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New Cam and Rockers - odd looking at 500+ miles


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Tony D brings up a good point.  You're pumping the oil in before the filter.  Assuming the pressure relief valve behind the filter works, it shouldn't matter much, but, who knows, maybe there's a problem at the filter area.  That would starve both the head and the crank. 

 

Another thought - remove the cam and towers and see if oil is coming up through the block orifice in to the channels under the towers.  It's one step back from removing the head, but should be a lot easier.  If you have oil there, then the problem is probably in the towers.

 

And, as mentioned, the other possibility is that there is plenty of flow up through the head, it's just going somewhere else before entering the camshaft and spray bars.

 

And thanks for the puzzle.  It beats Sudoku.

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Tony D brings up a good point.  You're pumping the oil in before the filter.  Assuming the pressure relief valve behind the filter works, it shouldn't matter much, but, who knows, maybe there's a problem at the filter area.  That would starve both the head and the crank. 

I guess maybe I'm confused - on my engine (N42 block) the pressure sender feed is tapped off from the main oil gallery - the one that feeds the main bearings and the head.  It is definitely after the filter.  Is the N42 block unique in this? Seems like everybody keeps saying that the sender is before the filter, or maybe I'm just mis-reading something...

Edited by TimZ
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You're right, my mistake.  And I've made the same mistake before, trying to figure things out from the Engine Lubrication diagram and casting shapes on the block (I think you replied that time also).  I went out and stuck a hose in the oil sender hole in a short block I have and it blows out the center hole where the filter sits.  Which is also a direct shot to the oil jet at the top of the block, you can see a thin wire jammed down the jet through the oil filter center hole.  There's a casting bump between the sender boss and the passage from the pump but it's not what it looks like, that 's what got me, plus the black on black diagram in the FSM..

So pumping oil in to the oil sender hole then could push oil backward through the filter toward the pump, assuming the check valve (anti-drain-back valve) in the filter can't hold 120 psi.  Could be where some of the pressure was going.  I don't know how much could squeeze past the pump.  A rig that feeds oil through the filter center hole would mimic what the system does in use and might make things more clear, to me anyway.

 

I don't really know much about the L6 oiling system, just giving the neophytes view, and learning a tittle bit more along the way.

Edited by NewZed
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Ok, that makes sense....we had put a filter on our filler...

 

So that takes out the plugged filter. Anti drain back should not be affected by the pressure, just push it into its seat firmly.

 

But that still doesn't say the rod side clearance, or something in the bottom end isn't just POURING oil flow out! starving flow to the head.

 

All symptoms have been in the head....and priority oiling of the bottom-end is known to be the case...

 

So what down below could lose flow and starve the head? I know in high mileage JDM engines, the oil flow to the head was like that... From big bearing clearances down in the bottom end.

 

I agree, my first thoughts are that something is restricting the head orifice. But what if it's clear?

 

 

I had an L26 one time. LPG engine from a taxi! the ONLY L26 I saw in Japan while there....that engine ran for close to an hour we attempted to figure out why we simply could NOT get oil flow to the top end. We didn't have the head off...

 

Never got it working. Kinda freakishly scary we would fire it up and idle it for 10-15 minutes...nothing appreciable coming out up top...

 

Put an L28 in it instead. Never did tear it down. Had the pan off... Changed the oil pump.... Just never figured out why. It made no sense why it should have been like that...

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I don't know if this has anything to do with this situation or not, but I did an extensive experiment with the "dual" lubrication method for the cam. I was driving my oil pump with a heavy duty drill and actually watched the results of the internally oiled cam and the spray bar combo. The oil from the spray bar didn't even reach the cam followers, and this was with a heavy duty pump with heavier pump spring. There was still decent pressure coming out of the cam holes, I believe enough to lubricate the cam, but the spray bar was doing no good. To me, it was just more things to go wrong and i eliminated the spray bar. I think the internally oiled cam is WAY more than enough lubrication for the cam-especiallly if you see how it sprays out those holes.

There is a thread on Classic Z somewhere that i started, but I'm to lazy to look it up.

Hope you find your issue, I have enjoyed watching your build 

 

I'm kinda thinking we're overthinking things at this point, and madkaw pretty much had the answer back on post #17, especially considering that the restrictor orifice in the block has not been opened up.  You've kept the restriction the same and pretty much doubled the head's oil flow requirements.

Perhaps try shitcanning the spray bar and blocking off it's supply holes and run that same test with just the internally oiled cam.  

Given the cam specs that were mentioned this sounds like a pretty aggressive cam, but I haven't seen what the end goal of this engine was.  If its a street/track car that won't see sustained high rpm, then just the cam should be fine.  

If you are really going to run this thing at 7500rpm for several hours at a time, then revisit the spraybar after you've pulled the head and enlarged the restrictor orifice in the block.

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I'm a little surprised the OP didn't do the drill trick after the first cam ate it.

I did it just out of curiosity and to prove the double oiling method wasn't folk lore.

If I had lost a cam, I would have had even more motivated.

 

Since I am posting I am going to throw this out to you guys pertaining to oil pressure issues. If the block oil supply hole WAS enlarged for better oiling but the HG hole was not, would that somehow effect pressure?

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I'm a little surprised the OP didn't do the drill trick after the first cam ate it.

I did it just out of curiosity and to prove the double oiling method wasn't folk lore.

If I had lost a cam, I would have had even more motivated.

 

Since I am posting I am going to throw this out to you guys pertaining to oil pressure issues. If the block oil supply hole WAS enlarged for better oiling but the HG hole was not, would that somehow effect pressure?

I doubt it - the hg hole is huge in comparison. It's something like 5mm id.
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Remember there are TWO oiling holes for the head. One near the front of the block, and one near the middle of the block. They don't need to be opened up much unless you're running molasses for motor oil. I have PLENTY of oil flow at idle, 18psi oil pressure, using both a drilled cam and a spraybar.

 

I also turn my engine 7000-7200 multiple times every time it's out, usually every stoplight if I get the chance....

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Remember there are TWO oiling holes for the head. One near the front of the block, and one near the middle of the block. They don't need to be opened up much unless you're running molasses for motor oil. I have PLENTY of oil flow at idle, 18psi oil pressure, using both a drilled cam and a spraybar.

 

I also turn my engine 7000-7200 multiple times every time it's out, usually every stoplight if I get the chance....

I'm pretty sure the oil hole at the front flows from the head to the block to supply oil for the timing chain tensioner, at least on the N42 block.  This may very well have been different on other blocks, as I know there was more than one oiling configuration for the tensioner depending on year.

 

NewZed - could you check this on your block?  I'm pretty sure this is right, but I am working from memory here and the FSM doesn't show it at all.  My recollection is that the front oiling hole does not go to the main oil gallery, just the tensioner.

Edited by TimZ
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Major edit - stuck a hose in the oil sender port and blew air while blocking the filter center feed.  A strong stream comes from the middle hole, but nothing from the front hole.  So Tim Z's description seems right.  Nissan runs oil up through the head then back down in to the block through another restrictor jet to the tensioner.  So if your font jet is too open you could probably lose pressure to the tensioner.  Looks to me like a finely tuned system that probably shouldn't be messed with, too many ways to go wrong.

post-8864-0-73892100-1382319116_thumb.jpg

post-8864-0-69839100-1382319123_thumb.jpg

Edited by NewZed
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I mentioned the second hole long ago, as some might recall, Honseweitz personally said the only hole to be opened up  was the middle of the block---that is the one that increases oil flow to the top end.

 

"Perhaps try shitcanning the spray bar and blocking off it's supply holes and run that same test with just the internally oiled cam. "

 

This is EASILY accomplished with some pop can scraps. Even gasket material. But it should not be an issue if there is sufficient flow from the pump.

 

The head gasket hole indeed is huge, unless someone used RTV on the head gasket (seen that before!)

 

This is where drilling holes and using plugs at overhaul time comes into it's own. I remember drilling and plugging Vega heads apprenticing in the machine shop... later, checking oil flows and cleaning passages was a snap!

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Thanks NewZed!  Also in the your pic on the right, you can see the outline of the HG passage to get an idea of how large it is.

 



I mentioned the second hole long ago, as some might recall, Honseweitz personally said the only hole to be opened up  was the middle of the block---that is the one that increases oil flow to the top end.

I remember you mentioning this - just thought I'd elaborate on it a bit...

 

 

"Perhaps try shitcanning the spray bar and blocking off it's supply holes and run that same test with just the internally oiled cam. "

 

This is EASILY accomplished with some pop can scraps. Even gasket material. But it should not be an issue if there is sufficient flow from the pump.

 

Agreed - I'm just going back to the notion that since the restrictor orifice hasn't been opened up, there's just never going to be enough flow for both, especially at low rpm, and the cam is getting starved just so the spraybar can dribble oil on the rocker posts.

 

It does seem like this works for some and not others - I wonder if perhaps the front oil passage does go to the main gallery on other blocks?

 

This is where drilling holes and using plugs at overhaul time comes into it's own. I remember drilling and plugging Vega heads apprenticing in the machine shop... later, checking oil flows and cleaning passages was a snap!

 

That's how I knew!  After cutting threads for the plugs and oil squirters last year, I had to track down every passage in the block and make sure it was completely clear.  I had a couple of "Oh, so that's where that goes" moments! :mrgreen:

 

Speaking of the squirters - a 30psi internal relief like what was done on the squirters (i.e., the spraybar wouldn't flow oil until pressure reaches 30psi) would be a great addition for those billet spraybars that are stickied in this forum...

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Well, actually, with those BMW Squirters, why wouldn't you just make a billet spraybar and use the same squirters to direct oil flow to the cam lobes instead of messing with drilling holes in the bar that aren't repairable?

 

Now, someone is going "Oh, SHIT!"

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Well, actually, with those BMW Squirters, why wouldn't you just make a billet spraybar and use the same squirters to direct oil flow to the cam lobes instead of messing with drilling holes in the bar that aren't repairable?

 

Now, someone is going "Oh, SHIT!"

OH SHIT!

 

That is a good f-ing idea.

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This is where drilling holes and using plugs at overhaul time comes into it's own. I remember drilling and plugging Vega heads apprenticing in the machine shop... later, checking oil flows and cleaning passages was a snap!

 

During the full rebuild, the press fit plugs were all removed and the oil galleries cleaned METICULOUSLY.  Engine has to come out to have the freeze plug spikes (I forget what they are called) installed anyway.  I guess I have no choice but to remove the head.  Incidently, oil temp has a major impact on flow as seen by some vids another HybridZer sent me.  My videos were with 10W30 redline at like 65 degrees.  

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  • 5 months later...

Thought it was about time for a small update on this saga.  I pulled the head off of the engine a while back so I could drill out the oil supply restrictor in the block to .125".  With the head off, I found some odd wear on the bores.  So, I sent the short block back to my engine builder to be disassembled, checked, and specifically for some touch up honing.  We suspect the wear possibly came from running too rich during attempts to tune the carbs... and possibly bits of the metal from the cam problems causing some havoc.  

 

According to my engine builder, all crank journals, rod journals, respective bearings etc. were fine.  The cylinder walls weren't perfect.  So, we went ahead and honed it as planned.  Short block is being reassembled now and will be on the way to me soon.  I'll be pulling the oil galley plugs on the head and checking to be sure there is no debris or obstruction.  Plan for restart includes:

  • Red Line full synthetic oil - high zinc content
  • Red line assembly lube on cam lobes
  • Block heater to heat oil north of 100 degrees for startup
  • Pressure oiling kit to blast oil through all oil galleys just before startup
  • Rebello camshaft spray bar - replacing the factory oil spray bar
  • Same induction set up - everything adjusted as prior, when engine last ran - assures quick initial start up

With the oil restrictor now .125" instead of ~ .078" and no chance of any restriction (everything will be tripple checked), along with the list above, I think I will not have another repeat of this problem.

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  • 5 months later...

The assembled short block is back home and I started final engine assembly yesterday.  This was something I wasn't expecting:  

 

post-4218-0-18009600-1413850772_thumb.jpg

 

This head gasket is a nissan comp multi layered steel (MLS) one.  The oil supply hole to the head (the one mid way front to back on the block) is what we are looking at.  Interestingly, the hole, which is now almost twice the diameter of what it was when the engine was run last, is not lined up with the opening in the gasket.  This is the case on the block, but not on the head, meaning there is misalignment of this opening between the 280z block and the 240z head (E88 casting).  Now, the "restrictor" in the block is recessed maybe a half to one millimeter below the deck surface, so the partial "blocking" of the hole is not the same as if the restrictor was flush with the top surface of the block.  Not ideal however.  

 

So, I took the gasket off and carefully opened up the hole in the gasket a bit.

 

post-4218-0-14531700-1413850784_thumb.jpg

 

The goal at this point is to get it fired up again this weekend.

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