I know this forum mostly talks about small blocks, but there must be someone here who has experience with these GX390 clones. As far as modifications go, I plan on running billet rod/flywheel, .308 cam, 65lb valve springs, chromoly pushrods, stock carb with larger jet, high flow air filter, and a header pipe; all standard Stage 2 parts. No milling, porting or polishing.

Any idea what I could expect horsepower wise? Aiming for around 25-30 horsepower and about 6000-6500 RPM. Does this sound feasible?

 

[DynoDon]

No

 

[SquidBonez]

No

To the horsepower estimate? RPM estimate? To all of it? I managed to come across a dyno sheet from a 420 race engine, but it had an aftermarket carb and I have no idea if it was milled/ported/polished or not. 35 horsepower, 38ft-lbs, & a little over 7000 RPM. I imagine I wouldn't be making quite as much power since I'll still be using the original carb with a larger jet rather than going the aftermarket route, so I wanted to get some estimates. Here's the sheet:

 

[flattop1]

The two things that are big variables . Horsepower, expected and actual are not always the same . There should be a big gain at any rate .
#2 the carb is going too be a limiting factor . The stock carb will provided good response just not max response.

 

[OVALTECH1]

as above the carb will be your choke point and limiting factor. However if this is gonna be a woods/mud buggy it should have all kinds of grunt like that.

 

[BLACK DEATH]

Old post but a 308 cam with stock compression?
you can use single 50 lbs with 308 lift.
‘I think your combo is kinda not in sync