Checking valvetrain geometry/correct pushrod length 340
#587050
01/18/10 09:42 PM
01/18/10 09:42 PM
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Joined: Oct 2009
Posts: 248
near St Petersburg, FL
Lifsgrt
OP
enthusiast
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OP
enthusiast
Joined: Oct 2009
Posts: 248
near St Petersburg, FL
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I'm in the middle of checking proper valvetrain geometry and pushrod length on a 340. It's a hyd flat tappet cam. It appears I need a solid lifter to check the properly, as a dry (new) hyd lifter just compresses when the crank/cam is turned. I could disassemble the lifter and install a spacer to replicate the properly lashed hyd lifter for testing, and I see Hughes offers an adjustable lifter for testing purposes. Any thoughts? My friend has already bought the first set of pushrods, and these put the swept area on the valve tip outboard of the valve centerline. Thanks
B3 1969 Charger R/T SE, 440/727 with 3:91s running 11.07@120
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Re: Checking valvetrain geometry/correct pushrod length 340
[Re: Lifsgrt]
#587051
01/18/10 10:11 PM
01/18/10 10:11 PM
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Joined: Mar 2003
Posts: 15,491
the boonies
aarcuda
I Live Here
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I Live Here
Joined: Mar 2003
Posts: 15,491
the boonies
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its really hard with hydraulics. they squish. either shim it or run it and get them pumped up and then try adjusting but you'll find some leak down faster than others. i just went with a solid cam cause it was too darn hard adjusting the hydraulics
if the intakes is off, you can do it visually. or use a really light valvespring with a pumped up lifter so it wont squish
It's got a cop motor, a 440 cubic inch plant, it's got cop tires, cop suspensions, cop shocks. It's a model made before catalytic converters so it'll run good on regular gas.
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Re: Checking valvetrain geometry/correct pushrod length 340
[Re: Lifsgrt]
#587052
01/19/10 01:37 AM
01/19/10 01:37 AM
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Joined: Nov 2003
Posts: 36,040
Lincoln Nebraska
RapidRobert
Circle Track
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Circle Track
Joined: Nov 2003
Posts: 36,040
Lincoln Nebraska
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get a junk hyd lifter and epoxy the cup solid. Using a solid one may have a different depth on the cup & w this hyd one you'll be duplicating your exact dimentions. One less variable that could throw you off.
live every 24 hour block of time like it's your last day on earth
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Re: Checking valvetrain geometry/correct pushrod length
[Re: moper]
#587056
01/19/10 08:33 AM
01/19/10 08:33 AM
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Joined: Oct 2009
Posts: 248
near St Petersburg, FL
Lifsgrt
OP
enthusiast
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OP
enthusiast
Joined: Oct 2009
Posts: 248
near St Petersburg, FL
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Valve stem sweep starts just outboard of the centerline of the valve, then continues out from there to about 1/2 way to the outside edge of the valve (so 2/3 to 3/4 to the outside of the valve.
Thanks for the input, standing by...
B3 1969 Charger R/T SE, 440/727 with 3:91s running 11.07@120
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Re: Checking valvetrain geometry/correct pushrod length
[Re: Crizila]
#587058
01/19/10 01:42 PM
01/19/10 01:42 PM
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Joined: Aug 2003
Posts: 8,716
Baltimore/Denver
64Post
master
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master
Joined: Aug 2003
Posts: 8,716
Baltimore/Denver
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Quote:
Quote:
Valve stem sweep starts just outboard of the centerline of the valve, then continues out from there to about 1/2 way to the outside edge of the valve (so 2/3 to 3/4 to the outside of the valve.
Thanks for the input, standing by...
If, when using a solid test lifter and the valve closed, the rocker to valve stem contact should start on the inboard side ( closest to the rocker shaft ). If the contact starts on the outboard side, the pushrods are too short. Ideally, you want the rocker to wipe equally on both side of the valve stem center line as the valve is lifted through the entire travel.
John, how does pushrod length affect rocker geometry/sweep pattern?
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Re: Checking valvetrain geometry/correct pushrod length
[Re: 64Post]
#587059
01/19/10 02:01 PM
01/19/10 02:01 PM
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Joined: Jan 2003
Posts: 25,200
Upper Midwest
MoparforLife
Too Many Posts
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Too Many Posts
Joined: Jan 2003
Posts: 25,200
Upper Midwest
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Quote:
Quote:
Quote:
Valve stem sweep starts just outboard of the centerline of the valve, then continues out from there to about 1/2 way to the outside edge of the valve (so 2/3 to 3/4 to the outside of the valve.
Thanks for the input, standing by...
If, when using a solid test lifter and the valve closed, the rocker to valve stem contact should start on the inboard side ( closest to the rocker shaft ). If the contact starts on the outboard side, the pushrods are too short. Ideally, you want the rocker to wipe equally on both side of the valve stem center line as the valve is lifted through the entire travel.
John, how does pushrod length affect rocker geometry/sweep pattern?
I have been wondering that too. The pivot point on the rocker shaft remains constant. all shorting the push rod will accomplish is is to lessen the preload on the lifter and if way too short create lash on a hydraulic cam or excessive lash on a solid lifter cam. It won't change the rocker pivot point center to the valve tip. Changing push rod length is no different than changing pre load or lash setting which have no effect sweep pattern either.
Clean it, if it's Dirty. Oil it, if it Squeaks.
But: Don't fix it, if it Works!
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Re: Checking valvetrain geometry/correct pushrod length
[Re: MoparforLife]
#587060
01/19/10 04:26 PM
01/19/10 04:26 PM
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Joined: Oct 2003
Posts: 7,506
Az
Crizila
master
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master
Joined: Oct 2003
Posts: 7,506
Az
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Quote:
Quote:
Quote:
Quote:
Valve stem sweep starts just outboard of the centerline of the valve, then continues out from there to about 1/2 way to the outside edge of the valve (so 2/3 to 3/4 to the outside of the valve.
Thanks for the input, standing by...
If, when using a solid test lifter and the valve closed, the rocker to valve stem contact should start on the inboard side ( closest to the rocker shaft ). If the contact starts on the outboard side, the pushrods are too short. Ideally, you want the rocker to wipe equally on both side of the valve stem center line as the valve is lifted through the entire travel.
John, how does pushrod length affect rocker geometry/sweep pattern?
I have been wondering that too. The pivot point on the rocker shaft remains constant. all shorting the push rod will accomplish is is to lessen the preload on the lifter and if way too short create lash on a hydraulic cam or excessive lash on a solid lifter cam. It won't change the rocker pivot point center to the valve tip.
First, just to clear any confusion, on a fixed shaft system, pushrod length ( by itself ) will not change rocker arm geometry - but in order to have the correct rocker arm geometry, you usually have to change pushrod length (if you are going over 1/2" lift - and for sure with a valve stem height change). You need to be looking at both sides of the rocker arm. With the valve open 65% ( small block )of the total valve lift, the rocker to valve stem contact should be in the middle of the valve stem. At the same time, the rocker arm adjuster screw ( set to show about 1 thread below the rocker surface - or the pushrod cup as close to the rocker as possible )should be in a straight line with the pushrod. Seldom can you get both parameters right without shiming the stands ( draw back to fixed geometry system ) and changing the pushrod lengths. You will also have to contend with rocker to spring retainer clearance issues. Although I think shaft systems are much more stable, Magnum ( chevy ) style systems are much easier to set up - usually just a pushrod change. Sorry if my previous post was confusing. I was basically addressing the fact that his valve stem to rocker contact point ( with the valve closed ) was on the wrong side of the valve stem.
Fastest 300
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Re: Checking valvetrain geometry/correct pushrod length
[Re: Crizila]
#587061
01/19/10 04:33 PM
01/19/10 04:33 PM
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Joined: Jan 2003
Posts: 25,200
Upper Midwest
MoparforLife
Too Many Posts
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Too Many Posts
Joined: Jan 2003
Posts: 25,200
Upper Midwest
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Quote:
Quote:
Quote:
Quote:
Quote:
Valve stem sweep starts just outboard of the centerline of the valve, then continues out from there to about 1/2 way to the outside edge of the valve (so 2/3 to 3/4 to the outside of the valve.
Thanks for the input, standing by...
If, when using a solid test lifter and the valve closed, the rocker to valve stem contact should start on the inboard side ( closest to the rocker shaft ). If the contact starts on the outboard side, the pushrods are too short. Ideally, you want the rocker to wipe equally on both side of the valve stem center line as the valve is lifted through the entire travel.
John, how does pushrod length affect rocker geometry/sweep pattern?
I have been wondering that too. The pivot point on the rocker shaft remains constant. all shorting the push rod will accomplish is is to lessen the preload on the lifter and if way too short create lash on a hydraulic cam or excessive lash on a solid lifter cam. It won't change the rocker pivot point center to the valve tip.
First, just to clear any confusion, on a fixed shaft system, pushrod length ( by itself ) will not change rocker arm geometry - but in order to have the correct rocker arm geometry, you usually have to change pushrod length (if you are going over 1/2" lift - and for sure with a valve stem height change). You need to be looking at both sides of the rocker arm. With the valve open 65% ( small block )of the total valve lift, the rocker to valve stem contact should be in the middle of the valve stem. At the same time, the rocker arm adjuster screw ( set to show about 1 thread below the rocker surface - or the pushrod cup as close to the rocker as possible )should be in a straight line with the pushrod. Seldom can you get both parameters right without shiming the stands ( draw back to fixed geometry system ) and changing the pushrod lengths. You will also have to contend with rocker to spring retainer clearance issues. Although I think shaft systems are much more stable, Magnum ( chevy ) style systems are much easier to set up - usually just a pushrod change. Sorry if my previous post was confusing. I was basically addressing the fact that his valve stem to rocker contact point ( with the valve closed ) was on the wrong side of the valve stem.
Clean it, if it's Dirty. Oil it, if it Squeaks.
But: Don't fix it, if it Works!
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Re: Checking valvetrain geometry/correct pushrod length
[Re: Lifsgrt]
#587065
01/20/10 10:29 PM
01/20/10 10:29 PM
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Joined: Jan 2003
Posts: 25,200
Upper Midwest
MoparforLife
Too Many Posts
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Too Many Posts
Joined: Jan 2003
Posts: 25,200
Upper Midwest
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Quote:
Thanks for the input guys. We'd figured out that the length of pushrod doesn't change the swept area. John, are you saying if you shim the rocker shaft to correct the swept area, the effective lift will change? The current plan is to shim the shafts to get the geometry correct (centered swept area), then measure the pushrod to meet the adjuster with 1-2 threads showing at proper lash. Thoughts? 
The effective lift won't change much, Effective lift will actually change depending on how deep you set your preload or on a solid cam how much lash you have do to the change in angle of the push rod.
We were testing a set of rockers to get a full 16 that were as close to identical as we could. (took 3 sets of new name brand rockers to get one matching set) Any way we were using a sloid lifter and the lift was off to what he had the cam ground to. Followed up bu shimming a hyd. lifter to the preload he uses and then the valve lift was right on. all due to the change in push rod angle.
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Re: Checking valvetrain geometry/correct pushrod length
[Re: 451Mopar]
#587066
01/20/10 10:37 PM
01/20/10 10:37 PM
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Joined: Sep 2009
Posts: 172
Mooresville, NC
Intense RT Dan
member
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member
Joined: Sep 2009
Posts: 172
Mooresville, NC
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Quote:
First, just to clear any confusion, pushrod length does not change rocker geometry on shaft mounted rockers which have a fixed pivot point. Stud mounted rockers like on a Chevy are affected by pushrod length because this determines the height of the rockers pivot point.
Without modifying the rocker stands, the shaft mounted rockers can be raised with rocker shaft shims if the rockers are too low (or shorten the valve stem height.) If the rockers are too high, you could use valve stem lash caps or lengthen the valve stem height.
Pushrod length for hydraulic tappets should preload the lifter about 0.040" +/- 0.020".
This works for stamped rockers or adjustable rockers with the adjuster set correctly for clearance and oiling (depends on type of rocker/adjuster/pushrod ends used?)
Refreshingly accurate.
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Also very important is t omake sure that your installed valve height is tight.
