Running Hot Since L20B Installed

[rcjone]

'71 4 door, L20B, 38mm SU's, A87 head, B/W Trans.

Been running VERY Hot since the new engine was installed.

The stock 2-row radiator was replaced about 2.5 to 3 years ago with a 3-row.

New mechanical temp gauge.

@ 65 Mph & 85℉ It was @ 210.

In traffic, stop/go @ 95℉ It was @ 215.

Don't know if this is too hot but most people I have spoken to think so, as I do.

I have the shroud on.

I have checked the 160 thermostat with a temp gauge, ok.

I have had the radiator flushed.

I have added Water Wetter.

Have a 1 row cooler on.

Hesitates on acceleration when hot, have the heat shield.

I suspect this is due to the fuel maybe boiling,

Input from Bluebirds List was a bit indecisive.

So what do y'all think?

 

[ The boiling point of gasoline varies.

At atmospheric pressure, it's between 100 and 400 oF. A primary cause of this variance is the various additives in the gasoline from different refiners designed to meet different octane requirements.

Anwsers.com ]

[I'm BLUE]

I just ripped apart my L24 ,,, Cooling Jacket was full of Sh$t ,,, ( Like a yogurt cup full ) ,,, I cleaned it out with a pressure washer AFTER knocking out all the core plugs to do so ( they were bad ) ,,, then I pulled the head ( since engine is being rebuilt ) ,,,, 2 of the cooling passages between #3 and #4 were block :blink: ( with rust/debris :angry: )

 

My experience with flushing radiators/blocks is unless you continously change anti-freeze every 2 years , the only TRUE way to clean em is to open the suckers up and let errrrrrr have it :D

 

what is your timing , compression , head shaved , and is your block bored ?

 

Proper coolant mix ?

 

Water in Oil ?

 

---> Compression Check ? <---

 

Does your Radiator have "cold" spots a full temp ?

 

Is your Radiator Cap any good ?

 

Clutch Fan any good ?

 

Thermostats are sometimes bad right out of the package !

 

Do you have leaky/blown head-gasket ?

 

Sounds like you might be running lean as well :huh: ???

[I'm BLUE]

old timers use to put "close line pins" on the fuel rails 4 or 5 or so in a row about 1-2 inches apart ,,, neat trick ,,, insulate your fuel line as well ,,,

 

Is your exhaust running ajacent to the fuel line underneath ???

[Braden]

ummm dude you do realize the l20b takes a bigger radiator, thats why the core support on the 620's changed when they changed over to the 2.0 to account for the bigger radiator

[datzenmike]

160 is way too cold. 3 core rad is plenty of cooling. Everything you have mentioned looks just fine so perhaps that mystery after market temp gauge is lying? Hook the Nissan sender back up and look at the stock gauge, bet it reads normal.

 

One thing, try checking your advance, should be about 12 BTDC. Try slightly more advance until it pings under acceleration then back it up just enough to stop it. Retarded ignition will cause a hot engine.

 

Look at lower rad hose and rev motor... does it collapse from the suction?

 

 

The L20B motor always had a fuel return line to prevent the gas boiling in the lines. If you don't have one then boiling gas is normal and doesn't mean the engine is over heated.

[MicroMachinery]

If your temp reading at the thermostat is 160, then it is very likely that your gauge is wrong. Do you have a laser thermometer?

 

If it's not wrong.. then I'm wondering about the "running lean" scenario. If you had a smaller displacement engine, running those 38mms at a certain setting was probably fine. Unless you re-set the carbs and re calibrated for your L20, you're going to have a problem there(I would imagine; I haven't used them before). If you've swapped from, let's say an L16 to an L20b, your displacement just shot up 25%. There will definitely be an increased demand for fuel, as you're taking in that much more air. However, like I said before, I don't have much experience with them. If they self adjust and compensate, and the only adjustment they have is for idle mixture, then I withdraw my comment.

[rcjone]

To:

DTP: Engine was completely rebuilt last year. New expansion plugs. No oil in water. No clutch fan. Head not shaved. Dished pistons to be able to run 87 gas.

"Is your exhaust running adjacent to the fuel line underneath?" - No,

 

ghettobraden; Dude, 3 Row, not 2.

 

datzenmike: The reason I went to a mechanical temp gauge was the stock gauge was reading WAY high, close to red on hot days.

 

MicroMachinery:No laser thermometer but running lean is possible as I have been mucking about trying to get better that 18.5 mpg!

 

When blondes have more fun, do they know it?

[zerow]

I'm going to go out on a limb here, but my buddy's car used to overheat like that. It ended up being a clog in the heater core. Run the heater (I'm from Southern California, roll the windows down first...) and run the heater full blast. See if the temp drops and is consistant with the heater on. If it doesn't drop, then it sounds like its not making the bypass it should and keeping the heat up. Either way, it will take the heat off the engine and get any trapped air pockets out of the system. A quick check for (hopefully) a long term solution.

 

I had my Corolla in Europe that would run hot with the heater on. Once again, a coolant bypass issue. Once the blockage passed, it was smooth sailing and trouble free once again. Took a few time with the heater on and off, but it worked itself out.

[I'm BLUE]

hmmmmmmmmm this is a doosey !

 

my apologies , I meant to say originally ^^^ is your "fan clutch" working ? ( many a time I have seen these go bad ,,, they basically stay locked on ,,, sounds like an equilavent "roaring" but you may be famaliar with the sound :)

 

(1) Check your Raditor for "cold" spots ? (clogged or partially clogged)

 

(2) Back Flush the heater core as Zerow indicated ^^ ( disconnect inlet/outlet hoses ,,, run a garden hose through it ,,, you can buy attachment to do this for a little higher pressure ;) )

 

(3) Again a $5 thermostat ( as they go bad out of package brand new , I would say 1/4 of the cheapy's do ! ) this would be a good way to go ,,, let the air bleed out of the system and install in correct direction;alignment :D

 

(4) Have you checked/replaced your sending unit/cleaned the connection's ? Micro has a good idea with the laser temp gun ^^^ :D

 

(5) Not to be-little you , but how do you know the thermostat is "good" if it is running 210+ degree's on the free-way :) ? ( gauge wrong ? )

 

(6) Pull the valve cover off and see if your getting enough oil collection in the head ;) ( there should be plenty in the valley area , and if you are using a Fram oil filter , do not ever use them again :mellow: )

 

(7) Better to run a little fatter than a little leaner ( don't want to burn those valves ;) ) ,,, synchronization tools are cheap when you get your carbs dialed in early ! you'll be very satisfied for the price

 

(8) Check to see if your exhaust is plugged lately ? ( mufflers detoriate , create immense back pressure , loss of power and running a bit warmer can result ,,, is specific for each car case though ! cut it off if it is really old , and stick a free-flow version of a muffler on there.

 

(8) lastly , If it were me , I would compression check ( use Anti-Seize on Aluminum threads liberally ) ,,, there are goofy rebuild places in Oregon ,,, not saying all are shit , but I have seen MORE than 3 engines that have "run hot" or "blown up" after being "rebuilt" from 3 different places of business :o ,,, One of these was a 1-2 turn-around complete long-block rebuild ( which makes me think they are not being remotely clean about things ) ,,, The Toyota engine from one of our trucks had been back in for 3 warranty claims before the thing ran "good enough" to depend on for our drivers :unsure: ---> overheated and blew up 2 times before ( seized the first time from what I understand :blink: )

 

Ok have fun and these are just options to scan over ,,, sometimes the little things can make big problems :D

[I'm BLUE]

Try taking the thermostat out then re-seal it , and see if your indicate's the same reading's ,,, if so could be sender/gauge related or possibly much worse ! They have kits to drop in the coolant to test for blown head gaskets if you think it might be going that way...

 

Have you re-torqued the cylinder head bolts within specified range since the head-gasket was resealed ?

 

Just some thoughts and good luck ! :D

[rcjone]

I live in Sacramento CA, heater hasn't been hooked up for many years.

I put the thermostat in a pot of water on the stove and watched it open @ 160 +, also can see the gauge drop @ 160...it's a working'.

Carbs are Z-Therapy rebuilds, however I have messed with them to get better than 16mpg. Yesterday I richened them up just a wee bit. No change. Got up to 215+ at the off ramp

after a longish 65 mph run on the freeway. Air temp was about 92.

Muffler `seems' fine, I can put my hand over the pipe, feels normal.

The engine was built by a guy that has been working on Dimes since 1971. He rebuilt his own motor and has built a F.I. one for his wife, to mention a few. I trust him.

No oil in the coolant.

Cylinder head was retorqued after abbot 700 miles or so.

 

Fun in Central Cal..!

 

The way money goes so fast these days. they should paint racing stripes on it.

- Mark Russell

[datzenmike]

Carbs are Z-Therapy rebuilds, however I have messed with them to get better than 16mpg. Yesterday I richened them up just a wee bit. No change. Got up to 215+ at the off ramp

after a longish 65 mph run on the freeway. Air temp was about 92.

Muffler `seems' fine, I can put my hand over the pipe, feels normal.

The engine was built by a guy that has been working on Dimes since 1971. He rebuilt his own motor and has built a F.I. one for his wife, to mention a few. I trust him.

No oil in the coolant.

Cylinder head was retorqued after abbot 700 miles or so.

 

I don't see why you would be getting 16mpg. 26 would be better. This is odd or a symptom. Does it go alright? Accelerate good? Does it struggle at all?

 

Pull your plugs and read them. Extreme lean, the porcelain insulator inside will be bright white. Good running is a light tan/brown color. Go for a several mile trip at highway speeds, and pull over and shut off the motor. Check the plugs right there. This will give a good indication of how it's running at cruise speeds.How are you richening the mixture? Jet change? Try even richer and see if problem goes away. In my experience, very lean runs like crap.

 

Mechanical advance sticking and not fully advancing at high speed? Will act like retarded ignition and fuel will be ignited too late and be still burning on the way out of the cylinder and transfer lots of heat to the water jacket around the exhaust port. Poor mileage and power.

[zerow]

I live in Sacramento CA, heater hasn't been hooked up for many years.

How is the system set up for the removed heater? Loop with rubber hose? Or simply through the heater core and no electrics to the fan?

The SU manifold - Are you running the coolant bypass or is it blocked off? 215 is still really high IMO.

I'm starting to lean on timing as a cause for higher than normal temperatures, but its a hard call.

[dryheat]

Ahhhh ... this sounds all too familiar. My 71 Wagon ran really hot after I put in an L20 with a weber downdraft. The faster I went on the freeway the hotter it got. I was running a 160 thermostat and the temp would get up to 195+ and even hotter in traffic.

 

I spoke to a long time Datsun guy and he recommended to try burping the engine ... which I did and while it's still not as good as I would like it ... it is running 15 degrees cooler. Basically he told me that since the block is 3/4" taller than an L16/18 that there was air trapped inside the thermostat housing / head / upper radiator hose area and was creating steam. I jacked up the front of the car as high as I could and topped off the radiator while the engine was running.

[zerow]

Ahhhh ... this sounds all too familiar. My 71 Wagon ran really hot after I put in an L20 with a weber downdraft. The faster I went on the freeway the hotter it got. I was running a 160 thermostat and the temp would get up to 195+ and even hotter in traffic.

 

I spoke to a long time Datsun guy and he recommended to try burping the engine ... which I did and while it's still not as good as I would like it ... it is running 15 degrees cooler. Basically he told me that since the block is 3/4" taller than an L16/18 that there was air trapped inside the thermostat housing / head / upper radiator hose area and was creating steam. I jacked up the front of the car as high as I could and topped off the radiator while the engine was running.

Good call dryheat. I forgot about that one. That may do the trick. Its all too logical, really. The highest point on the engine is the thermostat housing, which holds the temp gauge sensor, both holding steam, which is water over 212 degrees.

[banzai510(hainz)]

there is a little gille valve on the stat, I cut them off and drill a 1/8 hole in there so the air can escape to the rad.

 

try another rad cap(its my last resort)

 

adding a heater core to the circut aids in coolingput a Weber DGV oin there ans see how it ruuns

[datzenmike]

Good call dryheat. I forgot about that one. That may do the trick. Its all too logical, really. The highest point on the engine is the thermostat housing, which holds the temp gauge sensor, both holding steam, which is water over 212 degrees.

 

Can't see the trapped air being hotter than the water below it. I've heard of thermostat slow to open and gauge low reading if there is a bubble there keeping the hotter water away from them. Besides the thermostat is highest so when it opens air would burp out if it didn't get past the small hole Hainz mentioned.

 

What does it read when idling for a while???

[rcjone]

When the car was first setup I was getting 16+ mpg, since then 18+. The advance is free and move ok when I push it with my finger.

I changed the plugs 6 wells ago, the porcelain was very very light brown.

[rcjone]

Sorry for the break in my reply, hit Return...

Car surges a bit on take off, when real hot more than a bit even driving at a steady pace.

The heater is out of the loop, just a rusty pipe sticking thru the firewall.

The longer it idles the warmer it gets, as I said it got to 215+ after a run on the freeway and I had to sit and idle at the offramp.

 

The original point and click interface  was a Smith & Wesson invention.

[hogboy52]

I can tell you for sure how to make a motor get lousy fuel mileage, low power, and to always overheat. That is to retard the timing. I have not seen any mention of you checking the timing or what the results were. the best timing for these motors is around 35 deg. @3k-3.5k rpm. The factory specs are 11.5 deg. advance weights and 11.5 vacuum advance plus 12 deg. initial, though in reality they need some tweeking to reach that. Later motors had devices to retard the spark to speed warm-up burn off hydrocarbons etc. These can cease functioning and keep the ignition always retarded.

[I'm BLUE]

I can tell you for sure how to make a motor get lousy fuel mileage, low power, and to always overheat. That is to retard the timing. I have not seen any mention of you checking the timing or what the results were. the best timing for these motors is around 35 deg. @3k-3.5k rpm. The factory specs are 11.5 deg. advance weights and 11.5 vacuum advance plus 12 deg. initial, though in reality they need some tweeking to reach that. Later motors had devices to retard the spark to speed warm-up burn off hydrocarbons etc. These can cease functioning and keep the ignition always retarded.

 

Look again , timing mentioned early on ;)

[I'm BLUE]

Look again , timing mentioned early on ^^^ ;) ,,, solid advice though :D

[zerow]

All right, back on the timing issue. I have re-read this post. Twice. So, I have new questions:

 

Are you running a matchbox distributor (small black ignition module on the outside of the distributor)?

If, Yes, Next question: What does the module say on it? E12-80, or E12-93? If he's running the late module, that thing is already retarding his timing on the ignition side, causing the overheat. It needs to be E12-80. If the whole assembly is off by one tooth at the oil pump, he is not getting a full adjustment, and that could cause the retarded timing, and the overheating.

[rcjone]

No matchbox.

Timing and the radiator core seem to be the only things left ! Argh...

 

Handle every stressful situation like a dog. Piss on it and walk away.

[datzenmike]

You have three types of timing on your distributor. Three (3). There's the vacuum advance, static timing and mechanical advance. If you checked the timing with a timing light you have only done part of the job. I believe you when you say you timed the motor to 12 degrees but what is it doing when revved up? There will always be 12 degrees and the mechanical advance should add another 20 or more when revved up to 3K.

 

Disconnect the vacuum advance. Start engine and use a timing light. Check the 12 degrees static advance at idle and then slowly rev the motor to 3,000 RPMs. the timing should advance into the 30+ degree range.

 

Zerow, very good on the 12-E-93 matchbox. A guy on the realm had one and it idled fine but when revved it would retard by 20 degrees. The 12 E 93 is meant for use with the EFI computer.