OzFab
Well-known member
Just about everything works in theory, it's not until you put the theory into prictice that you find out it doesn't work 
40 Series TC Gearing
- Thread starter aham2003
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bob58o
SuckSqueezeBangBlow
Here is some info on "Big Block" RPMs
Some have stuck a rod in this engine, it could have been lack of break in time I don't know. If I were you and had the cash I'd get the rod and cheater cam from Vegas. That cam will get you some rpm you will not get much over 5K without a cam, and that cam is cheap. You not supposed to need all new valvetrain with that cam like others do, you need springs I was told and can run the button on both valves, might need pushrods if you going to scream it a lot. The rod is key, you really need it if you want to spin it hard, the cam is too the stock one is not that good over 4K. If you get the Vegas rod its longer (the 460 rod) it will raise your compression some, so note that or get std 390 rod and cut your head what you want. I only cut .050 and run 4 degree key so I can run cheap gas. That is cheapest way, really consider the whole 460 engine it has all the parts to run 6K rpm and the cam, really for the cost its worth it and the block is better to boot. You can put a larger cam in the 460 and some valvetrain parts for more yet, its nice you already have the rod in it. But all depends on what you want to spend, what motor you want. You can't run any cam with stock rod it will blow, running at 6K will blow the stock rod as well if you can get it to rev that hard stock. Most stock cam only rev to 5500 at most down a road in a cart, I think mine only 5200 or something and I have 1.3 rockers in it too. A 390 block will usually rev 500 more than a similar 420.
You must richen up the carb if you mod the airbox or exhaust, its a given or it wont run well. Some have problems with the plug get a ngk from NR racing or someone if you do. Mine still has stock plug in it no issues. If its lean you can put the choke on part way and it will run better, is how you can tell. Jet drill sets are $10 on amazon or get a torch tip cleaner and file it out.
The lifan has a rev limit coil you have to buy the honda replacement ut2 from NR to get rid of it, its the only one I know of so far.
Stock clone usually run about 4300 and float valves. Run about 5300 in a lifted cart with HD springs and advance key, give or take.
I recommend running 10 gal of fuel through it before you go over 4500 rpm to break them in. It took mine a while I could feel it.
And
My clone has the 1.3 rockers, ported and .050 cut head, custom 1" header into car muffler, car airbox, jetted stock carb, 4 degree key, HD springs, etc. It does about 5200 best I can tell with the cheap tach that dies at over 5K rpm, that is 38mph on 22s in my cart. But it pulls pretty good from about 3K up, pulls hard at 3500-4400, pulls hardest at 4K. Stock cam, all stock in the block except for governor removal. Above maybe 4600 power is falling off, above 5K it does not have much.
It might pull more rpm with a larger carb I don't know, but been told with stock cam you don't get much more. A cam would really take better advantage of my ported head and a larger carb. Geoff cheap cam said to pull 6K or near it. Its the stock cam with more duration, so it can rev free and blow right by 4500 where the stock cam falls off. It does make more power, not a ton, but the extra rpm make more HP for sure. A larger cam will do more but requires HD valvetrain maybe other mods too. Big cam will open the valves higher and faster, the cheater cam just opens them same but longer....I was told....so valvetrain gets more rpm but not more lift forces on it. Though running 1.3 rockers with a lower lift cam is same as higher lift cam 1:1 rockers, but I don't think it gets the lift a big cam does. You can see the lift numbers on some sites.
---------- Post added at 09:08 PM ---------- Previous post was at 09:03 PM ----------
40 MPH with 18" Tires and 6:1 Gear Ratio is 4500 RPM.
Which is about what I would expect with stock cam and stock springs.
Some have stuck a rod in this engine, it could have been lack of break in time I don't know. If I were you and had the cash I'd get the rod and cheater cam from Vegas. That cam will get you some rpm you will not get much over 5K without a cam, and that cam is cheap. You not supposed to need all new valvetrain with that cam like others do, you need springs I was told and can run the button on both valves, might need pushrods if you going to scream it a lot. The rod is key, you really need it if you want to spin it hard, the cam is too the stock one is not that good over 4K. If you get the Vegas rod its longer (the 460 rod) it will raise your compression some, so note that or get std 390 rod and cut your head what you want. I only cut .050 and run 4 degree key so I can run cheap gas. That is cheapest way, really consider the whole 460 engine it has all the parts to run 6K rpm and the cam, really for the cost its worth it and the block is better to boot. You can put a larger cam in the 460 and some valvetrain parts for more yet, its nice you already have the rod in it. But all depends on what you want to spend, what motor you want. You can't run any cam with stock rod it will blow, running at 6K will blow the stock rod as well if you can get it to rev that hard stock. Most stock cam only rev to 5500 at most down a road in a cart, I think mine only 5200 or something and I have 1.3 rockers in it too. A 390 block will usually rev 500 more than a similar 420.
You must richen up the carb if you mod the airbox or exhaust, its a given or it wont run well. Some have problems with the plug get a ngk from NR racing or someone if you do. Mine still has stock plug in it no issues. If its lean you can put the choke on part way and it will run better, is how you can tell. Jet drill sets are $10 on amazon or get a torch tip cleaner and file it out.
The lifan has a rev limit coil you have to buy the honda replacement ut2 from NR to get rid of it, its the only one I know of so far.
Stock clone usually run about 4300 and float valves. Run about 5300 in a lifted cart with HD springs and advance key, give or take.
I recommend running 10 gal of fuel through it before you go over 4500 rpm to break them in. It took mine a while I could feel it.
And
My clone has the 1.3 rockers, ported and .050 cut head, custom 1" header into car muffler, car airbox, jetted stock carb, 4 degree key, HD springs, etc. It does about 5200 best I can tell with the cheap tach that dies at over 5K rpm, that is 38mph on 22s in my cart. But it pulls pretty good from about 3K up, pulls hard at 3500-4400, pulls hardest at 4K. Stock cam, all stock in the block except for governor removal. Above maybe 4600 power is falling off, above 5K it does not have much.
It might pull more rpm with a larger carb I don't know, but been told with stock cam you don't get much more. A cam would really take better advantage of my ported head and a larger carb. Geoff cheap cam said to pull 6K or near it. Its the stock cam with more duration, so it can rev free and blow right by 4500 where the stock cam falls off. It does make more power, not a ton, but the extra rpm make more HP for sure. A larger cam will do more but requires HD valvetrain maybe other mods too. Big cam will open the valves higher and faster, the cheater cam just opens them same but longer....I was told....so valvetrain gets more rpm but not more lift forces on it. Though running 1.3 rockers with a lower lift cam is same as higher lift cam 1:1 rockers, but I don't think it gets the lift a big cam does. You can see the lift numbers on some sites.
---------- Post added at 09:08 PM ---------- Previous post was at 09:03 PM ----------
40 MPH with 18" Tires and 6:1 Gear Ratio is 4500 RPM.
Which is about what I would expect with stock cam and stock springs.
Poboy kartman
Senior Moments Member
Just about everything works in theory, it's not until you put the theory into prictice that you find out it doesn't work
True...but for the most part....we are dealing with reasonable expectations based on past experiences and very little theory...
Theory is speculation....calculations are concrete mathematical equations...only subject to the flaws in imput or corrupt equations....but repeatable...and much more likely to be fairly accurate than theory.
OzFab
Well-known member
However, as we've all seen many times before today, a speed calc app will spit out correct numbers based on input but, the numbers input are theoretical, that's when the practice & experience are needed... which is why forums such as this exist, for the experienced to pass on their knowledge &experience to those less experienced... now I'm just rambling...- Status