"Fun" with adjustable rockers and hydraulic lifters

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TWX

KHAAAN!!!
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Hey, nice forum...

I'm building a 408 stroker motor for my Cordoba out of a 360, and having gone through a rather large rigamarole I'm nearly done assembling the thing. When I was talking to Edelbrock about the aluminum heads they strongly recommended adjustable rockers. I found a set at the recent car show that I attended for $75, and the seller claimed that they were original equipment from a 273. Ductile iron, clean, very lightly worn shafts, and ball-cup pushrods that were all decent. Thing is, I'm not sure how to set these things up with hydraulic lifters. Currently I have the adjusters just tight enough that I can barely spin the pushrod with my fingers.

The other issue that I'm having is that I'm worried about interference between the pushrod cup and the cast portion of the rocker. It seems that the pushrods might possibly be ever-so-slightly too long. The cup portion can be taken out of the pushrods, so if I do need to shorten them, how should I go about it? Would it make more sense to just take them to a machine shop and have them take 1/16" or the like off of them?

The main reason why I bought them when I found them is that I'd like to ultimately go to 1.6:1 ratio rockers instead of these 1.5:1 units, but since most of the aftermarket higher ratio rockers require ball-cup pushrods this seemed to be an easy and inexpensive way to get part of the way there now, so I don't have to also buy pushrods later.

Any suggestions?
 
tighten until you feel a very slight drag on the pushrod as you rotate it - then turn 3/4 turn more - that should give you ±.030" pre-load. check to see if you have 1-2 threads showing on the adjusting screw - if not, your pushrods are too long.
 
I think you will find the 273 solid lifter push rods are to long for a hydraulic lifter application. The T/A and AAR 340s had hydraulic lifters and adjustable rockers. Those pushrods were 7.25" in length.


Chuck
 
A friend of mine told me something similar over the phone last night. Someone on Allpar suggested shimming the rocker shaft up a short distance. I'm going to look for shims, and if I can't find the kind I'd like then I'll try to find grade-5 washers that have the right inner and outer diameters, which I'll then bend to shape and install... Assuming that the oiling bolt hole will still pass properly...
 
TWX said:
A friend of mine told me something similar over the phone last night. Someone on Allpar suggested shimming the rocker shaft up a short distance. I'm going to look for shims, and if I can't find the kind I'd like then I'll try to find grade-5 washers that have the right inner and outer diameters, which I'll then bend to shape and install... Assuming that the oiling bolt hole will still pass properly...
Click to expand...
When people talk about shimming the rocker shaft, there talking about .030 or close to that. Not the thickness of a flat washer. The proper way is custom pushrods.
 
You need shorter pushrods than the stock 273 solid pushrods, ones intended for a hydraulic flat tappet lifter and adjustable rockers. Crane, comp etc sells them in sets. If in doubt check their websites for the dimensions and measure what you have to figure out if what you have is correct.

Once you get the right set up, you set the preload in the following way: Bring each valve around to its heel (0 lift). Using the adjuster, take the slack out of the pushrod until it just goes away. Then you need .020 to .060" preload. Since your adjusters have 24 threads per inch, one turn on the adjuster = 1/24 of an inch or about .041", turn them in one full turn and set the lock nut, no more than 20-25 ft lbs torque (dont ask me why I know). repeat for each valve until completed.

If you still have the friction adjusters I recommend replacing them with the lock nut style, which again crane, mopar etc sell.
 
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