Head cooling on cylinder #5 - solutions?

[jgkurz]

Hmm, I haven't noticed any change in warm-up time or operating temp at all. But then again, the car runs against the 160 degree T-Stat I have all the time except in heavy traffic when it's 100+ out. Perhaps it's because I have both 5 and 6 running back into the water pump, uncooled.

 

John - Now that I know that doing just 5/6 seems to work, I plan on eliminating the stock T-Stat housing and running them all into some sort of runner or something, as Tony D, et al. have talked about elsewhere. Also, FWIW, I've blown a head gasket at number 4 without blowing 5 or 6, so I'd guess doing all three rear cylinders would be worth it.

 

Great info Sean. Thanks for responding.

[Tony D]

I've found that someone else used different thermostat arrangements for cooling the Z independent of my surmising. And they did it to great effect.

 

I think there are legs to an alternate arrangement. "Amot Truck Thermostat" do a search and be surprised! LOL

[X64v]

Can you elaborate Tony? Searching "Amot Truck Thermostat" both here on hybrid and in Google didn't come up with much.

[datman]

I think its been mentioned on here before but I was looking at the cooling system on my 72 Alfa GT junior yesterday, It has a pipe from each cylinder back to a common rail then joins the thermostat housing..very neat solution for such an old engine and its only a 1.3L. I'm going to copy that onto my car.

[Tony D]

http://www.who-sells-it.com/images/catalogs/4086/20156/ct/2009-street-rod-parts-000094.jpg

 

Lower left Corner... that little box don't need to be on the side of the head. And when liberated as to where the flow goes...you can port and duct and move all sorts of stuff through smaller hoses to a remote housing and thence on to the rad-i-diddy-ator...

 

Since a schematic of the flow was put up earlier, check this page out, for what I think the solution would be:

http://pdf.directindustry.com/pdf/amot/06v-j-valve-thermostatic-control-valve/15809-10648-_2.html

 

They make housings that are big and bulky, I just haven't dicked around with the AMOT application catalog to get dimensions to make one out of a block of aluminum. The tolerances aren't that critical, just the o-ring that seals, and you can buy them in 5 degree increments. They come in all sizes, so if you only wanted to increase the flow in the back of the head over a given temperature (say 190F) then you can run a split cooling system with a smaller amot controlling that section of flow control, while the main thermostat is set to 160 (or whatever...)

 

Big trucks use these style thermostats because you can flow a gob of water through them and they are very good at controlling tempperature long term. I just liked the appeal of one of their smaller ones controlling heating throug the Carb Bases (another project...don't ask!) which shuts off once the car is warm---like the stock 73/74 carbs did! Get gooder cold drivability with the controlled vacuum leak, and then shut the flow off and cool that manifold for warmed-up power... But it works in this application as well.

[X64v]

Tony, those are very interesting. I've been mulling this over, trying to figure out how to properly size the lines or restrict the flow above the cooler cylinders to keep them all at the same temperature (i.e. if all cylinders have the same size lines, won't #1 still run cooler than #6? etc.). What if one used 6 of the smallest sized of these valves to control flow from each cylinder separately? This way each chamber would be regulated to the same water temp, and all the water exiting would just run directly to the radiator, no 'main' T-Stat needed. Your thoughts?

[Tony D]

That would work, but be extremely complex. The issue is the 'knifing' of the flow through each of the respective cylinders as it comes forward.

 

Coming forward is the problem. If all the water for the head exits out above each combustion chamber, then they ALL can go to a common thermostat housing because the flow will be greatly equalized.

 

Even Nissan Recognised this EARLY in L-Head development. The FIA heads DO NOT run thermostats like we have, they have three LARGE water passages and a separate manifold with the thermostat in the end of it. Much like the four cylinder L-Heads have going to heat the manifold...

 

The LY is similar, with a separate water manifold taking water off much higher into a separate manifold and to the radiator throug a thermostat mounted separately.

 

Note the OS Gikken Head has the same (almost looks identical to the LY) water manifold off the intake side of the head with the thermostat in the end of it.

 

And all the above were specifically designated for HIGH OUTPUT N/A USAGE in endurance racing. Nissan knew there was an 'oops' when pushing the envelope for the L-Engine even in N/A trim. But few people run their cars like those racers, so it usually doesn't show as an issue.

 

Large Horsepower Turbo Engines of the 80's had similar setups, the photos are out there...

[Careless]

http://www.who-sells-it.com/images/catalogs/4086/20156/ct/2009-street-rod-parts-000094.jpg

 

Lower left Corner... that little box don't need to be on the side of the head. And when liberated as to where the flow goes...you can port and duct and move all sorts of stuff through smaller hoses to a remote housing and thence on to the rad-i-diddy-ator...

 

Since a schematic of the flow was put up earlier, check this page out, for what I think the solution would be:

http://pdf.directindustry.com/pdf/amot/06v-j-valve-thermostatic-control-valve/15809-10648-_2.html

 

They make housings that are big and bulky, I just haven't dicked around with the AMOT application catalog to get dimensions to make one out of a block of aluminum. The tolerances aren't that critical, just the o-ring that seals, and you can buy them in 5 degree increments. They come in all sizes, so if you only wanted to increase the flow in the back of the head over a given temperature (say 190F) then you can run a split cooling system with a smaller amot controlling that section of flow control, while the main thermostat is set to 160 (or whatever...)

 

Big trucks use these style thermostats because you can flow a gob of water through them and they are very good at controlling tempperature long term. I just liked the appeal of one of their smaller ones controlling heating throug the Carb Bases (another project...don't ask!) which shuts off once the car is warm---like the stock 73/74 carbs did! Get gooder cold drivability with the controlled vacuum leak, and then shut the flow off and cool that manifold for warmed-up power... But it works in this application as well.

 

I was looking at BMW 330ci thermostat housings today and came across this:

 

 

I think it uses the same principle?

[WizardBlack]

I was looking at BMW 330ci thermostat housings today and came across this:

 

 

I think it uses the same principle?

 

LOL, I just installed that very housing and a water pump on my Dad-in-law's 3 series. That is not what you think it is. It's an inlet and an outlet from the block. The in and out ports are pointed downward in the picture; the t-stat pokes into the block (and it molded into the plastic housing). The two water hose fittings (pointed to the right and to the left-rear in the pic) are for the bottom and top of the radiator. It's basically like our water pump inlet and thermostat housings joined at the hip (with no intermix, etc.). There's also a sensor in it, obviously. That part is about $90 IIRC. It's actually, IMHO & AFAIK, an aspect of BMW's that people gripe about. It's made of plastic and incorporates several items in it that will fail (sensor and t-stat).

So, the short answer is, no. It is separated.

[WizardBlack]

BTW, take a peek at Subaru cars. They have a separate header tank that sits on top of the engines that might be useful for rerouting some stuff and keeping the air pockets removed. It has a standard horizontal tab to mount it to anything with two 8mm bolts, features a (second) radiator cap and all hosebarb inlets and outlets.

[jeffp]

I had an opportunity to speak to an individual that by far is the most knowledgeable on the topic of keeping the engine cool. Very nice conversation, very nice man.

One thing that I found that really helped the cooling was to increase the water flow through the engine. I mentioned the LD28 pump and he agreeded that was more then likely the pump to use. Good on that one guys. I was impressed when that tid bit of information made it to this post, where the knowledge will be utilized and not continually debated! Maybe thats why I am posting here first? Anyway: I was sugessted to me that the water flow through the engine could be increased by 3 times what it is stock. Now that made me start thinking again, and that can be quite expensive LOL in order to increase the flow of the water we need to make some observations regarding blocks to start, and gaskets next, the proper flowing thermostat next, and this is what I would like to show what I have been able to come up with for a replacement part that will flow much much better.

I took some pictures, as a comparsion, (to the MSA 160 degree thermostast, the nissan part is better) to a part I just bought, primarily as a sample part to compare, and boy what a difference in parts!

Here is the pictures of the parts next to each other with a set of calipers to see the difference.

First comparison:

and the second comparison:

NOTE: I have never posted pics here, sorry if it doesn't come out correctly.

 

Here is the link to their web page.

http://www.stewartcomponents.net/Merchant2/merchant.mvc?Screen=CTGY&Category_Code=Therm

 

 

I believe this is an ideal retrofit for the Nissan period. Take a look and let me know what you think.

REGARDS:

Edited June 2, 2009 by Drax240z

[ktm]

Jeff, it always seemed to me that the stock thermostat would be a restriction even when it is fully open. Does that thermostat fit the stock L-series housing (stupid question for the night)?

 

By the way, about the LD pump, I may have bought the last one in the US 2.5 weeks ago according to Courtesy Nissan (though I hope not). I bought it after reading this thread again. I just need to find the time to install it.

[TimZ]

I was using the Stewart Components thermostat

http://www.stewartcomponents.net/Merchant2/merchant.mvc?Screen=CTGY&Category_Code=Therm

 

...which looks very similar- its basically a Robertshaw high flow unit with some bypass holes drilled in it. With this thermostat I had some serious problems getting the car to operating temp, especially on cool nights when the temps often wouldn't go above ~165 degF (195 degree stat). On warmer days the temperature would often swing from 170 to 200 degF for no apparent reason.

 

Surprisingly, I tried putting a stock thermostatstat back in, and it worked just fine. I had installed the high flow unit when I was trying to use the electric water pump - apparently it wasn't helping but I couldn't tell.

 

It could be that the bypass holes were contributing to the problem, but I suspect that the opening gain for the high flow stat didn't match the characteristics of the engine.

[Tony D]

The aluminum bodied AMOT thermostat will allow FULL bypass from the head back to the inlet of the pump until cracked open and you start running water through the radiator. The opening for the AMOT will be radiator hose size when fully open.

 

The flow improvement using the AMOT will be the total elimination of the external bypass lines and internal passages. Jeff has found already what I noticed long ago...there is a shunt from the head to the inlet to the pump that is almost 10mm in diameter that goes from the hot side of the engine straight back to the inlet of the water pump. Add to that the external bypass line which is anywhere from 8mm to 10mm, and on earlier engines there are sometimes two internal bypasses of identical diameter at the front of the engine.

 

This is a considerable amount of flow that is stopped from going through the engine instead of the radiator. Plug those holes, give the water some place to go while warming up, and you get more flow through the block when you need it.

[jgkurz]

I'm having good luck with the Mr Gasket High Performance Thermostat p/n 4367. As long as I have air going through the radiator my car stays cool. If I'm stopped in traffic idling with the A/C on it starts creeping past half way on my water temp gauge. I have a single 16" electric fan without a full radiator shroud. It keeps up most times but just can't move enough air going through the large FMIC, Condensor and Radiator while idling on super hot days. Not much is going to solve that other than a shroud or more fan capacity. On my last track day it was about 82deg F and the water temp stayed well below half way on the gauge at all times. I've have never punished the car like I did that day and it stayed cool. Again, I believe this is because I had plenty of air moving through the radiator. One other tidbit, I use a ArizonaZ Aluminum radiatar, LD28 water pump, 60/40 EthylGly mix with Water Wetter and a 22psi cap to reduce boil in the head. Once I bypass cyl 4, 5 and 6 I'll go back to a normal psi cap.

 

Mr Gasket Thermostat:

http://tinyurl.com/mlduz4

 

[jeffp]

 

By the way, about the LD pump, I may have bought the last one in the US 2.5 weeks ago according to Courtesy Nissan (though I hope not). I bought it after reading this thread again. I just need to find the time to install it. >

 

The thermostat will fit the Nissan housing closed I am sure, however open it needs more space, so what you can do, and I have already done the same, is to make a spacer plate to provide the debth needed to open the part. Easy build, all I did was get a piece of flat plate, cut it to the approx size. I did the hole in a 4 jaw layth then after that was done completed the outer dimensioning to the thermostat outlet on a belt sander. That worked very well, and I was able to keep all of the stock components intact in the process.

The LD pump, if you bought it a few weeks ago, then more then likely it was the last new part from Nissan. Tom told me when I bought two, there was one left in North America. So it just may not be available any longer.

 

<...which looks very similar- its basically a Robertshaw high flow unit with some bypass holes drilled in it. With this thermostat I had some serious problems getting the car to operating temp, especially on cool nights when the temps often wouldn't go above ~165 degF (195 degree stat). On warmer days the temperature would often swing from 170 to 200 degF for no apparent reason.

 

Surprisingly, I tried putting a stock thermostatstat back in, and it worked just fine. I had installed the high flow unit when I was trying to use the electric water pump - apparently it wasn't helping but I couldn't tell.

 

It could be that the bypass holes were contributing to the problem, but I suspect that the opening gain for the high flow stat didn't match the characteristics of the engine. >

 

I checked out this part and bought one bypassed, and one not bypassed. The pictures that you see are when the parts are up to temp and open. I thought the new part closed a little slow as compared to the MSA part, so you may have something there. But it seems to me that a spring designed to open and close the thermostat based on temp can be regulated well.

Also, I did the electric pump to STOP the cavitation of the pump. I figured if I could stabilize the flow rate with the electric pump then problem solved. I will give this part a try and see how it goes in my car. The fact that you could get the temp to stay low is a good thing I think, at least it is an indication that you can keep the engine cool, maybe not temp regulated as good as you like, and me for that matter, but now there is some head room right. I have never been able to keep the engine as cool as I needed to. One time with two pulls back to back my engine got to 110 degrees C or so and that was to hot, the engine started running differently. The part needs to respond to the engine temp and modulate the thermostat accordingly to maintain the correct temp. It very well could be that this part will not sufficently regulate the temp. I have two parts to try.

 

< The aluminum bodied AMOT thermostat will allow FULL bypass from the head back to the inlet of the pump until cracked open and you start running water through the radiator. The opening for the AMOT will be radiator hose size when fully open.

 

The flow improvement using the AMOT will be the total elimination of the external bypass lines and internal passages. Jeff has found already what I noticed long ago...there is a shunt from the head to the inlet to the pump that is almost 10mm in diameter that goes from the hot side of the engine straight back to the inlet of the water pump. Add to that the external bypass line which is anywhere from 8mm to 10mm, and on earlier engines there are sometimes two internal bypasses of identical diameter at the front of the engine.

 

This is a considerable amount of flow that is stopped from going through the engine instead of the radiator. Plug those holes, give the water some place to go while warming up, and you get more flow through the block when you need it. >

 

That just may be the best answer Tony. Getting the part installed is a different story though, but the part is a good design in my opinion.

I have been looking at the hole in the block, and I think the bypass can be plugged on the front cover, so there is still water in that area, which I think is also important for heat transfer in the front of the block. I don't think the front bypass is beneficial, but the rear bypass, now there is something there possibly. I do remember, that some configurations or applications did not have the two outlets on the rear fitting to the head, and it went directly to the heater core hose. I have the hose that goes directly to the inlet of the pump from the rear fitting at the rear of the head. That may or may not be helpful. Also Tim, since you could not stabelize the temps with the bypassed thermostat, maybe the thing to try is getting the part that is not bypassed, and drilling you own bypass hole in the part. The part I have has a significant change in the bypass flow rate over the MSA part. That may get you where you want to go.

I guess it is time to pull the Z down again, Frank and I blew the head gasket again, but nothing like it was the first time. I was able to drive the car home, god knows what that did to the head, but it can be welded, and skim cut on the surface to square it away again.

 

Anyway, the thing to avoid is dead heading the pump when the engine is not up to temp. So maybe by plugging the front bypass and using the bypassed thermostat will be the ticket. And Tony, the rear bypass on my engine will have to be addressed also to stop the recirculation of the water without the water passing through the radiator and getting cooled.

 

I have also completed some R&D on the cylinderhead mating surface and noted some changes in block design from the N42 to the F54 blocks. Seems the F54 block is missing about 6 holes that the N42 has for flow directly under the spark plug, you know right in the combustion portion of the chamber. I will have that hammered out here shortly. I just need to decide which block will get the work. Then there is the issue of the head gasket used, and that to will have to be addressed, and I have also noted the differences between the steel Nismo head gasket and the standard felpro, and Nissan stock gasket that will be adressed.

Lots of stuff going on with this topic to say the least.

[WizardBlack]

I have also completed some R&D on the cylinderhead mating surface and noted some changes in block design from the N42 to the F54 blocks. Seems the F54 block is missing about 6 holes that the N42 has for flow directly under the spark plug, you know right in the combustion portion of the chamber.

 

I'm confused by this. Are you saying you are unaware of the differences between the two blocks and the fact that the F54 has fewer holes down the length on the passenger side? Ie., more coolant flow is directed to the rear of the head when it leaves the block.

[jeffp]

 

I wasn't aware of this change a few weeks ago until I got both blocks together to compare. The coolant holes that are missing in the F54 block effectively created stagnant water flow to that combustion chamber, or at best slower flow in the combustion area of the chamber.

 

I am trying to stop the flow from one end of the block to the other and out, but rather flow through all combustion chambers and out at the same rate, and time. This way, you get better cooling over the entire surface area of the head and block, and less "hot spots" because of the restricted coolant flow. Keep in mind the goal is to increase the total coolant flow through the engine.

Well after some investigation, there are only a few ways to increase the coolant flow through the block and head. Also, the bypass in 5&6 are good, but 3 requires a bypass also. Looking at the block and the head, making note of the holes that are functional for water flow from the block to the head, it becomes very clear the flow of the water will be slowed because of where the water holes are placed in the block. The head has been designed very well in regards to flow, so my thinking is to mate the block to the head water passages more closly then they are stock to increase the total flow through the block. The more water that can get to the radiator to be cooled and back out to the engine the better.

[johnc]

The LD pump, if you bought it a few weeks ago, then more then likely it was the last new part from Nissan. Tom told me when I bought two, there was one left in North America. So it just may not be available any longer.

 

They are available, just bought a new one today. Think industrial diesel supply, not Nissan dealership.

[BRAAP]

...Does that thermostat fit the stock L-series housing ...

 

 

In short, the T-stat on the left will NOT fit the stock housing. I considered using one of those thermostats years back in the L-6, but when I tried to install it in my thermostat housing, it became painfully clear it would not fit! The body of the Thermostat is too large at the bottom. I then rifled through all my thermostat housings of various L-6's from early L-24 through late L28ET looking for one that it fit. I recall finding at least one that did it allow it to fit, but only fit in the closed position. It would not be allowed to open up as the engine warmed up...

 

I think I just read above that JeffP was modifying a housing to accept this style of high flow T-stat.