checking pushrod length w/ hyd. lifters - Hot Rod Forum : Hotrodders Bulletin Board
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Old 11-03-2007, 03:14 PM
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checking pushrod length w/ hyd. lifters

How should I do this? The lifters are stock gm lifters, but I dont know ow to check which pushrod I need because the lifters are hydraulic. How would you usually do this?

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Old 11-03-2007, 05:25 PM
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Quote:
Originally Posted by awoodman
How should I do this? The lifters are stock gm lifters, but I dont know ow to check which pushrod I need because the lifters are hydraulic. How would you usually do this?
Unfortunately one of the lifters has to be solid to take any variable from the hydraulic's free floating plunger out of the measurement. You usually can't by just one solid these days, but you can often get a single hydraulic. The latter can be gutted with a piece of correctly lengthened hardwood or metal spacer installed to take up all the space between the bottom of the inner bore and the bottom of the plunger.

Bogie
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Old 11-03-2007, 06:07 PM
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The lifters have a spring under the plunger to hold the cup up. You can order one of these handy checkers from Summit or Jegs for a few bucks. Just get the correct size for your stud diameter.

Use a stock pushrod and then install the tool and measure the gap on either the pushrod side (need longer rod) or at the valve side (will need shorter rods), then just add/subtract from the length of the rod you are using.



Mark
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Old 11-03-2007, 06:54 PM
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So with that tool I won't need a solid lifter of anything? How does it work? Do you push/screw it onto the stud all the way? And How do you know if the tip of the rocker is rolling on the valve stem the right way? I heard somewhere that those tools only measure the roller tip location when the valve is closed, so they don't work correctly.

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Old 11-03-2007, 07:45 PM
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They just slide down the stud and rest on either the valve stem OR on the pushrod. It is designed so if you get the correct length pushrod, (by measuring the gap) the roller will be in the center of the valve stem. I used it on my engine (in the picture) and when I put the actual roller rocker on, it sat on the stem just fine and made the correct pattern when cycled through one full turn.

You can use the same lifter with this that you are going to use in the engine. Like I stated, the lifters have an internal spring so the cup is up tight at the top.

You can also buy an adjustable pushrod and fiddle with it for a few days getting the correct pattern on the stem. One of the biggest problems is getting the EXACT length pushrod you need. Short of having a set custom made, you can choose some that will be very very close. Mine ended up needing to be .100 shorter than stock and it was fine.

It does not have to be absolutely perfect, unless you are building a $20,000 engine.
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Old 11-04-2007, 12:46 PM
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I heard somewhere that what you can do is rotate the engine until the cyl. 1 intake valve is on the base circle of the cam, then color on the valve stem with a black felt tip marker, put an adjustable pushrod in, set the rocker arm on the stud until it hits both the pushrod and valve stem and then thread the rocker arm nut onto the stud until you just start to feel it tighten(so it doesn't compress the spring in the hydraulic lifter at all) and then just wiggle the rocker arm back and forth a few time, take the nut and rocker arm off, look where the line that it made is. I guess its supposed to be around 1/3 of the way toward the exhaust side of the stem, starting at the intake side of the stem. Does this sound familiar to anyone/is it actually do-able without getting solid lifters to use? Thanks
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Old 11-04-2007, 04:50 PM
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pushrods

I assume this is close to a stock engine??? Does it still have the stock stamped steel rockers??

I have tested almost every method out there over the years to get the correct pushrod length. What i have found is that the pushrod that gives you the most lift at the valve is the correct one.

Now, the tools you need to find that out are not worth the investment for you to do one engine.

If you are running stock valve lengths,stock rockers,the heads and block have not been cut more then .025" total the factory pushrod is fine..

Keith
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Old 11-04-2007, 06:06 PM
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The engine isn't even close to stock. Hyperutectic pistons, compcams .502/.51" lift hydraulic roller cam, scorpion roller rockers, EQ lightning 180cc heads w/ 2.02/1.6" valves. My next big step is pushrod length checking. Ill see if my machinist has a solid lifter i can borrow, but if he doesnt, does that method that I tried work? Thanks
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Old 11-05-2007, 04:49 AM
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pushrods

ok,,all that info was not in your first post..

Other then the rockers your pieces are still stock enough to need a stock length pushrod,,, but because of the rockers you need to check it.But i guess you all ready know that.


This is the way i do it. You need to make a lifter (solid) the same length as your hyd lifters with the pre-load. So if you check the length of a lifter right now out of the engine then subtract the pre-load, lets say .060" you need a lifter that length. You can take the hyd lifter apart and shim the cup with washers to get the correct length, but don't forget to put it all back before final assembly of the engine.

Clean the valve tip with wax and grease remover and also the rocker arm roller that contacts the valve. Mark the top of the valve stem with a black sharpie. Install the stock pushrod and rocker. Set to zero lash and then cycle the engine, (by hand) 2 times or so. Remove the rocker and measure the width of the contact patch on the stem. If it's in the .060 wide range your good to go on pushrod length.

Keith
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Old 11-05-2007, 05:42 AM
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-DETERMINING PUSHROD LENGTH AND VALVETRAIN GEOMETRY/COMP CAMS-
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