440 DuroMax valve train?

Big Bob

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I had my engine torn apart to put in a cam and such. Like the dummy I am I lost the valve lash caps! I ordered new Honda GX 390 caps and seals ( My engine had no seals) So I finally got them and the caps seem much too large diameter wise. I haven't put clay into them but I think the cap actually rests and pushs on the valve keepers not the valve stem. I checked the fit of the seals and they are larger than the valve stem as well. Then I tried the lash caps off my 208 Briggs clone and they seem to fit fine. I didn't measure but I am pretty sure the 440 valve stems and 208 valve stems are the same size. Being the engine, which I've had over a year, never had valve seals I'm thinking of putting the smaller small block clone valve lash caps on. No seals no problem I assume.

Just wanted to run this by you before I pull the trigger.
 

Hellion

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Don't be a dummy! 😄
Get a tackle box, an old muffin tin or one of those magnetized nut 'n bolt trays to hold all the tiny bits as you disassemble.

You really have to know your engine series (by precise code and serial number) as Honda and clone engine specs (features) are all over the place. You can't just order "Honda GX 390" lash caps or other parts and expect them to apply to, or fit your engine. There's probably a hundred different GX 390 engines (GX 390A, GX 390B, GX 390C. GX 390D, 1234...) in the lineup with various tweaks and improvements, it's maddening.
Some Hondas have the valve keeper over the valve stem, some don't.

Don't be "pretty sure" but measure to avoid disappointment and/or look up the parts numbers.

Briggs isn't nearly as bad because they made the parts more interchangeable over the course of development...at least before they too sold out to China making clone OHV engines for them.
 

Big Bob

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Don't be a dummy! 😄
Get a tackle box, an old muffin tin or one of those magnetized nut 'n bolt trays to hold all the tiny bits as you disassemble.


I very seldom loose stuff. I have no idea how I lost them.
It is curious that the valve stems are so slim. I have a briggs CR950 and the valve stems are the same size.

I'll start that research thing. Just about everywhere I look it shows Honda 390, Predator 420, Duromax 440.
 

Big Bob

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Why not just get a replacement from DuroMax?

I've contacted them online to find where I can do that and haven't had any luck. If you have a link to factory Duromax parts please share.

The valve stems on the 440 are the same as the small block engines. 5.5 mm. Most of the big blocks, GX390/Pred 420 use a 6.5MM valve stem. Pretty sure that is why there are no valve seals on this. The small block seals won't work and the big block seals won't work. The small block seals don't fit over the valve guides, but do fit on the valve stem. The big block seals fit the valve guide perfect but are 6.5 mm on a 5.5mm seal! The small block Honda and clone lash caps fit perfect. The big block valve lash caps are way too big.
Hopefully Duromax will contact me back.

I've run this engine for for almost a year in a Go Kart I built with basic mods. Re-Jetted the carb, exhaust. I am putting it in a golf cart now and have added a 275 cam, billet rod, billet side cover, billet flywheel, Mikuni carb. I am probably going to a different valve train. Roller rockers and adjustable pushrods. The stock rockers on these are at an odd angle in my opinion. It's like they put in 1/4" too short push rods. I'll get a pic and post it later.

So to anyone wanting to go with a big bore 440 Duromax remember, measure your valve stems before ordering stuff! Like most clone Chinese stuff there can be a variance in parts they install. On my 440 the ARC rod, Flywheel, Side Cover all fit perfect. I did have to do a little grinding on the camshaft to clear the rod. But that is common.
 

Big Bob

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Here are some pics. The pushrods are stock 390/420/440 lenght at a tad over 6.5" The stock rockers sit pretty fair. The Champion shaft rockers look like way too much angle. The engine is at TDC and set to just touching the valve cap. Pics may not be in order. The third pic should be of the extreme angle of the Chamion shaft rockers.
 

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Big Bob

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I think the only way I can run the Champion, or probably any aftermarket rocker, is if I get longer push rods.

Send me your thoughts.
 

Big Bob

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Don't be a dummy! 😄
Get a tackle box, an old muffin tin or one of those magnetized nut 'n bolt trays to hold all the tiny bits as you disassemble.

You really have to know your engine series (by precise code and serial number) as Honda and clone engine specs (features) are all over the place. You can't just order "Honda GX 390" lash caps or other parts and expect them to apply to, or fit your engine. There's probably a hundred different GX 390 engines (GX 390A, GX 390B, GX 390C. GX 390D, 1234...) in the lineup with various tweaks and improvements, it's maddening.
Some Hondas have the valve keeper over the valve stem, some don't.

Don't be "pretty sure" but measure to avoid disappointment and/or look up the parts numbers.

Briggs isn't nearly as bad because they made the parts more interchangeable over the course of development...at least before they too sold out to China making clone OHV engines for them.



LOL. back to this. I bet I did not loose my big block caps. It;s just I figured they would be bigger. They are on the 390 and I assume the 420. But on the 440 they are the same as a 212 or clone small block. My other engine is a Ducor 208 cc block with a Briggs 208 head. The 440 caps ended up in that tub.

I use a pill box that has 14 compartments for Jets and stuff like these tiny caps and seals. You can pick those up cheap and they really help in organization. I have a pill box for those tiny cable ends and such. On bigger stuff like bolts and such I use kitchen type containers with snap lids. I am a 71 yr old fart on a walker for at least another 6 months. Just like every mechanic I lose stuff once in a while. LOL
 

Big Bob

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BTW, on those Champion shaft rockers (which I had on my other engine and liked them) are built on a pedestal. I think I could machine the pedestal down around 1/4" and level them out. If not I'll order some roller rockers and adjustable pushrods.
 

Denny

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It’s not so much about them being level as it is about them riding on the center of the valve stem. You want the rocker tip to ride in the center because you don’t want to wear stems, guides, or bend valves.
 

Big Bob

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It looks like longer pushrods are needed. Those severe angles kinda bother me.

Yup, I think it would run for 3 minutes and start getting real noisy as it sends metal into the crankcase causing Armageddon Destruction and may even cause puppies to die. No way would I crank it up. Even the factory angle looks a little uneven. I think the new DYNO 275 Cam has a different base circle. There's a name for that but I forget what it's called. A lot of aftermarket cams are like that. The lobes indeed have more lift and duration but the base is built different so there is more clearance for the connection rod. I ain't pulling the cam out, but I wager the base circle of the factory cam is larger than the DYNO Cam.



. 1694886276806.jpeg
 

Big Bob

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It’s not so much about them being level as it is about them riding on the center of the valve stem. You want the rocker tip to ride in the center because you don’t want to wear stems, guides, or bend valves.
Absolutely. Like I said, that is a 3 minute run time affair. With longer push rods it would be okay. Everythink else on this engine is good to go. I guess I'll bite the bullet and go with some roller rockers and longer cut to fit push rods, Not sure if I want 1.2 or 1.3 ratio rockers. I have 40 lb springs in it. Any advice on rockers/valve train/source?
 
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