It is currently Sun May 03, 2026 5:11 am

Board index » Tech and Fab » Air Cooled Engines

All times are UTC - 5 hours [ DST ]




Post new topic Reply to topic  [ 4 posts ] 
Author Message
 Post subject: rod lengths???
PostPosted: Mon Jul 06, 2009 3:15 pm 
Offline

Joined: Sun Aug 03, 2008 3:15 pm
Posts: 303
Location: laurel indiana
i wanna hear some talk bout rod lengths in stroker engines 82mm,84mm cranks..the diffrent sizes short vs long.. stock, 5.5, 5.6, 5.7,what works for what and what doesnt??? does the longer rods change the powerband rpm??? shorter rods shorter engine life??? thanks...


Top
 Profile  
 
 Post subject: Re: rod lengths???
PostPosted: Mon Jul 06, 2009 3:33 pm 
Offline
WB Contributor
User avatar

Joined: Mon Nov 05, 2007 7:52 pm
Posts: 1405
Location: Zanesville, OH
From my knowledge bank.....accuracy around 90-95%

A shorter rod will produce more bottom end power because of a shorter throw. This will also increase wear on pistons and the like because of the angle of the rods/pistons.

A longer rod will produce more topend power because the throw is longer. This also straightens out the piston/rod angles and will have better life.

Depending on the size of the motor also has a lot to do with it. In my 2332 I like the 5.6 A lot of kentucky guys like the 5.7 in the same motor. 2387 I have heard like 5.5's but we are putting a set of 5.6's in that one also. We pretty much are all running 5.6's around here.

_________________
2332cc Air Cooled Screaming Meanie. Predator Singleseat.

"Lets go get stupid"


Top
 Profile  
 
 Post subject: Re: rod lengths???
PostPosted: Wed Jul 08, 2009 5:58 pm 
Offline
BOTM Winner
User avatar

Joined: Mon Dec 25, 2006 1:57 pm
Posts: 1343
Location: Patrick Springs, Virginia
Rod ratios are a tricky thing. Everything has to work together as a package. Changing one thing in a set up can make a big difference. Kyle is correct in his statements. I want to add one thing.

Two motors side by side, both identical let's say both of them are 2276 with the same heads, cam and compression. One has stock length rods and one has 5.7 rods. Both motors will make the same power (close) but the shorter rod engine will make it lower in the rpm range. The longer will make it higher in the range and will rev higher. Both will run differently because of the different air speed through the heads. This is a direct result of the piston speed being different and the time the piston spends at TDC.
Air speed will be different in both so they will both need different camshafts to run great (or the same). It depends on what you want the motor to do, you can't have it all. You have to sacrifice on some things to gain on others. You can design a motor to run the way you want for the most part. Talk to experienced engine builders and you can learn a lot. You will also get conflicting opinions. :|

_________________
________________________________

Buy the best and cry once.


Top
 Profile  
 
 Post subject: Re: rod lengths???
PostPosted: Wed Jul 08, 2009 10:01 pm 
BIGGER is better! 8) 6.0 carillo rods all the way.


Top
  
 
Display posts from previous:  Sort by  
Post new topic Reply to topic  [ 4 posts ] 

Board index » Tech and Fab » Air Cooled Engines

All times are UTC - 5 hours [ DST ]


Who is online

Users browsing this forum: No registered users and 0 guests


You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot post attachments in this forum

Search for:
Jump to:  
Powered by phpBB® Forum Software © phpBB Group