440 HP RPM redline

[Mike Szadaj]

What was the redline for a 1968 440 4bbl 375 HP motor as defined by the company? I notice that it seems each Tic-Toc-Tach has a 5000 RPM redline. Does that mean that all 440's, 383's, and Hemis had the same redline? Were factory installed tachometers just eye candy? Has anyone ever compared one to a dwell tach reading?

 

[Mike Szadaj]

By the way, what brought up this question in my mind was because I finally hooked up my Tic-Toc-Tach to the coil. Much to my amazement and joy, it works! Since I also a while back installed a quartz clock movement, I now have a fully functioning Tic-Toc-Tach.

 

[Lefty71]

Well, guessing here, but I dont think any motor came from the factory with anything tighter than '933 green stripe hemi springs ( or their equavalent) at the time of production. I'm pretty sure valve float is about to happen, if not already a problem at 5,000 rpm with those springs. So, I would conclude that from a factory engineered standpoint, you are kind of on your own so to speak if you plan to try and rev beyond that. Meaning, you arent making more power in any factory engineered car beyond 5k anyway are you, because you've past the peak power range?? Need to see some bone stock dyno numbers. Now, the 426 hemi Chrysler rated at 425@5,000, but a Hemmings dyno showed that factory stock motor to be capable of 495hp @ 5,900 rpm, stock, with cast iron manifolds. Valve float?, who knows? Not my opinions, just sayin.

 

[Mike Szadaj]

Now, the 426 hemi Chrysler rated at 425@5,000, but a Hemmings dyno showed that factory stock motor to be capable of 495hp @ 5,900 rpm, stock, with cast iron manifolds. Valve float?, who knows? Not my opinions, just sayin.

This goes back to my OP. That hemi would have had a factory tach with a 5,000 RPM redline. So what is that tach really telling you? If you obey it, you won't ever rev beyond 5 grand, and yet the engine can easily surpass that. How is a redline determined? Is it the point at which you are at risk of blowing the engine?

 

[mopar 3 B]

On a limb try not to push it beyond 5600. But have been told there is no real reason to go beyond 5400.

 

[Don Frelier]

Since the a stroke length is shorter, a 383 can be run at a higher rpm than a 440. The piston speed and resulting momentum become very high, so much that the rods and caps get stretched. That's why a race engine has light pistons and strong rods.

 

[Dennis H]

Chassis dyno stopped pulling at 4850. No need to go upstairs. Rev limiter set at 4800.
All the fun is in the basement anyway.

 

[Kern Dog]

I spin my 440/493 over 5500 and it is still pulling hard. I had it on a Chassis dyno in 2006 and it peaked at 5400. Since then I have changed several things. 3/4 point lower compression but with a bigger cam and headers. It probably peaks higher now, BUT....
You cannot trust the factory tach! It reads lower and reacts S L O W E R than a good aftermarket tach! If you are to the floor and upshifting according to the stock tach, you really need to take that into consideration.
"Redline" is a term that is hard to clearly define. Sometimes, people run past the power peak so that the engine is still pulling strong when hitting the next gear and the next.
Once I was messing around on the street, racing some guy with my 76 Camaro 350 4 speed. It was a slightly hotter than stock rebuild but not am 8000 rpm mill. I had the radio up loud and we were speeding up, then slowing for the cars we caught up to. I got around a car while in second gear and kept in it until it started sputtering. I looked down to see the tach closing in on 7000 rpms and floored the clutch pedal while lifting off of the throttle. I was so "in the moment" with the music and the excitement, I didn't upshift.
No damage done but I was worried for awhile that a rod knock was going to develop soon.

 

[Stroker68]

Since the a stroke length is shorter, a 383 can be run at a higher rpm than a 440. The piston speed and resulting momentum become very high, so much that the rods and caps get stretched. That's why a race engine has light pistons and strong rods.

I have a 383 based motor. 6800 peak. Screamers.

 

[Mike Szadaj]

I am not looking to push it to the limit. I just started wondering what the factory said the redline was on the big blocks.

That's why a race engine has light pistons and strong rods.

Luckily, while never a Six Pack, my engine has Six Pack rods in it. Must have been left overs.( It's a 1973 block)

 

[Kern Dog]

I find it funny that many used to ditch the heavier Six Pack rods and just use regular 440 LYs when the factory specifically designed the 6P as the stronger units.

 

[Dennis H]

5500 rpm.

 

[Kern Dog]

Is that a recent picture?

 

[Dennis H]

6 months, don’t remember. As soon as rev limiter was raised, broke the rod on first WOT romp.

 

[Kern Dog]

Well, I'm glad that didn't happen today or now. You have some cruisin to do, right?

 

[krazykuda]

Rev it until it blows, then back off 200 RPM....

That's your red line....

 

[66Satellite47]

The "Red Line" is a mythical number, which when exceeded, puts you into the "danger zone". The RPM potential of any engine and it's ability to live are based on MANY factors, ignition capability, valve springs, cylinder head efficiency, cam shaft design, and ultimately strength of the connecting rods/bolts & crank shaft along with good oil supply. A stock BB Mopar RPM is limited mostly by cylinder heads. Much above 5000 doesn't yield much. Better flowing heads & bigger cam can bump that up a fair amount. The crank & rods are generally good for lots more.

 

[moparedtn]

Factory rating for the '68 440HP was 375hp @ 4600 and 480lb-ft @ 3200.
If the engine is stockity-stock, letting her run much past 5k RPM is pretty much a waste.
I know most of mine over the years (all 440's from that time period) were pretty much
willing to go past 5k, but there wasn't much point to it.

 

[Cranky]

ChryCo did upgrade to the larger heavier 6 pack rods but they installed the same bolts the LY has.....and that is the Achilles heel.

 

[1 Wild R/T]

I find it funny that many used to ditch the heavier Six Pack rods and just use regular 440 LYs when the factory specifically designed the 6P as the stronger units.

Those Sixpack rods are heavy, they add zero metal around the big end & use the same 3/8" bolts... The big end & bolts are the areas where failure occurs... Instead they added material in the beam section of the rod which rarely breaks so honestly they are no stronger then LY rods & the extra weight actually creates more load as the RPM's go up...