In need of safe higher rpm's

[Notsoezgo]

So I ordered another Duromax 440 and I would like to safely break in then modify this engine to be able to higher rpm's (6000?). Could I get opinions on what I need for this engine?

[raydhd]

Billet connecting rod, HD valve springs and push rods, preferably shaft based higher ratio rocker arms while you are ordering the push rods. For more valve train safety automotive type valves, valve retainers and keepers. Over 5600 or so rpms a billet flywheel should be added. Also to make power up in the 6k range carb and camshaft upgrades will be needed. P.S. I bumped up my $650 VC 460 to give you some ideas.

[slonomo]

HD valve springs and chromoly or billet pushrods at the minimum. If you want more power, get a camshaft. If you want max power and rpm get the Arc billet rod and a Mikuni carb setup. I don't know of any sponsors here that advertise their parts to fit the Duromax, but Vegas Carts has 460 parts still and they are supposed to be "clone" engines so.... There are other places to shop, just do a google on "honda clone engine performance" and you'll find a slew.

[Notsoezgo]

Originally Posted by slonomo

HD valve springs and chromoly or billet pushrods at the minimum. If you want more power, get a camshaft. If you want max power and rpm get the Arc billet rod and a Mikuni carb setup. I don't know of any sponsors here that advertise their parts to fit the Duromax, but Vegas Carts has 460 parts still and they are supposed to be "clone" engines so.... There are other places to shop, just do a google on "honda clone engine performance" and you'll find a slew.

I'm wondering if I would be safe enough up to say 5000 rpm with just HD valve springs and chomoly pushrods. I'm not planning to be past 4000 for long periods

[raydhd]

I ran the early VC 460 for almost 200 hours which had the stock clone cast rod. Most of the running was between 3000-4000 rpms. I did do some really short trips to my self imposed red line of 5200 rpms. I had the HD springs and push rods along with 1.3 ratio stud mounted billet rockers. BUT a safer way is just to add an ARC billet rod that can be bought at NRracing,Bullfrog racing or ARC themselves. I say this because IF the rod lets go it usually totals the engine.

[Notsoezgo]

Originally Posted by raydhd

I ran the early VC 460 for almost 200 hours which had the stock clone cast rod. Most of the running was between 3000-4000 rpms. I did do some really short trips to my self imposed red line of 5200 rpms. I had the HD springs and push rods along with 1.3 ratio stud mounted billet rockers. BUT a safer way is just to add an ARC billet rod that can be bought at NRracing,Bullfrog racing or ARC themselves. I say this because IF the rod lets go it usually totals the engine.

Good point raydhd, doesn't Vegas Carts also sell a good billet rod?

[raydhd]

No, at the moment they don't have any connecting rods. The gen 3 combo long rod that is in my cart presently with their flat top piston was a real bargain. I had asked Geoff if production was going to return and he said yes possibly at the end of the month BUT he had back orders of more than 160 of them. BUT the long rod will only their piston where the ARC 4.41 unit goes with the stock dished pistons. P.S. If I were starting from scratch like you are I would also start with the 440 Duromax with its 10 bolt block and 92 mm bore

[Notsoezgo]

Originally Posted by raydhd

No, at the moment they don't have any connecting rods. The gen 3 combo long rod that is in my cart presently with their flat top piston was a real bargain. I had asked Geoff if production was going to return and he said yes possibly at the end of the month BUT he had back orders of more than 160 of them. BUT the long rod will only their piston where the ARC 4.41 unit goes with the stock dished pistons. P.S. If I were starting from scratch like you are I would also start with the 440 Duromax with its 10 bolt block and 92 mm bore

I'll check out the ARC 4.41 rod, thanks. Red beard has built 3 carts with Duromax engines I believe. On your first 460 with the cast Rod how did you choose the 5200 rpm redline?

[raydhd]

That was the recommendation at the time. Again at the time I had the stock clone cam with added 1.3 rockers. It would rush up to about 4500 rpms and the just wend its way up to red line. Without the 1.3's it would taper off in the 3800 rpm range. I am still using that original VC 460 it just has been upgraded to the Gen 3 VC rod and piston along with the torque cam. Then on top a .075 milled and ported head with NRracing 1.3 shaft rockers with their matching push rods.

[slonomo]

Originally Posted by Notsoezgo

I'm wondering if I would be safe enough up to say 5000 rpm with just HD valve springs and chomoly pushrods. I'm not planning to be past 4000 for long periods

I was told the soft cast aluminum connecting rods are good up to 4500 rpm. I'm sure if you run in that rpm for long periods of time it will oval out the rod eventually. Keeping clean clear oil is key here. I would say if you are in doubt, spend the $130 and get the Arc rod, just make sure you get the proper length or you'll have an issue with clearance or with low compression depending if you go longer or shorter. If you look at the Arc rods they have a spec on them. I would measure your rod and go from there.

If you are going that far, you might as well get the dremel out and clean up and port match the head. The short side radius is fat on these heads and will clean up easily. You can remove all the casting marks. Port matching is super easy as well. Just make sure you use some dye so you don't take too much material off.

You can shave the head for more compression, but I'm not into that, I like a lower compression engine for easy starts and less chance of blowing head gaskets out. Also if you shave the head you have to watch your valve clearances if you use performance cam and rocker arms. A bit more tricky.

The carbs aren't all that good on these carbs. There are lots of alternatives but clearance is an issue with some carts. I'm partial to the Mikuni CV carbs, but the VM series is also excellent, both easy to work on and tune. These are the same carbs that motorcycles use so you'll have excellent idle, smooth acceleration, and improved response. Jetting can be tricky, but it's not rocket science.