420 predator


New member
I plan on putting a 420 on a racing mower. Now what I need to know is the torque specs and does the govenor look the same on the inside as the 212?? I have heard that you can run 212 valve springs inside the 420 springs to help with valve float. Also what size jet with a filter? Any help would be appreciated.
The governor does not look the same but it is pretty obvious when you open the case. I got mine out in about 30 minutes. As the the rest of your question I would also love to know the answers.

Good luck
the springs are supposed to fit in.
torque specs for the bolts? google up a bolt torque chart.
what type air filter and pipe?
I wouldn't use the 212 springs they are weak...just call parsons racing, he can hook u up. The springs are pretty reasonable and not worth chancing it....he will also have all the torque specs in his head lol he does a great job
Connecting rod bolt M8 x 1.25----- 10 ftlbs
Cylinder head bolt M10 x 1.25----- 25 ftlbs
Flywheel nut (special nut) M16 x 1.5----- 83 ftlbs
Rocker arm pivot lock nut (special nut) M6 x 0.5----- 7ftlbs
Rocker arm pivot bolt M8 x 1.25------- 17 ftlbs
Crankcase cover bolt M8 x 1.25-------- 17 ftlbs
Muffler mounting nuts M8 x 1.25------ 17 ftlbs
when installing aftermarket parts use manufacturer's torque values
With an open air filter with filter adapter AND a an open header, I would suspect a .038 jet would be a place to start. I have seen a #36 being too lean typically and a #40 a tad rich on an otherwise stock engine. Many variable of course. Good luck.
I have done a lot of work on this engine as I prepped one for my kart and ran it for almost 2 seasons.
The governor is in the side cover on big blocks. Its EASIER and faster to remove than a small block. You can use 10.8 springs inside the stock springs and you'll be good to around 6000rpm, or, Vegas's aftermarket "gold" springs also work well.
I found mine to be too picky with jetting with the temperature and air density changes our area saw, so I installed a T-handle adjustable main jet from stout racing, drilled the main jet to .048" and then the adjustable needle simply replaces the float bowl bolt and restricts it back down.
Buy some good grade 10.9 flange head bolts and solid side cover dowels, and throw the stock side cover bolts and hollow dowels away. I also use Loctite on my rod bolts as my personal preference, but you must be super careful not to get any into the bearing area! I use a toothpick to put the Loctite in the female threads and then insert the bolts.
All this stuff is about $50 and an evening at home to install.