ZSPEED77 Posted March 31, 2008 Author Share Posted March 31, 2008 It's been over a year since my v8 swap and it still overheats on the highway. The changes I've made since the last time I posted are as follows: 3 row radiator- '69 camaro spec (can't remember if I had that or not yet) High flow water pump (don't remember if I had that on before or not) I cut hood vents right above the belt area which is where the radiator fan tends to blow. Built a ram air system in front of the radiator enclosing it from the front grill to the radiator. Added the stock pan from the bottom of the radiator to the crossmember. Last week changed my heads to Dart heads, new set of headers, put in a comp cams 260 cam. (previously had a crane, wanted to try a diffeent cam for other reasons) My car runs about 10 degrees cooler with the above mods but I cannot run on the highway unless my fan is on still. The car runs at about 210 at 70mph, no a/c, 85-89 degree weather. (soon to be 100 degree) Quote Link to comment Share on other sites More sharing options...
Nealio240z Posted March 31, 2008 Share Posted March 31, 2008 This is your problem. Ok... lets try to put this to rest... I had this exact problem for a year. SAME SET UP AS YOU. It has nothing to do with the fan at all since its only freeway speeds and not in traffic... I went through everything as you did, did everything I could to stop it. I finally went to a wind tunnel. This is a very common problem with this set up. - Think of a hollow point bullet- It pushes air infront of its self creating a pressurized cavity just in front of the bullet. Same with your car. Too much air is going AROUND your front end and not THROUGT it. The air inlet of the airdam NEEDS to be sealed to the lower crossmember of the radiator, use a fabricated piece of sheet metal and high temp aluminum fiol tape to construct this, otherwise all this air is going under the car not throught the radiator. Seal the sides holes that the wireing harnesses goes through, seal the 3" gap above your radiator to the hood. Make a sheild out of cardboard first and then metal- pop rivet it into place and use a 1/2" hose cut lengthwise along the leading edge that contacts your hood (for a good seal). There should be a gap between your radiator sides and the frame- seal these with pipe insulation. You really just need to seal up the radiator (all edges) to the frame, and the frame to the airdam. There should be nowhere for the pressurized air to go but throught the radiator. -Also remove your license plate from blocking the air flow-relocate it. This dropped me to running at 240 to 165. This will save your car from overheating. It taskes time to do but its worth it... Quote Link to comment Share on other sites More sharing options...
ZSPEED77 Posted March 31, 2008 Author Share Posted March 31, 2008 "Built a ram air system in front of the radiator enclosing it from the front grill to the radiator." This does include the airdam as well. If the air makes it to the grill (upper or lower) it had no choice but to go through the radiator. My next test will be without the bumper. On a side note I did a test on the highway without the hood. It took a little longer to heat up but still did anyway. I then removed my ram air box which exposed the top of the radiator to open air. It ran a few degrees cooler but not much. I've pretty much decided that I have a high pressure area in my engine compartment but I haven't figured out how to overcome it yet. Quote Link to comment Share on other sites More sharing options...
jasper Posted March 31, 2008 Share Posted March 31, 2008 I've had partially clogged radiators do exactly what you are desribing. Low speeds, engine doesn't produce a lot of heat. High speeds, lots of heat. Radiator can't get rid of heat, no matter how much air flow you have. Get an infrared heatgun and check each radiator tube for equal heating/temperature! Quote Link to comment Share on other sites More sharing options...
sakh260z Posted September 7, 2009 Share Posted September 7, 2009 I almost have the same setup as u have and I also have the exact same problem as u did.how did u overcome with that mysterious overheating problem? Quote Link to comment Share on other sites More sharing options...
kiwi303 Posted September 7, 2009 Share Posted September 7, 2009 Hmm... I see a BRAAP-attack looming for spelling, grammar, txt spk, and other associated abuses of the rules Quote Link to comment Share on other sites More sharing options...
ZSPEED77 Posted September 8, 2009 Author Share Posted September 8, 2009 I almost have the same setup as u have and I also have the exact same problem as u did.how did u overcome with that mysterious overheating problem? I never really solved it but it is better under control. I pretty much expect my block to be the main issue. I will know for sure when I change it out sometime in the future. I've had to flush out my block because it has a reddish brown mud in the coolant passages and it never seems to go away. I currently run around 210 on the highway with a/c and my Taurus fan on low speed. We've had around 60 days of 100 degrees + weather here and it seems to be doing ok. The high speeed did come on a few times which is around 220 degrees for the sensor I am using. Removing my front bumper helped alot although I really don't drive over 70mph. It would probably run hotter if I did. I currently have 2 sets of hood vents. The radiator fan blows through the front set. On the rear set I put on the covers from MSA that look like mini cowl induction scoops. I recently reversed them so that they are facing forward. When I did that I reduced the inside temp a whole lot. Before I did that my firewall was generating so much heat that it felt like a convection oven inside even with the a/c. It definately feels alot better now. It didn't help the engine any though. Quote Link to comment Share on other sites More sharing options...
Miles Posted September 9, 2009 Share Posted September 9, 2009 I was chasing overheating issues with the JTR radiator. Did all of the things most people do to resolve the problem except for controlling water flow. Finally I bought a set of Moroso water outlet flow restrictors. I removed the thermostat and installed the middle sized Moroso outlet flow restrictor. My engine used to run 240 + deg. Now it runs 180 - 185 deg on 100 deg days. Quote Link to comment Share on other sites More sharing options...
sakh260z Posted September 9, 2009 Share Posted September 9, 2009 upper hose has too much pressure in it.and on stand still by 2500+rpm temp goes to +230.(my z has a goodwrench 350 with new wp and 5 raw rad and dual spal 2780 cfm fan) I have changed the head gasket with no improvment on overheating issue.any ideas will be appriciated Quote Link to comment Share on other sites More sharing options...
saxfiend1967 Posted October 5, 2009 Share Posted October 5, 2009 yes I have the high power Ford fan. But not from a Taurus. I have one from a Thunderbird and one from a Mark 8 or whatever that car is. The fan fits the radiator like a glove. It actually looks like it was made for it. I bought two since they were so cheap. I also have an air dam and the original pan that sits in front of the radiator. With the Ford fan I can feel the air being pulled from as far as the bumper. I could never feel the belt fan pull that hard. My friend and I have considered airflow problems out of the engine compartment since my auto tranny fills up the tunnel but there is no easy way to test that.I have thought about a possible headgasket issue. Unfortunately I couldn't tell from a possible loss of water because it would get so hot it would blow out the overflow bottle. I have no driveability problems either. too much timing or not good enough gas. check timing at 3000 rpm ,if its over 36 back it down and se what happens. I have a 72 mach 1 ,it has to have 124 octane if you run any less it overheats too. other suggestions radiator cap pressure too low,thermostat too low.a lot of people remove thermoostats ,dont ever do it. the thermotat hold coolant in the radiator to cool it down as well as heat it in the block. ok hope that helps Quote Link to comment Share on other sites More sharing options...
saxfiend1967 Posted October 5, 2009 Share Posted October 5, 2009 upper hose has too much pressure in it.and on stand still by 2500+rpm temp goes to +230.(my z has a goodwrench 350 with new wp and 5 raw rad and dual spal 2780 cfm fan) I have changed the head gasket with no improvment on overheating issue.any ideas will be appriciated same for you check radiator cap ,thermostat and timing. make sure carb isnt leaning out .a couple of jet sizes make a huge difference.the only other thing is run a good aircleaner. if you dont run it the air across the carb creates vacuum ,if its too small it wont run right either,B I knopw this sounds stupid but make sure you have the right water pump and the thermostat is in right side up too. I dont mean offence by that ,I have paid lots of stupid tax. I chased a problem for 6 months with m,y z grumpy vette and everyone else said go back to basics first but no not me I was too smart for that. 6 moths later I find two spark plug wires crossed STUPID TAX!!!!!!!!!! Quote Link to comment Share on other sites More sharing options...
hoov100 Posted October 5, 2009 Share Posted October 5, 2009 too much timing or not good enough gas. check timing at 3000 rpm ,if its over 36 back it down and se what happens. I have a 72 mach 1 ,it has to have 124 octane if you run any less it overheats too. other suggestions radiator cap pressure too low,thermostat too low.a lot of people remove thermoostats ,dont ever do it. the thermotat hold coolant in the radiator to cool it down as well as heat it in the block. ok hope that helps I run 40 degree's on cheapo 91 with almost no valve overlap, no thermostat, 9.50:1, no advance and it runs fine temp wise, stays at 210* with air temps being 115* on the freeway and sitting still. high oil temps will also cause a rise in coolant temp, but its most likely going to be aero problems causing the problem. Quote Link to comment Share on other sites More sharing options...
sakh260z Posted October 6, 2009 Share Posted October 6, 2009 thanks for the suggestions but after I've been through all these, no improvement is seen.now I think the wp is not working properly when hot 1 Quote Link to comment Share on other sites More sharing options...
hoov100 Posted October 7, 2009 Share Posted October 7, 2009 thanks for the suggestions but after I've been through all these, no improvement is seen.now I think the wp is not working properly when hot did you do any of the aero mods to the front? Quote Link to comment Share on other sites More sharing options...
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