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Old 15-07-2013, 17:21   #16
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Re: Running with no thermostat in 4-108

Gaskets were put on right.
Plenty of water spitting out the exhaust. (almost a jet boat).
I have propped it so it can reach Max Continuous RPM 3,000.
There is plenty of opinions on whether this is advisable or not with the 4-108?
My next step is to pull the heat exchanger off and recheck it.
I love a challenge.
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Old 15-07-2013, 17:41   #17
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Re: Running with no Thermostat in 4-108

Is it possible that it could be a supply problem? If the pump and or lines are under sized they can supply sufficient water to cool the engine at a given rpm but can't deliver enough at higher rpm.
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Old 15-07-2013, 17:53   #18
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Re: Running with no Thermostat in 4-108

Is it possible the bearings are too tight, the reason I suggest this I had a factory rebuild 351 ford engine prof. installed in my truck. The mechanic used 3 batteries to start it. It overheated in 2-3 min with a new rad and water pump. He pulled the pan and checked the mains with plastgage their was no clearance at all.
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Old 15-07-2013, 21:51   #19
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Re: Running with no thermostat in 4-108

Quote:
Originally Posted by btrayfors View Post

After fixing everything else on my 4-108, I put on a larger (Perkins 4-154) heat exchanger some 13-14 years ago and haven't had cooling problems since.
I like hearing that. How much modifying did the swap out take?
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Old 16-07-2013, 10:54   #20
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Re: Running with no Thermostat in 4-108

The perkins 4-108 heat exchanger that I have is 12" long by 3" dia.
The perkins 4-326 heat exchanger is 14" long by 3" dia.
To ask a silly question "does that extra 2" make that much difference?"
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Old 16-07-2013, 10:58   #21
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Re: Running with no Thermostat in 4-108

It did in my case.

It was not too much trouble fitting the larger one....just minor mounting adjustments.

Another thing which surprised me: the mechanic I flew in asked me to blow into the old heat exchanger (which had just had the muriatic acid and cleaniing treatment), and to blow into a brand new one and compare. It was easy to see that the new one had much less back pressure, i.e., was much easier to blow into.

And, just to be sure, you said the gaskets were put on correctly. Want to be sure we're talking about those on each side of the thin steel plate which fits between the circulation pump and the engine block, not the belt-driven raw water pump.

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Old 16-07-2013, 16:51   #22
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Re: Running with no Thermostat in 4-108

If your SW flow is fine and your closed circuit water flow is fine, and your propeller change has not contributed to problem and your heat exchanger is clean and your thermometer is telling the truth and you are not demanding too much speed. If any of these are not true, then I don't think extra 2" would be beneficial except maybe the last.

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Old 01-08-2013, 15:36   #23
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Re: Running with no Thermostat in 4-108

Many thanks for all the excellent advise. I soaked the slightly dirty heat exchanger for 10 min in Muriatic Acid and 25% water. The engine now runs about 10 degrees cooler.
2,000 rpm at 175 deg 6 knts
2,500 rpm at 180 deg 6.5 knts
3,000 rpm at 185/190 deg 7.2 knts
I intend to run about 2,500 to 2,700 as cruising RPM, It is nice to have some RPM in the bank.
Will look into maybe changing up to a 14" 4-236 heat exchanger.
regards
Mark
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Old 21-07-2014, 16:00   #24
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Re: Running with no Thermostat in 4-108

After all of the usual solutions failed, by coincidence, I discovered that the voltage regulator for my Balmar high output alternator was out of commission and causing the alternator to exert excessive load on the engine while not doing my batteries any favors. Installing a new regulator and adjusting if for correct batteries and belt size now delivers water temps 160 - 170.

Check to see if you have any accessories on the engine that might be doing this.
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Old 21-07-2014, 18:22   #25
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Re: Running with no Thermostat in 4-108

Quote:
I have propped it so it can reach Max Continuous RPM 3,000.
The engine should reach 4000, if not you are over
Propped.
Of course you can still run Max Continuous at 3000 with
A correctly pitched prop.
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