Gen II Hemis and Longer Strokes above 4.25

This issue can up and would like a little input on the subject. Is it true the 426 hemi don't like strokes above 4.25? Some guys said they run better with a shorter stroke. The masses agree that bigger is better in bores but what about strokes?

Here is what they are not telling you....The longer the stroke, the shorter the skirt on the piston, the more critical the bore diameter is and a few other things. You want to control the piston gap to .003" ish at that level because the piston wants to shingle in the bore and whips out the cross hatch on the thrust side pretty quick..

So a shorter stroke has a longer piston skirt and is less sensitive to this issue. So in an aluminum block, I wouldn't go over a 4.5 stroke, and even then, the bores have to be real nice...Cast iron, much better. I have a 605 w/4.75 stroke, and it actually has gone faster down the track in the same car with the same internals than my aluminum Indy block did.

4.5 bore x 4.5 stroke is the most popular with the most availability....I would stay away from longer strokes that that. I have seen guys making +800hp NA on Hemi's that were 528 cubes on pump gas. so they have a lot of potential.

Probably one of the best ( power vs life expectancy) in the big inch Hemi world is the 572ci - 4.5 bore X 4.5 stroke. The alky classes have used 4.5 stroke for years as well. If those are any indicators for you . I have a 528 nach asp motor now that needs attention and an trying to convince my self NOT to make it a 572. Also have a 525ci Blown motor with a 4.5 crank so I guess I feel they're safe,

What type application are you wanting to talk about, street, strip only or street and strip? What type of fuel and is the motor in question N/A or does it have a power adder?
Different strokes for different folks
A lot of falsehoods get discussed over and over and some become knowns as truths when they are not

Myself I'm looking for a street strip car. I have a new never used early 4 .375 bore Indy aluminim block, along with a Callies 4.5 crank and Manley Pro rods with 2.2 rod journals. Also have a set of fully ported Mopar aluminim heads. Not sure which direction on intake, possible 871 blower. Getting ideas from the guys on here. Looking into 800 HP level. Would be easy with blower, don't know with a Mopar crossram I have laying around. 93 pump gas or E85 fuel. Any ideas would be helpful.

Yep, hemis w/ more than 4.25" stroke run like crap.

Haven't had any issues w/ my 4.5"x4.5" hemi to speak of. After 15 years of abuse, it finally had enough wear in the bores that I decided to go bigger. Had to buy new pistons anyway, so I took it out another .010".

Longer stroke = higher static CR with the same intrusive dome shape (or smaller dome for the same CR), lower rod ratio gets the piston away from TDC faster, captures more volume at the same IVC point ABDC.

Most modern Top Fuel engines are 4.188 bore by 4.500 stroke. Hemi's love stroke.

Really, that is a question I have asked a couple of times and no one seemed to know. I had started a thread asking if you were building a new engine that was rpm limited per class rules, which feature would take priority, bore or stroke with a 555 limit? The answer I got was typically bore size due to how large an valve I could run and still clear the bore. I was asking this on NA motors, so maybe valve size on a blown motor doesn't matter as much. So are all the BAE motors typically that way too? Most of them claim somewhere between 521-540 cubes, so I am very curious which way those are setup...

I always assumed the small bore was for more head gasket material.

Or thicker cylinder walls for more rigidity?

No one think piston speed has a factor?????? Rpm is a relative term for valvetrain but for bottom end numbers I refer to piston speed.... So you have an engine that has the heaviest piston, and you want it to travel 9 inches (4.5 stroke) per RPM instead of 7ish inches(3.750) per rpm.

And .003ish piston to wall? every piston manufacture has there own specs that they send with the set....... because every piston will grow differently depending on the material they are built out off and bore size.

Fuel engines run 4.5 to 4.625 stroke depending on the tuner - the longer stroke allows for more burn time and spark lead from what I have been told. Since they are limited to 500" the bore can vary slightly also by tuner but I would think the small bore would give more strength to the liner - RPM wise the fuel cars were approaching 10,000 RPM until they started limiting RPM by pulling the timing back at 8100 RPM to bring down speeds - but I would guess they are topping out close to 9000 RPM now

"Blown" + "fuel" means "all bets are off".
There is still no calculation, test, prediction, formula, simulation, model, etc. as to why some engines behave differently under those conditions. All of the valve area per inch, bore/stroke. rod ratio, cam events have produced no known useful results. A winning NA engine may be a complete dog with 40 psi. The Gen-1 Chrysler 392, for many years the only supercharged engine to build, did nothing worth mentioning NA. The Dodge 325 poly NA engine beat the Dodge hemi NA engine, reverse from the boosted results.
What you see winning races is largely empirical, based on:
1. Did it lose, blow up? Don't do that again.
2. Did it win, survive? Do the same thing with tiny tweaks.
3. Repeat.

This reason and sleeve thickness plus a small-ish bore is easier to keep the fuel lit off.

I've been told by a reliable source that the NHRA blown alcohol motors are shifted around 11,500 RPM
That was several years ago on a BAE #8 billet hemi with their best heads, not sure of the bore and stroke used back then though

The Back up BAE my father bought from a No Prep King guy was built for the 2019 season, that's BAE is 4.32X4.50(528CI) with BAE heads 2.525DIA Intake valves, 1.90 something exhaust

10,500-11,500 depending on some of the other factors ,

typically BXS is either 4.187/4.20 the 420 bore puts you @ 498 CI .., with the 4.50 crank , the 4.625 crank guys use 4.125 bore , which is right around 495CI also , sleeves for the 4.125 bore are special order had to come by.

90% of these TF guys are running the 4.187X4.5 combo.

My TFX hemi for my 66 dart project is a 4.187 bore with a Bryant 4.625 ,509 CI with AJPE 426 Stage7 heads, with a F 3D-106 Procharger.

If you already have the parts then use them. 800 hp shouldn't be a problem with good heads and a big cam. Might not be super friendly for street driving though, especially with a cross ram. The only problem with the 4.50 stroke for a street engine is that you'll have to use an external oil system. The external oil systems tend to leak and/or lose prime so they can be a hassle in a street car.

hi

my 4.5 stroke does not have externanl oil system