Is a stroker engine the right choice for your street car?

The following was written by George Pence, one of the luminaries in the Pantera and 351C communities. He addresses one of the modern issues with stroker 351C engines, but you can extrapolate this to any engine, really.
I think he makes some interesting points.

Why I’ve Glossed Over the Subject of Stroker Crankshaft Kits and Very High Horsepower Street Motors

I used to think 500 horsepower was a good goal for a 351C powered performance car; the 351C 4V was designed as a 500 horsepower race motor and it is rather easy to assemble it to achieve that power output, so why not take advantage of the motor’s capabilities? I also thought stroker kits were great because they made that 500 horsepower goal attainable at lower rpm. But over the years I’ve changed my opinion regarding the importance of having a 500 horsepower street motor; and I’ve changed my opinon regarding the benefit of a crankshaft with a longer stroke.

I know a fellow who had purchased a brand new Z06 Corvette a few years ago. It was equipped with the 427 cubic inch LS7 motor with a 4" stroke crankshaft, 505 horsepower, big back tires, low center of gravity, and a modern sophisticated chassis. He had owned the car about a month, when one sunny Saturday afternoon he found himself cruising down a freeway with very light traffic. He thought it would be a good opportunity to feel what the car was like with the electronic traction control switched off. So he turned it off, and he pushed the acelerator pedal toward the floor while crusing at about 70 mph. The rear end of the 'Vette immediately lost adhesion and went side ways. The car began spinning in uncontrollable circles across the freeway and crashed into the barrier in the middle. The owner was able to crawl out of the wreckage and only sustained minor injuries, but the one month old 'Vette was totaled.

That story is what convinced me to change my opinion on stroker motors for older street cars that aren’t equipped with traction control. Considering my position with Pantera International I have a responsibility to the public to offer advice that has their safety at heart. Being in this position I also hear about the problems owners don’t share with anyone else. There seems to be one or two Pantera owners every year who quietly replace their expensive high output motors with motors that are a little more sedate, having found their high output motors were too much for the chassis to handle and were no fun to drive on the street.

My Pantera “sports car” weighs at least 3200 pounds, it is equipped with 325/25ZR20 Michelin PS2 rear tires on 12" wide wheels, about the best street tires money can buy. The stock stroke 351C which powers my Pantera can light up the rear wheels at will, and there have been a few occasions when it has kicked the rear-end out in corners when I didn’t want it to. I personally wouldn’t want the motor to have any more crank arm leverage than what it already has. In fact I think a 3.25" stroke crank would be better, I think my Pantera would negotiate challenging roads faster if the motor had less crank arm leverage.

There are many aspects we must consider when we decide to modify an automobile. For instance, will the car be just a “fun car” or will it be used as serious transportation? Will the car be operated on the controlled road surfaces found at race tracks, or will it be operated on public roads having unpredictable road surfaces? Will the car be operated strictly in warm dry conditions, or will the car be operated on cold, wet or icy surfaces? We must consider the traction limits of both the tires and the chassis, and in some instances even the cooling capacity of the radiator can be a limitation (Cobras).

My comments below are geared towards older cars which aren’t equipped with electronic traction control, operating on public roads with street tires; such as sports cars and high performance street cars, Mustangs, etc.

Things got out of hand in the 1960s. The automakers involved in the horsepower wars installed motors in production cars with so much torque it dangerously overwhelmed the tires, chassis and brakes of the vehicles they propelled. Introduction of the 351C 4V marked Ford’s return to sound engineering practices, the automaker looked ahead to performance cars with balanced performance. Indeed, the 1971 Boss 351 had the quickest acceleration times of any show room stock Mustang until the introduction of the 1999 Cobra Mustang. The Boss 302 was a fantastic performance car, but it was hindered by a 6150 rpm rev limiter and 3.50:1 factory gears. With the rev limiter removed and lower gearing the Boss 302 would have given the Boss 351 stiff competition. The big block 428s & 429s made too much horsepower at low engine speeds, they overwhelmed their showroom stock chassis and street tires. The 428 had far too much “crank arm leverage” (crankshaft stroke) for a vehicle as light as the Mustang. When you’re spinning your tires you aren’t accelerating. The mid-size 351 was a better balanced package, exactly what Ford had intended it to be. The Boss 351 didn’t loose the honors of fastest Mustang to a stable mate with a larger motor either, the 4.6 liter motor in the Cobra Mustang is smaller; but the 1999 Cobra Mustang was a better balanced package than the Boss 351.

Consider two Panteras, the first weighing 3000 pounds and powered by a 500 horsepower motor; the second weighing 2700 pounds and powered by a 450 horsepower motor. Both Panteras have a weight to power ratio of 6 pounds per horsepower. All else being equal the two cars should accelerate at the same rate of speed … but all else isn’t equal. Traction will be easier to control in the lighter less powerful car. It will handle and brake better too. The lighter Pantera would be a better balanced package.

Building a 351C based stroker motor is contrary to the spirit of the 351C. It returns to the excesses that Ford designed the 351C to leave behind. I’m convinced if a high performance street, sports car or road racing enthusiast wants a 500 bhp engine the standard displacement 351 is a better choice than a stroker displacing 383, 393 or 408 cubic inches. A smaller motor builds power more gradually as the engine speed rises, it doesn’t make 400+ foot/pounds of torque abruptly at 2000 rpm like a stroker does, the power is delivered in a manner that is easier for the average driver to control, or to put it another way, in a manner making it harder for the tires to loose adhesion.

Choosing balanced performance over brute force is my recommendation. Build a 400 to 450 horsepower 351C, a task which is not difficult or exorbitantly expensive; keep the power delivery controllable; equip the car with the lightest wheels, the best tires, performance gears, lightweight drivetrain parts (drive shaft and axles), the best shocks and the best brakes you can afford; lower the chassis; and lighten the vehicle to improve the power to weight ratio. Truly going fast on street tires is not a matter of how big or powerful the motor is, but how well balanced the package is.

Copyright © 2011 by G.Pence/Pantera International

Yes and No.

Thought provoking article, but I think he is speaking to the Pantera audience more than a Mustang / Cougar audience. I know my Cougar has mediocre brakes, poor handling, and a flexy chassis, and skinny tires. I don’t pretend to be Mario Andretti or John Force. What I do like is lots of low speed, low end, torque. Nothing can deliver that like a 427, 428, or 429. It isn’t about balance, it is about imbalance. A six cylinder Camry will blow my doors off, but what fun is driving a Camry?

I’m with Bill, I’ll choose brute force. I don’t care how quick I can get around the corners and I don’t need traction control to keep me out of the median.

Lesson learned here is that not all folks that can and do afford to drive Z06’s, should.
I also think any driver that uses the phrase “the car lost control” should seroiusly consider alternative transportation or at least stay off the highways.

High powered cars and low powered drivers…

I read that piece a while back, I particularly liked the lever arm illustration/analogy.

George’s whole point is made to daily driven street cars. Like Jeremy Clarkson famously queried Eric Bana “600 hp on leaf springs… are you mad?”

I think he makes a fair point with regard to mechanical advantage. A well rounded package is probably even more of a priority in a ponycar that doesn’t have all the goodies that a Pantera has going for it.


When I purchased my Z06, I went to the Z06 forum and proudly announced my purchase. The resounding response that I received and all other newbie Z06 owners get is “Keep it between the ditches”. There is soo much power going to the ground that is is near impossble to maintain control on full sudden acceleration. I respect the power!!!

Just remember, The longer the stroke the higher the piston speeds and the more likely of a failure.

I wanted a bit more torque than the stock (pathetic) 180hp 351W-Variable Venturi provided to help accelerate my 4000-pound car.

My 393W (4.030 bore x 3.85 stroke) was built as a low RPM torque motor rather than a high-RPM screamer, since it is a daily driver and occasional tow vehicle. It is only 9.5:1 compression to run on 87-octane regular unleaded. With proper parts selection, I more than doubled that demonstrated to a 395 horsepower at the pavement and the torque is also somewhere between 460-480.

FWIW Don, a stock 460 has a stroke of 3.85" and a 400 has a 4" stroke, and those did not have excessive piston speeds since they were also built for low rpm torque. The problem is that those pistons are heavy, and as such they are subject to higher stresses than a stroker motor built with lightweight pistons.

Doesn’t change the speed the pistons travel as well extra stress on rods,rings and wrist pins. To each his own, But I will take a large bore(427) over a long stroke(428) any day of the week.

How about a stroker that’s the 427 bore (or slightly over) with the stroke of a 428?

Yeah, and since F=ma, the acceleration * the mass of the piston assembly is what creates the overall force on everything from the crankpin outward. So, there’s a function of the actual terminal speed the piston assembly reaches, along with the acceleration to reach that speed which is greater for a longer stroke engine with the same bore relative to a shorter stroke engine. 429/460, 427/428, 351/393/408/427, etc.

And then there’s the rod:stroke ratio and the resulting geometry from inserting larger stroke cranks in an attempt to just get more cubes, which has an impact on how the power is delivered through the rev range, piston acceleration, piston speed, etc.

Then, all of that has an aggregate effect on intake and exhaust pulse, optimal camshaft lobe design including valve timing, etc.

As engineered from the factory, the 4v Cleveland is a remarkably well designed package, aside from some bean counter induced shortcomings. With regard to al l this geometry and how the who bottom end works with the engineered tricks of the cylinder head, the stock stroke is really the path to building a not-so-twitchy driver street car, as George mentioned in his essay.
I don’t know enough about the FE stuff, but I am quite curious to see what you guys have to say about that. In my experience, the 390 was a pretty formidable engine. But the 427 is an odd standout in terms of bore:stroke:rod length.

Think you already know this Al, but “The Tool” had one in Royce…


Think I got something backward there. :buck:

I’m just glad I wasn’t drinking coffee when I read that, Bob.

Well played sir.

And I thought you already knew that my GT-E had one as well. A stroker that is, not a tool. :gaptooth:

Having not run a stroker, I don’t have much input on the subject, but I can assure you that even a 2v cleveland is capable of more than enough power to scare the shit out of you.

If you have the means and the desire for 500+ horsepower, most road racing organizations (SCCA, NASA, HSR, etc.) have driver instruction events. Would be some of the best money ever spent not to mention the fun you’ll have.

A stock 351 c with stock heads in a cougar feels like it has no power till about 3500 rpms. That’s why my Cleveland is now a 383 with trick flow heads.

My 69 has a 393W stroker. This was a daily driver for years and that extra stroke gives you more lower end torque and moves the whole power band a bit lower as well. On my combination I’m running unported Edelbrock heads (170cc intake runners), 9.5:1 cr, shorty headers, a mild roller cam and mild intake (Weiand Stealth). The engine has just a slight lope at idle, super smooth throttle response and decent mileage. Driveability is perfect. A little taller gears in the rear and a bit looser stall converter and the whole combination is matched perfectly for the street. I don’t have a tranny with OD (yet) so on the last road trip a long while back I swapped 2:75s in the rear. Even with 2:75 gears in the rear it spins the 255/60/15 tires easily. I can’t imagine having any issues with this combo. If you can stroke it, go for it. These days the ability to run big block power in small block packages is easy to do and not that expensive.
No regrets whatsoever.

Sure it has to be a balanced combination as the OP said but that’s rule #1 no matter what combo you have whether it’s stroked or stock cid.