Bypass heater-core, engine acts strange. - Hot Rod Forum : Hotrodders Bulletin Board
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Old 06-07-2008, 07:20 AM
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Bypass heater-core, engine acts strange.

Motor is small block 350, 180 tstat stock viscous fan with shroud. Engine has comp 265H. Engine previously cammed really nice and unstable, idle set screw was VERY touchy. Last night I decided rather than blocking off the fitting on top of the water pump and on top of the intake off, I would run a 3/4" heater hose from the top of the wp to the intake. I see no problem in this since coolant is originally ment to go that path (wp, heater core, intake). I start is up and the idle isn' that nice cam quality sound. Hard to describe but it isn't rythmatic, it is like a surge you could say. Temps hit 221 IDLING (take with IR gun at tstat housing) with the 180 then drop to 195. Engine is no where near as touchy as far as response to idle set screw adjustments. Now is this something I could have induced, and is this bypass routing correct? Only difference beside that last night was 88 degress with a 77 dewpoint and high humidity.

-Ray

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Old 06-07-2008, 08:48 AM
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I did the same thing recently with my 350. The heater core developed a leak, and I bypassed it just like you described, running a hose from the water pump to the manifold. I've seen no difference in any of the engine's characteristics. The idle has remained the same, as has the temperature of the engine.
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Old 06-07-2008, 10:12 AM
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possible the +30 degree temps, high humidity and dewpoint I am hoping?
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Old 06-07-2008, 11:13 AM
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Nothing about bypassing the heater should cause your issues. Look for a coincidental other problem... maybe moved the distributor while messing around the heater core?
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Old 06-07-2008, 12:05 PM
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Whatever it is/was, it is not happening today. Idles nice, took it for its maiden voyage of 1.2mi, and idles so low it stalls at stops. Firing it up in the garage though, idles great. Needs some qjet tuning i suppose!
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Old 06-07-2008, 12:51 PM
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Just a thought, is your carb loading up a little?
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Old 06-07-2008, 07:57 PM
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Carb was loading up a little ove a week ago before I got the idle mixture dialed in.
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Old 06-07-2008, 08:30 PM
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A carb loading up is generally caused/corrected by float level, not by idle air adjustment, in my experience.
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Old 06-08-2008, 06:27 PM
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But what made the temp go up so much? If the timing got retarded or the carb went real lean it could cause it, I would look at the carb and or all of the vacuum hoses real close.
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