Not a Cobra owner but thought I would post my limited roller cam experience.
One of the best things about roller cams is that you don't have to worry about having a lobe go flat during break-in like a flat tappet. You get a lot more area under the curve than for like duration flat tappet cams and with a smoother idle. (We've graphed quite a few different cam lobes and there is no comparison.) Might be just my imagination but it seems like a lot of people are having problems with lobes going flat recently. Maybe the lack of
zinc in the
oil? My brother lost 15 lobes during break-in of a Comp solid cam last year. What a pain-metal everywhere. Had to pull the motor so we switched to a spare 427 and custom solid street roller in his Fairlane. That car was a mid 11 second car with the flat tappet cam but it's got quite a bit more power now. I've switched cams a lot years ago and never had any problems before.
Roller cams cost a bit more but I think they are well worth it. I'm running the Crower street roller listed in their catalog (16462) in a 428 Mustang. I'm even using a bronze gear and not having any wear problems yet though I will switch to a Crane steel gear if it starts to wear. Only have a few hundred miles on the cam so far. The Crower street roller requires springs slightly stronger than for a stout solid lifter cam so I think street longevity won't be a problem. Crower recommends only 166 lbs seat pressure but I shimmed mine to 180 lbs. I was previously running a Crower hydraulic with slightly more duration (16256). Haven't had a chance to take it to the track after the cam change but it sure pulls harder. I have a slightly wilder custom street roller from Bullet Cams which I plan to try after running the Crower for awhile.
I know there are worries about roller lifters falling apart but from what I have looked into, as long as you don't go crazy with the spring rates or wildness of the cam there shouldn't be any problem with street use of a solid roller. I would think most people who run these type engines don't put 50k miles a year and check valve lash, etc on a regular basis anyway. There are solid roller lifters by Crower and Crane that give pressurized
oil to the needle bearings if you have the lifter
oil passages in your block which should help.
I guess I could have used a hydraulic roller but I understand that you have to be really careful with the spring rates to get it to work. I know some guys have figured out the right combo but I think I will stick to the solids.
Can't imagine going back to a flat tappet cam.