long rod vs short rod? - Moparts Forums

Register Log In Moparts Forums Unlawfl's Race & Engine Tech long rod vs short rod?

Print Thread

Page 1 of 3

1

2

3

long rod vs short rod? #633297 03/07/10 09:08 PM 03/07/10 09:08 PM
Joined: Jan 2005 Posts: 656 G griff70440 OP mopar
griff70440 OP mopar G Joined: Jan 2005 Posts: 656	Hi I have a 6.535 rod in my 511 and its time to re ring and put new bearings in the motor. my question is would it be worth it to change the rod to a longer one?any HP gains?(I know I have to change the pistons too) this is my combo now 400 stroked to 511 345-1`s jesel rockers and belt drive mid 7`s roller 14-1 compression(ross pistons) tunnel ram w/2-1050`s rod lenght(6.535) thanks mike

Re: long rod vs short rod? [Re: griff70440] #633298 03/07/10 10:22 PM 03/07/10 10:22 PM
A Anonymous Unregistered
Anonymous Unregistered A	Nope, not worth it.....it's like peeing in the ocean to raise the tide.......not even noticeable.......The rod just connects the piston to the crank........ Wayne

Re: long rod vs short rod? #633299 03/08/10 12:27 AM 03/08/10 12:27 AM
Joined: Oct 2007 Posts: 4,206 New York polyspheric master
polyspheric master Joined: Oct 2007 Posts: 4,206 New York	And there are a large number of people, including me, who hold the opposite opinion. This group also includes all auto, airplane, motorcycle, diesel and tractor engine manufacturers and builders for the last 100 years. Your choice. Boffin Emeritus

Re: long rod vs short rod? [Re: polyspheric] #633300 03/08/10 12:39 AM 03/08/10 12:39 AM
A Anonymous Unregistered
Anonymous Unregistered A	Quote: And there are a large number of people, including me, who hold the opposite opinion. This group also includes all auto, airplane, motorcycle, diesel and tractor engine manufacturers and builders for the last 100 years. Your choice. Opinion is one thing, facts are another..... Show me some actual dyno numbers that actually amount to anything that would be enough to change the MPH of a 3,700LB car at the drag strip.........I'll be holding my breath...... Are YOU saying the OP is going to see a power gain by swapping rods and pistons, while keeping EVERYTHING else equal??? Wayne

Re: long rod vs short rod? #633301 03/08/10 12:53 AM 03/08/10 12:53 AM
Joined: Jan 2004 Posts: 27,347 Today? Who Knows? 1_WILD_RT Management Trainee
1_WILD_RT Management Trainee Joined: Jan 2004 Posts: 27,347 Today? Who Knows?	Quote: Quote: And there are a large number of people, including me, who hold the opposite opinion. This group also includes all auto, airplane, motorcycle, diesel and tractor engine manufacturers and builders for the last 100 years. Your choice. Opinion is one thing, facts are another..... Show me some actual dyno numbers that actually amount to anything that would be enough to change the MPH of a 3,700LB car at the drag strip.........I'll be holding my breath...... Are YOU saying the OP is going to see a power gain by swapping rods and pistons, while keeping EVERYTHING else equal??? Wayne Wayne, Start Breathing... Be spending allot of money for no measurable change

Re: long rod vs short rod? [Re: 1_WILD_RT] #633302 03/08/10 06:33 AM 03/08/10 06:33 AM
Joined: Dec 2008 Posts: 1,200 UK 6 602heavy pro stock
602heavy pro stock 6 Joined: Dec 2008 Posts: 1,200 UK	Long rod/short rod both have their advantages/disadvantages , in my view comp height would be the deciding factor on rod length , more so when using power adders , i would always lean towards a long rod over the short one due to side loading , lots of opinions on this although no real performance gain when using either rod. Ever been asked rod length when having a cam speced for you're motor?...............

Re: long rod vs short rod? [Re: 1_WILD_RT] #633303 03/08/10 08:35 AM 03/08/10 08:35 AM
A Anonymous Unregistered
Anonymous Unregistered A	Quote: Quote: Quote: And there are a large number of people, including me, who hold the opposite opinion. This group also includes all auto, airplane, motorcycle, diesel and tractor engine manufacturers and builders for the last 100 years. Your choice. Opinion is one thing, facts are another..... Show me some actual dyno numbers that actually amount to anything that would be enough to change the MPH of a 3,700LB car at the drag strip.........I'll be holding my breath...... Are YOU saying the OP is going to see a power gain by swapping rods and pistons, while keeping EVERYTHING else equal??? Wayne Wayne, Start Breathing... Be spending allot of money for no measurable change Yeah, I'm the little blue guy in Oklahoma...... Wayne

Re: long rod vs short rod? #633304 03/08/10 10:26 AM 03/08/10 10:26 AM
Joined: Oct 2007 Posts: 4,206 New York polyspheric master
polyspheric master Joined: Oct 2007 Posts: 4,206 New York	Opinion is one thing, facts are another..... Great answer. I'd explain, but you're already too smart. Boffin Emeritus

Re: long rod vs short rod? #633305 03/08/10 11:14 AM 03/08/10 11:14 AM
Joined: Feb 2004 Posts: 6,257 acworth / N. georgia - south e... cheapstreetdustr master
cheapstreetdustr master Joined: Feb 2004 Posts: 6,257 acworth / N. georgia - south e...	i wont argue if the change should be made.. or if in this situation it will mean much difference in output. however to ignore the elephant in the room..(ie;whats the differnce in rod length matter?) i would direct the attention to the port volume of the head and the cam being used.. a longer rod..as a matter of fact...gives more piston dwell..at top and bottom. if the intake port volume has a smaller ratio to cubic inces.(lacking sufficient port volume) then the longer rod and the right cam event timing..could produce more power.. understanding/knowing this can make a difference. Imho. combustion chamber efficiencies will also factor. so it WOULD be relevant...atleast for arguement sake.. again..it may not be relevant in this motor.. but theoretically its relevant. it would factor in when starting from a clean sheet of paper and what approach you want to take. again..fwiw. cheapst. 365" Iron J heads,,3480lbs best 1.39 60ft on SS springs.10.54,124 mph ...6.67 1/8th et.average 60fts 1.46 w/ small cam &.063 no2 pill tagged & insured [image][/image]

Re: long rod vs short rod? [Re: cheapstreetdustr] #633306 03/08/10 12:24 PM 03/08/10 12:24 PM
Joined: Jan 2007 Posts: 3,695 nc E emarine01 master
emarine01 master E Joined: Jan 2007 Posts: 3,695 nc	Power gain is not the only way to look at this question, what about failure rate and longevity,

Re: long rod vs short rod? [Re: emarine01] #633307 03/08/10 12:49 PM 03/08/10 12:49 PM
A Anonymous Unregistered
Anonymous Unregistered A	Quote: Power gain is not the only way to look at this question, what about failure rate and longevity, The OP asked if there are any horse power gains......and this isn't a Comp Eliminator motor....... Wayne

Re: long rod vs short rod? #633308 03/08/10 12:54 PM 03/08/10 12:54 PM
Joined: Feb 2004 Posts: 6,257 acworth / N. georgia - south e... cheapstreetdustr master
cheapstreetdustr master Joined: Feb 2004 Posts: 6,257 acworth / N. georgia - south e...	Quote: Quote: Power gain is not the only way to look at this question, what about failure rate and longevity, The OP asked if there are any horse power gains......and this isn't a Comp Eliminator motor....... Wayne Understood... cheapst 365" Iron J heads,,3480lbs best 1.39 60ft on SS springs.10.54,124 mph ...6.67 1/8th et.average 60fts 1.46 w/ small cam &.063 no2 pill tagged & insured [image][/image]

Re: long rod vs short rod? #633309 03/08/10 01:00 PM 03/08/10 01:00 PM
Joined: Jan 2003 Posts: 9,997 Frostbitefalls MN (Rocky&Bullw... gregsdart master
gregsdart master Joined: Jan 2003 Posts: 9,997 Frostbitefalls MN (Rocky&Bullw...	Don't worry about the rod length, just pick a piston that is the most stable for the rings for good seal and long life for your app. The 6.535 length is just fine. Roughly a 1.3 pin height is great as well. Lots of guys are running that setup with excellent results. 440Jim is an excellent example. Not many are as fast as his car running similar cams,heads,etc. You can engineer something to the Nth degree, for a very small return, or you can not worry about whether you got that 1 or 2 hp and spend the money racing. Last edited by gregsdart; 03/08/10 01:03 PM.

Re: long rod vs short rod? [Re: cheapstreetdustr] #633310 03/08/10 01:01 PM 03/08/10 01:01 PM
Joined: Jan 2007 Posts: 3,695 nc E emarine01 master
emarine01 master E Joined: Jan 2007 Posts: 3,695 nc	Ok I see your point, From what I have read there is a small power gain on the long rod but it would not be cost effective to change an existing set up unless money was no problem, Something to be considered @ the planning of a new build

Post deleted by Defbob [Re: polyspheric] #633311 03/08/10 01:30 PM 03/08/10 01:30 PM
A Anonymous Unregistered
Anonymous Unregistered A

Re: long rod vs short rod? #633312 03/08/10 01:43 PM 03/08/10 01:43 PM
Joined: Nov 2004 Posts: 6,890 North Alabama M Monte_Smith master
Monte_Smith master M Joined: Nov 2004 Posts: 6,890 North Alabama	There is something to be said for skirt loading, dwell time and a few other things, but in the big picture, the rod connects the piston to the crank and thats it. Most high end motors, do tend to stuff as much rod in as possible, but that is as much about weight as anything. A .100 on rod length is a good deal less weight than a piston with a .100 more compression distance. Also boils down to intent and purpose of the motor. As said, the original poster asked about his combo in particular...so will a longer rod give him more power...NO Monte

Re: long rod vs short rod? #633313 03/08/10 02:39 PM 03/08/10 02:39 PM
Joined: Oct 2004 Posts: 8,165 Left Coast B BobR master
BobR master B Joined: Oct 2004 Posts: 8,165 Left Coast	Quote: Nope, not worth it.....it's like peeing in the ocean to raise the tide.......not even noticeable.......The rod just connects the piston to the crank........ Wayne PERFECT analogy!

Re: long rod vs short rod? [Re: BobR] #633314 03/08/10 03:27 PM 03/08/10 03:27 PM
Joined: Feb 2004 Posts: 3,441 Mo. S supercomp master
supercomp master S Joined: Feb 2004 Posts: 3,441 Mo.	Our 500 with 6.535 rods made 845 hp with single carb on gas. Simple build. I don't think a longer or shorter rod would have made much difference.

Re: long rod vs short rod? [Re: griff70440] #633315 03/08/10 04:30 PM 03/08/10 04:30 PM
Joined: Jan 2003 Posts: 5,875 communist bloc of new jersey J jamesc master
jamesc master J Joined: Jan 2003 Posts: 5,875 communist bloc of new jersey	would i bother changing the rod length, no. would i generally put the longest rod in an engine i could from the start, yes. i know a shorter rod can have positive effects under certain conditions but overall i prefer longer rods. Yunick always preached longer rods and he had a bit of experience.

Re: long rod vs short rod? [Re: griff70440] #633316 03/08/10 04:37 PM 03/08/10 04:37 PM
Joined: Jan 2003 Posts: 31,029 Oregon A AndyF I Win
AndyF I Win A Joined: Jan 2003 Posts: 31,029 Oregon	I'd use the longest rod that fits when building the motor but now that you have it together I doubt that I'd go to the expense of changing parts. Not sure you can put much longer rod in there anyway. Maybe a 6.70 Chevy rod will fit in a low deck but that would be about the extent of it. Not like an RB block where you can run a 7.10 rod and still have plenty of room for the rings.

Page 1 of 3

1

2

3

Moderated by Al_Alguire, Hotwheelsjr, moparts, not_a_charger, RangerDan440, tboomer

Hop To

Powered by UBB.threads™ PHP Forum Software 7.7.1