Similar builds

[blykins]

Any engine that's not built for the rpm will come apart.  You can't really lump stroke into that argument at all.   Most 427's have been twisted way higher than most 428's and with factory rods, you will find a weak link. 

I see no reason to bypass the longest stroke crankshaft you can get, unless it's a rules engine or a restoration. 

[cjshaker]

The stroke has nothing to do with how quickly an engine revs, how high it can rev, or how much  torque it will make.  If you build a 427 and a 428 equally the same, with the same heads, same cam, same intake, same compression ratio, etc., you will end up with almost exactly the same horsepower and torque. 

The stroke doesn't make for a lazy engine or a zippy engine.  I've seen extremely lazy 352's and I've seen 4.500" stroke engines that will zip and rev to the moon. 

Stroke = rev is a really big wives tale.

I respectfully have to disagree. Math and rotational forces say otherwise. Show me a 427 or 428 that can rev as high as a 289. I've seen 289's that run up to nearly 10,000 rpm. I don't believe you will EVER see a long stroke (or any stroke FE) that can go that high. Yes, they are different engines, but it's the rotational forces, side loading, piston speed, weight etc. that are the limiting factors.

As for nearly identical HP and TQ numbers, what about the RPM at which those numbers are made?

And comparing a "lazy" 352 to a 4.5 stroke engine that "zips to the moon", then obviously the 352 was not built to the level of the 4.5 stroke engine. And I'd venture to say that you could never make the same torque with that 352 as you would a 4.5" stroke, given the same general build criteria. Lots of general speak here that doesn't really hold water, in my opinion.

[blykins]

I can show you a 4.180" stroke engine that will turn 9000 easily. 

The only reason bore size should ever come into the equation is if the valves are really shrouded.  Otherwise, displacement is displacement is displacement and the engine doesn't know that it's a 427 or a 428.   We have to remember that an engine is just a fancy air pump.   Displacement is volume and volume is just a combination of bore and stroke.  If you get to 427 with a large bore and short stroke or a small bore and large stroke, it's still a 427 and will behave the same. 

Now the caveat here is that it is dependent on the factors that you described:  component weight, piston speed, etc.  However, the *stroke length* doesn't make the engine rev or not rev.   

Obviously a 352 won't make the same torque as a 4.5" stroke engine, but that wasn't the point that I was trying to make.   Go grab the throttle of a factory 352 2V engine and wing it.  Now go grab the throttle of a 12:1 4.250" stroke FE.  You will instantly know the difference and the result isn't because of the stroke. 

[blykins]

Here's one that will put a few wives tales out to pasture.....

Not only is it a LOOONNNNGGG stroke, but it's grossly undersquare. 

https://www.sonnysracingengines.com/engines/drag-racing-engines/extreme-pro-stock-2025-hp-racing-engine

5.750" stroke peaking at 7800, would probably go above 8000 in a race.  No trouble making the long arms get up there and get with it.

Here's a 5.875" stroke peaking at 8000. 

https://bangshift.com/general-news/mountain-motor-a-closer-look-at-the-1005ci-2100hp-naturally-aspirated-monster-from-sonny-leonard/

[chilly460]

Back in the heydey of the nostalgia super stock stuff, call it 2003 maybe? Pat Burke was turning an FE 9300+rpm, pretty amazing stuff.  Booze Bros weren't far behind that RPM either, they all sounded insane in the burnout box

[mbrunson427]

Back in the heydey of the nostalgia super stock stuff, call it 2003 maybe? Pat Burke was turning an FE 9300+rpm, pretty amazing stuff.  Booze Bros weren't far behind that RPM either, they all sounded insane in the burnout box

I called Pat for some random reason one time, maybe for a part I was looking for. We got to talking about his NSS engine. He said the class was limited to either 430 or 440 cubes. He ran a 4.0" stroke. Was an offset ground truck crank, small journals, aluminum rods.

[chilly460]

Yep, talked to him the pits a bit, full carbon fiber intake was pretty wild as well. 

[bugsbunny]

Have to agree with cjshaker on this one. He stated that his explanation was "general speak" and his general observations are spot on.

While yes it is technically possible to create a long stroke motor that can achieve and withstand high rpms (ie 7800), it also comes at a cost ($91,000 in the example given), with every component being modified (we're not talking stock FE parts here) and many parts constructed from unobtainium (hence the 91k price tag).

I once viewed some engineering videos where 3 single cylinder engines were constructed identically with the exception of bore and stroke. One had an equal bore and stroke, one had a larger bore with shorter stroke, and one had a smaller bore with longer stroke. All 3 engines were identical in displacement, identical valve sizes, identical cams, carbs, and heads.

The engine with identical bore and stroke was tested first and used as a baseline. The test measured hp, torque, and max rpm. Compared with the square engine the short stroke version topped out at a higher max rpm, the long stroke version had a lower max rpm. I don't recall what the hp differences were between the three, but the long stroke version did make the most torque.

If the long stroke engine in this engineering video had been modified (larger valves, different cam, lighter rod & piston, head work, carb work, recurved ignition, etc.) then I imagine it too could have achieved the same rpm or higher than the short stroke motor. But when all things were equal, the short stroke motor achieved the higher rpm (as cjshaker was saying).

[blykins]

Here's the thing though.....no one discussed the price tag, weights, etc.  There's a general stigma floating around on the internet that "long stroke engines won't rev".   Undersquare engines won't rev.  Best scenario is big bore and short stroke.  My general complaint is against those internet "generalizations".  For every generalization, you can find opposing data....i.e. the 4" stroke FE up above turning 9300. 

I'd be interested in seeing the engineering video that you were referring to.  It would be easy to skew the results with a valve package that was more suited for a big bore.

I've built a lot of 428 and 427 combinations over the years.  With similar head flow, cam specs, compression, etc., they are all right there with each other on hp and torque. 

[My427stang]

I think this discussion went way off of the original discussion and Brent's original answer.  In that case, the 3.98 stroke vs 3.78 stroke, or even a 4.25 stroke will all rev equally with IMHO very little additional cost.  New pistons are a wash on all three combos, rods are likely MORE expensive for the 3.78 and 3.98 and crank cost depends on your tolerance for new or used.  Certainly not much different on those builds to drive to 6500 rpm or so

It's not just the stroke that determines ability to rev, and in fact, the stroke can add benefit for a given deck height as well.

- Longer stroke uses a lighter piston
- Longer rod uses and even lighter piston given the same deck

Say we compared the two builds I have going on, a 456 side oiler 3.98 stroke and a 457 428-based 4.25 stroke.  The bob weight on the 427 based motor is almost 2400 grams, the 428 based is 2000 grams, and I am using a heavy rod on the 428.  I was in the low 1900s on the last one with a bigger dish and Molnar rod.  Even without the lighter combo, the two in the garage now have a difference of .88 of a pound for each bobweight.  That's 3 1/2  lbs difference across the entire crank......even with a more modern rod and piston on the short stroke motor, you won't gain back the difference.  Now 3.98 to 3.78,  the difference in piston weight is still an advantage to the long stroke, with minimal changes closer to crank centerline. 

Comparing it to a 289, I can't see how this applies, hardly apples to apples as component weight is significantly different.  In that case, too many different variables to say that a SBF stroke versus FE stroke defines RPM.  Every single component on the SBF is drastically lighter.

I didn't chime in earlier, but within the limits of most of the FEs built here, go for as much stroke as your combo allows, unless you have a good reason.  As far as the 427 vs 428, I think there may be some small differences due to valve shrouding, but it depends on the build, and there may be some gains in other areas with the longer stroke.  Regardless, I would expect power to be very close to the same if all other components were the same between a 427 and 428

[frnkeore]

I have a question and these are the specs:

427, 4.265 x 3.98 = 454.89 CI

428, 4.13 x 4.25 = 455.48 CI

Heads are the same @ 2.25 IN x 1.74 EX, as well as all other components other than rotating assy.

Will they have the same HP?

Same question for a SBF:

302
4.04 x 3.00 = 307.66

260
3.8 x 3.40 = 308.48

Heads, 2.05 x 1.6 valves.

[Hipopinto]

Great question Frank!

This is what I’m wondering but I’m thinking they should be very similar

Thanks
Dave

[67xr7cat]

I'd say years ago a 427 basically picked up where a 428 left off. A low riser head either be about the same. Want more power be a MR, HR, or TP head which requires the bigger bore of a 427. Today with good aftermarket heads can make the power that used to require a 427 with the good factory heads, actually many time even more, but not need the large bore.

Heck a 390 with a 4.125" stroke is about 430ci and will make the power with some TFS heads easier than say a 427 MR.

Now a 427 block is a stronger piece then a 428 block and the larger bore allows more cubes for a given stroke so I'd say a 427 still picks up where a 428 leaves off, just withe heads and strokers of today the that switchover point is a good bit higher then in 1970.

[My427stang]

So let me caveat this that all I did was plug some numbers into the Camquest software, which is free, easy to plug numbers in but I have no idea the assumptions associated with it, or how capable the "guesser" is.  However, it is an easy one to get to on my desktop and had some saved files to lean on

Plugging no changes except for the bore and stroke Frank had, I got the that chart.  Is it accurate?  Who knows, but it does show what I suspect real world would show, ever so slight advantage to a bigger bore for breathing, but not really enough to make a wild difference

Keep in mind, I cannot validate the accuracy, I don't even use this one or compare it to real dynos, but it was an easy one to change data and copy/paste. 

FE on top, SBF on bottom

[My427stang]

Just for laughs I did the FEs on Pipemax, came out almost the opposite.  Pipemax is a pretty good program, but who knows now