Thread: tappets

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can you run soild flat tappets on a hyd. flat tappet cam?

or are the closing ramps to fast for solid tappets?

By flat tappet, I am guessing you mean lobe. I would say, no. You need a roller lifter for a flat lobe cam. There is too much rebound with that type of cam.
You can substitute solids for hydrolics if it is made for non-roller lifters. You will need to be able to adjust the rockers however.
How much rpm are you trying for?

4500rpm. solid flat lifters seem to make more torque.

tappets are lifters...

"You need a roller lifter for a flat-tappet cam" WTF???

"4500rpm. solid flat lifters seem to make more torque." Based on what criteria?

Based on other peoples experiance.

On Desktop dyno 2000 solids make more torque.

Man, is this thread wandering around.

First, definitions:

Flat tappet doesn't mean cam lobe lobe. Tappets are valve lifters. The word tappets comes from the sound the old lifters made (TapTapTapTap).

There are solid (or mechanical) lifters, hydraulic lifters, solid roller lifters and hydraulic roller lifters. The first two are often referred to as flat tappets, the second two types are often referred to as roller tappets.

Flat tappet camshafts have a slight angle on the lobe, which causes the lifters to rotate and spread out the wear. Roller tappets do not have that angle.

Now, back to the real question, which (restated) was: "Can I run solid lifters on a hydraulic cam?"

I suppose you can, why would you want to? You're going to have more trouble keeping the valve train adjusted, and the assumption that you will get more torque or horsepower at any point in the RPM range won't hold water. You're not going to change lift or duration by running solids. I assume the perceived advantage is higher rpms with not pump-out of the lifters. If you have good hydraulic lifters, you usually get valve float before the lifters will pump out.

Finally, a hydraulic cam is ground for hydraulic lifters. The lobe profiles - particularly the acceleration ramps - are designed for hydraulic lifters. Putting solids in there is liable to cause premature cam/lifter wear and leave you with a box 'o junk for a motor.

You can zero lash your hydraulic lifters and get pretty much the same result as a solid.

On Desktop dyno 2000 solids make more torque.

With the same camshaft? Why would that happen?