denk

When using a Hydraulic Flat tappet Cam with Adjustable Roller Rockers mounted on pedestals, what valve lash is to be used?

Long story short: This is an engine I used for a Drag car and am trying to detuned it for the street by using a different cam set up rather than the solid lifters type previously used.

CatSkinner

Tried looking for an answer, got some definitive numbers for a racing engine, but a lot of vagueness for street. I'd venture to say 16 thousandth is a reasonable number from everything I've read. If anybody's got a better number, please speak out.

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Prius repellant, just add gas.

chipset

how " much " of a drag engine do you have ? If it is pretty beefy you will have to do a
lot more than changing the cam and lifters to get it streetable.

denk

The only items 'leftover' are 0.030" overbore and 12:1 pistions.

Do you think that would make a big difference?

CatSkinner

The .030" shouldn't be an issue, but I'd thinkn the 12:1 pistons might make it a little rough on the low speeds, not unbearable, but rough.

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Prius repellant, just add gas.

xdclevo

You don't run any "lash", you actually have lifter "preload", which means the pushrod is pushed into the Hydraulic lifter a certain amount. Usually around the 40 thou preload mark, but can be down to near zero preload with certain setups.

And be carefull trying to run too much compression on a small Hydraulic cam. People talk of what compression pistons they have, but what actual static compression do you have when its all worked out? Piston volume, head chamber volume, head gasket thickness, piston to deck height etc.

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10.70 @ 125.00 on the black fun top
408 Cube Cleveland.

Big Block Ford

As xd said there is no valve lash on hydraulic setup.

There is a factory setting but this is with the lifter completely bled down or collapsed using a tool on the rocker arm to slowly bleed the lifter down, and that is 3/8-inch. This is hardly ever done and may not be so relevant with parts so different to factory but it could give some sort of starting point to measure to so perhaps helpful to you.

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Lance
71 429SCJ Mustang

Reverb

If you measured your pushrods with a solid hydraulic lifter (as you should - take the internals out etc) then there'll be no lash - you measured with zero pump so you should install with zero pump up.
How did you measure your pushrods? You know they will change length with the different cam and lifter setup.