Quote:
Originally Posted by Dave Bisschop
Really, please lay out some of these iron headed flat tappet combo's that are being bolted together by your average enthusiast and running sub 11.50's first time out in 3800+lb cars that have plenty of vac. at idle for power brakes and run on 91 octane. Not saying this kind of performance can't be accomplished with iron heads and a flat tappet as we've done it ourselves but the combo's are much less street friendly for your average owner.
Formula8, FYI we have dozens of customers running the hybrid setup like you are doing with zero issues using the Crane 99893 springs installed at 1.780-1.800".
Overall the hyd. roller set-ups have been very reliable and 95+% of the ones we've sold (well over a thousand at this point) are using Comp cams hyd. roller lifters and the 99893 springs and out of those we've had some issues with about 2-3% of the lifters. We have customers with tens of thousands of miles on their set-ups with no issues.
I'm all for having some extra spring pressure for a little more insurance especially for those running the solid roller lifters and turning higher rpm (above 6000), but having 200 on the seat and 600 open on a 245/252 .400" lobe lift cam is overkill. For years and about 500 passes (same set of Comp Cams 859 lifters) we ran a 279/283 @ .050" .650" lift solid roller in our 413ci iron headed engine in our 65 GTO with 200lbs on the seat and 575lbs open pressure going through the traps at 7500-7600rpm with no valve float issues, the lifters never failed and were put in a street motor when we sold the car.
Way more spring pressure than required not only eats up power it also puts more strain on valve train parts and cam bearings so while I always prefer to have a little extra, having way too much isn't the way to go either.
We use beehive springs on occasion and P-dude has a great set-up that he's proven to work very well, but at the end of the day I'm always looking at the most cost effective way to do things while maintaining long term reliability. For most of the hyd. roller combo's we do we've had nothing but success with using the 99893 springs and chrome moly retainers, we can certainly set-up customers heads using the same springs and retainers P-dude uses but there's a $400.00+ extra cost involved. There are some cheaper beehive springs available as well but we've seen some reliability issues with some of them so I just prefer a dual spring personally. quoting Steve C. this is a very good reason why "I've been fortunate over the last 20 years or so. I've only had one instance with a solid roller application that almost led to issues... I broke the inner coil on a dual valve spring and limped home."
If he would have had a beehive or single spring fail it would have led to catastrophic engine failure.
We do a lot of CNC porting and head machining work on LS heads for other shops in our area and what's interesting is that they are typically removing the beehives and going with a dual spring as they get into larger cams
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Dave, thank you for taking your valuable time to add to this thread.