5.7 VS. 6" Rods - Team Camaro Tech
Engine General Engine Discussion.

LinkBack Thread Tools Display Modes
post #1 of 6 (permalink) Old Oct 14th, 09, 09:13 PM Thread Starter
Senior Tech
Join Date: Jun 2001
Location: Rochester Mn
Posts: 7,749
Smile 5.7 VS. 6" Rods

I am assuming that your question is about "Why would you want 6" rods in a 327 ?"

First, I must say I am not an engineer, so I'm not schooled on all the science of it.

Here is a quote I found:

There are many articles on the web, to explain the reasons. Do a google search with the words : 6" rod vs 5.7" rod

This picture shows what compression height is.

Here is a chart from Ross pistons, showing the differences with different rods etc.

Notice that when you go from a 5.7" Rod to a 6" Rod, your Compression height (CH) also changes by that .300" .

So, why a longer rod ? My understanding is that the angle of the rod to the crankshaft is different, so the actual turning of the crankshaft is easier there by making more H.P.

Correct me here guys ! Let's hear your comments...

69 Camaro -originally a LM1 car. 327, Edelbrock E-streets, hooker, DUI performance distributors, ultradyne cam, stewart, TRW etc. Vintage Air, AGR steering, Corbeau GTSII seats, 700R4 transmission, 12-bolt w/Eaton 4.11:1

Last edited by TJS69; Oct 14th, 09 at 09:54 PM.
TJS69 is offline  
Sponsored Links
post #2 of 6 (permalink) Old Oct 14th, 09, 09:38 PM
Gold Lifetime Member
Join Date: Dec 1999
Location: Yorkville, Illinois USA
Posts: 22,121
Re: 5.7 VS. 6" Rods

I "think" the biggest difference if the amount of time (in degrees of crankshaft rotation) that the piston "hangs around" top dead center. This lets the fire get moving without lighting it so soon, you can run less advance.

There are also differences in "leverage" on the crank, and piston speed.

here is a recommended ratio of rod length to stroke, though I can't remember what exactly it is, 1.7:1 or so??

To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.

To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
New website for my vert is coming together. Do ya like the slide show on the home page?
JimM is offline  
post #3 of 6 (permalink) Old Oct 14th, 09, 10:47 PM
Gold Lifetime Member
T-Bone's Avatar
Join Date: May 2005
Location: Beaverton, Oregon
Posts: 72
Re: 5.7 VS. 6" Rods

Yes, like Jim said the number of degrees of rotation that the piston "hangs around" TDC is longer with longer rods. But for a street motor it probably would only be a few HP difference at peak HP RPM.

The way I like to think of it is: The piston is near TDC and the fuel/air charge is ignited and burns. Then the hot, high-pressure cloud of combustion gas is "pressing hard" against the piston. The longer the piston can stay near TDC the longer the gas can "press hard".

I've seen some near identical engine builds with long and normal 5.7 rods, and they were within a few HP.

Sorry for the rambling.
T-Bone is offline  
post #4 of 6 (permalink) Old Oct 15th, 09, 12:15 AM
Gold Lifetime Member
wiskeesour's Avatar
Join Date: Nov 2006
Location: A van. Down by the river.
Posts: 6,359
Send a message via Yahoo to wiskeesour
Re: 5.7 VS. 6" Rods

Well, Ive have seen identical engines except for different rid lengths be on opposite ends of the RPM hp/trq range.
Longer rods were more torq down low and shorter rods were more HP up hi.

The piston speed is the reason I like longer rods. IIRC, I used a 6" rod and a 283 piston in a 230ci 6cylinder with an OFFY and 2 2bl carbs and it was awesome.

AE2(AW) Harley Moody, USNavy
"Master-at-Arms" for the CDWJB!!
November 26th, 2008 was my last day to serve my country as a member of the World's Greatest Navy.
Thanks Chief.
To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
wiskeesour is offline  
post #5 of 6 (permalink) Old Oct 15th, 09, 04:50 AM
Super Moderator
Bess-68's rule
Everett#2390's Avatar
Join Date: Sep 2000
Location: Va Beach VA
Posts: 31,715
Re: 5.7 VS. 6" Rods

As said, the two reasons are the better angle, read straighter alignment, of the rod to the crankshaft journal, for transfer of force and less piston scuffing/friction against the cylinder wall.

Your Butt Meter would have to be finely calibrated to feel the difference. Longer rod is great for building a torque monster, but with the added weight of longer rod, rpm is kind of limited, all else being the same, meaning a shorter rod engine will rpm higher.

Give a man a rescued dog for the health of both their souls. May 2017 ROTM Winner - Thank you!
To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
CUBS - 2016 World Series Champions - Thank you, Joe Madden enjoy your next chapter.
Everett#2390 is online now  
post #6 of 6 (permalink) Old Oct 15th, 09, 05:12 AM
Join Date: Dec 2003
Location: NORTH EAST
Posts: 938
Re: 5.7 VS. 6" Rods

We have found in our cirlc e track engines going from a 5.7 to a 6.250 rod they both make peak power at about the same RPM per say 6500 example but the longer rod engine at 7500 will make about 30 horse over the short rod engines 2 barrel engines, The longer rods will carry ithe HP longer.

We do use different cam profiles with the longer rods as they doi breath different!!
CNC BLOCKS N/E is offline  
Sponsored Links

Quick Reply

Register Now

In order to be able to post messages on the Team Camaro Tech forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.

User Name:
Please enter a password for your user account. Note that passwords are case-sensitive.


Confirm Password:
Email Address
Please enter a valid email address.
NOTE we receive a lot of registrations with bad email addresses. IF you do not receive your confirmation email you will not be able to post. contact support and we will try and help.
Be sure you enter a valid email address and check your spam folder as well.

Email Address:


Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page
Display Modes
Linear Mode Linear Mode

Posting Rules  
You may post new threads
You may post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On

For the best viewing experience please update your browser to Google Chrome