@gokartgod 0 #1 Posted October 7, 2021 Looking for some advice here. Have experience with 212's but no experience with the hemi 420's. Currently, the engine is stock except for the stage one kit to hold the place for the Mikuni 34mm and custom exhaust. Looking for top end performance. The only part I currently have is a billet flywheel with timing adjustment. Need to do some porting and polishing at the end of all of this. Want to install -Billet rod -Mod 1 or .308 Cam -Chromoly push rods - 65lb dual Springs -Mikuni 34mm 1: Will the stock spring retainers and keepers work for the dual springs? If not what do you recommend? 2: Is 65lb springs the best option for my build or should I use 50lb springs? 3: 308 Grind Cam or Mod1 Grind Cam? Will I need to clearance the piston to clear the valves? (https://www.ombwarehouse.com/dynocams-308-grind-welded-lobe-gx390-core.html) (https://www.ombwarehouse.com/dynocams-mod1-grind-welded-lobe-gx390-core.html) 4: 4.410 or 4.450 Billet rod? Will I run into clearance issues running the 4.450 rod? 5: Mikuni 34mm Round Vs Flat? 6: Is there anything I am missing or anything you would recommend I change? Share this post Link to post Share on other sites
Maxwell-8 4,366 #2 Posted October 7, 2021 (edited) @Snoopy11 will be glad to help! I am more for the old and stock stuff. Edited October 7, 2021 by Maxwell-8 1 Share this post Link to post Share on other sites
Snoopy11 5,717 #3 Posted October 7, 2021 9 minutes ago, Maxwell-8 said: @Snoopy11 will be glad to help! That he will! It all depends on what rpms you wish to run, buddy! I am taking for granted that you have... or plan to remove the governor. This is the only way to achieve the performance you want in the top end. One thing you will definitely need is an ARC billet rod. You will have to clearance your cam for the rod to fit... you will need to grind in between the cam lobes, and a little off the actual rod so that the rod does not hit the cam. This is perfectly normal. There is also a tab on the upper left side of the engine that has to be ground off for clearance. Either rod would be fine. You aren't going to get that much performance from the 4.450 rod... without buying a stroker crank. You also need to remove the balance shaft. Contrary to dummies on youtube, you do not need to remove the bearings that are pressed into the block if you remove the balance shaft... I will answer question 1 first. Yes, they would work. No you shouldn't use them... LOL. Definitely run stainless from OMB warehouse. The stainless kit comes with 50 lb springs... which should get you in the 6,000rpm range. If you want, you could buy the 65 lb springs... that would get you in the 6,500+ rpm range. https://www.ombwarehouse.com/stainless-steel-valve-kit-for-predator-420-hemi.html Go with this cam... period... http://www.nrracing.com/product-p/dynomod1-390.htm If you can find some, I would go with some 1.3 ratio rockers... but most places are out of stock. These are the ones you need: https://www.ombwarehouse.com/roller-rockers-1-3-ratio-predator-420-hemi.html I have an appointment, so I will be back on later today... will answer more questions then. Don Share this post Link to post Share on other sites
Snoopy11 5,717 #4 Posted October 7, 2021 3 hours ago, @gokartgod said: Mikuni 34mm Round Don Share this post Link to post Share on other sites
Snoopy11 5,717 #5 Posted October 7, 2021 (edited) By the way... what exactly are you putting this on...? Maybe some pictures? Absolutely not trying to be rude, but just keep in mind, this site is for Wheel Horse tractors... nobody is going to be happy if they find out that they gave all this advice for a go-kart... when they thought it was for a horse... There are other sites for that... Just trying to keep everyone on the same page! Don Edited October 7, 2021 by Snoopy11 1 Share this post Link to post Share on other sites
Snoopy11 5,717 #6 Posted October 7, 2021 I would add here... I have seen little to no performance gains from a 4.450 rod. That is just my experience. Stroker crank... yes... performance gains in those... Don Share this post Link to post Share on other sites
Snoopy11 5,717 #7 Posted October 7, 2021 You could run these rockers as well... https://www.ombwarehouse.com/dj-2102-ph-pred-hemi-1-2-ratio-roll-tip-rocker-set.html Don Share this post Link to post Share on other sites
Pullstart 64,676 #8 Posted October 7, 2021 5 hours ago, Snoopy11 said: s site is for Wheel Horse tractors... n yeah, but going fast is fun too on occasion… some of us just don’t know as much about go-fast small engines. lately I’ve got this itch to get back into the stand up jet ski world. If I do, I’ll be sure to share my shortcomings and injuries with my tractor friends 2 Share this post Link to post Share on other sites
Snoopy11 5,717 #9 Posted October 7, 2021 1 hour ago, pullstart said: stand up jet ski world No way... More than injuries and successes... I need pictures of you actually doing it... Don 1 Share this post Link to post Share on other sites
Pullstart 64,676 #10 Posted October 7, 2021 10 minutes ago, Snoopy11 said: No way... More than injuries and successes... I need pictures of you actually doing it... Don If I get back into it… you know I’ll take a picture or video. No way did I ever flip… well… intentionally! My first stitches however, we’re from running myself over with a Tigershark 650 wave runner during a crash. I slipped 3 discs on my stand up chasing the coast guard ship in Lake Michigan though. Biggest. Air. Ever. sorry @@gokartgod, off topic… Share this post Link to post Share on other sites
