Join Date: Apr 2001
Location: Central West Virginia
Re: Solid flat tappet to solid roller
I tend to agree but not with the last bit. I Haven't had anything to do with those particular heads but looking at their published flow data....they are virtually done at .500 lift... gain only 4cfm at .600 and flow drops at .700".
I would tend to think that because the heads are "done" early in the
piece flow wise, you are unlikely to gain much going to a roller.
In other words, if the current cam is meeting head (piston) demand , which is quite high with a 393, you will gain nothing by opening the valve sooner or giving it more lift as the heads flow "window" is already "full".
The smaller the head is for the combo, the more 'strangled' it is going to be. In this situation, it is very beneficial to get the valve open to where it needs to be as quickly as possible... then hold it there as long as possible before setting it down... all while staying within the required duration. A slow acting valvetrain on a small set of heads will give the engine 'asthma'. LOL
Nobody said a 0.800" roller was going to be installed in this 393W with RPM heads. A good roller with the proper lift would probably give this engine a nice little pick-me-up... especially if the solid cam that's in it now is on the slow side.
If the engine already had more cylinder head than it could really use, a roller probably wouldn't be worth that much over a good, modern solid flat tappet with the right specs.