pushrod length (quickie)

[Turbo 6 Justin]

okay trying to get this damn motor into the car for the nats so time is real short one thing we kind of forgot about is the pushrod legth. details comp cams 212/212 454 lift cam comp lifters stock head gasket with ARP bolts to 70psi and .006 off the head none taken of the block. WIll the stock pushrods work? saving the several hours to take the manifold off again and check all this would be a big help in getting the car down there. So the basic question has anyone run this combo before and not had any cam issues, everything else on the motor is set just this last little snag.

Thanks!!!

 

[Scott231]

Why don't you simply measure the preload? With the intake manifold off, use a wire-gauge style feeler and measure the distance the plunger has moved down inside the lifter.

Generally, the preload should be between .022 and .060. Best place to put 'em is right in the middle. About .030-.035"

There is a write up about this at www.gnttype.org/techarticles/

 

[Turbo 6 Justin]

okay I'll ask these questions because I am confused. But first scott I didn't want to have to take the manifold back off since we still need to get the motor in break in miles done and on a trailer set for the nats in the next few days.

Now onto my confusion, our lifters are hydraulic and as such they pump up with oil pressure so in my mind the lifter will 'look' different with presure on it, then you take a pushrod and press against it with the valve spring pressure and it pushes against the oil pressure??? so depending on oil pressure the lifter will be more or less compressed??? now on how to measure it. I have read the gnttype article but am still confused. do I measure from the center divot of the lifter, the 'wire' that holds it all together or the outer edge? I assume I measure one of these against the top of the lifter body??

basically I get confused with the first measurement, after that I throw in the pushrods torque the rockers down and measure again. as long as it moves down .025-.060 I am good .035 is better but the rest is still okay (I understand how it effects the power band through the RPM range so no need to explain that).

thanks scott and anyone else who replies

 

[Scott231]

Measuring preload without removing the intake manifold

OK, ok. Here is how you can measure lifter preload without removing the intake manifold.

Remove a valve cover with the engine at TDC for a cylinder. With some sort of a straightedge (ruler), lay it across the head's valve cover mounting surfaces (top & bottom) so that one edge is against the pushrod for the TDC cylinder. Scribe a line on the pushrod.
Note: it may be necessary to remove the rocker shaft and remove the adjacent pushods so that the strightedge will fit.

Next, loosen the rocker shaft to the point of the rocker arms just barely touching the tips of the pushrods. Use the straightedge again and scribe a new line. The difference in the two lines scribed on the pushrod is the lifter preload.

How's that for non-complex?