427w small block ford rev potential

[Mark O'Neal]

That is why I write my own job cards...and why I pretty much stick with ROSS.

[Streetwize]

Generally you'd need a pretty big cam, induction and cylinder head for a 427W to be even remotely happy up there around 7000.

Something like a CHI Clevor head and intake with about 340 cfm of flow on the intake with a 260-ish @ .050 solid roller and .650-.670 lift would make peak power around 6500-6700 rpm and rev past 7000 pretty easily. and 11.5:1 is pretty normal for that type of build....so unless you're building a race specific car, I'd want to keep the torque and power in the more comfortable 4000-4200 peak FPS max of piston speed.

But generally....torque motors make good torque and roll-on power due to long strokes and faster piston speeds through the mid range. After the torque peak the piston rings, springs and bearings start to act like a friction brake, and the longer the stroke the more you have to coerce a torque motor to act like a Horspower motor, generally if you desire that kind of RPM I'd go shorter stroke where the internal frictional losses per each 100 rpm gain above the torque peak make the engine more efficient.

you probably could rev a not-High RPM purpose built 427 combo that high in a cobra, after all 2500 pounds isn't hard to push...but you'd just be abusing the internals in a not very 'happy" way. 5700-6200 is at the high side of a strokers "happy place" and winding out to 6700 or a little more through the traps at the track is only for a few seconds.

Better IMO to build a more mild motor, keep the internals more mild (the extra valvespring pressures and cam lobe profiles you need arent very efficient for cruising at 2400-3000 rpm after all) And just because you can doesn't mean you should. There's something to be said for not needing race type spring pressures and still making more power than you could ever need...and needing much less gear to do so.

A 3.25" stroke 331 tuned to make peak power at 8000 has the same piston speed as a 4" stroke 427 at 6500, so your piston travel/friction(heat) on the cylinder walls with a 427 @ 7000 is like a 331 turning over 8600, and the side-loading is higher too because of the increased rod angularity and longer bores.

I built my 427W (stock 351W block 4.04" bore and 4.17" stroke) with highly ported TFS Twisted Wedge heads and ported Motorsports Victor JR) to basically emulate the power curve of a street 427FE ....so I keep the revs to 5800-6000 but it'll rev to 6500, the natural peak power is probably around 5200 and the torque is absolutely wall-to-wall. I wouldn't push mine to 7K because I didn't valvespring it and cam it for that kind of RPM. I wanted that fat upper bottom and mid range sledgehammer torque like an FE...without the weight. It certainly doesn't lack for acceleration and my torque is impressive in any gear withing the limits of the RPM. my 427 was the very first stroker kit Coast High performance actually sold, and the 340 mopar rods had to be clearance so as not to interfere with the cam lobes, so I wish I had waited for the kits to catch-on, so I could have used H beam rods that allowed for larger cams and far less "trial fitting" during assembly.

Nonetheless I am extremely happy with the results.

BTW....I really enjoy all of Mr. Lykins' posts here, he is very informative and generous with his sharing of knowledge.

[Dominik]

If it is only about the sound of 7.000 rpm, why don't you build a smaller V8?