470cid 455 theoretical redline?
 

Just wondering limits. I have a 6000 limiter right now, MSD Module, and wondering with 4.25" stroke forged crank. Scat. Eagle 6.8" H beam rods, and icon .040 over flat forged pistons. 4 bolt, 70 455ho block with 72 #64 455ho heads. Ported. All bolts are ARP.

You have a parts breaking redline, then you have a breathing redline. The parts might be good to 7000 to 7200. But, the head, cam, intake and exhaust combo might not be able to get there.

This, ^^^^. Probably done at 6000 rpm or sooner. You could put it on a chassis dyno set what it does.

Your bottom end is fully good to over 6000, however your overall breathing system with that stroke is done by 5500 at best, even with the ported heads , and I am assuming they flow like 240 intake cfm @28.

Look at it this way super stock 455s with ported iron D port heads flowing 260 cfm and running a far bigger roller cam are shifted at 5800.
Even SD 455 super stock motors with there ported SD heads that started life at 185 CCs and are now for that type of racing ported to 280 cfm are being shifted at 6000 to 6200, and both of these motors are running heavily port single plane Intakes.

Just let a street 455 do what it does best, that being making big big torque that’s nosed over by 4200 which means making the 1-2 shift at like 5300 which will allow the rpms to drop right back into the peak torque cradle.

Only a dyno can tell you that .

a dyno will just tell you at what RPMs power and torque happen, a mechanical redline needs an educated mathamatical guess based on piston pin ring assy weight factored from speeds and loads with a given stroke then factor that against rod strength
and thats still a guess because of friction and loads of pulling intake charge into the cylinder pushing out exhaust ect.

or if you have a triple throw down rotating assy can the block and or other things like flywheel can handle it

i cannot get you there but in know the difference

there is a redline based on power output and then a redline based on things flying apart a theoretical redline is a guess on which one?

The Dyno will verify that, you can calculate the CHOKED-flow rpm based on the minimum Cross Sectional Area along the Inhale track, for a given CID.

Now where is that equation..Speed Tak has a good discussion and moght show the equation. https://www.speed-talk.com/forum/vie...t=1725&p=12290

My Head Porting Folder and Excel has it.

Dyno it. Takes all the guess work out of the equation.


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Assuming that any given motor that’s built with superior parts is safe at any rpm from coming apart the motor will stop gaining rpm at whatever point the rpm of frictional hp exceed’s the amount of crankshaft Hp that the motor is producing .

No Dyno's anywhere remotely close to me. And I was meaning the parts breakage RPM. REDline to me means massive danger. Not just engine ran outa breath.

Without a dyno, Then you'll need to go to the track and play with shift points, find a shift point that produces the best ET/MPH for you. Will take a bit of experimentation.

As far as mechanical redline, I wouldn't worry much about that with all the good parts inside. I'm betting you'll run out of cam and cylinder head long before the internal parts give up.

" Then you'll need to go to the track and play with shift points, find a shift point that produces the best ET/MPH for you."

Bingo !

And if your goal is bracket racing you and your car need consistency on race day.





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One thing that would help is if you posted up your cam specs and rocker arm ratios.

Stan

I'm sure you have this covered and everyone is assuming you do, but you did not mention oil pump/oil pressure/oil control in your bottom end.

Cam is a melling spc-8. Full Windage tray and crank scraper. But ya I am sure it'll run outa breath before parts breakage after reading these replies

400 block bored .060" over
4.185" x 4.250" stroke/ 467 cubic inches
Unported KRE d-port heads / 85cc chambers
Edelbrock RPM intake / Q-jet carb
Crower 60919 hyd flat tappet cam with 1.65 rockers
Doug's headers, 3" Pypes system with X crossover running
through 18" Xlerator mufflers

Peak power at 5300 RPM

Dyno Sheet: https://pontiacstreetperformance.com...455MikeG2.html


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Factory iron pushrod bulges assure the 455 will run outta inhale around 4600 rpm. Oh i could be wrong, like maybe 5200 rpm, but there is your rpm window.

Went 12.0 ET while staying under 5000 rpm with PORTED iron 48s and 3.31:1 gears.

What if? 4.3ish bore x 4" stroke
 

How do the characteristics of a 4.18ish x 4.21" or 4.25" stroke compare with a 4.3ish" bore x 4" stroke?

What if the 1970 455 had instead been a 4.255" bore x 4" stroke?

From the internet....

Reducing stroke means you lower the mean piston speed for any given RPM. Since it is usually piston speed which governs the maximum speed any engine design can run at, it's perfectly sound reasoning that reducing the stroke will increase the RPM ceiling of an engine.

"But ya I am sure it'll run outa breath before parts breakage after reading these replies"

The example in my post#16 was meant to support this statement.



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Then it'd be a big block chevy :D