RPM limit for stock 383 & 440 bottom end?

[MizzouRT]

What are the rev limits on a factory 383 & 440 engines bottom end?  I never used a solid lifter cam so the hydraulic lifters were always the limiting factor.  With a solid lifter camkit, what is the stock bottom end good for?  I am guessing the 383 will have a higher limit due to the shorter stroke?  Thanks

[Road_Runner]

Taking into account that I did spin a bearing once (I missed a shift and saw the rpm coming back down past 7K when I looked down at the tach), I regularly shifted between 6500 & 7000 rpm in my 383 Roadrunner.  The top end was maxxed out but other than a good rebuild including double valve spring Crane Cam setup we didn't do anything special to the bottom half of the motor.  Again, it might have been stupid teenager luck, but the car seemed to hold up fine at those rpms.

Later, Jim

[73restomod]

The real key is piston speed, with factory parts, anything over 4000 ft/ min is really pushing it. With a cast crankshaft/pistons its more like 3500ft/min. With high quality aftermarket parts, 5000-4500 ft/min. is easily dealt with. The formula is
Rpm x stroke /6 = mean ft/ min

So a stock forged crank 383 would be fine up to about 7500 saying the pistons could take it....

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[HP_Cuda]

The real question you should ask is where do I make peak horsepower and torque. Basically anything after that you have hit the point of diminishing returns. Most big blocks probably stay under 5500-6000rpm and that's a generalization but probably the closest you will get to an answer.

The other thing you have to ask yourself is: Are my components balanced and up to the task? As you increase rpm and sustain it the smallest variances in your valve train and bottom end become large issues. Then you ask yourself, why is my crank walking the mains? Or what the heck is valve float?

A rev limiter can really be your friend if you miss a shift or have a foot made of demon desire!

 
B

[MizzouRT]

The comparison I had in mind was to the 435 hp solid lifter 427 that Bill Stephens always likes on Mecum.  It had the bigger heads and a factory redline of 6500 rpm.  With the 4 bolt mains, my understanding is the 427 stock bottom end was (like the 426) good for 7000 rpm.  Even if you put freer flowing heads and a solid lifter cam in a 440, I'm guessing the stock bottom with the forged crank might be maxing out around 6500 rpm?

[HP_Cuda]

I would guess that you would be in the 6500-7000rpm range if you have quality components and they are balanced like the dickens! Again it's hard to say without looking at Dyno output. You might be spinning a motor for no real effect.

[73restomod]

The other factor is the amount of force put into the main webbing of the block. This is determined by piston speed and the rotating mass. A heavier bob weight will cause main cap walk a lot sooner. I've seen 2 bolt main 440s turn over 8k without coming apart, of course they had flyweight rotating assemblies, studs, & billet main caps too.

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[1970 RT Challenger 1970]

It all depends on how good your engine was built by the factory and how good the parts are.

I remember years ago, my father blew up a big block engine in his station wagon just passing a car at 70-80 MPH.

The engine had 89,000 miles on it and one of the connecting rods broke. Sounded like all hell broke loose when it happened. Had a real nice clunking sound idling when we stopped, but it kept running.

Checked the oil right away and it was full of anti freeze to the top of the dip stick. We got towed and needed a new engine.

[dodge freak 2]

Any stock bottom end is 40 some years old now, I would say 5,500 max. How much when brand new ?

[Moparal]

If you have a stock bottom end and factory heads that haven't even been worked on porting wise, you should keep your power band under 6k. Your heads will not flow like you think they will.  Tq is what your after. winding up a 383 may seem cool, but the hp will fall off and the rpms will be of no use