Non Hemi Predator build, with $600-700 for HP parts

[csquared]

Hey everyone, first post to the forum, I just recently bought a non hemi predator for my Margay Expert III go kart build. I have a budget of $600-700 for go fast parts, so far I have removed the governor, oil sensor and plugged all the holes. As far as parts go, I have been looking around on a few websites and I'm getting confused on what parts can work the best with each other (max cam size without clearancing the block, valve size, stamped rockers or roller rockers and push rod length) I would like to use the flat top piston and Mikuni 22mm carb and 26lb valve springs and obviously the billet connecting rod and flywheel, I'd consider mild head work if its in the budget. The go kart will be used around the neighborhood/parking lot runs and the occasional track day, I would like the kart to have the best of both worlds ( top end and decent torque) as possible within budget, not trying to hang with the fastest.. I just want it to be pretty quick for what it is.

Thanks,

Chris

 

[ole4]

Did you measure the original piston depth at TDC? That is the in the hole measurement and you should measure it as it will help you determine which ARC rod to get. There are two predator flat top pistons I have seen the hemi piston which has a .020 shorter compression height (.550) and another which I think NR sells that has the non hemi .570 compression height. Depending which one will help determine which rod length to use. Isky black mamba cam will work well with the kart as well as a black mamba JR. I have a kart that I built a motor for and used the standard black mamba with a preimier magnum clutch with a 3200 stall and it was fun on the street, real strong top end. The next thing to look at is what head you have on the motor, is it one with 5mm stems with 27, 25mm valves and split keepers or does it have 5.5 mm stems and 27, 25 valves with slip off retainers. Let us know.

 

[csquared]

I haven't taken the head off the motor yet to determine piston depth, will be doing that soon. As far as the head, I have the one with the split keepers.

 

[super nate]

that's a gen three motor.. I have one myself in a minibike..nrracing has a rod and piston combo/drop in kit that works real nice, have it in mine ...using the nrracing 252 cam with stock rockers and pushrods 26lbs springs... mikuni vm22 ported head...turns 7700 rpm at 53mph with a 210 lbs rider in the eighth mile...not bad for a mild engine

 

[mrdoja]

I've taken a lot of great info from this forum, time to give back. My head is 5.5 with 25/24 valves with mild port/polish and upgraded to SS valves, retainers, billet keepers, stock rockers, 26lb springs with .075 shims (valve seat height now .835). +.040 ARC connecting rod with hemi flat top piston, after which I'm .035 in hole. Head gasket is .009 metal. Billet flywheel, Black Mamba cam. Previously was using a SA carb .615 22 pilot/37 main - top speed 50, max RPM 7400. After 1 week of testing I've finally gotten the china-copy Mikuni VM26 spot on, and what a difference; throttle/acceleration is completely smooth, mid-range hits MUCH harder, and now I peak at 8200 RPM and 56 MPH with 12/57 gearing (with 190lb rider)!! One thing with this carb; don't use the cone filter as the inside rubber where it meets the carb inlet restricts the air jets (caused unpredictable carb issues, and largest main jet I could use was 100). After figuring this out my jetting is: Pilot 22.5, Main 115, Needle clip set one from bottom.

 

[csquared]

Thank you guys for the replies so far. So basically I need to try and get the piston as close to 0 deck as possible right?? What about the head gasket, is there a size that works better or does it just come down to compression ratio? If I did end up running the Black Mamba cam or one similar, how well would the stock rockers hold or is it better to get the champion 1.1 rockers with that set up

Sorry for all the questions, I have been reading around on the site, just trying to get as much knowledge for my set up

Thanks!

 

[ole4]

You want the piston to head clearance to be around .030 so if you have a zero deck height you want around .030 between top of the piston and the squish area of the head so get a head gasket that gives you that. If your piston is .005 in the hole use a .025 head gasket. 0 in the hole a .030 gasket. Stock rockers will work but the old style champions are great, more robust and eliminate the need for the guide plate.

 

[super nate]

a friend of mine had the black mamba cam with reinforced rockers and they broke. me personally I like to over kill parts I would run billit roller rockers on any cam over 250 lift,just my opinion

 

[trinik7597]

It's the spring pressure you need to worry about when it comes to rockers more so than lift old style champions are a great cheap way to avoid problems .. but real Honda stamped rockers will hold up to that combo as well

 

[trinik7597]

Champions tend to be a little heavy so I like to lighten up the drive train when using them ... But it's not necessary for them to work well

 

[Prowler08]

I like using the non Hemi block, Honda crank, Hemi piston, ARC 3.403 Rod for 0 deck or .005 pop up and a .045 gasket, F275 Dyno cam, 1.3 rockers, 38lbs springs, gx390 carb on Alky and let her eat...
Pulls like a bear down low and doesn't stop till 8500rpm...

Or a .330-.356 cam and Champion rockers .260 duration still pulls hard down low, and doesn't stop pulling...

 

[csquared]

So I was finally able measure how far the piston is in the hole, it reads .020 in the hole all the way around. I also took a digital caliper and measured the stock head gasket, that came out to .35mm

With that being said, which rod would be ideal to use, and which flat top piston would work as well?