Checking pushrod length with stock rockers - Vintage Mustang Forums

 
Thread Tools
post #1 of 11 (permalink) Old 02-17-2017, 10:38 AM Thread Starter
Senior Member
 
Kelly_H's Avatar
 
Join Date: Apr 2010
Location: Austin, TX!
Posts: 5,318
Checking pushrod length with stock rockers

I'd like to check my pushrod length as I think that they're not quite right (too short). Maybe I should have checked that back before I went and put 10,000 miles on the engine, but whatever.

So I am familiar with the technique of using a pushrod length checker and a sharpie on the valve stem tip to "center" the roll point of a rocker. However, this seems like it would only work for roller rockers, which have a very small linear contact patch. But it seems like it wouldn't work for a stock rocker, which has a flat button on it similar to this:



Am I incorrect? It could be that the button is slightly domed so it would still leave a line using the Sharpie test, but I recall it being pretty flat on mine so wanted to check with others about how that test would go.

If the sharpie test won't work with stock rocker arms, how should I check pushrod length instead?


Calamity Jane 1966 Modified Fastback - Driven semi-daily!
Wrecked and rebuilt even better
289 v8, 4-speed, 3.25 9" rear, goodies and stuff.

See my travel blog here for my adventures: http://calamityjaneroadtrip.blogspot.com/
2014: 10,051 mile, 2-month-long road trip around America
2015: 3,000 mile trip to Knotts in CA, CO to East Coast, an engine rebuild or two
2016: East Coast to TX, Hot August Nights, more trips to the East Coast
2017: Several long trips in the works! Stay tuned
Kelly_H is offline  
Sponsored Links
Advertisement
 
post #2 of 11 (permalink) Old 02-17-2017, 12:04 PM
Senior Member
 
Join Date: Nov 2013
Location: La Jolla, Ca
Posts: 652
You are correct with the stock rocker having a slight curve(arc). I used to use dykem blueing, to check contact or for scribing lines, but the sharpie will work to check your contact patch.

Using those high dollar words like "linear" must be scaring your usual followers this morning.
Kid Mechanic is offline  
post #3 of 11 (permalink) Old 02-17-2017, 12:22 PM
Senior Member
 
Join Date: Sep 2016
Posts: 189
There is so much acceptability in a hydraulic system they would really have to be short ( a lot ) to have a problem.
Claudemiro is offline  
post #4 of 11 (permalink) Old 02-17-2017, 12:27 PM
Senior Member
 
maladezo's Avatar
 
Join Date: Jul 2015
Posts: 531
If the rods are short, it is possible to get a harmonic vibration going thru the valve train which will hurt performance a lot. Eyeball the rockers for level, you do not want them to rotate down too far. With adjustable rockers the adjustment threads should show much more above than below. More threads below will be too much rotating down. Seems to me, with stock rockers there is not much room for different lengths. Proper lash is the only concern.

'67 coupe, 390-S, 4spd.
maladezo is offline  
post #5 of 11 (permalink) Old 02-17-2017, 03:43 PM
Senior Member
 
rickgto's Avatar
 
Join Date: Jul 2011
Location: Illinois
Posts: 640
It'll work the same Kelly. The stamped or cast rockers might make a wider contact patch but nonetheless, they follow the same checking procedure. Keep in mind you should use a solid lifter with same dimensions (lifter face to cup seat height) or shim a good used hydro lifter to solid. Once you determine correct length, add .040" to .060" to accommodate lifter preload. Unless you're running solids that is....Also, as said, don't get to finicky to make each or all of them "perfect". Very close is good enough.
rickgto is offline  
post #6 of 11 (permalink) Old 02-19-2017, 05:17 PM Thread Starter
Senior Member
 
Kelly_H's Avatar
 
Join Date: Apr 2010
Location: Austin, TX!
Posts: 5,318
Gah! Forgot to get back on this thread.

Claudemiro and maladezo - your posts both a bit confusing? To clarify, I have adjustable stock rockers, not the ones that just bottom out on the stud. Now not sure if I should worry about it or if I should not and how much is "too rotated down"?

Rick - hadn't intended on using a solid lifter because I am not pulling the intake. I had just thought to pull off the rocker arm, color in the valve tip, put the rocker arm back, and then pull it off again and see where the line is. More difficult than that? Why would I add 0.040 - 0.060"?

I read an article in Hot Rod earlier and saw something they said about the stamped steel rocker arms: "These rockers used a very wide rocker tip with a very gentle radius that was extremely forgiving when it came to pushrod length. The pushrod length could be short or long and the broad rocker-arm tip would accommodate it.". True? Should I maybe just leave it alone?


Calamity Jane 1966 Modified Fastback - Driven semi-daily!
Wrecked and rebuilt even better
289 v8, 4-speed, 3.25 9" rear, goodies and stuff.

See my travel blog here for my adventures: http://calamityjaneroadtrip.blogspot.com/
2014: 10,051 mile, 2-month-long road trip around America
2015: 3,000 mile trip to Knotts in CA, CO to East Coast, an engine rebuild or two
2016: East Coast to TX, Hot August Nights, more trips to the East Coast
2017: Several long trips in the works! Stay tuned
Kelly_H is offline  
post #7 of 11 (permalink) Old 02-19-2017, 05:54 PM
Senior Member
 
rickgto's Avatar
 
Join Date: Jul 2011
Location: Illinois
Posts: 640
Absolutely correct. No matter stamped, cast, or roller tip, precise valve train geometry has more, or everything to do, with getting the cams full lift moreso than any wear problems. Exactly why I said not to get too involved. Don't want to get into rocker 101 but what happens when geometry is off is the valve will never see full lift and/or valve acceleration will be altered simply because the rocker's geometry is off. As far as using a solid lifter, if you check geometry with a hydro, it'll bleed as you're turning the engine giving a false reading. It'll appear as the cam having much less lift than it does and not printing on the stem correctly. In the nutshell, rocker geometry should have equal travel from start of lift, to full lift, across the valve stem. My advice is, with the miles you have and how happy you are with how it runs, leave it alone... You'll see no difference in power or reliability.
rickgto is offline  
post #8 of 11 (permalink) Old 02-19-2017, 06:06 PM
Senior Member
 
Woodchuck's Avatar
 
Join Date: Aug 2016
Location: Peoples Republic of Vermont
Posts: 2,123
Send a message via Yahoo to Woodchuck
You can't use a checking pushrod with a hydraulic lifter (that hasn't been modified). Your best bet, with 10k on the motor now, is to look at the contact patch on the valve tip to determine if it's off-center, by how much, and using some of that geometry from school to determine how much to add (or subtract) from the pushrod length.

Bart

What, me worry?
- Alfred E. Neuman

Woodchuck is offline  
post #9 of 11 (permalink) Old 02-19-2017, 06:08 PM Thread Starter
Senior Member
 
Kelly_H's Avatar
 
Join Date: Apr 2010
Location: Austin, TX!
Posts: 5,318
Hmm, interesting... not sure how I would get a hydraulic lifter to work for this reading then but I really am not interested in pulling the intake just to measure this thing!

There is actually a reason that I'm chasing my tail on this. When I rebuilt my motor last year, I basically replaced the old parts with new parts that were exactly the same spec (except for the pistons - upped the compression a bit in that department). Same bore and everything. However, the cam that I got from Lunati has a smaller base circle than my original cam did. Same lift/duration/LSA, but smaller base circle. I had to stab it in because they were 3 weeks late on the cam anyways and I was running out of time to get the motor together, but ever since then I have just wondered if now the pushrods are a bit too short. Not sure how forgiving the valvetrain is, and to be honest I'm not sure if the pushrods were even the right length originally (PO built the original motor) so probably it is worth checking if I can con someone into helping me out. I have to pull the springs anyways to do new valve seals so it seemed like a kind of reasonable "while I'm at it".

What is the general range of acceptability for good valvetrain geometry? I suppose what I'm asking is, should the pushrod length be close to within a tenth of an inch of "perfect"? A hundredth?


Calamity Jane 1966 Modified Fastback - Driven semi-daily!
Wrecked and rebuilt even better
289 v8, 4-speed, 3.25 9" rear, goodies and stuff.

See my travel blog here for my adventures: http://calamityjaneroadtrip.blogspot.com/
2014: 10,051 mile, 2-month-long road trip around America
2015: 3,000 mile trip to Knotts in CA, CO to East Coast, an engine rebuild or two
2016: East Coast to TX, Hot August Nights, more trips to the East Coast
2017: Several long trips in the works! Stay tuned
Kelly_H is offline  
post #10 of 11 (permalink) Old 02-19-2017, 06:23 PM
Senior Member
 
Woodchuck's Avatar
 
Join Date: Aug 2016
Location: Peoples Republic of Vermont
Posts: 2,123
Send a message via Yahoo to Woodchuck
How much smaller base circle....and, why, if you don't mind me asking?

Bart

What, me worry?
- Alfred E. Neuman

Woodchuck is offline  
post #11 of 11 (permalink) Old 02-20-2017, 02:10 AM Thread Starter
Senior Member
 
Kelly_H's Avatar
 
Join Date: Apr 2010
Location: Austin, TX!
Posts: 5,318
Well, I can't find the measurements of the new cam's base circle... old one was 1.5" though, according to my notes. The new one is definitely at least a tenth of an inch smaller but beyond that I can't say specifically by how much, which is terrifically useless.

As for why, I have no idea. I told Lunati to duplicate my cam. They screwed around, almost screwed me over, and finally ended up overnighting this thing to me along with my old cam that I had sent them for duplication. They have the same specs (lift, duration, LSA) but the new one is a smaller base circle. Would have sent it back and told them "no, I want EXACTLY the same" but by then they had already dicked me over enough that I had to have the car back in one piece in less than a week, which meant they had no more time to screw around some more trying to actually do what I told them to do.

Can you tell I'm a little bitter about my experience with this company? LOL.

At any rate, the cam is in there, it's broken in, it's got 10k miles on it, it ain't going anywhere. So I just want to make sure that the rest of the valvetrain is playing nice with it since I guess it's in there for the next decade or 100k miles or however long it takes me to kill the motor again.


Calamity Jane 1966 Modified Fastback - Driven semi-daily!
Wrecked and rebuilt even better
289 v8, 4-speed, 3.25 9" rear, goodies and stuff.

See my travel blog here for my adventures: http://calamityjaneroadtrip.blogspot.com/
2014: 10,051 mile, 2-month-long road trip around America
2015: 3,000 mile trip to Knotts in CA, CO to East Coast, an engine rebuild or two
2016: East Coast to TX, Hot August Nights, more trips to the East Coast
2017: Several long trips in the works! Stay tuned
Kelly_H is offline  
Sponsored Links
Advertisement
 
Reply

Quick Reply
Message:
Options

Register Now



In order to be able to post messages on the Vintage Mustang Forums 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 for yourself.

Email Address:
OR

Log-in









Human Verification

In order to verify that you are a human and not a spam bot, please enter the answer into the following box below based on the instructions contained in the graphic.



Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page



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 On
Trackbacks are On
Pingbacks are On
Refbacks are Off

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