Re: Gen II Hemis and Longer Strokes above 4.25
[Re: maximus]
#2895626
03/04/21 01:16 PM
03/04/21 01:16 PM
|
Joined: May 2004
Posts: 12,387 Taxes & Virus's R-US, NY
Dragula
I Live Here
|
I Live Here
Joined: May 2004
Posts: 12,387
Taxes & Virus's R-US, NY
|
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.
Last edited by Dragula; 03/05/21 07:09 AM.
|
|
|
Re: Gen II Hemis and Longer Strokes above 4.25
[Re: maximus]
#2895628
03/04/21 01:20 PM
03/04/21 01:20 PM
|
Joined: Dec 2006
Posts: 2,110 Byron, NY
W.I.N. Racing
top fuel
|
top fuel
Joined: Dec 2006
Posts: 2,110
Byron, NY
|
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,
'01 P1500, Blown/Inj BAE,/Veney ,Bruno/CS2,Dana 60 '01 Dodge 3500 S Cummins Auto, Fresh air kit, 4" Exhaust, '05 Dodge Magnum R/T - Too Much to list '60 Willys CJ5 '01 International LPX - Project,DT466, Allison '64 Plymouth Valiant, Inj 528 Hemi, 2spd
|
|
|
Re: Gen II Hemis and Longer Strokes above 4.25
[Re: maximus]
#2895689
03/04/21 03:19 PM
03/04/21 03:19 PM
|
Joined: Jan 2003
Posts: 13,363 Marion, South Carolina [><]
an8sec70cuda
I Live Here
|
I Live Here
Joined: Jan 2003
Posts: 13,363
Marion, South Carolina [><]
|
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".
CHIP '70 hemicuda, 575" Hemi, 727, Dana 60 '69 road runner, 440-6, 18 spline 4 speed, Dana 60 '71 Demon, 340, low gear 904, 8.75 '73 Chrysler New Yorker, 440, 727, 8.75 '90 Chevy 454SS Silverado, 476" BBC, TH400, 14 bolt '06 GMC 2500HD LBZ Duramax
|
|
|
Re: Gen II Hemis and Longer Strokes above 4.25
[Re: maximus]
#2895905
03/05/21 12:20 AM
03/05/21 12:20 AM
|
Joined: Oct 2007
Posts: 4,206 New York
polyspheric
master
|
master
Joined: Oct 2007
Posts: 4,206
New York
|
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.
Boffin Emeritus
|
|
|
Re: Gen II Hemis and Longer Strokes above 4.25
[Re: fbs63]
#2896007
03/05/21 11:48 AM
03/05/21 11:48 AM
|
Joined: May 2004
Posts: 12,387 Taxes & Virus's R-US, NY
Dragula
I Live Here
|
I Live Here
Joined: May 2004
Posts: 12,387
Taxes & Virus's R-US, NY
|
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...
|
|
|
Re: Gen II Hemis and Longer Strokes above 4.25
[Re: fbs63]
#2896080
03/05/21 02:24 PM
03/05/21 02:24 PM
|
Joined: Jan 2012
Posts: 2,645 Stuttgart, Arkansas
rickseeman
master
|
master
Joined: Jan 2012
Posts: 2,645
Stuttgart, Arkansas
|
Most modern Top Fuel engines are 4.188 bore by 4.500 stroke. Hemi's love stroke. I always assumed the small bore was for more head gasket material.
2011 Drag Pak Challenger
|
|
|
Re: Gen II Hemis and Longer Strokes above 4.25
[Re: rickseeman]
#2896087
03/05/21 02:34 PM
03/05/21 02:34 PM
|
Joined: Jan 2003
Posts: 13,363 Marion, South Carolina [><]
an8sec70cuda
I Live Here
|
I Live Here
Joined: Jan 2003
Posts: 13,363
Marion, South Carolina [><]
|
Most modern Top Fuel engines are 4.188 bore by 4.500 stroke. Hemi's love stroke. I always assumed the small bore was for more head gasket material. Or thicker cylinder walls for more rigidity?
CHIP '70 hemicuda, 575" Hemi, 727, Dana 60 '69 road runner, 440-6, 18 spline 4 speed, Dana 60 '71 Demon, 340, low gear 904, 8.75 '73 Chrysler New Yorker, 440, 727, 8.75 '90 Chevy 454SS Silverado, 476" BBC, TH400, 14 bolt '06 GMC 2500HD LBZ Duramax
|
|
|
Re: Gen II Hemis and Longer Strokes above 4.25
[Re: Dragula]
#2896109
03/05/21 03:42 PM
03/05/21 03:42 PM
|
Joined: Feb 2013
Posts: 154 Canada
cuda499
member
|
member
Joined: Feb 2013
Posts: 154
Canada
|
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.
Last edited by cuda499; 03/05/21 03:47 PM.
|
|
|
Re: Gen II Hemis and Longer Strokes above 4.25
[Re: maximus]
#2896166
03/05/21 06:24 PM
03/05/21 06:24 PM
|
Joined: Oct 2007
Posts: 4,206 New York
polyspheric
master
|
master
Joined: Oct 2007
Posts: 4,206
New York
|
"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.
Boffin Emeritus
|
|
|
Re: Gen II Hemis and Longer Strokes above 4.25
[Re: rickseeman]
#2896196
03/05/21 07:21 PM
03/05/21 07:21 PM
|
Joined: Nov 2003
Posts: 1,839 NW Indiana
fbs63
top fuel
|
top fuel
Joined: Nov 2003
Posts: 1,839
NW Indiana
|
Most modern Top Fuel engines are 4.188 bore by 4.500 stroke. Hemi's love stroke. I always assumed the small bore was for more head gasket material. This reason and sleeve thickness plus a small-ish bore is easier to keep the fuel lit off.
|
|
|
Re: Gen II Hemis and Longer Strokes above 4.25
[Re: Dragula]
#2896714
03/07/21 11:13 AM
03/07/21 11:13 AM
|
Joined: Feb 2021
Posts: 70 Souderton
Taylor
member
|
member
Joined: Feb 2021
Posts: 70
Souderton
|
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... 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
04 Ram 4x2 11.66@ 122 4750LBS ...phat pig Moves for fully loaded truck with NA 345ci Hemi 2020 1320 Challenger....stock daily driver.
|
|
|
Re: Gen II Hemis and Longer Strokes above 4.25
[Re: Cab_Burge]
#2896723
03/07/21 11:42 AM
03/07/21 11:42 AM
|
Joined: Feb 2021
Posts: 70 Souderton
Taylor
member
|
member
Joined: Feb 2021
Posts: 70
Souderton
|
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 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.
04 Ram 4x2 11.66@ 122 4750LBS ...phat pig Moves for fully loaded truck with NA 345ci Hemi 2020 1320 Challenger....stock daily driver.
|
|
|
Re: Gen II Hemis and Longer Strokes above 4.25
[Re: maximus]
#2896801
03/07/21 03:51 PM
03/07/21 03:51 PM
|
Joined: Jan 2003
Posts: 31,027 Oregon
AndyF
I Win
|
I Win
Joined: Jan 2003
Posts: 31,027
Oregon
|
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. 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.
Last edited by AndyF; 03/07/21 03:52 PM.
|
|
|
|
|