L16/18 cooling system questions

[Stitebunny]

I have searched quite a bit and have found some answers but looking for a couple more so asking for some help here.

I am putting an L18 in my 510 wagon in place of the original L16.

The L18 has an A87 head without the cooling ports on the manifold side. I understand this is from an engine that used the "stovepipe" manifold assembly. I'm planning on running a non stove pipe exhaust and the L16 intake with a Weber 32/36.

Question 1, do I need to modify the head to be able to take advantage of the cooling system ports? Or will I be okay if the manifold isn't heated/cooled by cooling system. The car will be an occasional driver in a mild climate.

 

Question 2, I don't have the thermostat by pass hose set up connecting the thermostat, intake manifold and radiator hose connection.

If a thermostat with the little jiggle valve is used, is that sufficient enough to act as a large enough bypass for proper thermostat operation?

 

What have some of you done with similar situations?

 

Thanks

[banzai510(hainz)]

Its up to you . I like not haveing holes then the intake manifold will NEVER leak water. Esp if one runs sidedraft Mikunis. Thats what I would keep the head for.

 

In winter yout want the holes in the head to warm up the manifold to keep the carb from freezing. On 510s there was 2 types of metal tubes that went to the manifold t heat. One has a port that cam frm the thermostate housing(U shaped) a later one didint have this. So depends what you have and what is going to be needed.   So I had both set ups. So depends what parts you have on hand.

 

I put a 1/8 hole in the thermostat.

 

On the head one can drill a 1/4 hole in the the head by centering a intake gasket. I make the hole 1/4 incase you want to go to sidedraft and maybe wont ike as bad or you can maybe plug it .    did this on my U67 and have been running since about 2003.  Maybe I could have gotten away with not drilling a hole but its ez to figure out. I was going up HWY 18 in winter and car was acting like running out of gas higher elevation. I pull over and carb was like ICED up.  So if you dont drive it often in winter I wouldnt worry about it

[Crashtd420]

I connected to a fitting under the thermostat instead of the intake then ran that over to the water pump....

 

If you dont do that you'll have to plug the fitting at the water pump.....

Personally I wouldnt just rely on the jiggle valve to let enough coolant through.... 

 

 

[bilzbobaggins]

I shot three holes in my thermostat on my L16.  Seems to work just fine.

[datzenmike]

The A87 had the holes for coolant as far as I know. Can you see the intake side of the head to confirm they are not there???? I think you'll find that they are.

 

The L16 intake is definitely coolant cooled/warmed. If for some reason the head doesn't have the holes just use the gasket to mark the holes and drill them out. I did this on the U67 head I have. As far as I know only the U67 does not have the holes.

 

The coolant flowing intakes warm the intake air when severely cold and absorbs and carries away radiant heat from the hot exhaust just an inch away. This allows the engine to operate smoothly in a wider range of outside temperatures

 

Jiggle valve is not as good as a proper by pass hook up. During warm up any coolant is going into the rad and cold rad water is displaced into the water pump and into the cold engine slowing the warm up. The by pass is just that. It by passes the rad and circulates partly warmed coolant right back into the engine and speeds the warm up. In addition more coolant is circulated around the exhaust ports and pushed out into the intake with a by pass. Z cars that race often drill extra by pass holes (not used on EFI engines) to force better circulation in the long front to back 6 cylinder head. This prevents the rear combustion chambers running hotter than the fronts.

[Stitebunny]

Thanks for the info all.

 

I can confirm there are no coolant holes in the manifold side of the head.

 

I think I will leave the head alone for now. If that becomes an issue I will revisit that then.

 

So to run a bypass hose, I need a line/pipe/hose going from the tstat housing (lower portion) over to the connection at the lower radiator hose connection fitting at the timing cover? Is that correct?

 

Any chance someone here has the original line? I will submit an ad in the classifieds if not.

 

Thanks again.

[banzai510(hainz)]

I just plug up the hose below the fuel pump. some thread that part other use a bolt and a clamp. The L shaped one. and delete everything the pipe and either plug the state hoousing or find one that dont have the bypass port built into it.         Like your running sidedrafts carb

[Stitebunny]

You don't agree about needing the bypass at all? The hole drilled in your tstat has been enough to keep it running normally?

 

You could still run a bypass with sidedrafts. ..

[banzai510(hainz)]

ON my 510 its been like that for years and has Mikunis 40s  WITH 3 CORE

My yellow 510 was plugged this way also and car has been that way for 30year before I sold it

 

I run a 160DEG GERERIC 54MM STAT with a1/8 hole.

 

However on 85 deg plus days I dont want to get caught too long in stop and go traffic as my Mikunis start to cook.

 

My 521 is stock and I have the bypass with the U shaped hose to the lower part of the stat ans still run a 1/8 hole. However I have a chinese 3 core and if i runn a 180 or above the radiator leaks like a sheeve so I put the 160 back in and seems ok with a quart to add every month as those a ?able radiators.

 

On those U shaped maybe 2-3 in hose I had the last one from renton Nissan when Wendy bought it for me. She used to be at Renton Nissan ans is smart on the older nissans if shes still there

 

as for this bypass U shpaed hose. LIke I said earlier there I think on the 72s there is no U shaped hose from tube to the lower stat housing. I have used both and maybe still have it.  so I have 2 state housing types. One with a hole and one that dont (just the temp hole)

Edited August 20, 2019 by banzai510(hainz)

[datzenmike]

The line down across the front of the engine is metal but you could just use hose for this.

 

The by pass has no other purpose but during warm up. As it's there anyway, coolant can easily be run through the intake and connected at a Y near the thermostat housing. 

[Stitebunny]

So what I'm understanding is that none of this has anything to do with engine cooling system operation as far as keeping the engine in the proper temp range once warmed up?

The bypass and manifold circuits are strictly for cold start driveability and getting to and maintaining a reasonable intake air/fuel temp?

If none of it is installed, as Hainz has done, I should have no issues in mild weather except possibly a prolonged warm up phase which may have little effect?

I guess I was thinking it all played into the greater cooling system circuit and may have adverse affects on normal engine running conditions.

[wayno]

I cannot speak for others, they say what they will, all what you typed above except for the last line is not true.

I have first hand experience with this subject, I built a LZ23 back in 2011 and installed it in my 521 work truck, to clean the engine bay up a little I put the early L16 thermostat housing on my engine, I do not recall anymore if I drilled  an 1/8th" hole in the thermostat but it had the jiggle valve.

I drove the truck to Renton WA and back to Vancouver WA to pick up some parts, around town it seemed to be fine, but on that trip I noticed after driving only 30 miles that the coolant/water temp was all over the place, it would get up near overheated(near H on the gauge) and then drop to almost cold, it did this the whole trip, it was all over the place, but I got over 23mpg on that trip.

After that trip on another day I was driving out to Battleground WA for a job going about 50mph, I got to the main street signal(always hit that one red), I started and the engine overheated, I was driving normally and it overheated for no reason, it had been fine for the first 15+ miles, soon after that it blew the head gasket, now I am getting fuzzy as it has been a while, but as I recall I blew another head gasket soon after that, maybe 3 months, I could not understand what the issue was, well I figured it out after that second head gasket, the only thing I had changed was that bypass, what I concluded was that the thermostat was closing while driving on short and long trips(50mph+), the water was not bypassing properly and the coolant was boiling in the head, I also was running a pressurized coolant system type radiator cap.

That second head gasket change I did a few things differently, I used an ARP head stud kit, I went with a  un-pressurized coolant system with a coolant reservoir, and I put the bypass system back in, I have not had an issue since.

The bypass works all the time, if it is cool enough outside the thermostat can close will driving down the freeway and the coolant can boil in the block because it cannot get past the thermostat because the thermostat housing is cool enough to keep the thermostat closed till it is overheating and then when it finally opens that cool water/coolant hots the overheated block/head it vaporizes and the engine starts puking coolant.

The thermostat needs to be drilled with an 1/8th" hole, or you need the bypass system for the engine to run properly, the L16 came with a thermostat with a hole in it, but since Nissan put a bypass system in place, after all the stock type thermostats with holes in them were sold, parts stores just sell everyone thermostats without holes in them now with a jiggle valve, the jiggle valve is to let the air out of the block/head when you fill it up with coolant, it works well for this, it doesn't work well as a coolant bypass.

As I said above, I have experienced this issue myself, and I got very tired of replacing head gaskets!!!

Edited August 20, 2019 by wayno

[datzenmike]

3 minutes ago, wayno said:

The bypass works all the time, if it is cool enough outside the thermostat can close will driving down the freeway and the coolant can boil in the block because it cannot get past the thermostat because the thermostat housing is cool enough to keep the thermostat closed till it is overheating and then when it finally opens that cool water/coolant hots the overheated block/head it vaporizes and the engine starts puking coolant.

The thermostat needs to be drilled with an 1/8th" hole, or you need the bypass system for the engine to run properly, the L16 came with a thermostat with a hole in it, but since Nissan put a bypass system in place, after all the stock type thermostats with holes in them were sold, parts stores just sell everyone thermostats without holes in them now with a jiggle valve, the jiggle valve is to let the air out of the block/head when you fill it up with coolant, it works well for this, it doesn't work well as a coolant bypass.

As I said above, I have experienced this issue myself, and I got very tired of replacing head gaskets!!!

 

Exactly!!! I've run without a by pass and the engine temp gauge was just barely reading but the rad hoses were rock hard with pressure!!! Like I said only (up till now) the U67 didn't have the coolant cooled/warmed intake but joined to the intake/exhaust manifolds and used exhaust heat to warm the intake. A poor idea as the heat riser valves eventually always are rusted in either stuck ON or full OFF mode and the intake cooked or froze. I put an earlier L16 exhaust and a later '79 coolant cooled intake and a proper by pass on my 710. 

 

If coolant warmed, the air entering the combustion chamber is at a more constant temperature and doesn't vary with the day to day (or even daytime to nighttime) outside temperatures. 

Also. The coolant in the intake also removes heat radiated onto the intake from the very hot exhaust just an inch away. Very helpful if in very hot temperatures. Now you might say that it only get very hot once or twice a summer but if it boils the gas in the carb (vapor lock and hard restart) and you can't get it to run just once, that's one too many times.

[Stitebunny]

Got it. That makes sense to me.  Thanks for the explanation wayno. Sorry you had to figure it out the hard way.

So I will plan to make a bypass circuit and forgo the intake heating for now at least.

Appreciate the info and help you guys always have.

[wayno]

Just drill a hole or two in the thermostat, it will let the cooler coolant out of the thermostat housing and let the heated coolant into the thermostat housing so the thermostat can open.

Next to the big hole is the little hole(jiggle valve) in the photo below, that hole I drilled is not near as large as the stock bypass but it seems to be large enough as long as the thermostat is working properly.

 

 

It likely will be hard to make a bypass, but you can get/buy everything off an L20b I believe, the issue then can be getting the thermostat housing off the head without breaking anything, it's hard enough getting all the bolts out of the thermostat cover, in the past whenever I seen an L20b in the wrecking yard I would grab everything I needed for the bypass(housing complete and piping), but now I don't need that stuff anymore as all my engines have it, and I rarely see anything with an L20b in the wrecking yard anymore when I go there, I have seen a few in the Sea/Tac area recently when I checked the Pick and Pull inventory but they get picked clean quite fast as they don't show up very often anymore.

Edited August 20, 2019 by wayno

[wayno]

This is what you are looking for if you decide to go not to drill your thermostat, you would need good hose also to complete the system.

 

It's much easier to just drill the thermostat unless you already have what is in the photo above.

Edited August 21, 2019 by wayno

[banzai510(hainz)]

I went with a pop cap type radiator cap if that matters but still run a overflow "mountaindew" bottle.

 

As Wayno experinced I delt with this issue before and the 1/8 160 seemd to work best and a pop rad cap(i noticed it sooner cause the cap popped)

 

By all means if yo can the pipeing I would use it but you have a nice head that can be used for a sidedraft set up later and dont want to drill holes in it.

Edited August 21, 2019 by banzai510(hainz)

[datzenmike]

The holes are superfluous to running side drafts and won't interfere. Heads with coolant holes don't leak with a good gasket. I drilled mine out and used them and the U67 head works just like a 510 head with 2bby Hitachi. I also lately, switched to R-1 carbs and don't use the coolant holes and it still works fine.

 

As to the 160 thermostat it should run best where it was designed to run 180F.  If it overheats or runs too hot with a 180F then something else is wrong.

 

Get a later coolant recovery rad cap and plumb the over flow pipe into a container. Coolant expelled from the rad is saved and when the engine cools it siphons back in keeping the rad topped up at all times. With this system in place I loose only a cup of coolant a year.

 

 

[Stoffregen Motorsports]

When I was young, and was always playing around with the engine in my 510s, having the holes plugged meant that I could remove the intake and not have to drain the coolant. This was nice, as we were always doing something with the induction.

 

Having the coolant run through the intake helps keep things cool, but as with small block Chevys and Fords, it is also a potential leak that gets into the engine.

 

Good gasket, plus studs (instead of bolts) holding the manifolds on, and clean, flat gasket surfaces are a must for keeping the gaskets intact. I always run a ring of high temp orange RTV around the water ports on both sides of the gasket as insurance. If you use the right amount, you don't even see it.