I was checking out rhoads lifters, they seem like pretty slick pieces. I understand how they work but what I'm wondering is how they affect an engine's dynamic compression ratio.

since the lifters make cams seem "smaller" lower in the rpm range will a higher compression ratio cause detonation?

say I have a cc306 and I run at 11.5:1 SCR and 8.5:1 DCR, will the lifters make my DCR in the lower rpm range over the safe range for pump gas by changing the intake valve closing point?

Or would a higher compression ratio not be needed in the first place with these lifters since they would keep the bottom end from getting sluggish?

 

I was looking into them myself. The negative I have heard is that they are on the noisy side. With todays high lift cams and new technology such as beehive springs and computer controls I'm not sure they have as much of market.

 

My opinion of them is leave them on the shelf, if you are losing lift at low oil pressure I would be afraid they never actually pump up. I have built two motor alike, one had regular hyd. flat tappet, other rhodes lifters, yes the rhodes lifter motor was always ticking the rockers even at high rpm with 60psi oil pressure, both motors ended up in one car at different times, the rhodes lifter motor always ran about .15 slower at the track.

A cam is designed to use the ramp angles to open the valve, not allow the lifter to act as a spring when opening.