Safe RPM Limit

[Charlie Brown]

Probably will get several differing opinions, but I'd like to hear what others have to say about a safe RPM limit for my 426 wedge. By safe I mean keeping the engine together - all the parts. Specs are as follows -
413 cid bored to 426
Forged stock Chrysler crank - fully machined
CP-Custom Pro Mod pistons
Main stud package
Ohio 440 race rods / ARP fasteners
Complete block machining by For Hemis Only which includes - square the decks, align hone main saddles, complete rotating assembly balanced etc.
Sidewinder aluminum heads
Comp Cams 924-16 valve springs - 112 lb seat pressure, spring rate = 347 / inch
10 degree locks
Lunati Voodoo 10230703LK with lifters - 1800 - 6200 rpm - .494 intake - .513 exhaust
Mancini 1.5 Roller rockers w/ Mancini Rocker shafts
Smith Bros. pushrods
ATI Damper
Melling HV oil pump
Opinions welcome

 

[topside]

Those valve springs seem a bit soft to me, I'd prefer more like low-400s over the nose.
Probably no reason to twist the thing higher than 6500, though...
What's the static CR, duration @ .050, carb & intake, headers or manifolds ?
Trans, converter, gear ratio & weight also play a big part in how well the package works together.

 

[snakeoil24]

5500 max

 

[33 IMP]

My opinion, that motor is safe to at least 6500. But,I'll bet the power is going away by 5500 with that mild a cam.
My 440 with a 257° .557 purple shaft runs just as quick at 5900 shift point as 6200.
I would start shifting your engine at 57-5800.

 

[66Satellite47]

I'd more valve spring pressure. I would like 130+ on the seat. Make sure the 924's can take the lift. You will be very safe at 6000 6200 RPM.

 

[4406bbl]

Lunati recommended nothing over 300 over the nose with that cam when I called. Quick math says you have 287 or so. Make sure you remove the inner spring when you break in the cam, and use driven br 15-50 break in oil. No reason to rev it past 6000, so shift it sooner. For what it is worth the guy that did my heads set it at 130 seat 340 open. He said 110 on the seat is not enough.

 

[dvw]

Rpm range (non dependent on rpm range needed for power) needs the following; light bob weight, strong rod, stable valve train. You make no mention of what rods or rod bolts you are using. No mention of bob weight (piston/pin/ rings/rod). Also no mention of valve type or retainer. My guess if these parts are nothing special 5800-6000 rpm would be my limit.
Doug

 

[mopar 3 B]

Rpm range (non dependent on rpm range needed for power) needs the following; light bob weight, strong rod, stable valve train. You make no mention of what rods or rod bolts you are using. No mention of bob weight (piston/pin/ rings/rod). Also no mention of valve type or retainer. My guess if these parts are nothing special 5800-6000 rpm would be my limit.
Doug

Ok! go back up and read #1 this time. But your right a safe limit would be 6000 rpm.
Lunati says 6200 rpm on the valve train so there is the limit. Doesn't make any difference what has been done to the bottom end.

 

[R413]

It won’t do any good to reach 6000, probably less. Are you going to race this at the track? Then you will know what makes it faster.

but what is the top limit before it blows up? Why go that high, it will quit making power way before it blows up.

 

[Geoff 2]

When you hear the bang, back off...
Just kidding.
I see no problem going to 7000 rpm because the quality parts/work, but the cam & valve springs will probably nose over before that.

 

[66Satellite47]

In my bracket drag motors I was a 7000 RPM guy. My ported heads and cams would get there easily. But the stock 440 steel crank did not like it. Staying around 6000 will live a long time.

 

[dvw]

Ok! go back up and read #1 this time. But your right a safe limit would be 6000 rpm.
Lunati says 6200 rpm on the valve train so there is the limit. Doesn't make any difference what has been done to the bottom end.

I did miss the Ohio Race rods. Looking them up they appear to be more than up to the task. So with this cam package I doubt that the bottom end would be the limiting factor on RPM. But to say bottom end doesn't mean anything when determining a RPM limit? I don't agree with that statement.
Doug

 

[Dennis H]

My warmed 440 stops pulling at 4850 per chassis dyno. No reason to go upstairs. Limiter set at 4800.

 

[Darter6]

I'll bet the power is going away by 5500 with that mild a cam.

Agree

 

[451Mopar]

As mentioned, the cam and valve springs are what will limit the RPM.

 

[Charlie Brown]

Below is listed what the cam / spring specs are.

cam specs: Lunati 60303
Hydraulic flat tappet
1,800-6,200
Duration at 050 inch Lift:226 int./234 exh.
Advertised Duration:268 int./276 exh.
Valve Lift with Factory Rocker Arm Ratio:0.494 int./0.513 exh.
Lobe Separation (degrees):110


Springs installed: Comp Cams 924
Dual
Outside Diameter of Outer Spring (in):1.509 in.
Coil Bind Height (in):1.175 in.
Spring Rate (lbs/in):347 lbs./in.
Inside Diameter of Outer Spring (in):1.125 in.
Inside Diameter of Inner Spring (in):0.697 in.
Installed Height (in):1.900 in.
Seat Pressure at Installed Height (lbs):112 lbs.
Open Height (in):1.200 in.
Open Pressure (lbs):355 lbs.

retainers are comp cams 741
locks 611 10deg.

Note that the springs were installed at 1.82 and 120 lbs seat pressure.
Seems the general consensus is that my engine should stay together in the 6000 - 6200 rpm range.
Am I in the ball park here?

 

[66Satellite47]

I did miss the Ohio Race rods. Looking them up they appear to be more than up to the task. So with this cam package I doubt that the bottom end would be the limiting factor on RPM. But to say bottom end doesn't mean anything when determining a RPM limit? I don't agree with that statement.
Doug

Doug, I completely agree, bottom end is critical. If it's solid, then the valve train is the limiting factor. At 6000 to 6200 it lasts a very long time. It appears that valve springs are a lot better today than in the '80's.

 

[33 IMP]

A steel crank, good rod, light forged piston shortblock is safe past 6500, if assembled properly.
You have good heads for top end power, and it sounds like the valvetrain was set up comprehensively, and probably good to lunati's recommendations.(6200)
My guess is still..... it won't make power to there, and there will be no need to spin it fast enough to worry if it will stay together.
Wondering how fast to spin it implies a question about shift point. It's time to experiment.

 

[mopar 3 B]

Sometimes the to shift at rpm's are an experiment. You would be surprised the look on some people's faces just after that last shift is made and they realize the battle has just been lost. Sometimes peak power has no bearing if it still keeps pulling. After all who runs top end at peak power or do you just stop at that sweet power spot? But then there are realities of the road and there are really no reasons to go beyond the sweet spot. The cam sheet says 6200 but do you really need to be there?

 

[66Satellite47]

Boy, I never based shift timing based on the cam card. I unfortunately ran my drag motors to 7000 RPM. Not good for OEM 440 steel cranks. 350 or 400 runs. Drag strip car. My bet is that 6000 RPM lives forever.