Talk Me Into a Big Block Swap

[sho305]

About all the clones are copy of the old gx390 honda and most all parts and performance parts interchange, except for the hemi head. Honda sued them is the story so they made that head to be different. There are other ones like champion brand that are good. Many different companies make them in china they make the briggs and kohler singles now too iirc. Some of them were not that good a lot of the older HF engines blew up but they use a different supplier now. Mostly that was from people not breaking them in before they took the governor off. The non hemi is just another clone right. The 390/420/440/460 is from bore and stroke changes, so they can use a different crank and rod and piston. Larger tends to give more torque which is good in a cart, that is why Vegas went to the 625 which is a larger version but not the same engine. But the 420 tends to be the most common and was the cheapest...and power differences are marginal with displacement changes. The vegas 460 however came with performance upgrades so it runs differently and its faster, they only sell it as a kit now last I looked. It has no governor.

[JPonLKN]

I am in the same boat, talk me into a big block, and started a similar thread in the Gas EZGo section...considering the significant cost difference between the single clones and the twin, is there any real reason to go to the big twin? What are the gains? Reading through various threads, it would appear to be smoother, but power, and ability to modify them for more RPM, power, torque appears similar, albeit less expensive for the single cylinder clones. Sounds to me like the best bank for the buck is to go with just about any of the single cylinder clones, with mild mods to get the RPM's up safely. (valve springs, rev limiter, intake filter, jets, maybe cam) Duromax appears to be the least expensive at the moment from What I can find at $300.

[sho305]

The twin is nice in some ways, it sounds cooler to some and its bigger it has more torque. All lawn engines run 3600 stock so no change in speed, there is a place making parts for HF twin now. It has pressure oiling and 9A charge the clones only 3A unless you spend more for the 18A lifan or swap to honda flywheel and stuff as posted here someplace. If you keep the starter gen on the cart you don't care anyway. The HF twin is pretty cheap for a twin at just over double a 420, the lifan sometimes can be found close to that. The vanguard is way more expensive, expensive parts are available for it and its a good engine, but cost is much higher. The twins do tend to make torque lower rpm and not want to rev a lot.

The clone 420 is cheap cheap cheap to do less than a rebuilt usually. Can be harder to make it quiet, though if you run it stock 3600 you can use a lawn muffler than might be quieter. Usually you can tweak the governor to 4K rpm on most engines. Power is not a twin but way more than stock carts especially an old tired cart. Most carts are 9-10hp a 420 supposed to be 15 but more torque due to it being larger really helps in a cart. The 421 gets the job done better than stock so its really a judgement call what one to get. I might do a twin next time mostly because I already did 420s. Someone said the home depot lifan was one sale for 302, but it has ut2 ignition with rev limit, which is better but limited rpm unless you buy the aftermarket coil. The duromax may not yet. The clones like to rev they make power about 2500 and up, and likely why they respond to mods so well. However a 420 will beat a stock cart any place have no doubt. Stock they can work great with stock clutches and everything, assuming they are not trashed and work well. You must put a rod in if you do a cam, high rpm will break a stock rod in a clone they don't oil well at high rpm and just aluminum. The VC 460 comes with a rod and cheater cam and HD block, its well worth it if you are interested in hopping up a clone a lot of it is already done and probably cheaper than you can do it for. While mine makes more power it makes a lot more rpm and so speed. But you can take that mod money and put HS gears in a cart with a twin and you are not far off, it likely cost more but its a bigger engine too. That said a stock 420 would pull HS gears too a lot better than stock engine would, but it takes go power away. On trails the clone is nice it pulls out of corners its fun to run with 22s and stock gears. The extra rpm/speed I only use to get to the next trail or burst of speed, I would not recommend screaming it for a long period get HS gears instead.

[Springbok]

I'm not looking for higher speeds. My stock motor will do 21 on flat ground with just me on it. And without seat belts or a roll bar I'd rather not drive at speeds higher than that outside of an emergency...lol. On an open golf cart, 21mph feels like 41mph in a car. I'm just looking for more hauling power when four adults are onboard. My cart has a 4" lift and rides on 22" tires.

My stock KF82 muffler is still in great shape, I'm going to try retrofitting it to the new exhaust. I imagine that the sound may be a bit louder than stock, but the stock muffler does a great job keeping my KF82 quiet so I hope that it will keep the clone that much quieter.

[Springbok]

I've got this gas generator in my garage that has what looks like a horizontal-shaft clone motor running it. Says 450cc/16hp. Not sure what kind of output shaft is on it. It appears to have an application specific side-cover on it that would need to be replaced. But I'm not sure I want to tear apart a good, working generator only to find that it has the wrong shaft or won't work for some other reason.

[slonomo]

Generator engines won't work unless you change the crank. They have a weird tapered crankshaft, and sometimes have a proprietary crank connection, especially with chinese made off brand generators. You'd be ahead of the game getting a Predator 420.

I have seen some adapters for generator tapered engines, but I have not used them. I'm not a fan of these sleeve type adapters because they can fail, not really that strong.

[Springbok]

What do you guys think of the Honda GX390 (the original motor the clones are based on)? Being a Honda are they more reliable than the clones? Seems like they're rated at similar horsepower and would check all the boxes for me as I'm trying to just get more low end power and not trying to gain tons of speed. Or are you just paying for the name? I'll pay couple extra bills for something if it's a more reliable engine.

Northern Tool sells several versions of the GX390. Some of them I can tell which features I don't need like the electric start or a special gear ratio for cement mixers, etc.

[raydhd]

With the honda you are going to have the UT-2 system. If you like the electronic governor limiting rpms maybe. BUT at twice the price of one of the other clones it isn't my choice. If you look in detail the weakest part of these engines it is valve train. I bought some genuine honda rocker arms to see if they differed in any way from the clone units. They did not. With the present situation I would get the 440 cc Duromax with its 10 bolt block and UT1 ignition system. I would add shaft rockers and HD push rods and valve springs for a really bullet proof set up with limited rpms. All this would be Way less than the honda.

[Springbok]

That 440 Duromax looks like a really nice option.

[raydhd]

I see those engines are selling out fast. Many suppliers are out of stock.