With the kind assistance of Mike Kewis and Chris Straub, I installed some Morel hydraulic roller lifters to replace the comps with the intention of increasing my seat pressure to address the valve float problem I was having.
Comparing the the Morels vs. Comps, they both appear well made and I never had any apparent problems with the Comp lifters. They still look brand knew and the internals and rollers are still nice and tight.
Using the Morel HR lifters and the "enhanced" version of the Pacaloy Beehives from Lunati, I was able to increase my seat pressure from 140-145# to 175-180# on the intakes, while still being able to keep my open pressure to about the same ~370#. The exhausts I set at a lower seat pressure... at about 150#.
I also removed the rev kit this time. It never seemed to help anything and I was always suspicious of it. Even talked to one guy who claimed it even caused valve float on his engine... cured when he removed it. Must have been a harmonics thing.
The Morel lifters are slightly taller and the piston in the lifter body sits slightly higher so I had to get shorter push rods. Since I spent all that money just to avoid very occasional valve float (but not very nice when it happens even once on a blower motor!), I couldn't resist and changed my lower pulley to add another pound of boost. Hard to beleive I am running a full 15lbs of roots boost and 36 degrees total timing on pump gas, but I am with no problems. I did creep up on this level of boost from 10-11 pounds, originally. I have 7.6:1 static compression and a wide band AFR meter to help keep things in check, though.
I haven't had her past 6,000rpm at full boost yet, but I can make a few comments. There are a few things I don`t quite understand, but she is running good..
1. Compared to the Comps, the Morel lifters sure are noisey little buggers on start up. The Comps never, ever made a sound. The Morel's sound like the pre-load is out of adjustment until the engine warms up. The first few seconds at start up, the ticking is loud enough that I would pull the suckers if they stayed like that, but it is only for a few seconds and they steadily get quieter as the engine warms up and by the time the engine reaches operating temp (160 degrees +), I really can't hear anything. If you were to hold a Morel roller lifter in one hand and a Comp in the other and shake them like moracas, the Morel lifter bar rattles a bit more than the Comps, but I don't think that is the cause. Holding the two, you will also notice the Morel lifters are a bit heavier, too. I understand that the Morel Lifter bodies are machined steel, while the Comps are a casting. I guess that is what causes the noise until the Morel's warm up. I heard the LS1 guys say the same about the Morels making noise at start up.
2. The exhaust note sounds different just cruising around, and I can't think of a good reason why, but definitely different. Maybe something happened inside my flowmasters or something, but she is different. Odd.
3. I did seem to pick up some power and response even at low RPM.. more than could be expected from going from 14 to 15 pounds, I think. However, at this level of torque, it makes the car a little hard to cruise stop lights. I need to tickle the throttle below the 2000 rpm start of my power band. Once I get to 2000rpm and above, she is a light switch in applying the throttle. I guess that is from spinning the blower a little faster, but seems to be more than the last time I added a pound of boost. I need to let out the clutch easily and shift into 2nd at 1500 rpm, or otherwise it is a snap of the neck and some rubber on the street. Too much power and a stick shift starts to get old fast on the street. Not sure how the 800+ft lbs of torque BBC guys do it on the street with their TKO600's
The true test will be when I get her back to the track. I have never floated the valves (that I know of) at the track, but they say it starts happening well before you hear it, so maybe I will pick up a bunch of power on top. Who knows. Need to get back to the track before it closes for the winter.
1973 RS Z28: 401ci Dart Little M, Littlefield 8-71 supercharger @14lbs boost, Callies Magnum crankshaft, Lunati Pro-Mod rods, JE pistons, 7.8:1 compression, AFR 227 Comp heads, T&D 1.6 shaft rockers. Reed solid FT cam (240/250@.050, .523/.542 lift, 112 LSA), QFT 750 carbs, Tremec TKO-500, Lemons headers, Moser 12 bolt, 33 spline axles & 3.42 gears