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Thread: 355 temp

  1. #1
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    Default 355 temp

    ive just built a holden 355
    Has a crane solid cam nothing over the top
    Its a street strip car
    What temp thermostat should i be running and im running twin falcon thermo fans what temp should they come on and off
    And is it worth having them on 2 switches so one comes on before the other ?
    Thanks

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    Being in Brizzy & it's mild climate, I would use a 160 stat. 160 is the opening temp, & to fully open takes another 20-30*. Many do not realise this.

    Good luck with the Ferd fans. I tried twin AU Falcon fans [ both fans at full speed ] on my GTO, replacing the trusty clutch fan. The AU fans ran noticeably hotter & came off the same day....................

    It would be a lot of buggarising around to have the two fans come on at different temps, for not much gain. As for on/off temps, you might want to try an adjustable switch to see what works best for your combo.

  3. #3
    casual poster BasicQ's Avatar
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    On around 95c, off 5c lower. I am sure others will help inform with what works for them.

    If you don’t have a controller yet check this out

    https://daviescraig.com.au/product/d...h-12v-24v-0444

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    HI
    Do u have a choke on your carby??
    Run whats considered a large radiator for your car . Small radiator cores place alot of demand on fan setup to work at peak performance .
    Thermostats either 160-182F 71--82Cel
    The 182F will give better warm up performance driveability and response will be far better than colder unit .
    Operating temp is best done by a screw in fan sender unit either 190-195f or 88--92cel
    Power supply to fans is critical ,The alternator must be at least 80amps . Big fans place alot of load on charging system

    https://daviescraig.com.au/product/d...h-12v-24v-0444
    staggered fan startup
    fan off at 5 cel below set temp
    either fin sensor probe
    OR preferred coolant sensor
    air con bypass

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    My suggestion, based upon some past expensive problems is to use a viscous clutch type fan if possible with the older-type engines, particularly if it’s regularly used on the street.

    Of course you must have a known good fan clutch a correctly fitted fan shroud and the correct fan.

    355s generate more heat than 308/304s which in turn generate more than 253s. Get the biggest and best radiator that will fit. A copper-brass radiator made here in australia. Dunno what car you have it in but we used to get the big stato radiators whenever we could fit them.

    I’ve run electric fans where circumstances demanded. The good ones need a lot of current . The main reason for staggered startup and shut-down is because startup current demand for the more powerful units can be excessive. So, for example, a fan motor might have a peak draw on startup of 50 amps which gets the fan and air moving from a standstill, but the running current under load might be more like 20amps.

    If you run twin thermo fans the staggered startup stops you browning out your circuitry. The staggered shutdown makes surge less of a problem.

    There is no cooling application where one fan is more appropriate than two. These systems are designed to run when you reach a certain temperature to pull that temperature down. You want that to happen quickly (I.e.two fans running at max power in an electric fan setup) and for it to turn off again once it’s back in the safe range.

    Regardless of any of this the cooling system will be ineffective if air can’t move through the radiator. Blocked grills, some aftermarket air dams and poorly constructed fan shrouds will kill an engine quickly. Also, those ridiculous pressed metal impellers on some after market water pumps are a disaster. I don’t know which knucklehead supplier brought them into the country but check to make sure you don’t have one.

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    If you stick with twin elec fans [ bad idea ], they can be turned on together if you have appropriate sized wiring And suitably rated relays. You can get compact relays from Jaycar that will switch 150 amps. The instaneous large current draw when the fans switch on is far lower than the starter motor current, which lasts for a longer period of time.

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    Yes but that ends up being pretty heavy duty wire for a few seconds of a duty cycle that might run for several minutes - hence why oem twin fan systems have staggered start up.

    By the way when I say “there is no cooling application where one fan is better than two”, I mean In situations wherer you have a twin fan setup installed.

    If you can provide sufficient coverage with a single fan alone then the single is a better bet. This comes down to the physics of a big square radiator and a single fan being better than a big oblong radiator with two fans.

    If I can choose I’d always go for an engine driven viscous clutch setup, but after that a single electric fan setup and then a twin electric fan setup. Just a matter of what packaging constraints you’ve got. I ended up with twin fans out of, I think an EL Falcon (??) on one of my projects and they worked ok.
    Last edited by Horaldic; 16-10-2020 at 12:24 AM.

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    Hi
    Remember the viscous fan diameters and radiator core sizes in USA cars of the 70`s are all bigger than the Ozzy Hq style radiator . HQ style has its origin from GM `60`s designs . The end result is Ozzy Holdens have only limited capacity to cool . Viscous hub always preferred but with caution . A good ozzy cooling system must work as a combo fan and radiator core size .
    eg twin elec fans at least 15 amps each 11--14 inch diameter
    radiator core preferred 2 x 1.25 inch core

    NB viscous hub fan may not supply enough air flow at idle especially with high cuin and hp engine ,a large rad will help
    the v belt drive might be a concern at high rpm
    elec fans cool air con condensors way better

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    Many years ago, I saw the flow for a 19" clutch fan listed at 6000+cfm; it was on one of the manufacturers sites, such as Derale or Hayden. I have yet to see any passenger car single or dual elec fan get near that figure.

    Many of the US cars with performance engines came with 19+" fans. My GTO with factory air came with a 19.5" 7 blade clutch fan & shroud. Some later GTOs came with 19.5" flex fans, 5 or 7 blade.

    I did a lot of testing of mech fans a few years ago, using a test rig that I made up. There were some surprises. My GTO factory fan did poorly, not as good as a Ford Falcon 18" plastic fan with multiple blades. The best fan was a 20" Chrys 7 blade clutch fan. I trimmed the blade tips to use with my GTO. For local GM cars, hard to beat the Ford fan. From memory, there was some cobbling reqd to fit the GM clutch, but nothing too hard.

    I protect my car while working ion it with bath towels; I have two sewn together. With the engine idling at about 800 rpm, I can stand 4 ft from the grille, & throw the towels at the car. The airflow catches & pulls the towels into the grille until I turn off the engine.

    A good clutch fan set up is hard to beat. Simple, reliable, works. But there are some things that need to be 'right'. The clutch should be a heavy duty unit for min slippage. If the clutch slips, fan turns slower, pulls less air. A no brainer. The Hayden clutches turn on at too high a temp for my liking. I adjust them by moving the spring tang for a lower turn-on temp. A shroud is USELESS unless the fan is a reasonably tight fit so that it pulls air. Obviously, if the gap between the blade tips & shroud is large enough, there will be no benefit gained from the shroud. Better off getting a larger fan & trimming the blades or getting a smaller shroud if the gaps are too big. Aim for 3/4" from tip to shroud, except at the top & right side, aim for about 1" to allow for engine torque. Also seal the shroud to the rad core. You want ALL the air to come through the core, not through outside gaps.

  10. #10
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    That "6000+ cfm" clutch fan won't be pulling anywhere near that when you need it most. That will likely be at 5000 + rpm while the fan is needed most at idle and slow speed traffic, once you get out on the open road a fan isn't normally needed.

    My HQ has a factory style 3 core copper/brass radiator with 2 14" electric fans on a shroud and the only time it ever started to get hot was one time when the fan controller died. With no working fans the car stated getting warm at idle/low speed but once I got on the open road the temp came back to normal and I managed to limp the car home with no working fans.

    Mechanical fans are simple and reliable but you're sacrificing small amounts of horsepower and fuel economy. IMHO a well thought out electric fan set up is a better overall proposition than a mechanical/clutch fan.
    Last edited by hq308; 17-10-2020 at 10:00 AM. Reason: spelling

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    Hi
    History of viscous coupling was to have high air flow at operational speed upto 2500-3000rpm at which point it slips . Achieving maximum cooling with minimal impact on HP and fuel economy .
    In ozzy cars we struggle to fit the USA larger diameter viscous clutch units which flow alot of air to our older cars

    By comparison OEM fixed bladed fans were only ever fitted to economy cars no air con, no heavy duty cooling package .
    Oem tried aggresive Multi fixed blade which ended up being noisey, consume fuel and HP

    To prove it comes down to design with some car makers doing it better than others . Toyotas regularly have good working fan hubs with good air flow over air con condensors . Most Holden and Fords donot . This is proved by the refrigeration high temps and pressures . Fords were still changing fan blade design in the 90`s . Early holdens fitted factory electric fans to assist with Idle air flow .
    In the end all changed over to electric because the hub fans could not supply air flow when required .

    summary
    Elec fans often require big radiator capacity
    viscous fans often need xtra cooling help
    Fan capacity and radiator size work together

    Ford Rangers and Bravo plus early Hilux /Triton all have pathetic air flow thanks to badly designed cooling fan setups . Most evident in how pathetic the aircon units work.
    All these vehicles were operated at high engine speed and load under testing at high temps 45cel ++

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