NHRA Pro Stock 500 ci bore, stroke, rod ratio...
#2716931
11/17/19 09:54 PM
11/17/19 09:54 PM
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Joined: Jan 2003
Posts: 15,439 Val-haul-ass... eventually
BradH
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This seems to have come up on one or two threads recently. Based on some tech articles I found online going back a few years, here are some generalized answers to these questions, NOT based upon current information.
Block deck heights under 9.0"... probably close to 8.6" or 8.7"
Bore sizes 4.70"+
Stroke range 3.5" to 3.6"
Rod ratio 1.6 to 1.7, depending upon how good the heads are (better heads used with shorter rod ratios)
RPMs... before the NHRA mandated the RPM limit (10,500?), sounds like some engines were turning 11K+, maybe even close to 12K
Interesting, but really hard to talk apples-to-apples with the majority of what's being run or built on here.
Google "NHRA Pro Stock bore stroke" and you should see a couple of articles that discussed this stuff.
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Re: NHRA Pro Stock 500 ci bore, stroke, rod ratio...
[Re: BradH]
#2717006
11/18/19 02:54 AM
11/18/19 02:54 AM
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Joined: Jan 2003
Posts: 6,148 Melbourne , Australia
LA360
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Some Mopar guys seem to really fixate on rod ratios, when in reality, most of the stuff they're running it would make very little difference changing it greatly.
The interesting thing about Pro Stock engines is everyone will be slightly different in it's make up, but they are often making very, very similar power.
Alan Jones
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Re: NHRA Pro Stock 500 ci bore, stroke, rod ratio...
[Re: LA360]
#2717052
11/18/19 09:33 AM
11/18/19 09:33 AM
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Joined: Jan 2003
Posts: 15,439 Val-haul-ass... eventually
BradH
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The interview w/ the Elite Motors engine guy has some interesting comments re rod ratio and head choice.
At the level those engines are, he said they were using upwards of 1.8 RR before the heads had evolved to where they could "keep up" w/ the faster acceleration from TDC of the lower RRs. As the heads continued to improve, they could lower the RR because the better heads weren't the restriction. No mention, at least in that context, of the downside of increased piston-to-wall friction w/ the increased angularity of the rods. However, given their pistons probably look like hockey pucks with valve reliefs, there would be less skirt surface area to be pushed against the cylinder wall, too.
At least this is in sync w/ the general idea I've heard that a longer RR is better when the heads are limited.
The WJ article I read was older, but confirmed some of the "where we came from" context of the later article.
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Re: NHRA Pro Stock 500 ci bore, stroke, rod ratio...
[Re: BradH]
#2717142
11/18/19 12:38 PM
11/18/19 12:38 PM
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Joined: Sep 2014
Posts: 4,457 Washington
madscientist
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I read an article last night I can't find today about a big (900 plus CID IIRC) Sonny Leonard engine and it had over an 8 inch long Rod in it and that was near a 2:1 ratio.
I've said it many times, had a pretty heated discussion with a well known PS engine builder about this very thing. Rod to stroke ratio makes a BIG difference when you are induction limited. I don't even know why that is questioned.
And the FACT is virtually every Chrylser based engine we discuss here is induction limited.
Talking about Rod ratio in a PS is a different discussion because the induction system is more than capable of feeding a paultry 500 CID at 10,500 RPM.
To make the blanket statement that Rod to stroke ratio doesn't matter is rediculous when the entire combination isn't considered.
Just because you think it won't make it true. Horsepower is KING. To dispute this is stupid. C. Alston
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Re: NHRA Pro Stock 500 ci bore, stroke, rod ratio...
[Re: madscientist]
#2717189
11/18/19 02:03 PM
11/18/19 02:03 PM
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Joined: May 2003
Posts: 6,567 Downtown Roebuck Ont
Twostick
Still wishing...
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Still wishing...
Joined: May 2003
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I read an article last night I can't find today about a big (900 plus CID IIRC) Sonny Leonard engine and it had over an 8 inch long Rod in it and that was near a 2:1 ratio.
I've said it many times, had a pretty heated discussion with a well known PS engine builder about this very thing. Rod to stroke ratio makes a BIG difference when you are induction limited. I don't even know why that is questioned.
And the FACT is virtually every Chrylser based engine we discuss here is induction limited.
Talking about Rod ratio in a PS is a different discussion because the induction system is more than capable of feeding a paultry 500 CID at 10,500 RPM.
To make the blanket statement that Rod to stroke ratio doesn't matter is rediculous when the entire combination isn't considered. Fair enough but most of these discussions on rod ratios here revolve more around piston side loading concerns even tho every BBC on the planet has what many here consider an unacceptable ratio. Kevin
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Re: NHRA Pro Stock 500 ci bore, stroke, rod ratio...
[Re: BradH]
#2717207
11/18/19 03:14 PM
11/18/19 03:14 PM
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Joined: Aug 2003
Posts: 43,257 Bend,OR USA
Cab_Burge
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I Win
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Bend,OR USA
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That article is over 4 yrs. old, I wonder what the hot parts are today with EFI?
Mr.Cab Racing and winning with Mopars since 1964. (Old F--t, Huh)
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Re: NHRA Pro Stock 500 ci bore, stroke, rod ratio...
[Re: BradH]
#2717211
11/18/19 03:17 PM
11/18/19 03:17 PM
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Joined: Aug 2011
Posts: 2,871 Pattison Texas
CSK
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Looks like it uses a piston-guided connecting rod set up.
1968 Charger COLD A/C Hilborn EFI 512ci 9.7 compression, Stealth heads, 4.10 gear A518 ODtrans 4100lb,10.93 full street car trim 2020 T/A 392 Stock 11.79 @ 114.5
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Re: NHRA Pro Stock 500 ci bore, stroke, rod ratio...
[Re: mopar dave]
#2717260
11/18/19 05:44 PM
11/18/19 05:44 PM
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Joined: Dec 2013
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GY3
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There is a Pro Stock Tech thread in the Naturally Aspirated section over on Yellowbullet. Nick Ferri posts over there quite a bit and is surprisingly forthcoming with answers to questions and what goes into those engines.
'63 Dodge 330 11.19 @ 121 mph Pump gas, n/a, through the mufflers on street tires with 3.54's. 3,600 lbs. 10.01 @ 133mph with a 250 shot of nitrous an a splash of race gas. 1.36 60 ft. 3,700 lbs.
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Re: NHRA Pro Stock 500 ci bore, stroke, rod ratio...
[Re: LA360]
#2717807
11/20/19 11:01 AM
11/20/19 11:01 AM
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Joined: Jan 2003
Posts: 15,439 Val-haul-ass... eventually
BradH
OP
Taking time off to work on my car
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OP
Taking time off to work on my car
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Val-haul-ass... eventually
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Some Mopar guys seem to really fixate on rod ratios, when in reality, most of the stuff they're running it would make very little difference changing it greatly. Piston compression height calcs for 10.700 RB W/ zero deck height: 3.750 stroke w/ 6.760 rod = 2.065 RR = 1.80 3.910 stroke w/ 7.100 rod = 1.645 RR = 1.82 4.150 stroke w/ 6.760 rod = 1.865 RR = 1.63 4.150 stroke w/ 7.100 rod = 1.525 RR = 1.71 4.250 stroke w/ 7.100 rod = 1.475 RR = 1.67 Not "fixated", just observant...
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Re: NHRA Pro Stock 500 ci bore, stroke, rod ratio...
[Re: GY3]
#2718379
11/22/19 01:17 PM
11/22/19 01:17 PM
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Joined: Mar 2018
Posts: 19 texas
thewolf1970
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There is a Pro Stock Tech thread in the Naturally Aspirated section over on Yellowbullet. Nick Ferri posts over there quite a bit and is surprisingly forthcoming with answers to questions and what goes into those engines. Nick is one of the most brilliant engine builders you will meet or ever know. Man has taught me stuff you would never think of.
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