Asked this before, but did not get a solid answer. HAve put a couple hundred miles on my 2056, and am diving in (under) to check the valve clearance. My web cam 494 cam card says to set lash to .006 on intake and exhaust. Stock spec is .006 on intake and .008 on the exhaust. I am running stock pushrods. Which setting should i go for?

If it were me I would follow the cam card. But I don't think you can use stock rods with the 494 cam. You need to do your valve geometry and use cut to length pushrods to actually get the most out of the cam, and increase the life of your engine.

Zach

Pushrod material dictates valve lash, nothing else impacts it as much.
The 494 has a fast ramp, that cam is very particular to valvetrain geometry.

BTW- Web does not build engines, their lash recommendations don't even mention or consider pushrod material as they are generic to all engines.

Is there an optimum pushrod compositon ??? Or is it that some engine / cam combos require steel and others require aluminium / alloy ??? I understand that some material will " grow " more than others but isn't there a common heat range for all the engines , or is it that some engines will run better in different heat ranges ( + / - ) than others ??? Jake you have done this data thing for a long while , maybe you can shed some light on this aspect ( heat range ) .

Jack / Jaxdream

Any time you play with the engine and make changes, you probably change the valve train geometry. This requires a different length pushrod to optimize it. Although back in the aircooled Super Vee days the rules required the stock pushrods and they could be shortened on a lathe with much trouble, Jake as the engine designer chose to use the chro-moly rods. Your engine, your selection. Regardless, this engine in question probably has incorrect geometry.

Stock pushrods are plenty strong, but they are very difficult to use with most cams due to their length that isn't easily adjustable.

I use our chromloly pushrods in all our builds and run zero valve lash with this arrangement.. We never have an issue until someone doesn't listen to our mandates and sets the valves by a book..

EVERY ENGINE requires the valve train geometry to be chacked as 11 variables effect the pushrod length and today with engines and parts being 35 years old+ most engines will see at least 5 of these varialbes applied..

JEFFDON... TO answer your original question, use .oo6ths intake and .008ths exhaust......the reason for the difference is that the exhaust valve will (grow) actually get longer due to exhaust temperature.....008ths valve lash will ensure you HAVE valve lash when the engine is very hot.....with aluminum pushrods.

We still don't know what pushrod material he is using.

Original post:






Aren't stock pushrods aluminum?

Oops, I guess I had two threads confused!

That said, I run .006 on both intake and exhaust with stock pushrods, but thats just me..

Easy to do around here. Thanks for the info!

You know/ I went through the valves at .006 each, and then did a hard look at my carb synch, and it ran better still.....did some twisties in the hills, and it pulled a bit harder, and there was much less down shift/down hill popping.

My new mallory dizzy should come in a few days, and I am stoked about that.