push rod length
Thread Starter
Instructor
Joined: Jul 2012
Posts: 110
Likes: 2
push rod length
Need some adv from the engine builders
Checking push rod length with porform tool
I have a hyd. cam with .500 lift. With lob on base, push rod installed, tool installed. There is about .033 thou. gap at valve tip. Is this ok, because of the preload needed for lifter. Thanks for your help
Checking push rod length with porform tool
I have a hyd. cam with .500 lift. With lob on base, push rod installed, tool installed. There is about .033 thou. gap at valve tip. Is this ok, because of the preload needed for lifter. Thanks for your help
Melting Slicks
Joined: May 2012
Posts: 2,192
Likes: 343
From: Allenton Wisconsin
For me the purpose of checking push rod length was to get the right rocker arm geometry or wear pattern of rocker arm to valve tip. Are you using the tool springs that are for checking the geometry and is your preform tool an adjustable one?
The way that we check for proper push rod length is to install very light duty springs on the two valves for one cylinder,
using a crankshaft turning tool we rotate the crank watching the wear pattern across the top of the valve stem. Adjusting the adjustable pushrod tool until proper pattern is achieved.
Measure the length of the adj. pushrod.
Proceed to the next valve and repeat procedure and take another measurement as the length might be different between intake and exhaust. T
The way that we check for proper push rod length is to install very light duty springs on the two valves for one cylinder,
using a crankshaft turning tool we rotate the crank watching the wear pattern across the top of the valve stem. Adjusting the adjustable pushrod tool until proper pattern is achieved.
Measure the length of the adj. pushrod.
Proceed to the next valve and repeat procedure and take another measurement as the length might be different between intake and exhaust. T
Le Mans Master
Joined: Mar 2004
Posts: 7,437
Likes: 1,463
From: Little Rock AR
Not a big fan of the plastic tool that fits over the rocker stud. It works fairly well for stock stamped rockers but most people are not using those anymore. It would get you close.
Better to use dye on the valve stem tip with the adjustable length pushrod to check for wear patterns. That works for any rocker arm regardless of manufacturer or type.
Better to use dye on the valve stem tip with the adjustable length pushrod to check for wear patterns. That works for any rocker arm regardless of manufacturer or type.
Le Mans Master
Joined: Oct 2002
Posts: 7,098
Likes: 378
From: Las Vegas - Just stop perpetuating myths please.
I use the ProForm plastic cheeter tool and like it. Close is good enough as you see p-rod lengths come in 0.050"increments unless you order custom. Always verify the marks after assembly.
Burning Brakes
Joined: Jun 2020
Posts: 881
Likes: 113
I like an adjustable p rod; both work.
FWIW, OE-type stamped shoe / slider rockers are far less dependent upon PR Length than are anything having a roller Tip.
Most of even the latest OE LS & LT motors' rockers do have a roller Fulcrum but still have a Slider Tip.
It's been proven via SpinTron; most of the friction in rockers is in the Fulcrum and Not at the Tip. Counter-intuitive but true nonetheless.
FWIW, OE-type stamped shoe / slider rockers are far less dependent upon PR Length than are anything having a roller Tip.
Most of even the latest OE LS & LT motors' rockers do have a roller Fulcrum but still have a Slider Tip.
It's been proven via SpinTron; most of the friction in rockers is in the Fulcrum and Not at the Tip. Counter-intuitive but true nonetheless.
Le Mans Master
Joined: Mar 2004
Posts: 7,437
Likes: 1,463
From: Little Rock AR
I like an adjustable p rod; both work.
FWIW, OE-type stamped shoe / slider rockers are far less dependent upon PR Length than are anything having a roller Tip.
Most of even the latest OE LS & LT motors' rockers do have a roller Fulcrum but still have a Slider Tip.
It's been proven via SpinTron; most of the friction in rockers is in the Fulcrum and Not at the Tip. Counter-intuitive but true nonetheless.
FWIW, OE-type stamped shoe / slider rockers are far less dependent upon PR Length than are anything having a roller Tip.
Most of even the latest OE LS & LT motors' rockers do have a roller Fulcrum but still have a Slider Tip.
It's been proven via SpinTron; most of the friction in rockers is in the Fulcrum and Not at the Tip. Counter-intuitive but true nonetheless.
Le Mans Master
Joined: Nov 2003
Posts: 5,770
Likes: 694
From: Maryland
St. Jude Donor '05, '09, '15
Not a big fan of the plastic tool that fits over the rocker stud. It works fairly well for stock stamped rockers but most people are not using those anymore. It would get you close.
Better to use dye on the valve stem tip with the adjustable length pushrod to check for wear patterns. That works for any rocker arm regardless of manufacturer or type.
Better to use dye on the valve stem tip with the adjustable length pushrod to check for wear patterns. That works for any rocker arm regardless of manufacturer or type.
Tom
Race Director
Joined: Jan 2000
Posts: 13,011
Likes: 2,250
From: Corsicana, Tx
2020 C2 of the Year - Modified Winner
2020 Corvette of the Year (performance mods)
C2 of Year Winner (performance mods) 2019
2017 C2 of Year Finalist
Corvette Stories
The Best of Corvette for Corvette Enthusiasts
10 Revolutionary 'Corvette Firsts' Most People Don't Know
Joe Kucinski
5 Reasons to Upgrade to an LS6-Powered Corvette; 5 Reasons to Stay LT2
Michael S. Palmer
2027 Corvette vs The World: Every C8 vs Its Closest Competitor
Joe Kucinski
10 Most Common Corvette Problems of the Last 20 Years!
Joe Kucinski
5 MOST and 5 LEAST Popular Corvette Model Years in History!
Joe Kucinski
2027 Corvette Buyer's Guide: Everything You Need to Know!
Joe Kucinski
10 Things C8 Corvette Owners Hate (But Won't Tell You)
Joe Kucinski
10 Best Corvettes Coming to Barrett-Jackson Palm Beach 2026!
Brett Foote
Every Corvette Grand Sport Explained! (C2, C4, C6, C7, & C8)
Joe Kucinski
Dr. Detroit
Joined: Mar 2012
Posts: 10,091
Likes: 4,016
From: New Braunfels Texas
The video Jim posted is the correct procedure but not everyone can do this at home.
The stock sbc was 7.800 for pushrod length. This length was a nominal and was too short out of the factory for any engine that I have measured. Most all stock head small blocks that I have measured with a stock deck height are 7.850.......of course there are too many variables to set this number in stone.
You claim you have a .033 gap......add that to .020 pushrod plunge and you get the 7.850 number I mentioned assuming you used stock pushrods to "check" with.
You need an adjustable pushrod checker......
The plastic tool assumes bone stock geometry and is damn close for stock hydraulic stuff.....but not really the "right" way.
Jebby
The stock sbc was 7.800 for pushrod length. This length was a nominal and was too short out of the factory for any engine that I have measured. Most all stock head small blocks that I have measured with a stock deck height are 7.850.......of course there are too many variables to set this number in stone.
You claim you have a .033 gap......add that to .020 pushrod plunge and you get the 7.850 number I mentioned assuming you used stock pushrods to "check" with.
You need an adjustable pushrod checker......
The plastic tool assumes bone stock geometry and is damn close for stock hydraulic stuff.....but not really the "right" way.
Jebby
Thread Starter
Instructor
Joined: Jul 2012
Posts: 110
Likes: 2
The video Jim posted is the correct procedure but not everyone can do this at home.
The stock sbc was 7.800 for pushrod length. This length was a nominal and was too short out of the factory for any engine that I have measured. Most all stock head small blocks that I have measured with a stock deck height are 7.850.......of course there are too many variables to set this number in stone.
You claim you have a .033 gap......add that to .020 pushrod plunge and you get the 7.850 number I mentioned assuming you used stock pushrods to "check" with.
You need an adjustable pushrod checker......
The plastic tool assumes bone stock geometry and is damn close for stock hydraulic stuff.....but not really the "right" way.
Jebby
The stock sbc was 7.800 for pushrod length. This length was a nominal and was too short out of the factory for any engine that I have measured. Most all stock head small blocks that I have measured with a stock deck height are 7.850.......of course there are too many variables to set this number in stone.
You claim you have a .033 gap......add that to .020 pushrod plunge and you get the 7.850 number I mentioned assuming you used stock pushrods to "check" with.
You need an adjustable pushrod checker......
The plastic tool assumes bone stock geometry and is damn close for stock hydraulic stuff.....but not really the "right" way.
Jebby
Dr. Detroit
Joined: Mar 2012
Posts: 10,091
Likes: 4,016
From: New Braunfels Texas
Jebby
Thread Starter
Instructor
Joined: Jul 2012
Posts: 110
Likes: 2
This is with the push rod installed. For the checker to sit on the valve I will need to depress the lifter plunger down about .033. Longer push rod does not seam right, Am I just not getting it THANKS Jebby for your help
Dr. Detroit
Joined: Mar 2012
Posts: 10,091
Likes: 4,016
From: New Braunfels Texas
Looks like you are fine for length....the geometry will be close, but you will not know exact unless you have the light tension spring and roll it over.
It is very easy to do....and on stock head you only need to do one....all that is required is an air cylinder hold tool and the adjustable pushrod.
Jebby
Le Mans Master
Joined: Aug 2017
Posts: 8,336
Likes: 2,809
From: Cool Northern Michigan
Some aluminum head manufacturers suggest right from the get-go that a 0.100 longer pushrod will be needed. This is usually due to the extra meat on the cyl head surface and the extra height of the rocker arm stud pad.
I never used a soft valve-spring when I set-up my new aluminum heads & cam. And I just used a felt pen to mark / dye the valve-stem tip.
Keep in mind on a dual pattern cam that both intake and exhaust should be checked, because nether has identical lift.
You may end up buying 8 pushrods different than the other 8 if the wear marks shows to do so.
And then there's the guys that have 8 rocker arms with a different ratio . . . . . . .
I never used a soft valve-spring when I set-up my new aluminum heads & cam. And I just used a felt pen to mark / dye the valve-stem tip.
Keep in mind on a dual pattern cam that both intake and exhaust should be checked, because nether has identical lift.
You may end up buying 8 pushrods different than the other 8 if the wear marks shows to do so.
And then there's the guys that have 8 rocker arms with a different ratio . . . . . . .