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  #1  
Old 30-01-18, 13:58
James Baxter James Baxter is offline
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Preheating

1. If you preheat how do you maintain water system pressure. I may have missed it but I don’t recall seeing people pumping back up. Don’t you get a face full of hot water as the dry breaks release?
2. On big V engines with two radiators and one water pump, how do you ensure both radiators warm up? I have dry breaks positioned at one radiator inlet, and at the opposite radiator outlet. On my car the water has the option to flow two ways but takes the path of least resistance, which warms one radiator well, but the other less so but that means it went straight on, missed the water pump and engine!! There is less resistance if the water chooses to go straight on at the water manifold rather than go the tortuous route from one bank of cylinders to the other bank. It all works well with the engine running, hence water pump running, but with the preheater it’s a bit pants.
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Old 30-01-18, 18:12
AshM AshM is offline
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No the dry breaks do as the name suggests and seal off very quickly. Shouldn't see more than a drip thus pressure in the system is maintained.

You may need to juggle the in and out points or the direction to get most of the hot water around the engine. Rads less important but ideal if they see some heat. If you can get one connection on the block then that usually works ok. Doesn't really matter if a rad is cool once the engine has fired.
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Old 30-01-18, 18:53
James Baxter James Baxter is offline
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Thanks Ash. OK so am happy question 1. is addressed. I need to fill then tighten the water cap on the preheater tight to maintain as much pressure as possible. The cooling system and preheater will obviously neutralise, like when i fill the air shift bottle, so top up with footpump as and if required.
I also agree the engine is the first priority for heating, but it’s still a little counter productive for a slug of cold radiator water to douse the warm engine after firing. Very tricky to add water ports to it. I feel I need to throttle my easy flow water path, perhaps by squeezing flat an unsupported length of hose on the easy loop for half the time.
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Old 30-01-18, 20:11
AshM AshM is offline
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The mass of the engine and hot coolant vs a slug of cooler water doesnt seem to be an issue . Any cooler water soon gets mixed in and the temp gauge would barely dip.

If you can help redirect then all the better otherwise just leave it heating for a longer time and the warm water will circulate. A blanket or towel in the rad or over the engine helps also.
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Old 30-01-18, 23:32
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Nick A Nick A is offline
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How about an electric pump to push the water around the engine or maybe if you can reposition the pre-heater inlet and outlet ? Although it sounds like they are in the right place.
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Old 31-01-18, 00:42
James Baxter James Baxter is offline
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Naturally the New Techniques heater has an electric pump, but I totally take your point. Surely any V8 engine, where two radiators feed one water pump at the base of the engine suffers the same problem? You just preheat a short circuit, unbeknown. Maybe I’m taking this too seriously.
Another idea, is to route the preheater pipes into a long copper very tight U bend, or copper coil like an immersion heater, before the water then enters the engine coolant in series. Then immerse the copper u bend down into the engine oil tank, baffles permitting.
That would also warm the gearbox too in the case of the Xtrac, and the gearbox would be grateful.
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Old 31-01-18, 11:28
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Quote:
Originally Posted by James Baxter View Post
Naturally the New Techniques heater has an electric pump, but I totally take your point. Surely any V8 engine, where two radiators feed one water pump at the base of the engine suffers the same problem? You just preheat a short circuit, unbeknown. Maybe I’m taking this too seriously.
Another idea, is to route the preheater pipes into a long copper very tight U bend, or copper coil like an immersion heater, before the water then enters the engine coolant in series. Then immerse the copper u bend down into the engine oil tank, baffles permitting.
That would also warm the gearbox too in the case of the Xtrac, and the gearbox would be grateful.
My own experience is that on the GR55 with a NicMac it was fine. But GR37 with an EV it wanted to warm one bank more than the other, never totally got round the problem but it was frustrating and like you I felt there should be a solution hence my comments. Anything that brings the oil temp up is good news.
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Old 31-01-18, 12:29
AshM AshM is offline
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Our Judd KV was a bit warmer one side than the other so we left it on a bit longer.

If you can get water temp to 50 deg C that satisfies most piston to bore clearance requirements.

Oil would also have been nice but then you would be aiming for as hot as possible ie > 90 deg C.
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