How to determine a safe red-line?

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DartVadar

DartVadar

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I'm just curous if there is a way to determine a good redline on my 360, I just don't want to rev it beyond what it can safely handle.

It currently has about 500 miles on it, Ive been starting to get the revs up more and more frequently now, not just little bursts when the motor was newer. The highest I've taken it is a bit under 5k, and seems pretty happy and eager to go there. Its an LA360, ARP rod bolts with stock rods and crank (new bearings of course), with kb 107 pistons. I have the single springs recommended for the comp XE268 FT cam I have. Roller rockers and an 8 quart oil pan (bad for the street I know :banghead:)

I've read that for every 1000rpm you should have about 10psi of oil pressure. Hot I have about 43-45 psi @850-900rpm, and cruising @2000 I have about 64psi. I know my cam is good up to about 5600RPM, and I have enough oil pressure. Would the 5600RPM be safe? Its a street car with occasional trips to the track. Essentially I just want to know the limits of the motor so I can stay very far away from that point.
 
Hold it floored til it blows up....rebuild it and take 500 rpm off....I have never put a lot of stock in the 1k/10psi thing. Had a motor built by the best, at the time, race shop in NJ. Was a little 2.8 v-6 in a Bronco II. Never seen over 20psi or so of oil pressure. Put over 400k on that motor, never had a problem.
 
Assuming it was built well (which I'm pretty sure it was if it is still together at 500 miles), you should be fine to the limits of that cam. Usually, if it is going to break it will break very soon after the build.

Let me preface this with I have not used the KB 107's before, so I don't know their limits....but, if it were me, I would be totally comfortable up to 6500, but your cam will probably run out of steam around 6000....so I would take it to 6k and see what she does. Have fun with it. :D
 
Depending on cylinder head, it's likely done making power around 5400 or so. So 5600 -5800 would be a relatively safe level.
 
flyfish said:
....so I would take it to 6k and see what she does. Have fun with it. :D
Click to expand...

That's where I'd be going to. I have a stock bottom end, 80,000 mile engine in my car with a 268H cam, headers, intake and a 650 4V carb.

I spin it to 5500 and a tad more sometimes when blasting through the gears, no issues here....................yet! :D
 
To have 10lbs. Per 1K RPM's would be great but is not a mandatory thing. If you have 20psi at the finish line, your good.

You can safely put a red line for your engine at 500 rpm above the listed RPM range of the cam from the manufacture. (Though a 1,000 shouldn't be a bad thing for the engine.) The reason is rarely win you make more power above that and it would be a waste of time to exceed that.

The best red line guide is where the valve train floats. Meaning, the valve springs can no longer control the valves well enough to keep them where they belong when they belong there. That will normally happen well past your power making point.
 
What is your cam rated to? If it's 5800 set a rev limiter to 6000. Why because your cam is don't giving and there's no point really going past that.
 
Get a G-meter app for your phone,, put it where you can see it while driving..

Put it in first gear and go WOT,, note the rpm when the g-meter starts to drop-off, that's your shift-point/red-line..

hope it helps
 
Cam is actually rated to 5800, I was wrong, and heads are done at around 5400-5600, so 6 would be a more conservative safe limit.

Thought the cam got trashed a few days ago because on startup I had a loud ticking noise, this was after working the motor a bit the day before, and what made me want to find a safe redline. I took the valve covers off expecting the worst, but nothing was loose, and I was getting full lift everywhere. Turns out I had a pretty bad header leak, tightened it up and no noise. Definitely gave me a mini-heart attack when I first happened!
 
Next time you take it out for a drive, make a hard run in 2nd gear from down low, watch the tach for when it lays down, add 500 rpm to that and there's your mark. I suspect it will be some where's around 6000 rpm.
 
None of these are quite correct.

First, your shift points are WHERE the previous gear and next gear curves CROSS. You can easily determine this with some sort of G meter such as a G-tech, or a dyno run. You don't need to run all gears, just plot one, if that's all the road you have, and then calculate the other curves off of transmission ratio and take into account converter slip.

But those shift points DO NOT MEAN that just because your cam / piston/ etc combo makes power at 8800 RPM, that the rest of the engine is capable. Is the bottom end gonna hang in there? Valve springs? You need to do some serious thinking. If you have say, a strocker 318 with worn out old valve springs and "somebody" slapped a Great Big cam in there, then prolly not.........................

It matters not whether you plot HP, torque, acceleration G's or against RPM or MPH

 
crackedback said:
Depending on cylinder head, it's likely done making power around 5400 or so. So 5600 -5800 would be a relatively safe level.
Click to expand...

While the above quote doesn't tell you how to determine a redline--It is in fact something I agree with 100%. That cam and yours heads will be done by 5300-5400.

To ddetermine a safe redline requires taking into consideration the components of the engine, how they were assembled/machine/massaged as well as the actual power curve. Typically what I see on the dyno and how rapidly the power falls off after the peak will determine my answer. No need to turn your engine higher than 600rpm unless you "just have to" J.Rob
 
Run it at a drag strip on a good consistent day and try different shift points. What harmonic balancer is on the 360? stock, aftermarket, internally balanced...

As for the oil pressure being 64ish PSI reved up, is your bypass spring letting unfiltered oil by? The oil is to help cool the internals along with lubricating obviously, but if it's being forced through the system at a higher rate is it able to attempt to cool? Kind of like not running a thermostat for the coolant, if beat on long enough it may overheat.

I like the seat of the pants feel for the shift point or the certain tone of the exhaust at that point, but these responses will vary from person to person.....:)
 
DartVadar said:
I'm just curous if there is a way to determine a good redline on my 360, I just don't want to rev it beyond what it can safely handle.

It currently has about 500 miles on it, Ive been starting to get the revs up more and more frequently now, not just little bursts when the motor was newer. The highest I've taken it is a bit under 5k, and seems pretty happy and eager to go there. Its an LA360, ARP rod bolts with stock rods and crank (new bearings of course), with kb 107 pistons. I have the single springs recommended for the comp XE268 FT cam I have. Roller rockers and an 8 quart oil pan (bad for the street I know :banghead:)

I've read that for every 1000rpm you should have about 10psi of oil pressure. Hot I have about 43-45 psi @850-900rpm, and cruising @2000 I have about 64psi. I know my cam is good up to about 5600RPM, and I have enough oil pressure. Would the 5600RPM be safe? Its a street car with occasional trips to the track. Essentially I just want to know the limits of the motor so I can stay very far away from that point.
Click to expand...

just as soon as the oil light comes on then shift works for me every time .
 
lurchs66cuda said:
Run it at a drag strip on a good consistent day and try different shift points. What harmonic balancer is on the 360? stock, aftermarket, internally balanced...

As for the oil pressure being 64ish PSI reved up, is your bypass spring letting unfiltered oil by? The oil is to help cool the internals along with lubricating obviously, but if it's being forced through the system at a higher rate is it able to attempt to cool? Kind of like not running a thermostat for the coolant, if beat on long enough it may overheat.

I like the seat of the pants feel for the shift point or the certain tone of the exhaust at that point, but these responses will vary from person to person.....:)
Click to expand...

I have the stock balancer that I got the engine with, but next time I'll got to the track and mess with shift points, and get a gmeter out like suggested and chart everything.

As for the oil pressure, I don't think its open, but how would I know? the pressure still goes up as the revs go up from there, it doesn't stay there constantly (unless constant RPM). Cold I have about 76 PSI at idle, and goes down quite a bit as it gets warm. I have a HV oil pump and I'm running rotella 15:40 with a zinc additive, so that stuff is pretty thick when its cold. And the car doesn't overheat at all, the temp doesn't even fluctuate.
 
I wouldn't push a stock 360 much over 6000 as it has a longer stroke than the 340 which red lines at 6500 stock.
 
Go to the track,take a log book & learn. Experiment with shift points,all combinations react differently. Crackedback's comment's in post ,4 says it best. Be conservative on each adjustment,log each thing you do.One adjustment, at a time. (J.M.O,it worked for me.)
 
I have the KB107s at +.004deck. Been banging shifts at 6500 to 7200,depending on which cam is in it,etc., for 125000miles,cast crank,stock balancer/flywheel and all. Hughes cams seem to go on forever.Had the motor apart during its early miles to check on it. Found a migrating wristpin bushing once.Pistons were still tight and looking good.The G-Tech will tell you a lot. As usual 67Dart is double bang on.Nice graph, dont let the other-brand guys see it.
 
Stock cast lower parts I would never rev over 5500. Dont care what valve train you have. Cast parts are weak. If you want to rev to 6500 and up forged is a must. 5500ish is my limits for cast parts. A touch over wont hurt.

Remember the tug and shove of the rods big ends. Even a good rod bolt is only good at the clamp not at the center of the cap.
 
crackedback said:
Depending on cylinder head, it's likely done making power around 5400 or so. So 5600 -5800 would be a relatively safe level.
Click to expand...

RAMM said:
While the above quote doesn't tell you how to determine a redline--It is in fact something I agree with 100%. That cam and yours heads will be done by 5300-5400.

To ddetermine a safe redline requires taking into consideration the components of the engine, how they were assembled/machine/massaged as well as the actual power curve. Typically what I see on the dyno and how rapidly the power falls off after the peak will determine my answer. No need to turn your engine higher than 600rpm unless you "just have to" J.Rob
Click to expand...

I recommend listening to these two.
 
The theres 3 things I'd say for you to look at for red line and bottom end is first the weakest link there would decide the limit, everything you have should be good for 6500 rpm. Second valve springs and valve float would be the limit there. And third the power band no point spinning it to 9 grand when it's done by 5500.

shouldn't really need to push your engine past 6000 rpm make sure your valve float is at 6000 or more so you get even last useful hp out of your engine.
 
krazykuda said:
I wouldn't push a stock 360 much over 6000 as it has a longer stroke than the 340 which red lines at 6500 stock.
Click to expand...

LOL....you guys need to get outside more often...got stock 360 ...with that really long stroke..LOL.....running 7000+ thru the traps....

last year at Bakersfield it was cranking 7500 rpm .....

lets see..the short block was assembled back in 2006.......

I know ...if it was a 340 it would be a full second faster....and turning 9000 rpm....LOL
 
only your 360 knows, my 383 is somewhere between 5500 + 7500, hard for me to tell, it revs too quick. I found it likes 6400 for shift point.
 
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