ok, i've had my heads shaved, new valves and springs installed, screw-in studs and guideplate installed, 1.52 rollertip rockers and a new hydraulic cam put in. I bought the CompCam adjustable pushrod to check lengths. I made a "solid" lifter and found the correct pushrod length to be 7.700". This length with my homemade solid lifter puts the tip travel in the exact center of the valve stem. But when I used it with the hydraulic lifter and preload it half a turn (.030") this puts the rocker tip way towards the carb side of the valve stem.
When I measure from the bottom of the solid lifter to the top of the rod it is .025" longer than when i measure the 7.700 pushrod with the hydraulic lifter. So I should add .025" to the rod length plus lifter preload of .030 to get the correct length of 7.755". How does that sound?
I was surprised to see how differently the hydraulic lifter works in comparison to the solid. I guess the hydraulic will never let the valve reach the full potential of the camshaft. So I guess I just want to hear what you guys think about my technique...
Will hydraulic lifters ever get to the max lift of the cam? I guess I'll read up on hydraulic lifter behavior... And I'm actually going to switch to the CompCam268, but that shouldn't change the rodlength because of the same base circle the Comp hopefully keeps the same between the 262 and 268.

------------------
1968 Coupe (http://www.eden.rutgers.edu/~vath/Camaro/), 327/210hp project in process. PS/PB, Factory AC, adding camelhumps and a CompCam XE262
1986 Chevy Stepside (http://www.eden.rutgers.edu/~vath/Stepside/), dying 4.3L, TH-400, no A/C, 2wd, 1/4 million miles.

[This message has been edited by JIM68 (edited 01-17-2003).]

The travel will be pretty close if the witness mark starts just above center when on the base of the cam then goes to near center at full lift.
Take a MAGIC MARKER and color the valve tip then rotate the motor that way you`ll have a visual line showing the travel across the tip.
A hyd lifter will collapse about .005-.006 max

------------------
78 Camaro hyd cam 406
TH350-3.23 gear
11.86 ET
116.7 MPH

my hydraulic lifter went down alot more that .005". it went down pretty easy actually. that's why the pattern on the valve stem was so far off when i switched to the hydraulic lifter. it was depressing far down into itself. I don't know what they should be like or if i'm getting funny action because it's not filled with oil or just becasue it's not going over 800rpm. my insticts say to order the 7.750" Hi-tech rods from CompCams (#7970-16).

just to make it clear, my set up is NOT hydraulic roller, just plain hydraulic, with roller tipped rocker arms.

------------------
1968 Coupe (http://www.eden.rutgers.edu/~vath/Camaro/), 327/210hp project in process. PS/PB, Factory AC, adding camelhumps and a CompCam XE262
1986 Chevy Stepside (http://www.eden.rutgers.edu/~vath/Stepside/), dying 4.3L, TH-400, no A/C, 2wd, 1/4 million miles.

You hydraulic is collapsing due to no oil being supplied to fill the inside chamber.

As the lifter is on the base circle and no load applied, oil is pumped inside. Thus, as seen when engine is running with the valve covers off, the spewing of oil onto the fenders from the rocker arms.

When cam rotates more and starts to push up the lifter, the valve spring pressure pushes down on the inside cylinder. This is allowed because of two oil bleed holes and a check valve inside of lifter. When sufficient lift is introduced, cam rotates more, these two bleed holes come out of alignment and the lifter now becomes solid, oil is trapped inside until cam rotates through its cycle and spring pressure is released. Cycle repeats itself on the next revolution.

One can hand pump-up the lifters by pouring oil of sufficent quantity into a 1-3 lb coffee can to submerge the lifter. Then place a weight, or push down with a push rod the inner cylinder and pump the lifter to fill with oil. Stop when no more air bubbles are coming out.

As bigred-72 suggests, use your solid lifter results to determine the push rod length. Five to six thousandths isn't isn't going to matter on the other end.

------------------
Everett "OBJECTS IN THE MIRROR APPEAR QUICKLY UPON RAPID DECELERATION"

The homemade solid lifter you used might have a different plunger height than the actual hydraulic lifters you are using. That might be what is throwing you off.

Just use a hydraulic lifter and pump it up with oil. Then mark the valve tip like the others suggested and rotate the engine a few times. Pull the rocker back off and look to see where the marker got scrubbed off. It should be a pattern that is across the center of the valve tip. Being off a little one side to the other is no big deal, but you really don't want to be close to the edge of the valve tip on either side.

IMO Usually SBC pushrods wind up too short if anything. Since your heads were milled the pushrods would in theory "act" a little longer so I bet you'll be just fine with a stock length pushrod. If I recall you're not running anything fancy that will significantly change your valve geometry one way or the other anyway.

[This message has been edited by Eric68 (edited 01-17-2003).]

[This message has been edited by Eric68 (edited 01-17-2003).]

Ok, so it definitely was the fact that the hydraulic lifter wasn't filled with oil. And yes my homemade solid lifter does have a highier plunger height, that is the .025" I need to add because i'll be using comps hydraulic lifters.

just a little trick if anyone else is planning on using adjustable pushrods: instead of adjusting the length by the adjuster nuts that come with the rod, just stack flat washers inbetween and tighten down the two rod pieces. I did this and it works out nicely, this way you can tighten down the rod and not worry about the stop nut spinning.

thanks guys

------------------
1968 Coupe (http://www.eden.rutgers.edu/~vath/Camaro/), 327/210hp project in process. PS/PB, Factory AC, adding camelhumps and a CompCam XE262
1986 Chevy Stepside (http://www.eden.rutgers.edu/~vath/Stepside/), dying 4.3L, TH-400, no A/C, 2wd, 1/4 million miles.