I'm not a regular poster, more of a watcher on the forum always trying to learn.
Attached a pic of the kart my daughters and I built, pic is from first assembly so she is clean. Has been lots of fun, main issues have been needing to add reinforcing to the steering tab on the king pins and then getting the chain alignment just right so it doesn't pry on the half-link. Also added more lighting for nighttime visibility. We have treater her rough and taken a lot of places and all has been reliable.
Starting out, it would do about 42 mph on flat pavement. Then modified with ARC adjustable billet flywheel, Paul's Hot Coil, 36mm Chikuni carb, we built exhaust header, changed to medium springs in CVT, and disconnected the governor. That got us to top out at 50 mph on flat pavement and much better acceleration. 50ish is top speed this thing should go, we want more low end grunt for mud and climbing. Once more mods are made we will change axle sprocket to keep her around 50.
As you can see, Predator 420 Hemi. We want to mod. When we do internal mods I want to do it all at the same time.
Concerns:
1. I use non-ethanol gas in all my small engines so 91 octane and don't want to be above a 10.5 to 11 CR. I wouldn't mind octane additive, but definitely don't want to run into using methanol. 420 Hemi literature says stock CR is 8.3. Question here is, without doing all the volume checks does anyone have a feel for how far the mods below will affect this? No matter what, we will end up doing the calcs as a learning exercise.
2. Do the mods planned below jibe together? Is there an inbalance in spring to cam selection?
3. I can't find data for the stock crank capacity/strength on a 420 Hemi, and can't find anyone online definitively stating changing out the crank. Does this need to be changed for mid-20s hp?
Plans for mod:
1. 280 Camshaft with a 811 grind from NRC
2. ARC 6274 con rod. This will give zero deck height. (not sure this is a great idea without having taken engine apart and measuring. Greater control of the outcome could come from getting the 6272 (stock length) and then milling especially given the ratio rockers)
3. 1.3:1 billet ratio rockers
4. New chromoly push rods
5. New stainless valves
6. 54 lb single HD springs
7. Will upgrade bearings in housing (but not to ceramic $$$).
8. All the ancillary items will be swapped for new
9. We will port the stock head
This may just come down to tearing her down and making measurements then ordering parts instead of ordering then building. Looking for input from experienced builders. Wanting to achieve mid-20s hp. Would expect to eventually break the series 40 CVT and have to upgrade.
Attached a pic of the kart my daughters and I built, pic is from first assembly so she is clean. Has been lots of fun, main issues have been needing to add reinforcing to the steering tab on the king pins and then getting the chain alignment just right so it doesn't pry on the half-link. Also added more lighting for nighttime visibility. We have treater her rough and taken a lot of places and all has been reliable.
Starting out, it would do about 42 mph on flat pavement. Then modified with ARC adjustable billet flywheel, Paul's Hot Coil, 36mm Chikuni carb, we built exhaust header, changed to medium springs in CVT, and disconnected the governor. That got us to top out at 50 mph on flat pavement and much better acceleration. 50ish is top speed this thing should go, we want more low end grunt for mud and climbing. Once more mods are made we will change axle sprocket to keep her around 50.
As you can see, Predator 420 Hemi. We want to mod. When we do internal mods I want to do it all at the same time.
Concerns:
1. I use non-ethanol gas in all my small engines so 91 octane and don't want to be above a 10.5 to 11 CR. I wouldn't mind octane additive, but definitely don't want to run into using methanol. 420 Hemi literature says stock CR is 8.3. Question here is, without doing all the volume checks does anyone have a feel for how far the mods below will affect this? No matter what, we will end up doing the calcs as a learning exercise.
2. Do the mods planned below jibe together? Is there an inbalance in spring to cam selection?
3. I can't find data for the stock crank capacity/strength on a 420 Hemi, and can't find anyone online definitively stating changing out the crank. Does this need to be changed for mid-20s hp?
Plans for mod:
1. 280 Camshaft with a 811 grind from NRC
2. ARC 6274 con rod. This will give zero deck height. (not sure this is a great idea without having taken engine apart and measuring. Greater control of the outcome could come from getting the 6272 (stock length) and then milling especially given the ratio rockers)
3. 1.3:1 billet ratio rockers
4. New chromoly push rods
5. New stainless valves
6. 54 lb single HD springs
7. Will upgrade bearings in housing (but not to ceramic $$$).
8. All the ancillary items will be swapped for new
9. We will port the stock head
This may just come down to tearing her down and making measurements then ordering parts instead of ordering then building. Looking for input from experienced builders. Wanting to achieve mid-20s hp. Would expect to eventually break the series 40 CVT and have to upgrade.
Attachments
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basic kart.jpg
