Realistic max rpm for 18.5 oppy with few mods? Save me from myself!

Realistic RPM for 18.5 oppy with intake and exhaust mods???

I'm hitting 6,200rpm pretty easily but even ththough I'm new to this I feel like im pushing my luck. Any advice? Im building it with/for my son and hate to grenade the motor, but gotta admit I'm overwhelmed by the crazy eyes and maniacal laughter when the new exhaust starts roaring.

I'm not an expert on these, I like them and run them myself.  From what I have seen, if you still have the governor installed, passing 4000 starts to get risky.  Without the governor, I have read where people racing them will wind them up to 6000.  Now if you have done some serious performance mods and added billet hardware, I have heard some pushing to 8000.

If you want to be safe and longer lasting, I would keep it 4k and under.  Factory max is 3600.  If you are looking for speed and take-off, I would do that with pulley swaps where possible or sprocket gearing depending on your application.



ps, these are starting to get old and they can blow even at normal factory rpm.  A lot of that is how you treat it.

Thanks for the reply, I appreciate it!

Check your oil before every time you ride it, oppys have a habit of burning oil and low on oil is the #1 cause of oppy failures, If it’s for the kid I would definitely Just leave stock governed throttle on it if you want it to last I personally wouldn’t be turning that high of rpms myself, but they can take some abuse as long as they are lubed up

What everyone else said and, there's not a set limit necessarily where it will just explode. Over time connecting rods are stressed and eventually will fail. You might get away with running it hard for a certain amount of time, but it's hard on stock cast rods. I haven't really blown up any engines myself. You can run them fairly hard for quite awhile. But it's a time and stress thing.

The guys who race go carts and tractors ect with stock connecting rods usually change them out every few races. As far as I know anyway. My guess would be 6000rpm is a bit high for all the time use. I would either run it hard and not worry about it, seeing how long it holds up (and if it blows apart build another one) or find some billet rods and then you (probably) won't have any issue.

Do you have stock valve springs and get to 6000? And what kinda tach are you using? I'm planning on building an opposed pretty soon also.