The old style is the same with the groove, but it doesn't have that second hole or groove in the main web in the block. I'm not really sure what the idea with that was.
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- Thread starter kidturbo
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But unlike the Howard's rod design, there is no specific angle indexing to control the oil flow to only a few deg of rotation. All oil coming into the main, has an easy path right back out that second hole. Which means it has to pressurize the complete cam assembly first.
Think about full grooved mains vs half groove. Trade offs of what you're attempting to accomplish. I can see their logic, remove the pressure from behind the bearing and run it all thru the main. However your actually starving the main bearing more now, and requires a bigger groove to accomidate the flow, and equals less surface area also.
Cold starts probably what's killing em..
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Think about full grooved mains vs half groove. Trade offs of what you're attempting to accomplish. I can see their logic, remove the pressure from behind the bearing and run it all thru the main. However your actually starving the main bearing more now, and requires a bigger groove to accomidate the flow, and equals less surface area also.
Cold starts probably what's killing em..
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I ran into a completely unrelated cold start issue on the twins that makes me think more deeply about this bearing change.
With the huge external oil coolers [2quarts], 12AN lines, and HP6 style filters mounted higher than the block ports , I knew cold starts might be an issue. So I found a non-drainback version of the oil filters. On first start, I had to crack the filters loose to just clear the air lock while cranking. It wouldn't make pressure after several attempts.
Ok not a big deal, until I let them set for a few weeks and noticed on next fire, took several seconds to make pressure. Besides the ecm gauge, I have old-school safety switches hooked to fuel pumps and a light on dash. The idiot light told the tale, gauge reading was true. Weird, maybe filter was leaking off. So changed em, and same thing. Drain back betwen pickup to pump must be trapping air before the pump, and the filter design sure wasn't helping matters.
For a fix, I went back to a standard HP6 style without the rubber drain back preventer. Still takes a bit to make pressure if ya let em set for a month, but now i can pull the ecm fuse and crank em till they the light goes out. From then on, they are good with no delay at cranking.
What I thought was a great idea at the time, ended up being a possible major problem. It takes about 10-20psi to push that spring loaded rubber seal inside those special filters open. Whatever is happening inside the pump, is allowing air around the gears. The pump couldn't clear it because the filter was holding the inlet line closed until it makes pressure.. Can't make pressure cause air in the pump. And only a paranoid engineer would realize what was actually happening to his grand design..
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With the huge external oil coolers [2quarts], 12AN lines, and HP6 style filters mounted higher than the block ports , I knew cold starts might be an issue. So I found a non-drainback version of the oil filters. On first start, I had to crack the filters loose to just clear the air lock while cranking. It wouldn't make pressure after several attempts.
Ok not a big deal, until I let them set for a few weeks and noticed on next fire, took several seconds to make pressure. Besides the ecm gauge, I have old-school safety switches hooked to fuel pumps and a light on dash. The idiot light told the tale, gauge reading was true. Weird, maybe filter was leaking off. So changed em, and same thing. Drain back betwen pickup to pump must be trapping air before the pump, and the filter design sure wasn't helping matters.
For a fix, I went back to a standard HP6 style without the rubber drain back preventer. Still takes a bit to make pressure if ya let em set for a month, but now i can pull the ecm fuse and crank em till they the light goes out. From then on, they are good with no delay at cranking.
What I thought was a great idea at the time, ended up being a possible major problem. It takes about 10-20psi to push that spring loaded rubber seal inside those special filters open. Whatever is happening inside the pump, is allowing air around the gears. The pump couldn't clear it because the filter was holding the inlet line closed until it makes pressure.. Can't make pressure cause air in the pump. And only a paranoid engineer would realize what was actually happening to his grand design..
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It happens. Sometimes you design something based on what you DO know, and something you don't know (like a new bearing design) forces you to rethink the original idea. We've all been there in one way or another.
Sounds like you need a few accusumps to pre-oil those beasts - https://www.cantonracingproducts.com/accusumpI ran into a completely unrelated cold start issue on the twins that makes me think more deeply about this bearing change.
With the huge external oil coolers [2quarts], 12AN lines, and HP6 style filters mounted higher than the block ports , I knew cold starts might be an issue. So I found a non-drainback version of the oil filters. On first start, I had to crack the filters loose to just clear the air lock while cranking. It wouldn't make pressure after several attempts.
Ok not a big deal, until I let them set for a few weeks and noticed on next fire, took several seconds to make pressure. Besides the ecm gauge, I have old-school safety switches hooked to fuel pumps and a light on dash. The idiot light told the tale, gauge reading was true. Weird, maybe filter was leaking off. So changed em, and same thing. Drain back betwen pickup to pump must be trapping air before the pump, and the filter design sure wasn't helping matters.
For a fix, I went back to a standard HP6 style without the rubber drain back preventer. Still takes a bit to make pressure if ya let em set for a month, but now i can pull the ecm fuse and crank em till they the light goes out. From then on, they are good with no delay at cranking.
What I thought was a great idea at the time, ended up being a possible major problem. It takes about 10-20psi to push that spring loaded rubber seal inside those special filters open. Whatever is happening inside the pump, is allowing air around the gears. The pump couldn't clear it because the filter was holding the inlet line closed until it makes pressure.. Can't make pressure cause air in the pump. And only a paranoid engineer would realize what was actually happening to his grand design..
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Are the oil Pump's Shimmed???I ran into a completely unrelated cold start issue on the twins that makes me think more deeply about this bearing change.
With the huge external oil coolers [2quarts], 12AN lines, and HP6 style filters mounted higher than the block ports , I knew cold starts might be an issue. So I found a non-drainback version of the oil filters. On first start, I had to crack the filters loose to just clear the air lock while cranking. It wouldn't make pressure after several attempts.
Ok not a big deal, until I let them set for a few weeks and noticed on next fire, took several seconds to make pressure. Besides the ecm gauge, I have old-school safety switches hooked to fuel pumps and a light on dash. The idiot light told the tale, gauge reading was true. Weird, maybe filter was leaking off. So changed em, and same thing. Drain back betwen pickup to pump must be trapping air before the pump, and the filter design sure wasn't helping matters.
For a fix, I went back to a standard HP6 style without the rubber drain back preventer. Still takes a bit to make pressure if ya let em set for a month, but now i can pull the ecm fuse and crank em till they the light goes out. From then on, they are good with no delay at cranking.
What I thought was a great idea at the time, ended up being a possible major problem. It takes about 10-20psi to push that spring loaded rubber seal inside those special filters open. Whatever is happening inside the pump, is allowing air around the gears. The pump couldn't clear it because the filter was holding the inlet line closed until it makes pressure.. Can't make pressure cause air in the pump. And only a paranoid engineer would realize what was actually happening to his grand design..
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Thought about it actually. However issue only arises if you let them set for a long period now. So kinda put idea on back burner while sorting out other issues.
This is what made me think of how startup relates to these L5P changes. Unless the centerline specs are off, not much else causes excessive main bearing wear in an engine. Even on the origional LLY engine that I spun a couple rod bearings clean out of, the associated main wasn't trashed. But it certainly showed more wear than all the rest. And that was all due to an isolated oil restriction only impacting a single hole for a few seconds at WOT.
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in 
?
Does a
in
?
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Depends... Are you there to see or smell it????
I only asked because I recently did some testing and was surprised to see they barely have enough pressure to keep the relief closed on the pump. It takes barely any pressure to push them open.
Sometimes it's in a zoo......Does a
in
?
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Yeah these have the Modified LML pumps. 1 or 2 washers. Have to look when I get one opened up again.
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Ya know it would be interesting to plumb one up to a regulated air hose and block off the outlet, just to see where they pop off at factory. Especially with a few years age on that spring. Then do it again with a washer or two in there. Think I might have a couple old LMM pumps in my spare parts box.
Here is what I measured on the original LBZ pump that came out of the motor I am working on. The last picture with about 30PSI Spring pressure is .200 worth of shim material. Hopefully that will allow the engine to make enough hot oil pressure to keep the squinters open at idle.
I assume you measured the installed height of the spring to be 1.5" and used the spring tester to determine seat pressure? Did you measure the spring rate and how far the valve has to travel before it starts bypassing?
I agree. Make ya a couple block off plates and put a fitting in the Outlet side where can pressurize that body. Then put some air to it to get real world values.
Always known they have a HOT pressue issue at idle. Also likely why GM padded the gauge outputs so lowest they read true is about 27psi, or it's zero...
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Always known they have a HOT pressue issue at idle. Also likely why GM padded the gauge outputs so lowest they read true is about 27psi, or it's zero...
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Yes. with that little cup which rest against the roll pin. I forget exactly what it measures at the bypass but it isn't much different...
I will have to pick it up and play with it some more. It's all disassembled right now.
Here is the LBZ pump. Not sure if the relief differs on an LML style pump. Maybe hard to see but the relief valve doesn't have to travel far to get to the open area to bleed off pressure. From were it's machined inside to the top of the opening is about 0.170.
The top of the little spool valve is also machined with a step too. So I would imagine that also effects the bleed off too.
The top of the little spool valve is also machined with a step too. So I would imagine that also effects the bleed off too.
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