well after my motor died, i would like to know the safe rev range for the motor, it's an 81 300. i took it out once and revved it alittle hard and it started to smoke burning oil like crazy. so wanna be safe this time.

 

the 300 powerband drops at 3500. I try to keep mine under 4000. Motor isn't made for high reving. Most of my shifts are done in the 2000's.

 

Same here, most of my shifts are in the 1500 to 2500 range, its rare when my "300" sees 3000 rpm. Its got 3.55 gears with stock tires and pulls strong in that rpm range. I believe I read somewhere this engine has a 4 inch piston with a 4 inch stroke which works out to being a big piston moving a long way which doesnt lend well to high revs. If it had little pistons and a short stroke then you could rev the p*ss out of it with out blowing it up but then it wouldnt have the torque its has.

 

what exactly failed?

 

the bore is 4 inch but the stroke is 3.98. my truck hits 3000 rpm shifts alot. i have 3.55s with 35s and if u mash the gas in first it hits 3000 eazy but thats the only gear it will.

 

I have a NP435 tranny and 3.54 gears.

In Granny I can reach 2500 rpm
1st 3000
2 3500, and the power starts to drop
3 3000 at 70 mph

90 mph is only 3400 in my truck.

 

My truck an 80 f100 which I just installed a tach in hits 4grand alot.
I have the offenhauser c intake with a 390 cfm 4v holley, msd coil blaster 2, msd 6a box, internals original with 180,000 miles on it pushed by a 3 speed tranny with the factory rear end.
In 1st gear I hit around 45 mph in 4000 rpm
In 2nd gear I hit around 65mph in 3800 rpm
In 3rd it keeps going and going and going lol

Future plans are to rebuild a motor with better internals, head work porting, twin turbos, 4 speed tranny, intercooler, oil cooler, home made headers. Im hoping for harder rpm's, faster response and a shot out off the line. Dont have any numbers of my set up now. Maybe I will take it to the track sometime, doubt it just like fooling around with the ole beast.

 

I have redline set on the tach pointer at 4K. It falls off the powerband bigtime after 3.5 even with a 4-bbl and a header. No need to wind the stock motor, all you'll git yerself is noise and worn parts. Even when I throw the cam in, I expect she'll sign off around 4.5, so there will be a rev limiter set for 5, and there ain't no more.

Yeah, what exactly failed? C'mon, tell us!

 

well i know i thru a rod, but i think i also snapped the crank. will be breaking it apart this week. i know i caused some of the(well all of it). i was stuck and it was getting dark and late and i was 4wheelin alone and i guess i over revved it and after that it was burning alot of oil. then i tried to get my friends truck and tow it back and the motor started knockin and i stopped checked it. added oil, and tryed to limp it to the next exit but that didn't happed.

 

i know u can safely, but not to wise, rev these up to 5000 rpm. it has 7 mains and built like a **** brick house, so it will take the rpm. its stupid to ever take it over 3500 and 3800-4000 because the peak hp is around 35-3800. althought they sound mean as hell being wound up to 4K

 

Mine used to sound like a PO'ed bumblebee in a Folgers can until I slapped the 3" pipes on 'er...

If you balance the lower end and use ARP fasteners (Fisher damper is a good piece too, but you can use a new stock one for warm street use), you can get 5 grand out of these things all day long, even 6 for brief spurts, if you have a good set of rods. A little shotpeening and magnafluxing never hurts. A windage tray helps too. I suppose a hi-volume oil pump is also a good insurance policy, but you might really want to get a better pump driveshaft and double-pin the distributor gear to go with that...

 

ya i meant a brick **** house...dam dislexia

 

The only real reservations I have about winding the bejezus out of the stock bottom end are the somewhat thin main journals (~2.4"---3" would be nice...) combined with the long arm. Plus, with that long arm, the pistons approach "Ludicrous Speed" (Spaceballs) when you spin 'er up there. That's a bit of stress on the rods, too, as they have the unenviable job of hanging onto that mass as it reverses direction at the top of the stroke (rods are actually stronger in compression than in tension or shear, go figure, right?). Which is incidentally when most of rod failure occurs, unless you blow a head gasket and hydraulic lock the cylinder. Cap lets go, small-end breaks, take your pick, it' still a bad day ...

Better to build these tractor motors for torque monsters and keep the powerband all under five grand or so, unless you want to set land speed records, or win mud bogs and tractor pulls. You can get between 250-300 reliable horsepower out of these things, but if you want the power, there's no replacement for displacement. A 351W will bolt in without too much trouble, and there's a mighty tempting $troker kit available and all sorts of good head$ and roller cam$, etc.

That said, cleaning up the head a little is worth some extra huevos within a sane RPM range. Especially that typical Ford disaster of an exhaust port. Won't lose any low-end either if you do it right. Might I suggest a rev limiter? One's going on here, for sure! Right now I rely on the tach pointer and that very-much-less-than-butter-shifting NP 435, but when the cam goes in, all bets are off!

 

You guys that shift at 1500 rpm - I don't know how you do it. I know that revving the whee out of any engine isn't good for it, but neither is lugging; you'll wear out the mains hardcore. Slow driving mode is this: Punch gas until 5" of vacuum, hold it there, when I'm at 10" vac/3000 rpm, shift. Repeat.

Oh yeah, that's with a boat on and/or going uphill... I never pay that much attention when I'm not loaded. Anyway, I know I still never shift below about 2300 rpm..... ever....

 

I shift at 2K when normal driving, 3K when really trying to move.