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-   -   Achieving Proper Rocker Arm Geometry (http://www.hotrodders.com/forum/achieving-proper-rocker-arm-geometry-207996.html)

beertracker 11-01-2011 01:49 PM

Achieving Proper Rocker Arm Geometry
 
I have been following this Comp Cams video regarding rocker arm geometry.

http://www.youtube.com/watch?v=Cqx8C...eature=related

Differences between my setup and the video are; I am using stock stamped rockers with ball pivot and hydralic lifters (filled with oil). Lifter is on base cirlcle. Is the video procedure valid with my setup or should I be doing something different?

My valve stem wear bands are too low on the valve stem so I am lengthening the adjustable push rod to move the band up toward intake manifold.

Note in the video they adjust the push rod length with out a poly lock. I tried this but couldn't get the band to move up by lengthening the push rod.

Here is what I am going to try next does this sound right?

Set the adjustable able push rod to stock length 9.125". Mark the valve stem with a marker.

Install rocker arm and tighten down poly lock until slight resistance is felt when rotating the adjustable push rod (zero lash). Lengthen the adjustable push rod until the rocker arm tip (center of contact area) is just inboard (toward intake) center of valve stem. Then give poly lock half a turn and screw down set screw.

Spin engine over a few times. Remove rocker arm and note position of wear band on valve stem.

Adjust push rod length & repeat as necessary.

BT

ap72 11-01-2011 02:51 PM

Quote:

Originally Posted by beertracker
I have been following this Comp Cams video regarding rocker arm geometry.

http://www.youtube.com/watch?v=Cqx8C...eature=related

Differences between my setup and the video are; I am using stock stamped rockers with ball pivot and hydralic lifters (filled with oil). Lifter is on base cirlcle. Is the video procedure valid with my setup or should I be doing something different?

My valve stem wear bands are too low on the valve stem so I am lengthening the adjustable push rod to move the band up toward intake manifold.

Note in the video they adjust the push rod length with out a poly lock. I tried this but couldn't get the band to move up by lengthening the push rod.

Here is what I am going to try next does this sound right?

Set the adjustable able push rod to stock length 9.125". Mark the valve stem with a marker.

Install rocker arm and tighten down poly lock until slight resistance is felt when rotating the adjustable push rod (zero lash). Lengthen the adjustable push rod until the rocker arm tip (center of contact area) is just inboard (toward intake) center of valve stem. Then give poly lock half a turn and screw down set screw.

Spin engine over a few times. Remove rocker arm and note position of wear band on valve stem.

Adjust push rod length & repeat as necessary.

BT

DO NOT adjust the pushrod length to move the wear pattern in or out, only adjust it to minimize the wear pattern. :nono:


If your wear pattern it very far from center you either need new rockers or to move the rocker stud location.

BTW, on stud mount rocker arms you very rarely see a pattern that is perfectly centered, just focus on minimizing the pattern rather than getting it perfectly centered.

beertracker 11-01-2011 03:37 PM

ok, how do I move a rocker stud location? :eek: Photos of the band is located under beertracker's photos. bt

SSedan64 11-01-2011 04:10 PM

Welding/filling the holes & redrilling/tapping. :nono: is the only way to change that.

ScojoDak 11-01-2011 07:43 PM

Quote:

Originally Posted by ap72
DO NOT adjust the pushrod length to move the wear pattern in or out, only adjust it to minimize the wear pattern.

#1. Wrong! Correct pushrod length achieves proper rocker tip placement to the valve tip.


Quote:

Originally Posted by ap72
If your wear pattern it very far from center you either need new rockers or to move the rocker stud location.

Wrong again! See answer #1. And if he was to buy new rockers to fix the problem (according to you), just what rockers would you recommend? Make/ratio/aluminum/steel?

Quote:

Originally Posted by ap72
BTW, on stud mount rocker arms you very rarely see a pattern that is perfectly centered, just focus on minimizing the pattern rather than getting it perfectly centered.

And wrong again! Where are you getting your advice? May I suggest you hire a lawyer and sue the person that taught you how to achieve proper rocker geometry!


Beertracker, the video is dead on regarding rocker arm geometry. DO NOT take ap72's advice.

Richiehd 11-01-2011 07:47 PM

Do you have adjustable push rod? Its a handy tool to use and not very expensive. FYI I think you need shorter pushrod, not longer. Watch the video on the same subject from DART

beertracker 11-01-2011 08:03 PM

:nono: I have all the tools as shown in the CompCams video I referenced previously. :nono: Nothing more to talk about here. :D

ericnova72 11-02-2011 12:29 PM

ScojoDak, you are the one who has it wrong :pain: , you are simply regurgitating the same incorrect method that Comp Cams and others still have up on their web site. Never was the correct method.

AP72's advice is actually the correct method.

Search "Miller Mid-Lift" here and around the web for the only truly correct valvetrain geometry info and how-to.

The info on Comp's site, and the referenced video couldn't be more wrong. Just as Jesel, T&D, and the older Lunati catalog...along with pro engine builders.

ap72 11-02-2011 12:51 PM

Quote:

Originally Posted by ericnova72
ScojoDak, you are the one who has it wrong :pain: , you are simply regurgitating the same incorrect method that Comp Cams and others still have up on their web site. Never was the correct method.

AP72's advice is actually the correct method.

Search "Miller Mid-Lift" here and around the web for the only truly correct valvetrain geometry info and how-to.

The info on Comp's site, and the referenced video couldn't be more wrong. Just as Jesel, T&D, and the older Lunati catalog...along with pro engine builders.

Thanks.

Its amazing how something so simple could be so messed up, if you draw out the geometry in an exaggerated fashion its pretty easily apparent.

cobalt327 11-02-2011 04:51 PM

Quote:

Originally Posted by beertracker
:nono: I have all the tools as shown in the CompCams video I referenced previously. :nono: Nothing more to talk about here. :D

THREAD on geometry.

A more recent thread on mid-lift rocker theory HERE.

Chris Kemp 11-02-2011 05:14 PM

The video is dead on! Been doing it this way for thirty years the only difference in what I used to do and what they are doing is that I have yet to try the newer adjustable pushrods. For years I would use different length tubes and it was a pain in the *****. I would wind up with some times as many six different length tubes in the same engine. Just like the video says "you gotta keep as much of that wear pattern on the center of the valve stem as you can get.

ScojoDak 11-02-2011 05:40 PM

Quote:

Originally Posted by ericnova72
ScojoDak, you are the one who has it wrong. you are simply regurgitating the same incorrect method that Comp Cams and others still have up on their web site.

Then what you need to do is write their technical staff that their 30+ years in the business is "regurgitating" incorrect info.

Quote:

Originally Posted by ericnova72
Search "Miller Mid-Lift" here and around the web for the only truly correct valvetrain geometry info and how-to.

I did thank you and what they enphasize is "then these loads will balance in a straight down direction upon the valve, and NOT be over-arcing and shoving the valve against the guide, causing excessive friction, heat, wear and horsepower loss." They're basically saying the same thing as all the other valve train companies are saying. That is to keep the tip centered!


Quote:

Originally Posted by ericnova72
The info on Comp's site, and the referenced video couldn't be more wrong. Just as Jesel, T&D, and the older Lunati catalog...along with pro engine builders.

You're saying they're all wrong? Youre living in a bubble with ap72!

gtotomm 11-02-2011 11:38 PM

Valve geometry
 
Comp cams info is old tech. It is wasted motion across the tip of the valve stem. Millers mid lift is the correct way to set up valve geometry. It can easly be achieved by changing rocker stud lengths and or rocker arms. I went through this on a 500ci bbc w/ dart pro 1 heads. My contact patterns were not centered(exactly) but the contact patches on the tips were .030 wide through the full lift of the valve, which gave me the least amount of wasted motion. There is absolutly no scrubbing of the roller across the tip of the valve w/ mid lift geometry. :thumbup:

cobalt327 11-03-2011 02:44 AM

Quote:

Originally Posted by ScojoDak
Then what you need to do is write their technical staff that their 30+ years in the business is "regurgitating" incorrect info.

Actually, several months ago I contacted Comp Cams regarding the info on their web page HERE on valve train geometry. I received no response from them.

Truckedup 11-03-2011 03:26 AM

I'm far from an expert on this...The mid lift theory....Smokey Yunick discussed this subject 30 years ago in one of his technical books.
Not a Chevy V-8 but on a vintage performance GMC inline 6. I had rocker geometry issues from changes in the valve stem height ,block and head milling.I spent some time with the engine mocked up cycling the valve train and "adjusting" the rocker geometry so the rocker went the same distance under center during lash and over center during full lift.And also keep the rocker contact near the center of the valve stem. This made sense to me from a mechanical viewpoint......I assume this is what's being talked about?


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