Re: Very high RPM on pump gas
[Re: hemienvy]
#2706717
10/14/19 01:52 PM
10/14/19 01:52 PM
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Joined: Jan 2003
Posts: 8,077 Tulsa OK
Bad340fish
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I don't know the compression ratio but a guy I know from Drag Week just finished up what I think is a cleveland headed 351 ford. 427 cubes 762 horsepower to the tires at 8300RPM on 93 octane. I don't know the RPM limits but an uneducated guess of mine would be in the 8500 range on pump gas. video https://youtu.be/s3oxTGDiGSc
Last edited by Bad340fish; 10/14/19 01:54 PM.
68 Barracuda Formula S 340
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Re: Very high RPM on pump gas
[Re: Bad340fish]
#2706718
10/14/19 02:08 PM
10/14/19 02:08 PM
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Joined: Jan 2005
Posts: 12,478 Kalispell Mt.
HotRodDave
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It depends on flame speed, with a much shorter stroke the pistons are actually moving slower MPH up and down thus you can run a higher RPM and not outrun the flame front. Like was mentioned motorcycle engines routinely turn 12-15,000 RPM on pump gas butt they are very small displacement but the flame speed and piston speed are probably similar to a stroker engine. A piston going 12,000 RPM with a 2 inch stroke is not traveling any faster on average than a piston in a 4 inch stroke engine running 6000 RPM.
I think what your considering is actually going to be tough because you need a big dome for a hemi to have much compression already, to get a small cube engine to have a lot of compression with those ginormous chambers you are going to need a massive dome that will make a heavy piston and take much longer for the flame front to work it's way around and that is not RPM friendly. Maybe you could weld up the sides of the chamber some like a GEN III hemi so you don't need as big of a dome. You will also still have things like pushrod weight limiting what you can do with the valve train.
Sounds like a fun project, I just don't think the pump gas is going to be a limiting factor.
I am not causing global warming, I am just trying to hold off a impending Ice Age!
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Re: Very high RPM on pump gas
[Re: hemienvy]
#2706724
10/14/19 02:32 PM
10/14/19 02:32 PM
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Joined: Oct 2007
Posts: 4,219 New York
polyspheric
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New York
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Basis for "9-10,000 RPM" with 3.25" stroke?
Boffin Emeritus
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Re: Very high RPM on pump gas
[Re: hemienvy]
#2706727
10/14/19 02:55 PM
10/14/19 02:55 PM
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Joined: Jan 2005
Posts: 12,478 Kalispell Mt.
HotRodDave
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I Live Here
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Light pistons, strong light rods, well balanced crank (center counter weights on a V8) light weight, big bore short stroke, really good flowing heads, light weight valve train (narrow valve stems, titanium retainers, beehive springs), on a pushrod engine you tend to want very high rocker ratios so your lifter and PR can have shorter travel, intake and exhaust carefully tuned to an exact RPM range instead of off the shelf stuff, a shorter deck and/or higher cam position for shorter pushrods, meticulous oil control considerations, smaller bearing journals for lower bearing surface speeds, flat top pistons for best flame travel.
I am not causing global warming, I am just trying to hold off a impending Ice Age!
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Re: Very high RPM on pump gas
[Re: hemienvy]
#2706745
10/14/19 03:38 PM
10/14/19 03:38 PM
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Joined: Oct 2015
Posts: 570 UK
rb446
mopar
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mopar
Joined: Oct 2015
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UK
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I don't know the full spec or CR (wasn't pump gas) of my old mates 351 Pinto that raced in the 80's, but I do know he ran a stock 351C crank and a [img] https://ibb.co/LnrQrkF[/img]stick, launched it around 7800, shifted it near 10000 rpm, ran a best of 8.16@164, survived for a while!!
Last edited by rb446; 10/14/19 03:57 PM.
1969 'Cuda 446ci, best 9.96@133.9 in 1990 1971 340 'Cuda, best 11.01@122.8 in 1987
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Re: Very high RPM on pump gas
[Re: hemienvy]
#2706761
10/14/19 04:43 PM
10/14/19 04:43 PM
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Joined: Aug 2003
Posts: 43,715 Bend,OR USA
Cab_Burge
I Win
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I Win
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Bend,OR USA
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I saw an ad for a 3.250-stroke Hemi crank. So I started wondering about how one would build a 9-10,000 rpm engine to run on pump gas. I thought there were some motorcycle engines that could rev "pretty high", but I don't have a number to put on that. You couldn't have 15:1 compression, but you probably would need a cam with lot of duration, or.....???? How would you build such a motor ? Big heads, low compression ? Let me ask you why would you want to do this, are you crazy 426 gen 2 type Hemiroid motors have inherently bad valve train geometry To answer your question with pump gas a good set of individual shaft rocker and the proper valve train and rocker gear may get you there but with that little tiny short stroke like that it won't have any torque to speak of N/A A stock stroke 426 Street Hemi with that type valve gear would be a lot better choice in my opinion for a high RPM street pump gas motor Torque is what moves the mass, NOT high RPM HP
Last edited by Cab_Burge; 10/14/19 04:44 PM.
Mr.Cab Racing and winning with Mopars since 1964. (Old F--t, Huh)
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Re: Very high RPM on pump gas
[Re: hemienvy]
#2706787
10/14/19 06:45 PM
10/14/19 06:45 PM
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Joined: Oct 2007
Posts: 4,219 New York
polyspheric
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New York
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I was asking how you arrived at 9-10,000 RPM as a target? The rod-breaking stress level @ 10,000 RPM is double that @ 7,000 RPM.
Double the budget, much less power than stock stroke. The whole "the heads will work much better with smaller displacement" has been tried by everyone in the last 80 years. The heads will work very differently, but not necessarily better.
The rod ratio goes to hell. Unless you want a boat anchor for a piston, the rod gets longer by half the stroke change (more if low piston weight is desired): 6.86" ÷ 3.75" = 1.83:1 ratio 7.11" (+ .25" longer rod) ÷ 3.25" = 2.19:1 ratio Do you know what that does to vacuum? To air motion around overlap?
You're throwing 50 years of hemi cam development over the cliff, and starting with a blank sheet of paper.
Ask Barton for the price on a complete set of rockers (take a stiff drink 1st).
Boffin Emeritus
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Re: Very high RPM on pump gas
[Re: polyspheric]
#2706847
10/14/19 10:13 PM
10/14/19 10:13 PM
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Joined: Dec 2007
Posts: 12,593 Great Neck,LI,new york
hemi-itis
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No need to spin them that hard. I have shifted at 7500 with a 4.5 stroke and it was still pullin!!
HEMI-ITIS has no cure. My condition is fully BLOWN!!
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Re: Very high RPM on pump gas
[Re: hemienvy]
#2706935
10/15/19 09:56 AM
10/15/19 09:56 AM
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Joined: Oct 2007
Posts: 4,219 New York
polyspheric
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master
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New York
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there's no reason on God's green earth to ever build a 10,000 RPM engine To win races
Boffin Emeritus
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Re: Very high RPM on pump gas
[Re: polyspheric]
#2706939
10/15/19 10:14 AM
10/15/19 10:14 AM
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Joined: Jan 2003
Posts: 2,316 NE Ohio
DoubleD
top fuel
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top fuel
Joined: Jan 2003
Posts: 2,316
NE Ohio
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there's no reason on God's green earth to ever build a 10,000 RPM engine To win races Unless you are running NHRA Pro Stock then 10,500 is your limit ...... If the rules of the class dictate a cubic inch limit then RPM is the alternative to make horse power - there was a car running a small HEMI on the salt flats as I recall - I would guess that crank came from a class racer at some point But that would be a real difficult and expensive way to make HP in a HEMI
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Re: Very high RPM on pump gas
[Re: DoubleD]
#2706954
10/15/19 10:57 AM
10/15/19 10:57 AM
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Joined: Feb 2005
Posts: 20,272 PA.
pittsburghracer
"Little"John
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"Little"John
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there's no reason on God's green earth to ever build a 10,000 RPM engine To win races Unless you are running NHRA Pro Stock then 10,500 is your limit ...... If the rules of the class dictate a cubic inch limit then RPM is the alternative to make horse power - there was a car running a small HEMI on the salt flats as I recall - I would guess that crank came from a class racer at some point But that would be a real difficult and expensive way to make HP in a HEMI Not to many pro stock guys on this site since AJ retired and our other member switched teams
1970 Duster Edelbrock headed 408 5.984@112.52 422 Indy headed small block 5.982@112.56 mph 9.38@138.67
Livin and lovin life one day at a time
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Re: Very high RPM on pump gas
[Re: polyspheric]
#2706985
10/15/19 12:36 PM
10/15/19 12:36 PM
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Joined: Aug 2003
Posts: 43,715 Bend,OR USA
Cab_Burge
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I Win
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Bend,OR USA
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there's no reason on God's green earth to ever build a 10,000 RPM engine To win races There is a member on here who has a BAE #8 race hemi that has been above 10,000 RPM a bunch of times I believe they where told by BAE that the blown alcohol racers are spinning their motors up to 11,500 RPM I would never advise any one to go their (above 8500 RPM) unless they had a unlimited budget and really like to do a lot of preventive maintenance while racing it
Last edited by Cab_Burge; 10/15/19 12:39 PM.
Mr.Cab Racing and winning with Mopars since 1964. (Old F--t, Huh)
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Re: Very high RPM on pump gas
[Re: hemienvy]
#2706992
10/15/19 12:46 PM
10/15/19 12:46 PM
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Joined: Feb 2013
Posts: 154 Canada
cuda499
member
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member
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Canada
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I saw an ad for a 3.250-stroke Hemi crank. So I started wondering about how one would build a 9-10,000 rpm engine to run on pump gas. I thought there were some motorcycle engines that could rev "pretty high", but I don't have a number to put on that. You couldn't have 15:1 compression, but you probably would need a cam with lot of duration, or.....???? How would you build such a motor ? Big heads, low compression ? You not going to do it with factory lifter placement and factory cam tunnel. Would need a staggered lifter pattern in block, preferably a keyway lifter. also would do it with a 55-60 cam with roller bearings.
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Re: Very high RPM on pump gas
[Re: cuda499]
#2707020
10/15/19 02:13 PM
10/15/19 02:13 PM
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Joined: Jan 2003
Posts: 19,537 Las Vegas
Al_Alguire
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Las Vegas
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Lots of variables to consider biggest being the differences in pump gas that's available out there, there WILL be a power difference in different brands of fuel. Next I would think being able to keep the water and oil temps under control would be another problem. Extra heat is going to make it more detonation prone, so I would imagine that would be a big concern. Next the RPM level you are looking at will create more heat inherently. Im not sure anyone has ever built a pump gas large non boosted automotive V8 type engine for that type of rpm. The parts needed to simply achieve that RPM are not generally whats seen in pump gas type mills. 10,000rpm is a LOT of RPM to be sure. We spin the heads up motor a little harder than that. We do it on a 100 octane fuel as well. However that fuel is HIGHLY oxygenated and of course leaded. FWIW that engine used to be an unleaded pump gas SB engine back when the car went 8.80's
"I am not ashamed to confess I am ignorant of what I do not know."
"It's never wrong to do the right thing"
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Re: Very high RPM on pump gas
[Re: polyspheric]
#2707165
10/16/19 04:27 AM
10/16/19 04:27 AM
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Joined: Nov 2010
Posts: 3,698 jersey
Spaceman Spiff
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jersey
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there's no reason on God's green earth to ever build a 10,000 RPM engine To win races Not since modified production died.
526 cubes of angry wedge, pushbutton shifted, 9 passenger killer!
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