CLASS RACER FORUM - View Single Post

Greg Reimer 7376 · 02-12-2019, 12:39 PM

I worked with a guy some time back who was our shop foreman. He was a Mopar wedge guy, and he knew Torqueflites inside and out. He was a self taught rocket scientist. He experienced a tendency toward lifter pump up on one of his rather radical streeters, he attributed it to not so much as valve float over the nose of the cam, but due to the long duration cam he had, the exhaust valves had trouble closing quick enough, and the lifters would tend to pump up. He got a set of solid lifters,16 adjustable push rods, and dropped them in on the hydraulic cam. He adjusted valves around .008" on both valves, then buttoned it up and went for a ride(ha,ha).The car liked it. It had more RPM in all three gears, it ran smooth at a steady speed, seemed like a win/win. He said that when he got off the freeway after a run of a few miles or so with a fully warmed up engine, it would steadily start idling worse and worse, and one time it stalled in traffic at the bottom of the offramp. Attempting to restart the engine, it cranked like it was low on compression (which it was).After a bit, it restarted, and in regular traffic, it seemed OK. What was happening was that the cylinder head temperature climbed at a hot idle, the valve stems and valve train components expanded due to the heat, and it took up the valve lash to the point where the exhaust valves weren't closing since the lash disappeared. After it returned to ambient temperatures, lash reappeared, the engine ran fine. We don't heat soak a stocker motor like that, so .008" or so lash wouldn't do this, but it might be a thing to consider. Another thing--a hydraulic lifter with a lot of spring pressure running at 6000+ rpm, would it be possible for the lifter height to decrease, allowing the maximum lift at the finish line to be less than the lift at a lower RPM? Is it possible for lash to open up at RPM like that due to the lifter starting to possibly retract the plunger?There's no way to adequately measure this while the engine is running, but the non-collapsible lifter might result in a little more lift at RPM's than we had with hydraulics. Just a speculation.

02-12-2019, 12:39 PM	#11
Greg Reimer 7376 VIP Member Join Date: Nov 2008 Location: Glendora,Calif. Posts: 1,111 Likes: 164 Liked 649 Times in 208 Posts	Re: Solid lifters in Stock I worked with a guy some time back who was our shop foreman. He was a Mopar wedge guy, and he knew Torqueflites inside and out. He was a self taught rocket scientist. He experienced a tendency toward lifter pump up on one of his rather radical streeters, he attributed it to not so much as valve float over the nose of the cam, but due to the long duration cam he had, the exhaust valves had trouble closing quick enough, and the lifters would tend to pump up. He got a set of solid lifters,16 adjustable push rods, and dropped them in on the hydraulic cam. He adjusted valves around .008" on both valves, then buttoned it up and went for a ride(ha,ha).The car liked it. It had more RPM in all three gears, it ran smooth at a steady speed, seemed like a win/win. He said that when he got off the freeway after a run of a few miles or so with a fully warmed up engine, it would steadily start idling worse and worse, and one time it stalled in traffic at the bottom of the offramp. Attempting to restart the engine, it cranked like it was low on compression (which it was).After a bit, it restarted, and in regular traffic, it seemed OK. What was happening was that the cylinder head temperature climbed at a hot idle, the valve stems and valve train components expanded due to the heat, and it took up the valve lash to the point where the exhaust valves weren't closing since the lash disappeared. After it returned to ambient temperatures, lash reappeared, the engine ran fine. We don't heat soak a stocker motor like that, so .008" or so lash wouldn't do this, but it might be a thing to consider. Another thing--a hydraulic lifter with a lot of spring pressure running at 6000+ rpm, would it be possible for the lifter height to decrease, allowing the maximum lift at the finish line to be less than the lift at a lower RPM? Is it possible for lash to open up at RPM like that due to the lifter starting to possibly retract the plunger?There's no way to adequately measure this while the engine is running, but the non-collapsible lifter might result in a little more lift at RPM's than we had with hydraulics. Just a speculation.