how to size radiator for custom builds?

[urbex]

My S80 is currently running a mildly modified AMC 258 in it, with an unknown crossflow radiator (I haven't been able to match it to something factory, may be a custom build, was in the truck when I got it, and it's not stock to the Scout).

It's been running hot since I got the truck, and I'm kind of at an impasse of what to do. I know the radiator could use a cleaning, as I can see some deposits in the tubes when I look down the filler neck, but it still flows well. My problem is that I have no idea whether it's big enough for the current setup or not. I don't really want to drop $100 to have it tanked only to find out it's still not cooling enough after. I've also been considering going to a V8 setup some time in the future.

I've got to believe that there's more to choosing a radiator besides "buy the biggest one you can fit", or a trial and error method until you find something that works. Maybe some kind of mathematical equation taking into account engine size/power, number of cores, aluminum vs copper/brass, etc.

[Jay Tabor]

do some tests..
all this needs to be done same day wx temp and pressure...
whats the thermostat in it?170*,180*?190*? i dont know*?
find out!
get a thermometer for rad, install a quality thermo couple mechanical thermometer in block at thermohousing so you dotn have to by guess by golly..
idle engine for a long time watch gauge- we hope its mechanical gauge by now????
or the useless lectric one in dash still?
does temp increase past ''normal' shouldnt get more than 5* above thermostat temp?
next fast idle it and watch temp do it increase or decrease?
are your fan belts tight for water pump?
next drive it at high rate of speed steadily-does the temp climb or drop.
once you have these facts we can help. if its idlign and temp increase, yet high idle drops it- look at fan belt, and air getting sucked past/thru rad.
put some cardboard in front of rad and high idle.
once you have results then you can pinpoint the prob[s].
all the time youre wasting gas look in rad while revviing engine- does coolant level drop at least an inch and some of the core tubes are exposed? does you see lotsa coolant flowign thru the tubes>? thats a sign of good water pumping.
look at bottom rad hose while revving the engine like you was daddy Garlits on race day- does it collapse? if so you just found your prob! get a new hose make sure it has a spring inside it, if not GET A spring AND PUT IN IT.
slow engine speeds and slow car speeds run hot-but high engine/road speed drop temp its the circulation,
if high speed raise temp its the rad not cooling enough- or coolant goes thru too fast.
make surte engine is timed correctly /
retarded timing will raise engine temps.

[Chris Leggett]

Theres lots to a radiator.

Tube spacing, fins per inch, tube, size, 1,2,3,4 row etc. A 258 isn't very hard to cool, a high hp v8 will be harder to cool. I'd take it to your local radiator guy and see what he says about it. Make sure that the fins have not lost their bond to the tubes. I see lots of that from our competitor across town.

[1310monster]

Which custom maker is best at building custom radiators for IH pickups? I dug my own out last weekto get the core size. Not very big...22" by 24" on a three core...for a 392? I have a 91 Ford Ambulance with a 7.3. That thing has a radiator big enough for a bulldozer. I bet it's three times the capacity or more. I'd like to have something to drop in and fit but should I just forget about it and retro fit?

[urbex]

Originally Posted by Jay Tabor

do some tests..
all this needs to be done same day wx temp and pressure...
whats the thermostat in it?170*,180*?190*? i dont know*?
find out!
get a thermometer for rad, install a quality thermo couple mechanical thermometer in block at thermohousing so you dotn have to by guess by golly..
idle engine for a long time watch gauge- we hope its mechanical gauge by now????
or the useless lectric one in dash still?
does temp increase past ''normal' shouldnt get more than 5* above thermostat temp?
next fast idle it and watch temp do it increase or decrease?
are your fan belts tight for water pump?
next drive it at high rate of speed steadily-does the temp climb or drop.
once you have these facts we can help. if its idlign and temp increase, yet high idle drops it- look at fan belt, and air getting sucked past/thru rad.
put some cardboard in front of rad and high idle.
once you have results then you can pinpoint the prob[s].
all the time youre wasting gas look in rad while revviing engine- does coolant level drop at least an inch and some of the core tubes are exposed? does you see lotsa coolant flowign thru the tubes>? thats a sign of good water pumping.
look at bottom rad hose while revving the engine like you was daddy Garlits on race day- does it collapse? if so you just found your prob! get a new hose make sure it has a spring inside it, if not GET A spring AND PUT IN IT.
slow engine speeds and slow car speeds run hot-but high engine/road speed drop temp its the circulation,
if high speed raise temp its the rad not cooling enough- or coolant goes thru too fast.
make surte engine is timed correctly /
retarded timing will raise engine temps.

I KNOW it's the radiator, I've already done all the tests, but for the info anyways -

Currently running a 192* thermostat, previously had a 180 in it. Not that it matters much, as I know the thermostat only determines the minimum temp that the engine will run at, having nothing to do with the maximum temp (unless of course, it's malfunctioning). Thermostat has been tested to open at the proper temp.

I have three temp gauges installed at the moment - a mechanical temp gauge going into the driver's side of the block under the intake, an electrical going into the back of the head at the the top, and an electrical in the radiator tank near the lower hose. They all read 220+ cruising down the freeway at 65mph. Current day time temps are in the high 60s/low 70s, night time temps high 40s/low 50s. Runs slightly cooler at night, but still higher than it should be. The block and radiator ones will routinely go up to 240 on a longer freeway run, the one in the head typically runs 15-20 degrees hotter than the radiator/block gauges, which I expected. My head isn't drilled for a gauge sender in the front near the thermostat neck like the earlier heads are, but because of the non stock belt routing, I really don't have the room for one anyways (power steering on driver's side, alternator and York A/C pump on passenger side. No A/C in truck, York is for the on board air system).

I can get temp to stay at 195-200 degrees at idle all day long, but then I also have an electric fan installed on an adjustable thermoswitch. No room for a mechanical fan. Electric fan, like most, has a built in shroud, and shroud is within 1/8" of the radiator fins. I currently have fan set to turn on at 210-215 degrees, but that was an attempt to get a bit of a buffer to keep fan from turning on while moving down the road at speed. Didn't work out too well, lol.

Same with the fast idle - it will stay at the 210-215 running at 2,000 RPMS locked in with the hand throttle for at least 30 mins (longest I've had it running at 2K while airing up tires on several rigs). Same with low speed trail crawling...it will do OK then, but if I start romping on it to get over an obstacle or through mud, it gets hot in a hurry. I could stand to switch to a fan that pulls more CFM, but that still won't resolve the running hot on the freeway problem.

Fan belt isn't tight, but it is properly adjusted. New belts all around approx a month ago, with MAYBE 100 miles on them. This is a weekend trail toy, not a daily driver.

As mentioned before, yep, temp most certainly goes up at high speed :P

Lower hose can't collapse - it's metal tubing, connected to radiator and water pump with straight rubber connectors. Same for the upper hose. Couldn't find replacement rubber hoses that fit right, so I permanently solved that problem

Water pump is only a few months old (new, not rebuilt), and water level does drop a bit when revved, and flow also increases. Due to the buildup in the tubes, it's hard to determine if it's increasing appropriately, but I would say that the pump is doing it's job. Before switching to a rigid tube setup, the pump would increase the pressure quite a bit in the upper hose (using the squeeze the hose and rev the engine method).

Timing is currently set to 14 degrees advance at 950rpm idle, with just a bit of idle lope. Brand new (not rebuilt/hacked together from junk yard parts) HEI distributor about two weeks ago. Vacuum advance hooked up to ported vacuum on Holley carb. Haven't played around with recurving either the mechanical or vacuum advance, just running it the way it came out of the box. I rebuilt the carb (Holley 390 4bbl) about a month ago, set the primary throttle butterflies closed a bit too much, and opened the secondaries a bit too much. There was too much of the idle transfer slot exposed before at roughly 750rpm idle, largely due to the bigger cam, so I opened up the secondaries a bit more with the stop screw...turns out I went a bit far, and 950 is the lowest I can get it to idle at now, lol. Not that any of this is really relevant, but I figured someone was going to ask why I have it set to idle so high :P

[Jay Tabor]

i kinda agree not enough heat transfer when engine/vehicle moving at speeds/
so what was the original q? ha!
I'd maybe think about going back to the 180* thermostat. gives you a 10 degree margin.
was your rad 2row core?
> so get a three row core or 4, its strange the small engine gets so hot.
a blockage in the engine block could cause that prob. how do you know theres no crud in the head or block.
maybe run some vinegar thru cooling system to scrub mineral deposits from block and rad.
flush it real good and refill.. try again.......
a question or two at a rad shop might get you answers to which rads/types/brands are most effective in heat transfer.
do consider its a higher horsepower engine, so it gets more gas= more heat, especially under load.
I dont think its lean mixture caused heat, just a lot more air and fuel.
a test is drive it somewhere and keep engine revs up- like 2nd gear instead of third, drive same distance same road speed, just different engine speed. see a higher engine speed lets say 2500rpm at 30mph engine is revving higher but loafing not producing as much power, as same trip at 1800 rpm- needs more gas to produce same power to achieve same road speed . . becuase the engine speeds arent in the same horsepower /torque curve.

[DavidWTravelallfan]

Since your using a 4 barrel carb on a inline 6 which isnt the stock carb. The proper fuel/ air induction has allot to do with the cooling ability. Dont see how that carb would work with that type of setup very well. The inline manifold dosent do much in the way of equal distribution from the carb, much less then a 4 bl holley.

[joe_r95]

Originally Posted by Jay Tabor

maybe run some vinegar thru cooling system to scrub mineral deposits from block and rad.
flush it real good and refill.. try again.......

Seems simple.... If you can see blockage in your radiator then theres your starting point. If its in your radiator its in everything, so give it a good clean out. If possible after youve run the vinegar or some other cooling system cleaner through it figure out a way to backflush your radiator. Keep in mind you may have to flush it several times to get all the gunk out.

[John Donnelly]

Why not take advantage of one of our vendors here that makes custom application radiators? They are in our machine shop forum.

Click for RND Fabrication

I bet they can give you all the help you need.

-John

[joe_r95]

Originally Posted by John Donnelly

Why not take advantage of one of our vendors here that makes custom application radiators? They are in our machine shop forum.

Click for RND Fabrication

I bet they can give you all the help you need.

-John

Got one for my 800 from them. Fits good, looks awesome.