JMortensen Posted July 12, 2003 Share Posted July 12, 2003 I recently installed header wrap on my Z and when I put it back together the water temps have been really high. This car used to very rarely use the fan at all, now the fan is on all the time. I was thinking about this some more and figured that it is highly unlikely that the wrap was the culprit, so I did a little more investigating. I took my infrared pyrometer and got the car warmed up, then took some readings on the radiator while it was idling. I found that it seemed to be able to hold about 205-210 degrees steady. When using the pyrometer, I found that I had about 205 all across the top of the radiator, and about 195-200 at the bottom. This was on both sides of the radiator. When the fan came on the area directly hit by it was 205 top and about 150 where the fan was sucking. I was looking for a cold spot, somewhere where the radiator was blocked possibly. Did not find it. It seems to me that the other part of the radiator (where the fan isn't) should do more than 5-10 degrees worth of cooling, even if there is no airflow. Is this right? Is the radiator just partially clogged and not capable of doing its job? Anyone suggest any other checks or tests I can do? Thanks in advance, Jon Mortensen Quote Link to comment Share on other sites More sharing options...
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JMortensen Posted July 12, 2003 Author Share Posted July 12, 2003 Thanks for the welcome. I've been on the zhome list for years, but I always thought this was strictly V8 conversions, so I never checked this place out. VERRRRRRRRRRY COOL. Shoulda been here years ago. As to the state of tune, I guess I could have provided more info. No detonation at this time. I tuned the Mikunis with an O2 sensor, so I know they're pretty close to right. I was always taught that if you made a change and had a problem, than that last change is your likely suspect, but since header wrap is such a weird thing to cause overheating (and I thought that the gasket would insulate the heat to some degree), so I was just going to run it by everyone to get some opinions. Seems like you agree with me on the last change bit, but I am still having a hard time imagining that wrap is the issue. Here's the gist of the motor: 280ZX flattop block E31 head 11:1 compression .490 / 280 cam newly rebuilt electronic dizzy D6K8 from 280ZX 15 degrees static advance, no vacuum 3x 44 Mikunis (didn't change any jetting while I was working on the car) MSA header MSD Mechanical Autometer gauge (pretty confident that its not a gauge problem) 240SX fan switch in lower rad hose comes on at 100 degrees C, gauge agrees that that is what it is doing The radiator is a 3 core 280 I got it 2 years ago in a parts car, and it was brand spankin at that time. Does that help? Thanks everyone, Jon Mortensen Quote Link to comment Share on other sites More sharing options...
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Drax240z Posted July 13, 2003 Share Posted July 13, 2003 Hey Jon, where are you from? Your name sounds familiar. Anyway, here is a thought. Is your thermostat opening? Sounds to me like you aren't getting much flow through your radiator... could be just a fluke that the application of your header wrap coincided with a thermostate failure. Just thought it would be worth checking, I'm not sure that is the problem... I agree that a 5 degree reduction in temperature is too little through a radiator, though I've never measured a Z one before. Typically in our FSAE car we were seeing ~40F temp change across the rad if I remember correctly. (but it is a little fuzzy) Quote Link to comment Share on other sites More sharing options...
JMortensen Posted July 13, 2003 Author Share Posted July 13, 2003 The only thing I did other than the header wrap is to rebuild the distributor. That's all. I just replaced the thermostat as well, with a 195 degree thermostat. I chose this thermostat based on the "How to Hotrod" book. Apparently the L6 makes max power about there. I would be curious to see what other members are getting down the radiator at idle. Thanks again, Jon Mortensen Quote Link to comment Share on other sites More sharing options...
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JMortensen Posted July 13, 2003 Author Share Posted July 13, 2003 I just caught your question as to where I'm from. Grew up in SoCal, lived in San Luis Obispo for 6 years, then just moved to Seattle area. Why I chose that thermostat: Prior to this the car would barely ever see 195 degrees. According to "How to Hotrod" the L series makes power there, and if I put in a 175 thermostat, the engine would see 180 maybe 5% of its life. You could watch the thermostat open and close on the temp gauge. I haven't yet found a thermostat that opens at the temp on the box. Even this 195 that I just put in opened at about 187. But that is the reason. Maybe a cooler thermostat wouldn't be a bad idea, although I don't know if it will prevent me from having to take the wrap off. I think the wrap experiment has been an expensive waste of time. Quote Link to comment Share on other sites More sharing options...
JMortensen Posted July 13, 2003 Author Share Posted July 13, 2003 With relation to fuel I forgot to say that I've been mixing 92 octane alternately with Tolulene and AV Gas to get around 95 octane. Tolulene when I was tuning the carbs, AV Gas after the tuning was done. And yes, I know that AV Gas runs a little leaner than regular fuel... Jon Mortensen Quote Link to comment Share on other sites More sharing options...
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JMortensen Posted July 14, 2003 Author Share Posted July 14, 2003 What again is this supposed to be for? You want me to take a reading of the plugs at cruise (like plug color), or the radiator temps? I know that the way the air/fuel isn't the issue. The O2 sensor read about .85 to .9 volts at 65, so thats about 13:1 to 12:1 air/fuel ratio. Since I've switched to the AVGAS I would have to pull plugs and check color to get air/fuel, but I'm no plug reading expert, so I think the O2 is going to be WAY more accurate in this instance. The only difference in the cooling of the car occurs when I am stopped. When I'm moving the car never gets hot. That's why its so confusing. You would think that with my foot in the gas the thing would get hot because I would be putting a lot more heat out at that point. But it seems to be only when I'm idling that I have a problem. I would be happy to check a plug, but I wanna know what you're looking for... Jon Mortensen Quote Link to comment Share on other sites More sharing options...
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Synlubes Posted July 14, 2003 Share Posted July 14, 2003 Jon, What type of fan are you using ? Stock, electric (pusher / puller) If it`s the stock fan, put a nice electric in it`s place. As far as the thermostat, A Nissan 180 degree. It will come up to higher temp with some hard useage, but run cooler with light duty use. Quote Link to comment Share on other sites More sharing options...
JMortensen Posted July 14, 2003 Author Share Posted July 14, 2003 14" puller. Got rid of clutch fan a while ago. Triggered by Nissan temp switch in lower rad hose from 240SX. The weird thing now is that it cools fine under hard usage. It gets hot when idling. I think I'm going to take the wrap off and see what happens. The one thing that always gets my panties in a wad is wasting money on $*&! that doesn't work. If nothing else I suppose this has been a nice commercial for Jet Hot. I don't think a coated header would pass nearly that amount of heat to the head. Thanks all, I'll update you on the situation when I get that crap off. Jon Quote Link to comment Share on other sites More sharing options...
Synlubes Posted July 14, 2003 Share Posted July 14, 2003 Just another thought, Take the radiator out and have it cleaned . It may have some clogs that can`t be seen looking down into it . Quote Link to comment Share on other sites More sharing options...
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