RPM or redline max how to figure???

[srpntlair1]

ok for the motor gods here, FIREfighter, chrycho and the rest...first of all thank you for all the help and info over the last few months my main question is...how do I figure a redline or max output or whatever you wanna call it as far as a motor can handle before it flies apart. or more specifically what aspects of my motor and drivetrain would you need to calculate that figure if it is possible. just wanna make sure I am within perameters of what she can and can't  do

[Ghoste]

Aside from the old joke about holding it wide open until it blows up and then backing off 100 rpm, it depends partly on where your intake, exhaust, cam and valvetrain have established your powerband and mostly on modifications to the bottom end and oiling system.  What changes did you make to those areas?

[jg68]

ok for the motor gods here, FIREfighter, chrycho and the rest...first of all thank you for all the help and info over the last few months my main question is...how do I figure a redline or max output or whatever you wanna call it as far as a motor can handle before it flies apart. or more specifically what aspects of my motor and drivetrain would you need to calculate that figure if it is possible. just wanna make sure I am within perameters of what she can and can't  do

It mainly depends on head flow & cam, what is the combo , i had a 451 low-deck that i shifted at 57-5800 & thats all it needed, anymore & it slowed down, it would buzz through the 1/4 at 6300, but it was finished at 6000, now this combo had iron heads, they are useally dead in the water at 6000, but the cam was good to 6700, so the heads were holding it back, to me, playing it safe with any BB mopar with stock caps, i wouldn't venture over 64-6500 to much, you'll just kill parts & stress things out, another thing you can do is, throw it on a chassis dyno & see were it peaks, this will be your shifting point, but that could still change once your take it down the track, but it'll give you a very good ball park, get you a shift light & rev. limiter too, they are your friends

[aifilaw]

technically, valve train is the deciding factor.... if you have a solid roller rocker and a well built/balanced engine you can spin it to obscene speeds even after it stops making "power".
The simple fact of the matter in reality is that redline is a function (in order of importance) of the valvetrain, camshaft, intake, heads, bore/stroke, and a few other factors.

To detirmine the proper redline for your engine, have it dyno'd. Look at your HP (not torque) curve and note when it peaks. Add 500 RPM and this is where people usually race-shift, add 700 RPM and this is where the redline should be (and by red line I mean, do not cross, its not only a waste, but a good way to destroy things).
Valve float and poor spring pressures are the primary reason why people have a redline and should adhere to it.

[firefighter3931]

ok for the motor gods here, FIREfighter, chrycho and the rest...first of all thank you for all the help and info over the last few months my main question is...how do I figure a redline or max output or whatever you wanna call it as far as a motor can handle before it flies apart. or more specifically what aspects of my motor and drivetrain would you need to calculate that figure if it is possible. just wanna make sure I am within perameters of what she can and can't  do

It mainly depends on head flow & cam, what is the combo , i had a 451 low-deck that i shifted at 57-5800 & thats all it needed, anymore & it slowed down, it would buzz through the 1/4 at 6300, but it was finished at 6000, now this combo had iron heads, they are useally dead in the water at 6000, but the cam was good to 6700, so the heads were holding it back, to me, playing it safe with any BB mopar with stock caps, i wouldn't venture over 64-6500 to much, you'll just kill parts & stress things out, another thing you can do is, throw it on a chassis dyno & see were it peaks, this will be your shifting point, but that could still change once your take it down the track, but it'll give you a very good ball park, get you a shift light & rev. limiter too, they are your friends

Joe's advice is bang on. The limiting factors are cylinder head flow and the cam. Regardless of the cam's duration the hydraulic lifter will limit the max rpm. Valvetrain stability becomes an issue above 6000 rpm with a hydraulic cam (lifter pump up = valve float) so that is a safe shift point. Unless the heads are heavily ported then the power will fall off at 6k anyway so there's no point in over revving it. 

I like rev limiters because they will save your bacon in the event of a missed shift (4 speed) or accidental shift into neutral (auto trans) 


As Joe mentioned ; the chassis dyno will give you lots of useful information and can be used to dial in the fuel and ignition curves. It's a valuable tuning tool that you should consider using to obtain the best possible performance for your combination. 



Ron

[Challenger340]

Sometimes, a good way to think of it is this way;

As long as the engine can "make power", and keep "pulling hard" against the load, it'll hang in there, and so will "whatever" quality parts !

Destructive harmonics, that cause the failures in even the BEST parts, occur when the engine starts to "freewheel", or can't keep pulling "hard" against the load, for whatever reason, lack of head, Cam, Valvespring etc.

Thats why sometimes you see guys running "less than stellar" pieces at high rpm's with no problems, and others with "gold" stuff, grenading their junk all over the track !
Keep the "mill" pulling against the load, or shift, and get it down where it can !

Just my 2 cents,

Bob out.

[MOPARHOUND!]

Sometimes, a good way to think of it is this way;

As long as the engine can "make power", and keep "pulling hard" against the load, it'll hang in there, and so will "whatever" quality parts !

Destructive harmonics, that cause the failures in even the BEST parts, occur when the engine starts to "freewheel", or can't keep pulling "hard" against the load, for whatever reason, lack of head, Cam, Valvespring etc.

Thats why sometimes you see guys running "less than stellar" pieces at high rpm's with no problems, and others with "gold" stuff, grenading their junk all over the track !
Keep the "mill" pulling against the load, or shift, and get it down where it can !

Just my 2 cents,

Bob out.

Also the reason you don't high rev an engine in neutral or park too show off for your buddies, etc.  Very hard on parts.