electric fan cfm question

[spdcrazy]

I recently installed a 3 core radiator in my 521. and due to this, clearance is tight between the rad and water pump which won't allow me to put a standard electric fan in. I bought and installed a spal 10in thin puller fan setup. I have found multiple cfm ratings on it, but it seems to be about 750cfm. at this time I do not have a shroud, (that is my next step) but it is struggling to keep temps in the norm now when its 40degrees out,

 

so my question is, would 750cfm be enough to pull through my three core?

 

if not, would a higher cfm pusher fan help if installed in addition to? I realize they might fight each other, but maybe I could mount the pusher on the passenger side while the puller is on the drivers side, combined with a efficient shroud?

 

or should I just scrap my small puller and go for a bigger pusher fan? I need this to be easily driven during Colorados hot summers.

[TENDRIL]

what is telling you its out of normal range,  your gauge? 

 

 

is there any way you can install a manual gauge to see what number its actually at? 

 

 

my sensor was telling me i was close to over heating but i installed a manual gauge and i was at 185-190 the whole time 

[TENDRIL]

the only time the fan really is effective is under 10-15 mph thats why they designed the clutch fan it stops being effective above 2500 or some thing like that 

 

 

so if its showing hot while driving something else may be wrong  

[spdcrazy]

yes i'm using a factory gauge. the electric fan is controlled by a 185temp sensor located in the lower rad hose, and it seems to kick on and off with the middle of my factory gauge, so I don't have exact numbers but it seems to match up.

 

 

while i'm driving it seems fine. my truck didn't have a clutch to begin with so it was running very very cold on the highway with my big radiator. system has been flushed multiple times recently as well

[TENDRIL]

so does it start to creep while in traffic or is it just weird, because its more towards the middle of the gauge now 

[TENDRIL]

if the fan cuts off that means its at or around 185 even if the gauge is in the middle, i would assume 

[spdcrazy]

while in traffic or sitting. like the fan isn't pulling enough air.

 

hence my wondering if 750cfm is enough for my big rad? or if simply the lack of a shroud is my problem. the fan is mounted on the drivers side, not middle. I don't believe it matters but maybe i'm missing some big point.

[spdcrazy]

to further the info, while sitting in traffic I can watch the temp rise a bit, and then hear the fan kick on like it should. it usually takes a min or two for the temp to decrease enough for the fan to stop. and at 40 degrees outside, I feel that is to much at this temp. am I incorrect?

[TENDRIL]

ok so with your setup there will always be delay and variance to your gauge because of the way the fan switches operate,

 

they have a range, so if a switch is a 185 signal it will probably kick on a little after 185 and stay on below 185 for a while, because of heat sink and transfer in the bi- metal switch,

 

 

with stock fans it will be more consistent as the fan is always moving when it should and is controlled mechanically so its more instant   

 

 

 

and to answer your question you could always add a small pusher, i have seen 9" 800cfm fans and to make it a pusher you can generally reverse the polarity 

[DanielC]

First, check the ignition timing.  

Second, you live in Denver.  Engines at higher altitude can tolerate more advance than stock timing at sea level. and can benefit from it.

 

If the timing is retarded, the piston is farther down in the cylinder bore as the fuel is burning.  So the heat in the burning fuel goes into the cylinder walls, and head, instead of pushing the pistons down.

[spdcrazy]

ok, this makes a bit more sense, didn't think about it that way. so with a constant mechanical fan, the temp is strictly regulated by the t stat. and now I've got a temp switch in the mix as well.

 

I had to go electric due to size restrictions otherwise I would have kept the mechanical. but I still feel that the temp was rising to much for a cold day like today. would the shroud do that much to help the situation?

[spdcrazy]

ignition timing was recently set. I thought I have some advancement issues so I took it to a Datsun shop and they set it. I don't recall the numbers exactly but they revved the engine and set the timing to achieve max timing with full advance, I think this allowed for about 8 degrees at idle. (keep in mind I didn't have issues with overheating when I used my mechanical fan with this radiator. it was actually the opposite, ran to cool in these temps)

[jrock4224]

i run two fans on my 521s 

pushers

[spdcrazy]

size? cfm? factory or aftermarket rad?

[TENDRIL]

and just to be clear this is a stock L16? 

[TENDRIL]

 had to go electric due to size restrictions otherwise I would have kept the mechanical. 

 

 

what size issue? 

[Lockleaf]

Flex-a-lite recommends at least 1250 cfm for a 4 cylinder motor. Going above that to account for the rad thickness would likely help.

 

https://www.flex-a-lite.com/blog/how-to-choose-an-electric-fan/

[jrock4224]

two pushers on a champion radiator.......

[jrock4224]

http://www.ebay.com/itm/331581590729?_trksid=p2060353.m1438.l2649&ssPageName=STRK%3AMEBIDX%3AIT\

 

 

appaently 750 cfm ea..... but i will add... my tired l16 with new water pump... runs warmer then most ... 2/3 up the gauge ...... i assume its a internal flow issue ........ my l20 ran cooler ... well the first one did and the second one ran liike my l16..... the lz in my 510 runs 2/3 warm .... just like these..... i run a 160 temp switch ... and still runs hot ... or warmer at least..... sometimes i wonder if its the fans blocking the radiator .... but they rarely turn on while driving ....not sold that the new sending units i get are the right temp anymore... as long as im not pushing coolant on the ground I'm not to worried 

[spdcrazy]

reason for the lack of room is the new larger fan sits closer to the water pump. have less than two in iirc between the rad and WP pulley

 

i'm running an l20b. does the 16 and 20 have major coolant flow differences?

 

at this time with the help of all ya all ratsun folk, it seems like I thought, I don't have enough cfm from the small fan.

 

i'll first attempt to build a shroud, then next step will be the largest pusher fan I can, and put if offset from my small puller.

 

we will see how the next steps pan out.

[datzenmike]

ignition timing was recently set. I thought I have some advancement issues so I took it to a Datsun shop and they set it. I don't recall the numbers exactly but they revved the engine and set the timing to achieve max timing with full advance, I think this allowed for about 8 degrees at idle. (keep in mind I didn't have issues with overheating when I used my mechanical fan with this radiator. it was actually the opposite, ran to cool in these temps)

 

Stock timing at sea level is 12 degrees so if you are a mile high you can try turning it up some. Eight degrees is way way way too retarded where ever you are.

 

If there is EVER a question about running too hot or too cold I say replace the thermostat. Get a good one over $10 not the $3.99 Chinese one from WallMart. There's nothing worse than chasing a problem that can't be fixed because it's assumed that the thermostat is fine. It's only $13 and if it doesn't help you have a spare, but best of all you KNOW it isn't the thermostat. They don't last forever.

 

A three core rad does not necessarily need a larger fan. Three cores will shed more heat because of the larger surface area even though the air volume moving through it is the same. The 521 generally has a 2 core and this is all you should need even if you were driving in Central America. If it's 40F and you have a 3 core rad and think you are over heating, then something else is wrong. (check timing and replace thermostat and come back with the results)

[TENDRIL]

or a bad sending unit 

[spdcrazy]

i'll work some more things out, however, without changing the counterweights in the el dizzy, i'm limited to about 8 at idle without over advancing at the top end. do you think this is a big enough prob to have the weights modified?

[TENDRIL]

do you regularly bring your RPMs to 5-6500k and hold them ?  i rarley ever would see 5-6k for more than 4-5 seconds i did about 110-120 in my 510 one time for about a mile or two and dont even think i passed 6k 

[DanielC]

I used to tow a two horse trailer around the Pacific Northwest.   I never had an overheat problem, although I would run the heater climbing a 6% grade, 5,000 in second gear, close to WOT, in 95 degree heat.

 

Datsun 521 trucks are over radiated, and under engined.  If you have an overheating problem, something else is wrong.

 

The timing needs to be set with a load on the engine.  Advance it until it knocks, then back off about two degrees.  Be careful if you have a loud exhaust system.  You need to listen for knock beginning.

With no load on the engine, and revving it up, you are getting both vacuum and mechanical advance.  Impossible to set the timing with any degree of accuracy that way.