Tony D
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Posts posted by Tony D
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"I am struggling with the concept that the forces present during cavitation within the Datsun water pump are strong enough to “mine” the aluminum from the front cover itself yet does no damage to the impeller blades, i.e. bent, broken, pockmarked etc."
I have seen cylinder liner failures from ductile spuncast iron due to cavitation damage! I could take some photos if I wasn't like 7000 miles from my "example liner" (now a convienient trash can!).
Many times the cast iron blades will be cavitated and erroded as well. Errosion due to electroylisis is a concern, but steam pocket formation within the head can ruin it for sure. It just has to happen consistently enough. in the head it happens at a different time than in the waterpump.
In higher-pressure applications, water erosion channelling can eat a stainless steel hardened impeller win less than 18 hours of operation significatnly affecting flow!
As for an L24 without a secondary external bypass line---no such animal! You may be missing it, but it's there! Even forklifts have it. Some engines are designed with a totally enclosed bypass hole----but the Nissan L-Series, like the Mercedes engine it was originally licensed from, both have dual circuit bypasses. When the secondary line is removed, the only way to insure no cavitation is to slow the pump at idle (larger pulley on pump) and keep the revs low until the thermostat is opened enough to accomodate that flow.
Braap, your observation of the 1/4" hole in the thermostate is probably about the minimum flow requirement so there isn't any problems. (Done by the racing team you mentioned above) this is another method for keeping the minimum flowrate through the pump while the thermostat is closed. Makes the engine slightly slower to warm up, but provides the required minimum flow to allow operation of the engine when cold, and the thermostat is closed.
Remember on a racing engine, people aren't starting it cold, and then driving away revving it to 3000 rpms 30 seceonds after the car is started! They will start it, idle it, maybe run it at fast idle to warm it faster, but no revving of any consequence takes place before the engine is at least moderately warmed. The street in this instance is far moreabusive than the track will ever be! Someone starting their car, then driving off and up to freeway speeds within 2 minutes is a prim canidate for cavitation for 30-90 seconds every morning he does it. Now it may take 1000hours of this cavitation to actually perforate a block, or other cast iron component, but a mazak die-casting will get eaten up quite handily under those conditions.
My "P" for the "A&P" was completed in 1986, but never finished the second phase of thetraining to get the Airframe certification---so much for "Military Training Opportunities" But afterwards there was more time to do things related to Powerplant Maintenance since I was lead at a 5MW (6.6MW Gross)LFG Recovery Site---when the Steam Turbine end of that project fell through I decided that being in Management and having your project pulled out from underyou was not a position I wanted to be in, so in 93 I traded off to OEM Field Engineering dealing with large stationary Air and Gas Compressors. My SAE subscription lapsed long ago, I really enjoyed the papers to keep up to date with technology and mandates, so that probably answers the rest of the question pretty much, eh? Having grown up in Michigan, and gone to school there, I know many classmates who went to GMI, or ended upworking for hte Big Three, and we kept in touch regarding a lot of stuff---since we all "tread the same water" as OEM reps in many cases, war stories and "inside tales" invariably get brought up. We all laugh at our collective human stupidity (or, probably more correctly, some customer's stupidity! I mean, when I have to field a call from a "Degreed Engineer" who goes off the handle because _this is an actual quote_ "Pump? Pump? WHAT PUMP? NOBODY TOLD US WE NEEDED A PUMP!" Er, Is it a Thermal Siphon? "Huh?" Er, yes, sir, er...you need a pump to provide 2.8 GPM for the heat rejection requirements of the Oil Cooler!)
But I digress...
Your last paragraph is probably what sums it up the best. As I said above, the drilling of the thermostat is an alternate function of the same thing. Something must allow not only minimum flow for the impeller, but must also allow the thermostat to get sensing the actual heat of the engine. This is one of the reasons I get so upset when people cap that bypass line off---exactly as you stated, if there is only flow through the backside internal orifice, the only way the thermostat gets hot water flowing over it is through conduction! This leads to a bad temp spike on initial startup internally---but rarely shows on the gauge due to reaction time issues. And once the thermostat gets opened, it slams open because of the rush of superheated coolant rushing past it that was resident in the head being recirced...
I would venture to guess that 95% of the people who are posting on the topic saying they have no bypass, have made on alternate provision like drilling the thermostat. That your engine builder did this says loads about his understanding about the functions and importance of the minimum flow, and what's required for a quick reacting thermostat.
Now, if you want to get into something really interesting, do some research on reverse-flow cooling! Where the coolant flows into the head first, then down the cylinders. Greatly decreases heat temperature, helps with cylinder bore sealing because there is a more even heating of the block, and the thermostat is continually bathed in hot coolant. I was involved in a reverse flow Pontiac Trans Am when I was in School, very intersting results. And curiously Chevy changed the coolant flow in their latest SBC Design. This was based on testing and R&D done back in the late 50's and early 60's, but wasnot widely known or publicized until the mid-late 70's.
But again, I digress...
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Lurch, how far down in the post did you go with reading?
Did you get to the very end to see the other photos, and not the Diesel Manifold?
On left, 38/41 from L28E, on right, something like 26/38 from L20E
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Yeah, I go down and read em, and reply.
Each comment has a specific reply, wouldn't want to group them all together, and insult anyone or cause the possibility of cross-talking between who said what when...
Besides, what else do I have to do? It's freakin' LIVERPOOL (and that is shouting!) for gawds' sake! Rainy, dreary, cold....
Eh, it's 9pm now, guess it's time for a couple of Pints 'o Guinness, and the rack...
On the upside, I got to take a ride home today in a Lotus Elise! :^)
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Just an aside, now that we've separated governmental mandates, and equipment that the Z was actually designed to have---I mean, am I totally off base in the arguement? If Nissan could save the money by leaving it off, ask youself the honest question: "wouldn't they?" I mean, EVERY engine designed for passenger car usage has a bypass line to prevent cavitation of the pump and it's pump cavity during times when the thermostat is closed, and the flow from the centrifugal pump is restricted below the flow curve for the impeller used.
That is the real reason for the bypass line---the "piggyback" usages of it for manifold heating, etc etc etc are one of those things that engineers do when they say "well, we have this line here that can be rerouted"...
I mean, if you plug off the second bypass, does the internal bypass flow enough water for the pump not to cavitate? You are effectively halving the flow through the pump during the warmup period.
This post has gone a long way towards revealing a lot of people's understanding of the workings of the Internal Combustion Engine, that's for sure. Some people even mentioned damaged housings relating to overheating---ever notice a "pockmarked" front cover in the water pump impeller area? An area so erroded it looks like at some time terrible corrosion had occurred, yet there is nothign there when you pull it apart but pockmarks in the diecast?
Care to venture a guess what the evidence of pump cavitation looks like?
I'm sure it's not the same circular gouging that occurs when an impeller thrashes the casing----but then again you wouldn't notice it if that's what you thought caused it, would you? Or you would simply thinkn "corrosion"...
Never "Pump Cavitation During Warmup"---when you know what cavitation looks like, you can identify it. And when you know cavitation is caused by a number of things, including too high incoming fluid temperature, insufficient flow, low NPSH....well you can see how these things can feed off one another. If you halve the flow coming in before the engine is up to temperature, you can get low NPSH while at the same time having an inlet temperature (that, while at a higher flowrate for the impeller would not cause a problem) that is high enough to cavitate the pump.
Curious, slowing the pump down helped prevent overheating...
Could that have been because slowing down the pump speed dropped the flow rates back within the design pump curve, and allowed the pump to operate without cavitating (which causes a flow loss, as well...)
I may know what I'm talking about after all. Though feel free to disagree, and do as you will. It makes no whit one way nor t'other to me. I just find it funny to read this stuff sometimes. I really do.
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I mistrust anyone who arrogantly insists they are right and everyone else is wrong all of the time... that is a sure sign they have issues with truth and facts.
That's uncalled for bj, and is simply an extension of your ranting elsewhere. I never said everyone else is wrong, nor have I said I am right all the time.
Though, you seem to have issues with reading comprehension regarding the other matter. I live in a world where more than one person can be right. But then again I'm not insisting anything. There can be two sets of facts that each are correct. If you fail to see that, or comprehend that, then I feel sorry for you.
Hell, I even found Zane's "Lion Rock" comment hilarious! I'm going to use it myself. Probably in response to a post by you in the near future. Lighten up, dude, quit taking yourself so seriously. I do.
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Tony, I’m not trying to be rude here, but you did jump into this thread sort of “screaming” and posting with a demeaning attitude.
I don't think I did that in the least bit. I emphasise certian words, perhaps I should edit it to use italics, but caps on a word actually conveys the way I speak. Anyone who has talked with me, and heard me speak will know that I will emphasise words with a raised tone. Not yelling, but there's no "half caps" unless I type a bunch of HTML in there. Not that I wish the emphasise Hyp...er, 'html in caps'...
Oh, wait, this is being P.C. now....
Would everyone feel better if I went back and edited my post to italics or bold italics instead of the caps for the individual words? I'm not typing in allcaps, only certian words.
And to the point in the post, many of the things you mentioned were mandated by the USEPA (er, acronyms are O.K. to capatalize, right? and O.K. is O.K. to capatalize as well, right?) and Nissan would have loved to run along without them. Matter of fact, in most markets outside the USA (er, USA is O.K. to capatalize, right?) these terrible abominations did not exist on the S30 series.
But one thing remained constant: the bypass line from the lower thermostat housing, to the pump inlet to compliment the internal bypass line on the oil filter side of the engine. It was available, and present in every market.
Please don't confuse a component designed by the manufacturer, and one dictated or mandated by a govermental agency! Remember the Honda CVCC was required to run a catalyst in 1981, even though the engine, due to superior engineering and design, met all required emissions criteria set forth by the USEPA. The EPA mandated EGR, they did not leave it up to the automakers to come up with their own, unique pollution remedies.
So please, remember things on an engine may be there from the manufacturer, or from the government.
The Thermostatic Bypass Line is not one of them. It's on SBC's from the 50's...
Now, as to this:
"On modern throttle valves, early ‘80’s and up, Nissan also added a coolant port to the throttle valves thus pumping 185+ degree coolant through and around the throttle valve. In fact, most, if not all auto makers are also doing this. (We tuners prefer to NOT preheat the incoming air charge)."
While you may not like to preheat the charge, the automakers do, due to the litigiousness inherent in the system these days. Throttle Icing---serious throttle icing, is nothing to sneeze at! Having gone through an almost tragic incident involving my throttle plates being blocked 1/4 open due to throttle icing, I tend to run a bit of preheat... This was more of an issue on carburettors, but it can happen at low throttle openings on EFI cars as well. Would I recomend removing the preheat line? Probably... I would also inform the owner why I was doing it, what he could expect in performance gains (er...minimal) and the oft chance that his throttle might stick partially open in some combinations of ambient temperature, humidity, and manifold vacuum situations. Does this have anything to do with water pump cavitation and the bypass line? No. But it does illustrate a point: Know why it's there in the first place before you go disconnecting things willy-nilly because someone on the internet said it was O.K.! Many people have grave misinformation about why some components are on the vehicle in the first place, and they are the dangerous parrots who squawk myths and legends and turn kids round the wrong way when advising them on this great internet medium.
Once people know why a component is installed, and what it's function is, then maybe they can make an informed choice about it's removal. But to just cap it, or yank it out....well whatever floats yer boat I guess!
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My two cents worth.
In my opinion' date=' the external cooling line from the waterpump inlet (bottom radiator hose) to the back of the engine over to the carbs through the carb thermostat through both carbs and back to the underside of the thermostat housing is NOT a coolant return line for block circulation when the engine thermostat is closed. The purpose of the line is to heat the carbs to more effeiciently atomize the fuel to reduce unburned fuel out the exhaust pipe therefore reduceing tailpipe hydrocarbons. Something the EPA was very woried about in the 70's.[/quote']
It is a bypass line, and in the later 73/74 cars, the circuit was modified to two circuits (one which had a thermostat that closed by 170 degrees...curiously the temperature at which the EGR became enabled...) But the other 10mm line remained flowing, thought through an 8mm orifice. The problem was that the cars had a vapor lock problem in those years, and restricting the recirculation on the line helps alleviate this. BTW, the "reverse thermostat" you mention goes to prove the point that the recirculation line is deemed crucial by Nissan, and after the thermostat is opened (the tropical thermostat Nissan has is fully open by 170 degrees, btw!) the line is not necessary.
All the cars had a bypass line, and when the SU's were removed, the line was changed to another routing. There is a big consideration for the EPA, to be sure, but even on the JDM engines, there is a 10mm line that goes from the thermostat lower housing, around the front of the block, to the pump inlet---going through nothing on the manifold---this is the way it is on my 78 Fairlady 280Z(X) while the 83 has the routing shown above. The difference between JDM, NON-US, and US Specific Models.
It's more of an anti-icing issue, really, and aids in cold start running, the JDM cars had the same circuit, because the SU's don't do a good job when cold. The circuit helps with getting the car off the starter circuit earlier.
Which in turn reduces the....
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This post is of interest to me because my car does not have one and I didn't think the engine had been modified before I got to messing with it.... '83 turbo...
Sure enough does---comes from under the thermostat, thorught the heater block in the throttle body, the heater block under the Cold Start Ari Vavle (whatever it's acronym is) then returns via a 10mm line around the front of the engine to the inlet of the water pump through the fitting that is vertical in the inlet to the pump.
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I opened an access panel once, and literally had the failure occur at THAT moment. As I pulled the panel back, something went FLYING out missing my laft hand by inches, and a terrible racket ensued.
I dropped the panel, my helper and I ditched and waited for everything to come to a stop (which, with that flywheel took a while...) It is very disturbing when you see big dents from INSIDE a piece of equipment while hearing it come apart. The thing that flew out? The entire piston/cylinder/rod/head combination, minus most of the rod cap, and one pushrod tube... Blew right off the gearcase, and flew away. We found it by the trail of oil it left on the clean flowthrough parking area concrete.
Oh yeah, it was a long day at safety...
Until that VERY moment, that very exact, specific moment, I was trying to figure out exactly how to make that engine fit mid-engined into my 62 Microbus. It ended when I saw that.
Similarly, the usage of the -60A GTC Turbine powerplant and gearbox reducer in the Z was the next thing I moved onto....until one of those chucked an exducer up through the roof of the hangar, and out onto the flightline one day.
It was then I decided to do safe things like Land Speed Race instead...
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Hell, he's selling two. Maybe I can put them together and make a KA48 straight eight.
Brazing John! BRAZING!
Make a VKA48!
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I never said they got it all right. Chevy has coolant internal recirculation, Ford does, Chrysler, everybody does!
And the "small hole" is not the same thing as the internal bypass. The internal bypass casues a quick warmup and gradual heating of the coolant mass, rather than a prolonged warmup that would occur with a 3/8" hole in the theromstat.
Every manufacturer used coolant bypass for warmup, and for other reasons. Not one doesn't use it.
Yet, here we are again, with someone talking anecdotally about it never causing any problems (that they can see---have they even looked?)
I mean, I got to ask why every single manufacturer in the world used that kind of bypass system--at added cost for external plumbing in almost all the cases, when they simply could have deleted it and saved millions of dollars?
You have to admit the car companies aren't in the business of leaving beneficial things in cars (oh, like power) unless there is a price increase. What makes anyone think this is any different? Why would they put it there if they could stuff that hose money in their pockets? Nobody has answered that question about the charity of the Big Three and everyone else giving us these little coolant bypass lines all over the place.
I have seen firsthand what coolant cavitation does to cylinder liners, and it's not pretty. You can eat through a casting, literally! Steam impingement is a bad foe...
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Obviously you have never witnessed a failure of the cylinder mounting studs on that Lycoming. If you had, you would seriously reconsider the project.
Put it in an Air Boat, instead, then when it goes, the debris flys around BEHIND you!
This is a hopped up version of the Continental Packette PE175. They sound pretty good, but water cooling? Forget it! They DO make a flywheel mounted fan conversion for these engines in stationary generator usage (probably out of the inventory by now, the units I worked on were being converted to Diesel quickly, and that was over 20 years ago now!)
Problem is, the fan is 3 to 4 feet in diameter. Not your quickest revving engine...
You want a 400HP Air (Oil) cooled engine for your Z that packages MUCH better? Go pick up a 930 Turbo Porsche engine.
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Did Rebello plug the internal passage on the oil filter side of the block as well?
If not, why not?
But it's internal, and nobody knows the answer---my bet is the did not plug that internal bypass. The external bypass is a balancing act, because the internal bypass hole is a "dead area" in the head when the thermostat is opened, and it will boil!!! If the thermostat is closed, thethermostat side of the head is a dead spot, and it can boil! Steam is not a good coolant. Incidentally, steam makes a great heat transfer barrier...
N/A really isn't that stressful when dealing with cooling systems anyway. Make twice the HP Briann is, and see if the cooling system is still up to par.
Like I said earlier, Nissan put how many hundred-thousands of these bypass lines on, all unrequired on a street car---they just wasted their money because they like to use odd-bits of tubing and hose... C'mon, I'm not buying it! If they could've left it off and saved a $$$, they would have, the US Spec 240's didn't have Splash Guards or Fan Shrouds for gawd's sake. You think something that could be deleted worldwide across the entire L-Engine line would have been deleted if it was so unrequired!
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that is what john is betting on...
They are from portable diesel compressors, and we are binning the engines on three of them, hence the availability of six turbos nobody will miss!
Unfortunately they are a bit much to handle in my checked baggage when I return to the USA.
And after what the bastards did to me in Newark raping me and stealing my Differential Coolant Pump (TSA IDIOT, thank-you-very-much!) after three continential crossings, I don't trust those bastards further than I could throw one of their portly countenances...
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Oh! Thanks Alan! One of the Service Engineers here has a project..he wants to use these Turbos on his Boat-Tail 69 Buick Riveria.
Being born in Michigan makes me GM-Averse! LOL
I will pass this information on to John here in Liverpool and I'm sure he can go from there without running a pound a minute on his cel bill!
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Thanks for the clarification, I didn't realize that it was absolute pressure.
Dude, it's Kpa, not Kpg! (Like Bare and Barg) LOL
Yep, the 240 is an absolute value.
I agree with the above, I ran 24degrees at 12psi, and was probably conservative at that, I NEVER heard ping.
Plus, that is where the old Corvair ran, and I knew that was a more strenuous environment.
I have been looking at the EURO-TURBO distributor...it is a Corvair Knockoff from Datsun! Has advance weights, and a pressure retard unit on it! I would KILL to have had access to an old Sun Distributor Machine to crank it through it's paces and verify what a STOCK NISSAN curve is set to regarding first RPM-vs-Advance, then Pressure Retard Rate per PSI, and Vacuum Advance per Inch Hg. This would have given us ALL some good baseline information about what Nissan thought was prudent.
Yeah, that's right, the EuroTurbos didn't have an ECCS, they had what looks like an N/A EFI ECU, No Cat, No EGR, No AAR, No O2 Sensor, and a Pneumatic Distributor---and were rated at 200hp!!! Kinda tells me something.
Oh, and a NEAT quirk on their pistons is a raised crown in the center of the "dish" to promote turbulence or something. They get ALL the good stuff Ex-USA!
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I actually know of someone who had cam towers shaved, but it was for rocker train geometry---basically so they didn't have to run some lash pad .280" think, or run non-standard length valves.
Again, that was for ALL SIX towers. I can see no reason only one would have a shim! I would call the seller and see what his explanation was--besides this needed the "bump"! LOL
Photos! I want PHO-TOS! LOL
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haha. im planning on getting that intake soon (soon being next year haha). there is a guy on classiczcars that has that intake i beleive. his name is Bubbleguinea. look him up. he might be able to help u.
He he he he! Yeah, Andrew will give empirical datum when asked. Just ask him, he's got the fastest 2+2 on the face of the planet! LOL
I think he did the dyno pull finally, so he might have numbers for you Re: Spork's Intake.
From all looks, it should be a good performer.
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JeffP now feels vindicated that even a Racer Brown cam needs to be DEGREED when installed.
EVERY cam needs to be degreed! If nothing else, getting it "as designed" as a baseline. Then make the runs retarded and advanced to see where the most useable power is occurring---most power under the curve.
It DOES make a difference!
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How can you argue with anecdotal evidence like that?
I'm sure they have cut and sectioned their heads to prove nothing is cavitating.
It's there for a reason, if Nissan could have left it off and saved the money for the tubing, clamps, and hose, don't you think they would have?
When you look at high-dollar racers that really are making power, they tapped holes in the head and made a manifold log out the intake side of the head so the coolant could cross and exit the head without having to move rear to front and go out only through the thermostat.
But guess what? That engine, with all it's mods, still had a -6 Bypass line.
I defer to experts, and not anecdotes.
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Japan.
It came from Japan.
The staged throttle bodies were stock in Japan, for the tip in response the marketthere demanded. It also allows for better fuel economy via throttle position and manifold vacuum advantages.
You need to learn how to search more efficiently. It doesn't mean looking through 20 pages, it means selecting your keywords carefully!
I know I answered it before, and there are photos posted!
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If it turns freely in the cam tower when everything is tightened down, that is what is important. I agree, someone probably replaced that tower and it didn't line up properly. No reason not to use it if everything aligns properly.
Ya know, I've swapped countless cam towers from head to head.
Hell, I've evne had them in a "Big Grab Box 'o Cam Towers" at one time.
The MOST that I EVER had to do was follow the Tome Monroe "Knock and Turn" method to get the cam towers to free up on the head. The towers tied together with the spray bar were from the same head, but who knows where the rest came from???
I could never see why ONE cam tower would need shimming---then again I am assuming it's a .015" shim---information or a photo hasn't exactly been forthcoming, so going further beyond "I Say-You Say-Anybody Got a Guess?" kind of discussion is to take the next step and do measurements and maybe snap a photo of the mutant.
I know I'm curious as to what it looks like!
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Got six KKK turbos from 5L Diesels sitting in my lap, going to the scrap bin. I am trying to look for some sort of cross reference to look up some maps.
Actually, they were on 10L diesels on a twin turbo layout.
From what I can tell, the part number is 5223 970 3150
The tag on the side gives the following information:
Kunde: 2145034
Grosse: 9514612
ATL: 90 921 1379
Ausf: 5223 970 3150
These are in decent shape, low hours, just hoping someone has a line to an information source that doesn't show up googling for the past hour. Found a South African Contract listing them, but not much more, I don't even know if they are K26, K27, K-XX? I know the Germans would put this on there for ID, but how can I find out what it means.
KKK Gurus?
Bueller?
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Normally those shims are 0.015" thick, and I can't see it rotating with that much of a bind in there!
It shouldn't affect the lash pads, as it would have to actually deflect the cam from the tower preceeding it---I don't see that happening!
Coolant Circulation Bypass Line
in Nissan L6 Forum
Posted
Please make constructive commentary from your observations, bj, or make no commentary at all. If you would have read the posts, you would have seen I deliniated the difference between an impeller thrust failure---which is so obvious any moron could diagnose it (case in point)---from cavitation damage which most people do not know about.
Nobody said every failure was caused by cavitation damage. Though you seem to imply that the most common cause of overheating is cover damage from failure of the pump bearings "catastrophically" -- causing impeller contact... Funny, I have never had any of my L-Powered vehicles do that---so that says a lot about your maintenance powers of observation compared to mine. (Just something to think about...)
Man, you have issues, please sort them out before posting usless barbs and counterproductive things like that last swarf.