1.4 ratio rockers installed

Just had a set of scat rockers and moly push rods installed in my 1915 with stock cam. sure woke it up low to midrange. steel push rods are a little noisy after hot though. running dual 40 solex with stock VS headers. i imagine the headers are the next project.
will do heads upon rebuild.

my mech. just about fell over when i said some of this group were running nill to .001 for valve lash with steel rods. mech said they must like to replace valves. any thoughts from the group on lash and steel push rods?

per my last post about the 1.4 rockers and weak motor. comp test was 3@125 lbs. and 1@130. does not burn oil. 4000 trouble free miles so far.

sorry i should not have used the at symbols
3 cylinders are 125 lbs and is 130 lbs and motor is 8.1 comp ratio.

Everybody I've talked to runs moly push rods at .000 lash cold. Your mechanic would rather err on the side of caution, which I understand since he doesn't want to rebuild the heads for free on somebody's car who doesn't know how to adjust valves properly.

Yeah, I agree......there have been a bunch of recent posts on valve lash, and I must admit, I was reluctant to go as tight as everyone else was telling me - anywhere from .000 at cold to .002"

It all has to do with Chromoly push rods. If your mechanic is from the "old era" as I am, all he's probably familiar with are the stock aluminum push rods, which expand at a much greater rate when hot than do the Chromoly versions everyone is using nowadays. To easily tell the difference, pull off a valve cover and touch a small magnet to a push rod. If it sticks, it's Chromoly. If not, it's aluminum.

Chromoly push rods can be reliably set at .000 lash (which, we've seen on here, is just the ability to gently turn the rod in your fingers (with only slight drag) when set right cold. If you're still timid (and a lot of us still are) then set them at .001 or .002 - they'll be a little louder when hot, but not too bad.

If you have aluminum push rods, then set them stock: .004 intakes and .006 exhaust (although many set them both at .004)

What you are relying on here, is for the engine to expand when hot (the whole thing actually "grows" ) but still remain within tolerable limits for valve lash gap. The Chromoly rods expand less, so can be set tighter when cold and are just right when everything gets hot.

Cool?

gn

Jerry,
Try this:
You know what you set the valve clearance when cold, right?

Run the engine until it's up to temp and where you say the valve train gets a little more clattery! Check the clearance now! I'll bet it a tad more than your initial cold setting.. ( I estimate a "tad" to be about .020 )
The point is this: The clearance will USUSALLY never be less than the cold setting (with the exception of valves stretching, seats in heads getting pounded into heads because of the excess spring pressures that are run)and those kinds of physical changes. The changes that happen from temperature USUALLY leave the push rods growing LESS than the rest of the assembly.
As long as the valves never hang open (closed is closed even if it's by .001) they won't burn, or leak compression.

Greg B

Gord; the VW manual recommends both intake and exhaust to be set at .006. I've read that some forum members like to go .004 and .006 (don't remember for which though...).

Manual, Shmanual......."real men don't need manuals"

In the drag car have chromoly push rods, 1.25:1 rockers, and have set them at zero from the beginning. There hasn't been any troiuble at all, and it's gotten some hard use, both track and street.

We also ran them with 1.4:1 rockers in the engine that's being taken down and brought back up for the Porsche. No trouble back then, don't expect any in the future. Rockers held up very well.

It's a great way to go, and produces less noise and less hammering on the valve caps. Gordon's right in saying the everything hinges on the expansion rate(s) of the motor as a whole and the different metals involved in it's components.

Luck with yours,

TC

Did you check valve lift/rocker contact aspect and fit new proper length pushrods, or did you just bolt them on? If you didn't match pushrod length for proper rocker to valve stem contact you may get accelerated valve guide wear.

valve geometry was checked. pushrods are 1/2" shorter and one mounting shim was used under the rocker monting bolts on the head. i guess i will attempt to do the zero lash
myself this weekend.