My Build!
Drifting
Joined: Aug 2005
Posts: 1,682
Likes: 3
From: League City TX
These are engines originally designed to run 1.6 or 1.7 ratios, most with roller cams. The ones that were originally designed to run 1.6 or 1.7 ratios and flat tappet had a much slower ramp rate than modern cams and more ZDDP in the oils. With a aftermarket flat tappet cam and the known problems with fast ramp rates and modern oils I wouldn't do this. I know the difference don't seem like much but a valve opens and closes 50 times a second @ 6000 RPM. The change in lift and additional pressures put on the lobe due to that change, opening the spring farther resulting in more open spring pressure on the lobe, additional pressure to the internals of the lifter and less than ideal valvetrain geometry all have to be multiplied by 50 times a second. Not a good choice. Better option is select a cam that is designed to open the valve farther but this can't be done without increasing the ramp rate or advertised duration. To safely increase the ramp rate (lift vs duration)at a certain point a roller cam becomes your safest and best option. If you don't want to drop the extra $ to go this route give up some lift and live with the lower power numbers.
But every small block Ford and every Olds motor has 1.6 rockers, every big block Ford & Chevy runs 1.7X rockers, and the Chevy inline 6 cylinders run 1.75 rockers. There are still a bunch of these engines out there without flat lobes or roller cams. More than a few of them are running fairly hot cams too.
Based on the cam the OP was planning to run, a 1.6 rr would increase valve lift about .030". I really doubt that will make the difference between his cam living or dying. Im not guaranteeing a performance increase, but it wouldnt scare me. Of course I am running a flat tappet cam with over .600" valve lift, so I dont scare easy.
