Vette Powered Posted September 8, 2009 Author Share Posted September 8, 2009 Ok. Here's were I'm at. I took the thermostat out and have about 30 minutes of run time on the car. With the a/c off and running at about 35 mph for long periods of time it stayed right at 180. Then I started the a/c up and ran it for about 10 more minutes again at about 35 mph. Temp. Jumped to about 190 but stayed there. Then I parked the car with the a/c off and let it run with hood down for about 10 minutes. Again, it stayed at 185 or so. For the last test I ran it with a/c on and parked for about 10 more minutes. It jumped to 200 but held than for a few minutes. Then out of the blue it jumped to 220 and I shut the car off. System looks like it working well but it will still get hot??? I'm going to try a 165 thermostat on the fan and see if this helps but I'll leave it as is for awhile to test. Any thoughts??? What is normal operating temp. For a carb. 383 stroker with big cam and dart 1 heads?? Quote Link to comment Share on other sites More sharing options...
Vette Powered Posted September 8, 2009 Author Share Posted September 8, 2009 Just a note... I'm using a Painless wiring kit for the fan. The thermostat is in the intake. (the temp gauge is in the block low) It is a 180 thermostat and is coming on about 10 degrees after the gauge reaches 180. (I would think this is because it's in the intake which is cooler) today I noticed that the fan came on at about 190 but stopped at about 205 then came on again at about 215. Why would the fan cut off then back on like that. It acted like it was cycling but temp. Stayed above there 180-190 thermostat temp. Again... Any thoughts? Thanks guys! Quote Link to comment Share on other sites More sharing options...
hoov100 Posted September 8, 2009 Share Posted September 8, 2009 get a 160* thermosat and make your fans come on at 175. Quote Link to comment Share on other sites More sharing options...
rsicard Posted September 8, 2009 Share Posted September 8, 2009 Vette Powered: The temperature sender should be in the intake manifold next to the thermostat housing. Having it down low in the block is giving false readings lower than where it should be. Is it an electrical (Wire) or mechanical sensor with a semi rigid metal tube running to the gauge? If it is the electrical sender, replace same and mount it in the intake manifold. Quote Link to comment Share on other sites More sharing options...
Vette Powered Posted September 8, 2009 Author Share Posted September 8, 2009 Vette Powered: The temperature sender should be in the intake manifold next to the thermostat housing. Having it down low in the block is giving false readings lower than where it should be. Is it an electrical (Wire) or mechanical sensor with a semi rigid metal tube running to the gauge? If it is the electrical sender, replace same and mount it in the intake manifold. It's mechanical and it's really low. It's by the headers. I thought the same thing but I'm worried. I just don't want to make a mistake and think I'm ok and burn the motor out. Quote Link to comment Share on other sites More sharing options...
Administrators BRAAP Posted September 9, 2009 Administrators Share Posted September 9, 2009 (edited) Tad, Doc’s post should be your starting point in figuring out what is going on. Heating problems are always a nightmare. Ample pump flow, retention time in the rad, airflow are the key. Alum rads are more efficient, so it's probably just adequate air flow. The 160 or 165 stat will work fine if you use one and will make more power IMO. Air flow problems can be the result of insufficient shrouding/sealing and IMO is the place to look in your case. Air flow is EXACTLY where I’d start as well. Been there done that trying to improve coolant flow, capacity, time in the radiator, LOTS of different thermostats, temp ranges and styles and none of that helped at all. Air flow mods is what helped the V-8 Z car stay cool. Also, regarding the Thermostat, it seems to get a lot of attention whenever overheating comes up and most of the advice given will be centered around the thermostat. Granted, the thermostat is a common fault in some overheating situations, but when a few different thermostats have been tried and there is no change in "how" the overheating react, chances are the "cause" for the overheating is related to something else. Due to how A/C functions, when it is operating, it is pulling the heat out of the cab of the car and expelling that heat to the atmosphere just ahead of the radiator in the condenser. As such, when the A/C is running, any air that goes through the condenser first is getting preheated so by the time it gets to your radiator, what air flow you do have through the radiator doesn’t have as much "room" left for more heat, (delta "T") i.e. the air through the radiator is already hot, so it can only accept very little more heat so the radiator remains hot! That is why your over heating issue is worse with the A/C running vs not. As mentioned earlier, when the A/C compressor is running, it is loading the engine a little bit more, causing the engine to work just a little bit more, absorbing a few HP at most, but that is nothing that would make the difference between overheating or not. Remember, your cooling system and even the A/C system, in their simplest forms, are merely “heat exchange systems”. Cooling system is exchanging heat produced by the engine out to the atmosphere through the radiator. This system works pretty well in most cars, adequate for L-6 Z cars, barely adequate to not adequate for most V-8 Z cars. This inadequacy is mostly due to inadequate air flow thorough the radiator so the radiator can do its job in exchanging heat that it pulled from the engine out to the atmosphere. Chances are your radiator is up to snuff. Your water pump and its driven speed as well as the thermostat are up to snuff. When the car starts to get warm, I'd be willing to bet that that temperature of the fins near the out of the radiator into the water pump is not much cooler than the fins near inlet of the radiator, where the coolant come in from the T-stat. Blow more air across the radiator and that temp difference from inlet to outlet of the radiator should become much greater, and the engine temp will also come down, i.e. cooling system is up to snuff, inadequate air flow "across" the fins of the radiator! My first V-8 I struggled with wanting to run warm as well. Using that formula that Doc supplied, I spent several months making changes. Every change I made to improve coolant flow and soak in the radiator made NO difference! Every mod I did that improved air flow to and through the radiator, DID make a difference. Then after the wind tunnel testing results came out, that solidified my finds that the Z car is weak in the are of air flow “across” the fins of the radiator, and a super wonder fan, in itself is not the wonder cure. Here is a brief run down on what I did. Car; ’75 280-Z, non vented hood, mild SBC 350, T-5 trans. No front bumper, no air dam. Car ran consistent 12.3 @ 113 MPH, was a daily driver! JTR GM radiator, Cheapo 14” slim fan. As much under drive for the water pump as I could get with stock pulleys. I first approached coolant flow mods. Like everyone else, I thought it was flow related. 1) Tried colder Thermostats, high flow thermostats, no thermostat! No change, car wanted to run warm, different thermostats only changed how fast and when it happened. 2) Found a crank and water pump pulley that went from under drive to over drive! No change! Still wanted to run warm, warmed up at the same rate etc. . 3) Disassembled the water pump, added a backing plate to the impellor and pressed the impellor closer to the housing, i.e. less clearance between the impellor and the housing and made the impeller MUCH more efficient at moving water through the engine! NO change! Still ran warm and heated up just as quickly! Though with the rad cap off and when the thermostat was open, (car running warm), there was noticeably more/faster running coolant through the radiator. 4) Removed the water pump and tapped the coolant bypass hole in the passenger side of block just under the water pump for a pipe plug, plugged it and drilled a small hole in that plug to restrict the amount of coolant bypass (thinking it may be short cycling too much hot water). NO change, car still ran warm, warmed just as fast! 5) Removed the engine from the car, (forgot exactly whey, I think it was oil leak related and ended up replacing all the gasket on the engine). Any how, when I removed heads I used different head gaskets with slightly different cooling passage ports! No change, car still ran warm! Then I looked at the amount of coolant thinking it didn't have enough coolant and was just passing what little coolant it had through the radiator too quickly so it didn't get a chance to exchange the heat to the atmosphere! Bought larger NASCAR Style radiator, (3 gallons of coolant vs 1 gallon). Theory was to more volume of coolant in the radiator has more time to exchange its heat to the atmosphere. Car still ran just as warm, just took longer to get there, but also took longer to cool back down as well! The added volume of coolant acted as a heat ballast/heat sink! In other words, no change, car still ran just as warm, just took longer to get warm AND longer to cool back down! Played with the car sitting still at home, allowed it to warm up and get up to approx 210 degrees, then lightly misted the radiator with garden hose, temp came right down! Let it warm up again, blowing air across the radiator from a distance with an air nozzle, (don't get too close or the air blast from the nozzle will deform the rad fins). Temp came right down. Ahh haa... With that I started to make changes in air flow through the radiator. Not having any of the info from the wind tunnel, I was going at it blind, so only made few changes and they ALL helped, making noticeable difference. Sealed the radiator to the core support air tight so no air could go around the sides of the rad, but only through it! Plugged all the other holes in the core support except the big one in front of the radiator! Sealed the hood to the upper rad core support so no air could flow between the hood and the core support! All this made the biggest difference of everything tried, improved the running warm situation noticeably, almost curing completely! My license plate was in the middle of the grill, removed it, that made just a little more improvement. That is as far as I got with it. With what I know now, I would’ve ran the smallest lightest radiator, (JTR radiator), done an air dam and a flat plate from the air dam back to at least the rad core support and sealed all that air tight. Built formed sheet metal air entrance that starts at the same shape as the grill opening and transitions to the hole in the rad core support. Hope that helps, Paul Edited September 9, 2009 by BRAAP Typos, LOTS of typos... Quote Link to comment Share on other sites More sharing options...
Vette Powered Posted September 9, 2009 Author Share Posted September 9, 2009 Paul, What can I say? This is a great help. The car has all the right parts. (big nice water pump, big aluminium rad), and everything checks out working well. It looks like I'm going to make a trip to HomeDepot to get sheet metal. What size metal are people using? I've read quite a bit through the wind tunnel threads but can't find what size is being used. I'll try the water hose test later today and post later. Thanks so much for the help!!! Quote Link to comment Share on other sites More sharing options...
John Scott Posted September 9, 2009 Share Posted September 9, 2009 I'm really not trying to add to anyone's misery, but why would my 383, aluminum head, solid roller get away with just mounting a Griffin radiator 1-55202-x, Weiand water pump(?) twin blower fans, no shrouds, sheetmetal or other voodoo and it cools fine in 90-100° weather, long waits in burger drive throughs etc. ? Timing OK, check for lower hose collapsing, too lean, impeller spinning but not turing water pump..? Quote Link to comment Share on other sites More sharing options...
rsicard Posted September 9, 2009 Share Posted September 9, 2009 Vette Powered: Try the suggestions by BRAAP. The first thing to do is to relocate the temperature sender as suggested THEN proceed with the tests suggested by BRAAP. Quote Link to comment Share on other sites More sharing options...
rsicard Posted September 9, 2009 Share Posted September 9, 2009 Vette Powered: Without taking the suggestions about checking flow and putting a GOOD water pump (http://www.stewartcomponents.com) for good flow and relocating the TEMP SENSOR and using BRAAP suggestions, you are not focusing in on the solution. Quote Link to comment Share on other sites More sharing options...
Vette Powered Posted September 9, 2009 Author Share Posted September 9, 2009 Vette Powered: Without taking the suggestions about checking flow and putting a GOOD water pump (http://www.stewartcomponents.com) for good flow and relocating the TEMP SENSOR and using BRAAP suggestions, you are not focusing in on the solution. I have checked water flow and it's great. I also have a large new water pump that is moving water very well. As for relocating the temp. senser, I have not done this yet. I'm getting different suggestions on that. Most people I've spoke with tell me you want the temp gauge to read at the hottest point. I guess I'm not for sure on that yet. It's a little scary. I would hate to make a mistake and burn the motor up. I will be putting a water hose on the rad. as a test though. Oh.. And sheet metal for the air box up front. I still have a "sitting still" problem that can't be fixed with that though. Believe me!! I want to get this car running strong. Quote Link to comment Share on other sites More sharing options...
dr_hunt Posted September 10, 2009 Share Posted September 10, 2009 I wouldn't worry about burning it up just yet. 230 to 250 is fine as long as your oil temps are not over about 270 or so. I have had instances where some engines just naturally run hotter than others, just a fact of life. Any speed above 35 mph then a fan does about zero good as the natural air speed is greater than the fan airspeed at a dead stop. Fans are for low speed cooling. I think it's highly probable that you need to seal the rad to the rad support. Plug all the holes that let air circumvent the rad and you'll be pretty close. Quote Link to comment Share on other sites More sharing options...
rsicard Posted September 10, 2009 Share Posted September 10, 2009 Vette Powered: There was a reason for recommending Stewart Components water pump. These are HIGH FLOW water pumps. I had a 1987 Chev Suburban with a 454 engine that always ran hot in the summer. Then I discovered Stewart Components. Purchased one of their water pumps for the 454, installed it and then the higher temp operation was cured. It always ran at the thermostat rated temperature. As for relocating the temp sensor, the HOTEST place is right near the base of the thermostat. Cool water flows from the pump to the block up through the block to and through the cylinder heads to the intake manifold and thermostat the hottest place for water in the engine. Quote Link to comment Share on other sites More sharing options...
grumpyvette Posted September 10, 2009 Share Posted September 10, 2009 (edited) BRAAP post is right on target Id also point out that 220F is nothing to get crazy over with a car sitting still, the radiator could obviously use more air flow and a more effective fan and duct work will help, your generally not going to have any problems if that 220F-230F in coolant temps is rarely exceeded, especially if it drops rapidly once your moving the car, before I added a transmission cooler my corvette almost always ran at 195f-210f coolant temps and oil temps in the 210f-235f range under hard driving and easily jumped up a few degrees in traffic. adding an oil cooler also keeps the engine temps top low for too long so I only run the trans cooler now but ID point out that almost all the hotter components in an engine are cooled by OIL FLOW and the OIL after its absorbed most of the heat transfers some of that heat to the coolant as it flows back to the sump, so an OIL COOLER and a 7-8 quart BAFFLED OIL PAN will go a long way to LOWERING the ENGINES total temperatures, the radiator needs to deal with, its not at all unusual to drop engine temperatures by 20 degrees with a 7-8 qt baffled oil pan and an oil cooler added to the engines oil system ID also suggest drilling 8 1/8" holes in the T-STAT flange so any trapped air will circulate and exit the system and you ALWAYS have at least minimal coolant flow http://forum.grumpysperformance.com/viewtopic.php?f=54&t=296 http://forum.grumpysperformance.com/viewtopic.php?f=57&t=1540 http://forum.grumpysperformance.com/viewtopic.php?f=57&t=149&p=183#p183 OIL COOLER Perma-Cool 12318 $195.95 http://store.summitracing.com/partdetail.asp?autofilter=1&part=PRM%2D12318&N=700+115&autoview=sku Perma-Cool 13311 $169.95 OIL AND TRANS FLUID COOLER Edited September 10, 2009 by grumpyvette Quote Link to comment Share on other sites More sharing options...
Vette Powered Posted September 10, 2009 Author Share Posted September 10, 2009 Thanks Grumpy! I'm working on the car now. I'll post updates later. Maybe some pictures too. Quote Link to comment Share on other sites More sharing options...
Vette Powered Posted September 11, 2009 Author Share Posted September 11, 2009 Ok. I ran the car again today for about 30 minutes. 15 driving and 15 sitting with the a/c on the whole time. It has a mind of it's own!!! It never got over 200??? Anyway... I think I'm going to do the air box up front and move the temp. gauge into the manifold. Below is a few pictures of the car and what we have been talking about. The a/c condenser covers the entire rad. So.... more test drives and some work ahead. Thanks again for all the help. I'll keep posting progress. Quote Link to comment Share on other sites More sharing options...
rsicard Posted September 11, 2009 Share Posted September 11, 2009 Vette Powered: That is a very big condenser for the air conditioning. It appears the temp sender is on the LH side of the engine screwed into the cylinder head. This is where the cooler water is coming up from the block into the cylinder head. Therefore this water has yet to pass through the cylinder head and get heated MORE. Just curious if you tried a somewhat fine spray of garden hose water into the front of the radiator when hot to see if it cooled down and what the results are. Quote Link to comment Share on other sites More sharing options...
jt1 Posted September 11, 2009 Share Posted September 11, 2009 The "mind of it's own" part makes me wonder if it still has some air in it. It's best if you have some means to bleed the air at the highest point of the system, usually the thermostat housing. Do you have a spring in the lower radiator hose? Sometimes it can collapse at higher rpm. jt Quote Link to comment Share on other sites More sharing options...
Vette Powered Posted September 11, 2009 Author Share Posted September 11, 2009 Vette Powered: That is a very big condenser for the air conditioning. It appears the temp sender is on the LH side of the engine screwed into the cylinder head. This is where the cooler water is coming up from the block into the cylinder head. Therefore this water has yet to pass through the cylinder head and get heated MORE. Just curious if you tried a somewhat fine spray of garden hose water into the front of the radiator when hot to see if it cooled down and what the results are. I was going to do the water hose test but I never could get her to heat up. It was a overcast day here in Texas so temps. were a bit lower. Still about 90 though. It raining today so I'll try it later this weekend. Quote Link to comment Share on other sites More sharing options...
Vette Powered Posted September 11, 2009 Author Share Posted September 11, 2009 The "mind of it's own" part makes me wonder if it still has some air in it. It's best if you have some means to bleed the air at the highest point of the system, usually the thermostat housing. Do you have a spring in the lower radiator hose? Sometimes it can collapse at higher rpm. jt I jacked the front of the car up really high and spent some time working air out of the system so there should not be much air. Oh, and yes I do have a spring in the lower hose. Quote Link to comment Share on other sites More sharing options...
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