New push-rods: steel or aluminum?

FWIW, I say use the kind thats is one solid piece they come in steel and stainless also.. Dont use the two piece they are too prone to leaks. But hey others may disagree..

Jeremie

I think Mike is talking about push rods, not push rod tubes.

Max

I used Berg CM pushrods but I have to wonder if those HD aluminum jobbies at aircooled.net were the way to go. According to the scuttlebutt, they're strong but don't have the extra weight of a CM. The problem with CM pushrods is that the valve springs have to counter that extra inertia a heavier rod creates.

RT

"Mike Rocket J. Squirrel Elliott"

Aluminum will work fine with that cam and stock or 1.25 rockers, and if you keep it within a normal rev range. Steel should be used if you plan to rev it over 5500, but if not, I think you'll find the steel are unnecessarily noisy.

opps should probaly read it better before I respond..in the case i have no idea! Jeremie

Use the minimum amount of rocker shim you can get away with. That preserves the geometry between the valve ends and the rocker pivots, which is critical for valve guide life. The swivel foot ends are a very nice touch.

If possible, I would stick with the original pushrods. Being made of aluminum gives them a particular thermal expansion which is 3x that of steel. The only reason to switch to steel is if you have large valve train loads which tend to bend the OE pushrods. If you have to switch to steel, then you will have to try to figure out where to adjust your valves, because it's all suddenly different with the different thermal expansion.

----------------------------------------------- Jim Adney snipped-for-privacy@vwtype3.org Madison, WI 53711 USA

-----------------------------------------------

With aluminum push rods you will have the same valve clearance (0.15mm) as on the stock engine. This is important if someone else might be servicing the engine in the future and he isn't informed with the altered specs. If you have dual valve springs, you need Heavy Duty ones, like the ones aircooled.net has. With single HD valve springs, you might be allright with stock alluminum push rods, but I don't know if you can find them unassembled so that you can cut them to the correct length. I prefer alluminum over steel but that's a perssonal opinion.

Adding shims under the rocker towers, is a lazy man's way to avoid grinding the end of the rockers. You don't need any special tools for this job, just grind the valve stem side of the rocker back for 1-1.5mm, so that the thicker face of the swivel adjusters has more room to back out. To grind the rockers get a 1" diameter stone for your drill. Grind the rocker so that the grooves cut durring grinding are parallel to the rocker's longitudinal axis. Then polish the rough area with a flap wheel atached to your drill. Remove the sharp edges arround the cut.

Adding shims under the rocker towers alters the geometry, and is only recomented / needed when you put lash cups on the valve stems, in which case the length of the valve / lash cup is increased.

You should also check if the top of the adjusters hits on the valve cover. If it does, you have to grind the back side of the adjuster screws and cut a new slot for the screwdriver.

Bill, '67 Bug.

This makes sense. Why use heavier steel push-rods in my bus, even with stronger springs? Bicycle frames and tent poles -- both applications where strength along the axis of the tube and light weight are critical

-- all use aluminum.

another problem with steel pushrods is they do not have the same expansion rate as aluminum. VW used aluminum for a reason, and when you use steel PRs, they often clatter like mad when the engine gets hot!

John Aircooled.Net Inc.