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Head cooling on cylinder #5 - solutions?


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Okay, I've been meaning to start this thread for a couple of days - in another thread I was talking about some problems (dropped valve seat) that I incurred recently on cylinder 5. I've heard several times that #5 is problematic due to water flow issues, and johnc posted the following in that thread:

 

Had that happen to the cylinder 5 in the ROD but the seat blew apart and I found most of it in the intake manifold. The cause was very slight detonation in that cylinder. What caused the detonation was a localized hot spot in the cylinder. This is a well known issue for high cylinder pressure L6 engines.

 

What cured the problem for my car was increasing the cooling system pressure to 28 psi to reduce nucleate boiling at that point.

 

ccbad.jpg

 

Now, my car is still street driven and I'm a bit concerned about running cooling system pressures that high for fear of blowing out my heater core - anybody know if that's a rational fear? This certainly would be the easiest cure for the problem, and contrary to popular belief I do like elegant solutions :mrgreen:.

 

I've heard of ideas of re-plumbing the water flow through the head - as I recall there are some bosses between the intake ports that can be tapped to allow water to be plumbed in in that manner, but I've never seen what that solution actually looks like - has anybody seen this done successfully?

 

Any other ideas?

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  I assume you did try to source the LD pump in Australia, I saw a thread and you mentioned you got it from Japan (?)

My thoughts on the Summary:   - The path of coolant through the L engines results in the rear of the head receiving the hottest coolant having stagnated water flow, insufficient for the he

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I cut in half a bunch of heads lately to investigate various ideas. One idea is just what you mentioned. Directly above each exhaust port is a nice open area that you could pull the water out from. I believe the water first has to flow past all 6 pistons before moving up and across the head for #5 and #6.

I am thinking about using a radiator bulkhead mounted water pump with 2 outlets. One outlet would go to the current front cover/front of the block. The second outlet would go around the block to the block drain lug under #6 so cooled water is going to the back as well as the front. Now if you tapped into the head above the exhaust ports and let the water flow out, it would eliminate the water having to pass over so many areas. Some of the problems I see are that you would have to block off the head bypass since the water is now being pushed instead of pulled. you will also have to block off the water pump opening. You would also have to plumb only cylinders #2-#6 leaving #1 as the current thermostat housing where the other 5 would collect and then go back to the radiator. #1 and the thermo housing is also a high point in the system so trapped air should not be a problem.

Here are some pics of the water pump, old nissan designs, as well as a manifold design I am working on

water_pump.jpg

nissanl6safarihead01oi6.jpg

e15.jpg

072421.jpg

throttle_bodies11.jpg

throttle_bodies21.jpg

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Well maybe this is why I blew out the head gasket at cylinder #5 during agressive tuning! Viola!

 

I used to run with one of these motors. Man I loved this motor:

alfa_twincam_engine.jpg

Look at the coolant runner over the intake...this motor design is from the stone age too. Hemi, dual cam, sodium valves, double row chain.......

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throttle_bodies11.jpg

Jeff, take a look at the Electromotive Turbo Setup...

They did exactly that in the photo, drilled holes in the cylinder head and used -6 or -8 braided hoses to a common header that went to someplace else in the cooling system near either the restriction, or radiator.

 

That engine was pushing 800hp...and I am probably sure they used the higher operating pressure cap as well...

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My L6 Always detonates on #6 But I did route my turbo water back there. For a problem that was obviously discovered way back in the day I'm surprised that the head cooling has not be talked about that much. I planned that this year I would try the electromotive approach to the cooling issue but I'm now sidetracked, my college just picked up a small 3d scanner. This Fall I'll be scanning an N42 heads exterior and then cutting up the junk head and getting in to all the internal passages for some extreme cfd test and if anyone has a p90 to donate I would love to get a scan of that as well.

 

 

 

tbs

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I have always had a suspicion that coolant flow around and over the combustions chambers of the L-6 could be suspect, but haven’t really had any substantial proof to support that claim, though I’ve talked to few others about the theory and left it at that, just a theory.

 

Being as this subject is headed right down the path I’ve been theorizing over, I just wanted to share some of this theory for you to chew on in hopes it might be relevant.

 

This is just one recent example that comes to mind... Overall coolant temps in a hot street N/A L-28 don’t seem to be an issue, though extended WOT sessions, there seems to be a rapid declination in how the engine runs, i.e. over a 30-second window at WOT there is marked engine performance difference. In our last dyno session, we used a Mustang chassis dyno which allows you to hold a steady RPM under all loads and with a low 8:1 compression ratio mild-hot street N/A L-28 engine under extended WOT conditions, the J&S Safe Guard knock protection would kick in pulling timing, but only after extended WOT loads. With the J&S disabled, we heard loud audible knock and a substantial decrease in power output at around the same point the J&S would've started to pull timing. We feel this started in one cylinder, but not sure which one. Coolant temps were slowing rising, but still considered safe, of course at the first sign of abnormal "anything", the dyno pull was aborted and the engine allowed to cool down with no load prior to shutting it down. Our theory is that the “combustion chamber” temps elevated much quicker that the coolant could remove that heat. We adjusted and set ideal AFR’s and ignition timing for max output at the varying coolant temps, (we stayed below that threshold that the J&S would kick in for our optimizing tuning effort), and found the cooler the water temp, the better the engine performed and it even sounded more “crisp” as well. Coolant temps as low as 160 F and the engine ran great, performance was in a steady decline as the temps rose and the exhaust note also reflected that being less crisp.

 

1) Without knowing for sure how the coolant is circulating over and about the chamber roofs, and also not knowing how clean the cylinder head casting is i.e. casting flash causing blockages, eddies, etc, there is just to much that is unknown that one could spend several years on an engine dyno and a few hundred core heads testing just this subject alone.

 

2) Theories for addressing the possible coolant flow issue over the chambers. I feel that an as cast surface offers pretty good heat transfer to the cooling medium, (coolant in this case), maybe with small raised fins across the chamber roof in line with the coolant flow would offer some bit of consistency in removing chamber heat. I feel that “consistency” in regards to chamber temps over a varying range of operating conditions is more important as we can work “around/with” that consistency to better neat the needs and abilties of that engine to produce power.

a) As pictured above, individual coolant outlets into a manifold with the thermostat just prior to the inlet to the radiator.

b) Individual coolant inlets in the block, one per cylinder. Not sure exact ideal location and depending on which side of entry, i.e. driver vs passenger, modified head gasket coolant passages.

c) Modifying/rearranging the coolant passages between the head and block seems like more of a trial and error by guess and by golly R&D endeavor. The dynamics of the coolant flow through and about the entire engine is so diverse with the substantial Delta “T” between the lower block and chamber roofs, pump variants, cylinder head casting differences and casting flash affecting actual coolant flow etc.

d) Be able to get inside of the coolant cavities of the cylinder head to clean up the casting flash, blockages etc. I don’t feel this last one is a realistic procedure within our privateers financial abilities.

 

Again, this is just some random theory that has been bouncing around in my noggin from some time and this thread looked like a good place to unload some of it.

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I used to run with one of these motors. Man I loved this motor:

alfa_twincam_engine.jpg

Look at the coolant runner over the intake...this motor design is from the stone age too. Hemi, dual cam, sodium valves, double row chain.......

 

 

 

A thing of beauty is a joy forever. My old man has a 2600; I should check to see if there is one of these coolant bars. I think there is, but if so I was ignorant of its purpose last time I saw it. Absolutely beautiful motor though.. its a poor man's ferrari.

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I have always had a suspicion that coolant flow around and over the combustions chambers of the L-6 could be suspect, but haven’t really had any substantial proof to support that claim, though I’ve talked to few others about the theory and left it at that, just a theory.

1) Without knowing for sure how the coolant is circulating over and about the chamber roofs, and also not knowing how clean the cylinder head casting is i.e. casting flash causing blockages, eddies, etc, there is just to much that is unknown that one could spend several years on an engine dyno and a few hundred core heads testing just this subject alone.

 

This has been my suspicion, too, and the reason that I started this as a separate thread. My suspicion is that the "#5 issue" is more due to eddy currents or cavitation caused by the flow path inside the head. That end of the head gets the coolest water, so I don't think it's an issue of the water getting progressively hotter from having to pass over all the chambers from back to front.

 

Tapping the head above the exhaust ports and returning the water to a plenum is an interesting idea, but I would think you would also want to modify the water inlet(s) to the head, so that the water could have an even flow path over each combustion chamber, and I'm not sure how that would be accomplished. It seems to me that if you left the water inlet at the existing port at the rear of the head, you would have to play some games to balance the outlet flow from each cylinder to keep from "starving" the cylinder that is farthest from the inlet - maybe something like use a -4 on cyls 5 and 6, -6 on 3 and 4, and -8 on 1 and 2.

 

It also occurred to me that if the problem really is mostly isolated to cyl#5 and if it is caused by eddy currents or cavitation, it's possible that the problem could be solved by simply tapping the water jacket at #5 and bypassing a small amount of water from there (maybe just use a -4 line), just to change the flow path a bit and eliminate the dead zone. This of course depends on exactly where the flow problem is located - you could just as easily make the problem worse. Those chopped up head pics would probably be pretty helpful here...

 

Personally, I'm kind of leaning towards the Evans NPG solution, but they require elimination of all water from the system, which isn't that easy without pulling the block. They have some flush chemicals that are supposed to help, though. Also, they mention requiring a higher flow pump, which I don't think is readily available for the L-series. Anybody know anything about the diesel water pump? I thought I had heard something about it having a higher flow capacity at one time.

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Anybody know anything about the diesel water pump? I thought I had heard something abou it having a higher flow capacity at one time.

 

Tim,

 

PM jgkurz and drag him into this. He's adapted the diesel pump. I only know bits of it... so best to get it staight from the horses mouth.

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water_pump.jpg

 

WOW, who makes that thing??? I find it rather interesting...

 

 

Just a thought,

 

But could you extrude hone the water passages to increase surface area within them? more surface area along with higher pressure...

 

Hummm, looks like we think alike, I was going to suggest just that but, kept on reading and it seems you beat me to it...

 

Extrude Honing would sure take care of the eddies and flashing problems IF that's the main cause...

 

Funny thing, 2 weeks ago I would have never known what an EDDIE is, if it weren't for the fact that I just got into Kayaking and the term is largely used in that sport... Sorry, just had to share.

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Extrude Honing would sure take care of the eddies and flashing problems IF that's the main cause...

 

Well, maybe, assuming that the extrude hone material doesn't have the same issue that the water does. For instance if if the problem is simply a "bump" in the flow path, the extrude hone would take care of it. If however, the problem was an area where there was no flow path, the extrude hone material wouldn't do much - its purpose is more to smooth out the existing flow paths, not to make new ones.

 

Also, smoothing out all of the internal passages would probably not help cooling efficiency - rough surfaces have more surface area, and a small amount of turbulence from the casting sand marks is probably also helpful.

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