Physical Differences Between Rocker Ratios - Team Camaro Tech
Engine General Engine Discussion.

Reply
 
LinkBack Thread Tools Display Modes
post #1 of 18 (permalink) Old Jul 11th, 09, 05:48 PM Thread Starter
Banned
Ron
 
Badbird's Avatar
 
Join Date: Jul 2005
Location: Dearborn Heights, MI
Posts: 3,176
Physical Differences Between Rocker Ratios

Hi....I just got done pulling the race cam out of my 327, I'm going with the L-79 hydraulic cam.....The motor is equipped with what appears to be new stamped steel roller tipped rocker arms along with adjustable rocker nuts.....I'd like to make sure, before I reinstall these rockers, that they are 1.5 ratio.....Is there a way to tell the differences between the various ratio rocker arms?.....If these rockers aren't 1.5 ratio, what would happen if I installed them with the L-79 camshaft?.....Would it change or alter the cam timing specs because that's something I don't want to do?
Badbird is offline  
Sponsored Links
Advertisement
 
post #2 of 18 (permalink) Old Jul 11th, 09, 06:30 PM
Moderator
Bill
 
Join Date: Aug 1998
Location: Waldorf Md. USA
Posts: 3,291
Re: Physical Differences Between Rocker Ratios

Ron,
The difference is in the distance from the center of the pivot point to the pushrod. The distance from the pivot to the valve has to stay the same. So if you have a known 1.5 rocker, and a good way to measure it, compare it to the ones you have and see what you got. Only other way is to actually measure valve lift on a cam with a known lobe lift and a solid lifter.

Bill Koustenis
Owner
Advanced Automotive Machine
Waldorf Md
1971 Chevelle "Heavy Chevy" original owner


To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
BillK is offline  
post #3 of 18 (permalink) Old Jul 11th, 09, 07:27 PM Thread Starter
Banned
Ron
 
Badbird's Avatar
 
Join Date: Jul 2005
Location: Dearborn Heights, MI
Posts: 3,176
Re: Physical Differences Between Rocker Ratios

That's just it, Bill!.....I don't have any other rockers to measure for comparison!.....I don't know what the rocker ratio is on these rockers!....Do you think you could measure one of your 1.5 and 1.6 ratio rockers?.....I don't want to get into anything other than the stock 1.5 ratio rockers as I read that an increase in rocker ratio will increase the cam lobe lift, something I don't want to do!
Badbird is offline  
 
post #4 of 18 (permalink) Old Jul 11th, 09, 07:36 PM
Senior Tech
george
 
Join Date: Sep 2006
Location: detroit
Posts: 2,291
Re: Physical Differences Between Rocker Ratios

And check your valvetrain geometry.Chances are the race cam has a small base circle and uses longer than stock push rods.Verify the sweep across the valve stem tip with the new camshaft, even with confirmed 1.5/1 rockers.

George
68 Camaro
8-71 blown 461 Rat on E-85
fatblock is offline  
post #5 of 18 (permalink) Old Jul 11th, 09, 07:53 PM
Senior Tech
george
 
Join Date: Sep 2006
Location: detroit
Posts: 2,291
Re: Physical Differences Between Rocker Ratios

Quote:
Originally Posted by BillK View Post
Ron,
. Only other way is to actually measure valve lift on a cam with a known lobe lift and a solid lifter.
Like Bill stated..you know your lobe lift off the cam card..install a rocker with a solid lifter at 0 lash and mount a dial indicator on the spring retainer with some preload and then zero the indicator.Rotate the engine to max lift and record the reading.If you have a .300" lobe and measure .450" ..you have a 1.5/1 rocker ratio.If you have a 1.6/1 rocker..you most likely will see .480".

George
68 Camaro
8-71 blown 461 Rat on E-85
fatblock is offline  
post #6 of 18 (permalink) Old Jul 11th, 09, 07:53 PM Thread Starter
Banned
Ron
 
Badbird's Avatar
 
Join Date: Jul 2005
Location: Dearborn Heights, MI
Posts: 3,176
Re: Physical Differences Between Rocker Ratios

George, to tell you the truth, I'm really leary of reusing either these rockers or the push rods!.....Do you know what the length of a stock push rod is for a sbc?
Badbird is offline  
post #7 of 18 (permalink) Old Jul 11th, 09, 08:01 PM Thread Starter
Banned
Ron
 
Badbird's Avatar
 
Join Date: Jul 2005
Location: Dearborn Heights, MI
Posts: 3,176
Re: Physical Differences Between Rocker Ratios

Quote:
Originally Posted by fatblock View Post
Like Bill stated..you know your lobe lift off the cam card..install a rocker with a solid lifter at 0 lash and mount a dial indicator on the spring retainer with some preload and then zero the indicator.Rotate the engine to max lift and record the reading.If you have a .300" lobe and measure .450" ..you have a 1.5/1 rocker ratio.If you have a 1.6/1 rocker..you most likely will see .480".

George....I don't have a solid lifter nor a dial indicator to check this out.....Probably best to just purchase stock rods and rockers, pretty cheap for a small block mouse motor!
Badbird is offline  
post #8 of 18 (permalink) Old Jul 11th, 09, 08:19 PM
Senior Tech
george
 
Join Date: Sep 2006
Location: detroit
Posts: 2,291
Re: Physical Differences Between Rocker Ratios

Quote:
Originally Posted by badbird View Post
george, to tell you the truth, i'm really leary of reusing either these rockers or the push rods!.....do you know what the length of a stock push rod is for a sbc?
7.794".

George
68 Camaro
8-71 blown 461 Rat on E-85
fatblock is offline  
post #9 of 18 (permalink) Old Jul 11th, 09, 09:02 PM
Senior Tech
george
 
Join Date: Sep 2006
Location: detroit
Posts: 2,291
Re: Physical Differences Between Rocker Ratios

Quote:
Originally Posted by Badbird View Post
George....I don't have a solid lifter nor a dial indicator to check this out.....Probably best to just purchase stock rods and rockers, pretty cheap for a small block mouse motor!
I agree that the initial cost is minimal.At least spend the time to insure the rocker sweep is valve stem tip/guide friendly.
If it is not..your looking at e-baying the new oem pushrods and purchasing customs.Why are you concerned with an increase of .030' lift and maybe 2* more duration with the L79 with 1.6/1 rockers?I doubt you have pv clearance issues after swapping out a race cam with tons of overlap.If i am reading you right..you are detuning for the street.Nothing wrong with that.How big was the race cam and why the old school/blueprint grind?

George
68 Camaro
8-71 blown 461 Rat on E-85
fatblock is offline  
post #10 of 18 (permalink) Old Jul 12th, 09, 11:46 AM Thread Starter
Banned
Ron
 
Badbird's Avatar
 
Join Date: Jul 2005
Location: Dearborn Heights, MI
Posts: 3,176
Re: Physical Differences Between Rocker Ratios

I don't know the specs on the race cam as I didn't install it, it was in the motor when I bought the car....All I know is what I was told from the previous owner that there was a small fortune spent on this motor and I believe it!....The previous owner bought the car non running so all he knew is what he was told!....The car was a non running project when I purchased it and it's obvious that this car was intended strictly for the drag strip!....The "old school/blueprint grind" is just my personal preference!.....I just want to finish and detune this motor to my liking and that includes the L-79 cam, stock pushrods and stock rocker arms.....There is no need to mess with the valve springs, if they handled the race cam then they will handle the L-79 cam!
Badbird is offline  
post #11 of 18 (permalink) Old Jul 12th, 09, 12:14 PM
 
Join Date: Apr 2000
Posts: 21,341
Re: Physical Differences Between Rocker Ratios

Are your head's p/r slots longer?

I say this b/c I bought a "Louis/Slotting" tool from Jegs to lengthen mine towards the rocker studs just to make dam sure that my CHEAP 1.6 ratio STOCK type rockers w/ a tall cam would be OK.

I'm shooting for right at .500" here.

pdq67



pdq67 is offline  
post #12 of 18 (permalink) Old Jul 12th, 09, 05:00 PM
Senior Tech
george
 
Join Date: Sep 2006
Location: detroit
Posts: 2,291
Re: Physical Differences Between Rocker Ratios

Ron..any numbers on the old cam that can help identify it?
Was it a flat tappet hydraulic camshaft that you removed?Prior to the cam swap..did you ever do a cranking compression test and if so,what was the psi?
Typically..high rpm performance shafts have a later intake valve closing point and the builder will up the static compression ratio to compensate.
What happens when you back down on the cam..the ivc point is sooner and builds cylinder pressure quicker at lower rpm.Great for torque..but now the higher static cr is not reqd and may bump you up and over 200 psi on the starter motor.This is not really pump gas friendly.
Interested in how it works out for you.

George
68 Camaro
8-71 blown 461 Rat on E-85
fatblock is offline  
post #13 of 18 (permalink) Old Jul 12th, 09, 11:20 PM
Senior Tech
 
Join Date: May 2001
Location: Ashby,MN, USA
Posts: 8,305
Re: Physical Differences Between Rocker Ratios

aren't the ratios of most non stock ratio rocker arms stamped on them?

you don't plan sincerity.
you have to make it up on the spot.

wanna hear about 20 years ago when i was too smart to know any better?
novaderrik is offline  
post #14 of 18 (permalink) Old Jul 13th, 09, 01:10 AM
Gold Lifetime Member
Harley
 
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: Physical Differences Between Rocker Ratios

FYI, stock chevy rockers arent exactly 1.5.they are more somewhere between 1.45 and 1.47 so make sure you use true 1.5 rocker. I just finished a flattop 882 headed 350 with the L79 cam and used true procomp 1.5 rockers on the exhaust and true procomp 1.6 rockers on the intake and its in a 68 short wife p/u. raost the tires at will and gets abbout 14MPG. more cab tuning and Ill probably get 15-16mpg if he keeps his foot out of it, but its so much fun to roast the tires at will even while moving 30 mph. ...lol

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 #15 of 18 (permalink) Old Jul 13th, 09, 02:36 PM Thread Starter
Banned
Ron
 
Badbird's Avatar
 
Join Date: Jul 2005
Location: Dearborn Heights, MI
Posts: 3,176
Re: Physical Differences Between Rocker Ratios

Quote:
Originally Posted by pdq67 View Post
Are your head's p/r slots longer?

Yes, they are, Paul.....Is this procedure typically done to use 1.6 rockers?
Badbird is offline  
Sponsored Links
Advertisement
 
Reply

Quick Reply
Message:
Options

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

Password:


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:
OR

Log-in










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