redline

[yusuf]

What engines can rev high the easiest? The 4.6? 302? 351 or 377? How high can a reliable pump gas street motor rev? Does anyone destroke motors?

Unless I'm wrong, some big blocks like the 460 have a 1.8 rod ratio, does that matter? Is it piston weight that makes them not rev as high?

Thanks in advance for any opinions.

[QuantumMotorsports]

Red line is all about the valve train. The crank and pistons could handle high RPM no problem. Hydrolic lifters however can't rev too high. The 4.6 will rev the highest because it has OHC. Since there are no lifters if has the highest reving capabilty. As far as the lifter motors, I'm not sure which ones can rev higher.

------------------
Michael Black
Quantum Motorsports
Norman, Oklahoma

1988 Merc Cougar 5.0 HO, P&Ped heads, 2.25" custom mandrel bent dual pipes, T5 five speed tranny
15.43 @ 91.08mph (not shabby for a 3600 pound car)
60' 2.453 Street tires suck!!!

[Unit 5302]

The 302 will rev the highest. The internal engine parts maximum speed is determined by piston velocity. Since the the 302 has a much shorter stroke, the pistons will be moving slower for the same amount of rpms.

There were some guys a few years back that made a couple cart or F1, can't remember, I think it was cart, competition cars that were 100% American. One had an Aurora V8, the other ran a 302. They had to be N/A, the 302 was winding to 12,000rpm, it won the only 2 races it was entered in, versus the hi-tech foreign motors it was up against. The Aurora was run in more races, can't remember what the finishes looked like.

[dinomite]

I believe that the redline is actually part of both of those, valvetrain and piston velocity. If the revs get too high two things happen: valve float and piston separation. Valve float is when the spring isn't strong enought to bring the valve down in time to get out of the way of the piston. A collision of this sort is nowhere near as serious as having a mismatched cam/high ration rockers/etc. Also, if the revs get to high, the piston will separate at the wrist pin, simply because it creates too much force going from one direction to the other. This can also happen if the connecting rod fails at the crank end.

[MiracleMax]

Yeah if you go buy the info in the auto math handbook, using a conservative 3500 fpm (feet per minute) plug it in like this;

RPM = (3500 x 6) / Stroke in Inches

7000 = (3500 x 6) / 3.00 (302 stroke)

but thats just saying how safely it can rev to.

As for easy reving the engine with the lightest recipocating mass and valve train will rev the easiest, because there is less to accelerate.

Each of the aformentioned engines has its tradeoffs, However if one was chosen as a purpose built engine I think the 302 would be the best bet. in stock hydraulic roller form the engine is limited to probably about 6000 rpm (probably even less if its tired), but give it a solid roller valvetrain with light weight components and it would probably clean house on the rest. Then again shorten the 4.6's stroke and give it a bigger bore and it would take the lead. Just depends on what your trying to do?

[chris91LX]

I'm not sure if this means anything or not, but I was told that the bigger cubic inch engines didn't need to rev as high to produce the same hp as a smaller cubic inch engine, ie the 460 vs. 302.

------------------
91 LX 5.0
Z t-5, 3:73 gear, Vortech 73mm Mass Air, Accufab 65mm TB, BBK underdrives, Crane HI-6S Ignition, BBK unequal length headers, Bassani x pipe, 2.5" Dynomax Super Turbo cat back, Kenny Brown Super Subs, Factory Five Control Arms, Mac cold air kit and more to come!

[MiracleMax]

Yeah, cubic inches equal cubic power. thats just because a BB engine makes more torque (all things being equal) at the same rpm. However the BB's heavier components take more time to accelerate when compared to the smaller motor's components.


Opps had to edit everything between the top and bottom here

Torque is a measurement of force and horsepower is a measurement of work which by the way, both are equal at 5252 rpm.

HP = (torque x rpm) / 5252

One of those wennie F1 motors makes something like 750-800 hp I believe at a screaming 15 or 16,000 rpm (maybe more). So we'll say 800 hp at 16,000 rpm. That rascal is making only 263 foot pounds of torque at 16,000 rpm to make 800 hp, now a BB making 800 hp at 6,000 rpm would be making 700 foot pounds of torque.

Whats all this got to do with the price of butter in China, glad you asked. It depends on what your trying to accomplish.

Given then medium in which you race it might prove advantagous to develop a high revving engine that produces the same power as it's larger alternative, due to space/weight limitations. Like in the case of an F1 car, both engines might produce 800 hp, but here where weight and aerodynamics are important, stuffing a big ol' honk'n BB in there will slow the car down due to it's weight and size. Or it might prove advantagous to take advantage of some kind of weight break due to a physically smaller motor that can rev higher even though you would lose some torque. this would be offset by its lighter weight (and I guess its faster/higher revving nature)

[yusuf]

So how high would a built street 302 or or 351 or 4.6 rev?

[MiracleMax]

It depends on what your trying to build/accomplish.

If your building a street car with longevity in mind then keeping the lift below .600 and staying in the neighborhood of 6500-7000 rpm will make it last, big lifts and hi-revs definitely lower engine life (which can for some engines that probably wouldn't be considered radical be measured in 1/4 mile passes)

Where are you planning on reving it to? Is it going to be carbed or EFI?

For a non-power adder engine, a high revving 302 is gonna need a steel crank, light weight forged rods/forged pistons and four-bolt mains (a P/A engine would need heavier duty components which add weight and increase strength, but everything is a trade off). Anyways such an engine can easily cope with 8000 rpm and probably more. As an example (and all BS aside) I have a smallblock chevy engine that has seen 9000 rpm more times than I care to think about. It features a cast crank, forged rods an cast pistons (all pretty lite weight), but it never stays there for more than a second or two. Besides the cam is a 278 adv. solid roller and makes peak power about 3500 below that, combined with the T350 tranny, it shifts best at 7000 rpm

If your talking hydraulic roller engine, using a 2.02 inch valve then probably the practical limit is in the region of 7000 rpm.

Solid roller cams open up some new avenues