gretchen/jason Posted October 6, 2006 Share Posted October 6, 2006 Ok i stuffed a Blown SBC in my z and with no hood can keep my z at 185 degrees when its 60 degrees outside when its 90 degrees im looking at 210 on the t stat with no hood . I run a 17 inch clutch fan with a shroud i fittied my self it cools ok at speed at idle well it gets a bit hot . Then i added a hood well on a 50 degree morning it runs 200 degrees when it hits 70 in the day time 210 is within site really quick . I got a radiator from Jags That Run best rad ive put in yet . Electric fans dont do jack for me , at idle they keep it cool but at speed they suck i had a fan that pulled 3,800 cfm and at idle nice and cool at speed it overheated really quick . The clutch fan has been the best so far ive even put exhaust fans in to suck the hot air out and still runs hot it needs to be at least 40 degrees with my hood to not go above 190 . My t stat only seals for about 3 days then it seeps past the gasket not external but internal like having no t stat ive tried 5 different brands of gaskets but still the same thing eventually the watter finds a way past like a free flowing system maybe this is part of th eproblem . Jason Quote Link to comment Share on other sites More sharing options...
Guest Mike Posted October 6, 2006 Share Posted October 6, 2006 Are you sure it's the right type of thermostat? If so, maybe you should try a different brand. Even the best manufacturers mess up from time-to-time. Or... maybe it's installed upside down? Quote Link to comment Share on other sites More sharing options...
buZy Posted October 6, 2006 Share Posted October 6, 2006 You might need a bigger rad mounted lower in the car to clear hood. Thats what I had to do, but your motor is more. Are your ex fans allowing the air to excape up through the hood or underneath? Blower under hood? Quote Link to comment Share on other sites More sharing options...
Pop N Wood Posted October 6, 2006 Share Posted October 6, 2006 Lot of engine. Maybe adding an oil cooler will help. I assume you have done all the standard stuff like flush the block etc. Make sure your lower radiator hose isn't collapsing. Needs to have a spring in it. Quite a few guys found that to be a problem. I assume your timing is good too. some guys have fixed overheating problems by adjusting that. Make sure you seal the shroud around the radiator to prevent air leaking past the rad. Beyond that, there was a guy on here who installed two auxilliary radiators (i.e. heater cores) either down in the wheel wells or off the front air dam brake ducts (can't remember which). He swore by them. I always thought this was an uneeded fix since most guys don't have to go to that extreme. But if your engine is radiacal enough maybe that is what you need (short of a bigger radiator). Quote Link to comment Share on other sites More sharing options...
gretchen/jason Posted October 6, 2006 Author Share Posted October 6, 2006 Well i had a 2 row rad in there before it made the heating problem worse , the lower hose is ok its a metal flex hose the T stat is in the corect way its just like the spot in the manifold where it sits is to deep . I tried a high flow pump this just made it worse as it flowed so fast the watter didnt have time to cool off . As far as the air from the fan it has to force its way past the engine to escape under the car i actually installed 2 blower fans to help suck the heat out not sure what to do i do now if i take the hood off all problems are solved but as it may snow here anytime that isnt a option at the moment Quote Link to comment Share on other sites More sharing options...
Mike kZ Posted October 6, 2006 Share Posted October 6, 2006 Have you bled all the air out of the system? You may have an air pocket somewhere. Quote Link to comment Share on other sites More sharing options...
MONGO510 Posted October 6, 2006 Share Posted October 6, 2006 Remove the thermostat, check for heating.Make sure water pump is pumping. If you still have problem check for cold spots in radiator. It could be plugged. Replace radiator with bigger unit. Quote Link to comment Share on other sites More sharing options...
Pop N Wood Posted October 6, 2006 Share Posted October 6, 2006 Sorry, just read it close enough to see the problems are only with the hood in place. Can you get a hood from a mid 70's Z with the two vents? I have those and they really radiate some heat when sitting in traffic. Quote Link to comment Share on other sites More sharing options...
mom'sZ Posted October 6, 2006 Share Posted October 6, 2006 ... I tried a high flow pump this just made it worse as it flowed so fast the water didnt have time to cool off ... That's not unheard of, if you operate at high RPMs a lot, it's worse. Perhaps that's the issue, try slowing down the flow, perhaps a restrictor plate in place of the thermostat. (summit sells them) Just something to try in an extreme case (as this seems to be). Or you could cut every other vane off the water pump impeller. Your thermostat leaking past internally sounds like another issue. Is the housing itself in good shape? Perhaps erroided? Quote Link to comment Share on other sites More sharing options...
buZy Posted October 6, 2006 Share Posted October 6, 2006 Is your rad filler neck mounted lower than your T stat housing? If so you might not be completely filling the system to full capacity. This would create an air pocket in the system. I totally agree the mid 70's hood would let alot of heat out compared to trying to force it out the bottom. FWIW I have a decent hood with a rear cowl and front scoops. I will sell cheap. If your interested just PM me. Quote Link to comment Share on other sites More sharing options...
gretchen/jason Posted October 7, 2006 Author Share Posted October 7, 2006 The hood i have is a custom hood from california its all fiber glass with a 4 inch cowl induction scoop as any stock hood will not clear my engine the carb itself sits 1 inch higher then any stock hood can handle due to the supercharger i even had to make a custom cold air ram air intake for my z so i could get a air filter on it . I actually took off the inspection doors on each side of the hood and that helped me out quite a bit im guessing the hot air just gets stuck under there somehow . The rad filler neck is higher then the t stat im using a rad from jags that run and its mounted very nicely with the mounts they sold me . I do wish the engine sat lower as 2 inches of the fan sit above the radiator but i had a shroud made to make up for the slack there if i could get the engine 2 inches lower that would be nice because i cant raise the rad or it hits the hood Quote Link to comment Share on other sites More sharing options...
Sumo Posted October 7, 2006 Share Posted October 7, 2006 It's like what Mike kZ said, it sounds like you have an air pocket. or maybe a leak in the headgasket forcing pressure in the system? Quote Link to comment Share on other sites More sharing options...
gretchen/jason Posted October 7, 2006 Author Share Posted October 7, 2006 Did a pressure check no leaks then a sniffer test to test for exhaust gasses in my rad fluid nothing ive noticed that at idle i cant get the clutch fan to pull as much air as i think it should even with a shroud on it as with the electric fan it was great at idle but no good at speed . Quote Link to comment Share on other sites More sharing options...
mom'sZ Posted October 8, 2006 Share Posted October 8, 2006 as with the electric fan it was great at idle but no good at speed . why would you need a fan at speed? seriously, I'm not trying to be a smart a$$ Quote Link to comment Share on other sites More sharing options...
gretchen/jason Posted October 8, 2006 Author Share Posted October 8, 2006 Well i thought the same thing to soi tried a test at 75 mph I turned the electric fan off and drove 75-80 mph and the temp got hotter and hotter with the fan shut off . So i turned it back on kept the temp about 210-220 turned it back off while still doing 75-80 mph never stoping and it climbed 240-250 degrees . Quote Link to comment Share on other sites More sharing options...
Guest Mike Posted October 8, 2006 Share Posted October 8, 2006 It sounds like you have an airflow issue. Do you have a modified grill or is there anything obstructing the airflow to the rad? Are there any mods at all on the front of the car? Quote Link to comment Share on other sites More sharing options...
Pop N Wood Posted October 8, 2006 Share Posted October 8, 2006 Do you have a chin pan? Datsun back fit a sheet metal pan between the frame rails and behind the radiator to help smooth out under car turbulence and improve air flow through the radiator at speed. It helped with my otherwise stock 240. Previaling wisdom on this site is overheating at idle is a fan issue, but overheating while moving is an airducting issue. Quote Link to comment Share on other sites More sharing options...
gretchen/jason Posted October 8, 2006 Author Share Posted October 8, 2006 Nope my z doesnt have those pieces i dont even have the fender well plastic inserts that go where the tires are . . I can add one no problem how far back from the lower radiator support does it go like to the steering rack ? And is it completly flat ? Does it attach to the lower rad support also ? Jason Quote Link to comment Share on other sites More sharing options...
gretchen/jason Posted October 8, 2006 Author Share Posted October 8, 2006 As far as front end mods i added a air damn from MSA the entire bumper and all is fiberglass teh type 3 air damn . the grill is from a 240 i removed bot turn signal housings from behind the grill so as to have nothing what so ever in front of the rad except for to K&N air filters about 7 inches long 5 inches across cone shaped filters . one on each side of the rad but off to the side a bit . Quote Link to comment Share on other sites More sharing options...
Guest Mike Posted October 8, 2006 Share Posted October 8, 2006 Air filters... what, do you suppose, is the percentage of blockage by those? What is the total area of exposed radiator area? If your best air flow happens to be obstructed by those, maybe that could be the issue? Quote Link to comment Share on other sites More sharing options...
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