I was wondering, what is the difference in the cam itself between a solid lifter and a hydraulic lifter. What would happen if you put hyd lifters on a solid lift cam and vice versa?

 

IIRC, it has something to do with ramp rates... a really 'quick' ramp on the lobe needs solid lifters. I don't know much more though.

 

Should be ramp profiles. Solid roller can have more aggressive ramps since there is no worry about a plunger collapsing.

Also got to becareful with the gear. Solid rollers sometimes don't come with the proper gear so you need to swap out distributor gears. For the most part now Comp cams and other companies put the regular hydra roller gear on them now.

Now if you're talking about solid tappets and hydra rollers that's different... Solid lifter cams have to have gradual ramps so the lifter doesn't try to grind or slide off the lobe. In that case the roller cam is made from harder metal. One reason why rollers are move expensive than tappets.

 

Solid lifter cams use a specific design to pickup and set the lifter down more gently. For this reason you cant use solid lifters with a hydralic lifter cam. You can however use hydrolic lifters with both style cams.

 

You sure? That sounds backwards to me...

 

Thanks, I wasn't going to try to swap lifters and cam, I was just wondering because I see some hydraulic cams with numbers close to milder solid cams.

 

I was pretty sure but now youve got me thinking. I checked a bunch of books but couldnt find anything. Maybe somebody else knows definitivly.

 

NO, you use solid roller lifters w/ a solid roller cam.

Hydro roller lifters w/ a hydro roller cam.

And flat tappet w/ flat tappet.

The solid roller combo is by far the most expensive way to go. But, as always, it offers the most performance from a camshaft. The ramps are extremely aggresive. Check out comp cams site and look through their tech articles. It shows the profiles of 3 different types of lobes. Solid rollers also require a very heavy spring starting at 450# to 800 or even 900# over the nose. If you use a hydro roller lifter w/ that pressure you will collapse the lifter and run the risk of detroying the lifter all together.

Furthermore, flat tappet cam lobes (hydro or solid) are tappered ever so slightly so when the motor is running, they literally rotate in the lifter bore. This helps keep the wear and friction down.

 

We're not talking about roller cams whatsoever.

Lets get back to the subject of flat tappet, hydraulic vs solid.

I was wondering the same thing, I thought you would buy solid lifters, and put them on whatever cam you wanted (ie. a hydraulic flat tappet cam), then maybe bump up the spring rate.... but yea, what is the difference in solid vs hydraulic flat tappet cams themselves?

 

Hydraulic cams have a slow ramp, to help seat the oil check valve in the lifter. They typically start actually opening the valve at about .010" of lobe lift.

Solid cams have a larger lash, usually .020" or so, before the slack is all taken up. THey usually have MUCH steeper ramps.

It is not generally possible to put hydraulic lifters on a solid cam, and have it work very well. The check valve won't check properly before the actual lift ramp begins. However, one can put solid lifters on a hyd cam, and sometimes that can be OK. Typically you'd adjust the lash to around .006" - .008" when doing that. One combo I know of that has worked out well in the past like that, was the old Comp 280HE cam in a 396, with solids on it; we just sort of had them laying around, and we could get all the cams we could stand for free (or close to it) anyway, so it didn't matter if it tore up. It worked OK though. It might have run a little harder that way than with hydraulic lifters on it, but we didn't do back-to-back tests, and it didn't get very many miles to where we could guess at long-term reliability. It did not however run as good as a 282S.

In no case that I can see would it be "better" to deliberately do that, than to use the right lifters and cam together.