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I've read somewhere that it CAN be done, but it's not an ideal solution. My brother installed a performance hydraulic roller in a small block chevy. The lifters are notoriously heavy and this thing went into valve float very quickly. You can't get crazy on the spring pressures because it collapses the lifters. There are rev kits that sit on the outer edge of the lifter. If you already have the solid cam, why go hydraulic? Looking to use it regularly? From what I've seen of hydraulic roller cams, Comp's Beehive springs , lightweight valves and pushrods would be a big help.

Anyway, like I said, I believe you can do it, but the solid cam's lift rate may be too harsh for the hydraulic lifter.
 

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No, you ablsolutely can not! Flat tappet lobes are tapered, roller lobes are straight and they are not hard enough for th surface pressure of a roller lifter. That's not all; a flat tappet lobe lifts the lifter near the edge, while a roller cam and lifters lifts it closer to the center of the lifter. Therefore, the cam lobes are completely different shape. If you have ever looked at roller cams, the lobe is almost oval. It's not because they are so big and quick, but because tehy work completely different. Believe me, it does not work.
 

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Look at me, I'm a dork. I thought he was asking if he could put Hydraulic roller lifters on a solid roller cam. You're right, jyrki, you cannot put them on a flat tappet cam.
 

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Is this question about installing retrofit cam and lifters into a motor that came originally with a flat tappet hydraulic cam? Sometimes engines need bushed lifter bores or plugged oil passages to install a roller cam, and the "retrofit lifter/cam" may avoid this.
 

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You can put any roller lifter (solid / hyd) on any roller cam (solid / hyd) . The difference is in the ramp angle and how quickly the valve will open, and the springs required for that opening velocity. I am actually having a hyd roller lobe ground for my 452 (boat) that I will be running a solid lifter on. The valve will have great velocity, and I'll run the lash tight (.018 -.020_).
 

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Cam is done. .606 lift, 246 duration, 280 adv duration, lash .020. The lobe is for a hyd roller, but with the solid I am running, it makes the ramps really aggressive. Should make really big power in spite of the small size (I have more way more duration @ .050 in the duster than the adv duration on this cam).


Also, I have never had to do anything to run a roller in a BB mopar other than change out the cam and lifters. But then again I've only run solid rollers. Can't see why it would be any different, but I've been wrong before.

What I do know is that putting any type of flat tappet lifter on a roller cam will cause immediate distruction of the lifter.
Putting a roller lifter on a flat tappet cam, even if the lobe survives for a short period of time, will most likely cause the valves to hit the piston. Why? Because the valve timing events on a roller are based on the center of the lifter, while the valve timing events on a flat tappet are based on the edge of the lifter. You will be off by about 30 degrees (or more), so take your existing cam by 30-35 degrees and see how long it lasts! When was the last time you heard  " My cam said to install it with a 114 centerline, so I threw it in there on a 149 LSA for beter performance...."
 
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