1) How fast your crank will spin providing your valvetrain will allow
2) As fast as your crank will spin safely
3) Where your engine stops making peak horsepower




I've heard all three things in the past day... I've ALWAYS known redline to be #1 and now I'm being told I was wrong by some people, and right by others. Who is correct?

 

#1 is the most logical, #2 is a different way of saying #1, and #3 could be like 2k for some cars

Bruce (90RS305)

 

Whatever comes first, depending on the build.

 

http://mclements.net/mrc-blog/blog-030725.html

that link seems to support #1 most.

 

whoever suggested #3 has a twisted sense of logic... the rpm 4 peak HP is called exactly that... the HP peak...

 

Spinning the motor past the HP peak is kinda dumb since it won't get you anywhere anyway.

Whats the point of this topic anyway?

-- Joe

 

Just wondering for the sake of argument.

 

You want to spin it a little over the HP peak When you go to shift so you stay in the hp range. This is Dependent on gear ratios

 

I've always known it to be #1 as well. What I "learned" through the McDonald's parking lot monkey spank grapevine is that redline is where you're liable to get valve float and have a piston smack a valve.

 

you should shift when you will be making more hp in the next gear. even if you are past your peak if you are still making more hp stay in the gear.

 

Red line? Not the line of fluids, right?

The maximum safe operating RPM of the engine, whether due to potential valve float, crankshaft stress, imbalance, etcetera. It is often not directly related to the peak HP RPM. Many SBCs are safely operated at 5,500 RPM but may produce peak power at 4,500 RPM, like TPIs.

If the engine has factory valve springs, red line should be more like 4,500-4,800 RPM, but it will be "governed" at that point anyway.

 

No, no, "red line" describes the sidewalls of the tires on Leno's Toronado...

 

The shift point is below redline.
Redline is where you could potentially be getting into trouble.

 

a stock 700R4 should shift before 5000rpm so that it doesn't hurt the engine right? (if it had factory valve springs)
I've never floored my car to see because i'm not sure if it would go above the safe rpm range or not.

 

Correct all 3 are right!

Heres the real defintion: A safety limit, as marked on a gauge.

 

I could argue for #1 or #2.

#3 is just wrong.

Most correct would be "where the red line is on the tach".

 

so did the car self desctruct yet token?

#3 is right Its all the matters

 

freethuggin4428: he said redline is the fastest you can safely spin an engine, period
freethuggin4428: so, are you willing to admit your wrong yet?
AnthonyM EMU: i'm not wrong
freethuggin4428: lmfao, whatever
AnthonyM EMU: obviously if TGO is split then there are multiple definitions
AnthonyM EMU: but i've always known redline to be max engine speed 8-)
freethuggin4428: nope
freethuggin4428: your 100% wrong

freethuggin4428: you spun your bottom half over redline
AnthonyM EMU: which you can do AT ANY RPM
AnthonyM EMU: you're more PRONE to doing it at a higher rpm yes
freethuggin4428: ommfg,
freethuggin4428: whatever
freethuggin4428: **** it
freethuggin4428: your ignorant
AnthonyM EMU: BUT IF IT CAN HAPPEN AT ANY RPM THEN IS YOUR REDLINE 0?
freethuggin4428: and do not learn
freethuggin4428: bye
AnthonyM EMU: the term "safely" is not a black and white line
AnthonyM EMU: it's very ****ing grey
AnthonyM EMU: there is no "safely" line
AnthonyM EMU: you can do this type of damage to the engine at ANY rpm
freethuggin4428: wow

freethuggin4428: the point was that after redline, engine damage is almost 100% going to happen
AnthonyM EMU: almost 100% going to happen?
AnthonyM EMU: then how do people take it "past redline" often and still have 100k+ miles on their motor?
freethuggin4428: cause tehy are idiots

freethuggin4428: you spun your engine faster that SOME of the parts were supposed to go
freethuggin4428: you broke it
freethuggin4428: your fauilt
freethuggin4428: end of story
AnthonyM EMU: saying "you could break something" is different from saying "you WILL spin a bearing at 5500 rpm!"
AnthonyM EMU: because you "might" spin a bearing at any rpm, albeit higher risk proportional to higher rpm
freethuggin4428: jesus
freethuggin4428: christ
freethuggin4428 signed off at 1:48:20 PM.



This is the kind of crap I put up with.

 

Jesus ****ing christ, I'm not gonna sit here and argue. Redline is the fastest at which you can spin an engine safely. Period.

 

so how do you determine that?

 

How should I know, I'm not an engine builder. Personally, I would say frmo the rpm rating of the lowest rated part, as I'm assuming most of these parts are rated for an rpm limit. UNless you have the expensive equipment to test for stress, and can properly figure out how much stress your components can handle (I'm no engine bulder yet, so, I'm not goign to sit here and tell you how you determine it), but, I know for a fact that revving an engine past redline causes problems.

 

My "McGraw-Hill Dictionary of Scientific and Technical Terms, Third Edition" skips from "Redler converyor" to "red liquor". "Redline" or "red line" is not listed as a technically defined term (and it's a pretty big book). Therefore, at least as far as McGraw-Hill is concerned, it is left to convention, rather than defination.

You know what, though? Who cares? Things that should interest you are the RPM capability of your drivetrain and rotating assembly, peak torque and HP points, and RPM after shift (or, to put it a different way, shift point to maintain maximum torque after shift).

If you have a cam that doesn't produce power before your valves float or you tear the rods off the crank, you've got a problem. If your transmission gear ratio drops your RPMs after shift to the point that torque is gone for a couple of seconds, you've got a problem. If you think the 4500 yellow and 5000 red lines on your factory dash tach are gospel even though you just put in an XE284 cam with roller rockers, beehive springs, titanium valves, forged pistons, forged crank, H-beam rods, ARP wavelock rod bolts, balanced rotating assembly, et al, you need some learnin'.

Does that wrap it up well enough?

 

red liquor is baaaaad stuff,worse than green liquor causes severe burns

 

I understand all of this. I'm just trying to explain to the boy that red line is not simply the fastest that the engine will turn, as he believes. BY his logic, if you took his stock POS 92 firebird 305, put say a 75 shot fo NOS on it, with all the proper precautions, fuel, timing, etc, then it would give that engine plenty of power to run past 5500 rpm's. In his logic, that woud raise teh redline, which is not the case at all. I even asked my teacher, who used to work for Stitta (sp?), a company in florida that builds custom high performance ford products, and is my Hot Rod street legal performance instructor at UTI, adn he said the same thign I've been trying to tell Anthony, that he so dearly loves to asy I'm wrong about. My teacher said the same thing almost everybody with intelligence has said - A redline is the fastest that you can spin an engine SAFELY. Period. I just get aggrevated when somebody flat out tells me I'm wrong, quote many sources who I also know are right, but still tells me I'm wrong.

 

"Redline" is usually defined as the maximum RPM your engine will spin before parts start to break. This is a MECHANICAL limit. putting a blower on your car, or nitrous, will let the engine build power at higher RPM, BUT!!!! it will NOT improve the engines ability to withstand higher RPM. Just the opposite. The added stress will actually increase the likelyhood of engine damage.