Guest Anonymous Posted May 2, 2000 Share Posted May 2, 2000 If anyone can help please jump in. I have a 81ZX with a 78 305 from a FireBird (rebuilt, vatted the block, stock heads, flat top pistons, roller rockers, mild cam) and 700R4 trans....3" single exhaust, Holley ProInject, and 4core radiator with 165 degree thermo. When the car is moving it runs cool but the minute I come to a stop the temp climes. I have added a pusher electric fan...no help, Cool taped the exhaust back to the cat....no help, 7 blade clutching fan....no help, HD flex fan....no help, tried two different radiators ...no help, used two quarts of "40 Below"....very little help, Full shroud....no help. I just can't seem to get enough air to move across the radiator when stopped....anyone have an Idea? Oh yes I have adjusted the timing from 0 degrees up to 12 degrees advanced and no help. I also have an "air/fule" meter and have run rich and lean with no change. Also have changed the water pump......HELP! Quote Link to comment Share on other sites More sharing options...
Administrators SuperDan Posted May 2, 2000 Administrators Share Posted May 2, 2000 Just a idea, my car ran real hot at idle when my timing was set to 15 deg. I reset it to about 22 deg and the temp dropped allmost 20 degrees. ------------------ Dan "I need bigger tires" Porter, 78 280Z, 383, 475hp, Comming soon T56, Move outa my WAY!!! http://24.4.88.44/members/dporter/DanZ.html Quote Link to comment Share on other sites More sharing options...
pparaska Posted May 2, 2000 Share Posted May 2, 2000 The four row radiators are not the easiest to get to work, since they are hard to get alot of air through. Ok for the L6, but the V8 needs more. I'd try an aluminum rad, either out of the 86 Camaro like JTR recommends or a Griffin. Sounds lik you've done all the important stuff. Pete "the other Pete" Paraska Quote Link to comment Share on other sites More sharing options...
Guest Anonymous Posted May 2, 2000 Share Posted May 2, 2000 Thanks......I fail to see how advancing to 22 degrees lowered the temp when everything you read say that it should go up.....but believe me I will try it. Also I have run a large truck aluminum radiator and it was worse. Come on folks put on you thinking caps because, lord knows I've run out of ideas. RePete Quote Link to comment Share on other sites More sharing options...
SpeedRacer Posted May 3, 2000 Share Posted May 3, 2000 Wow, sounds like a bit of a tough one. I think you'll find SuperDan is right about the timing as long as it doesn't kick back trying to start it. Hard to explain but the engine is more efficient with advanced timing (to a point) and uses less fuel therefore less heat. I know that you said you changed the waterpump but did you get a good high volume one? How about the pulleys, are you under-driving the waterpump? Ever think about trying an oil cooler? With two fans you should be moving enough air but maybe not enough coolant. Cooling that little ole' 305 shouldn't be too big a problem but if that doesn't fix it I'd call up the boys at Griffin Radiator http://www.griffinrad.com and order a two row (1.25" tube) aluminum radiator. If that doesn't cool it nothing will! Quote Link to comment Share on other sites More sharing options...
Rob Posted May 3, 2000 Share Posted May 3, 2000 With your problem only at idle, I would first try raising the idle speed to get more fan speed. If the tranny cooler is in the radiator, I would add a aftermarket cooler and route the fluid exclusively to that to reduce the load on the radiator. If still no improvement, I'd go to the biggest baddest electric fan I could find, such as the black max or the perma-cool which pulls over 1000 CFM. At idle, a very good electric fan will pull more air than a mechanical fan. Good luck. I know overheating problems can be frustrating. One more thought.. If your shroud did not help that's surprising. Maybe you need to reduce the clearance between the fan and the shroud. Quote Link to comment Share on other sites More sharing options...
John Scott Posted May 3, 2000 Share Posted May 3, 2000 One other thing to check. With the cap off, before it gets hot, can you see fluid moving through the radiator when the thermo. opens? Check for blockages. I had a really hot big block that had a slight compression leak into the coolant causing the fluid to foam, resulting in overheating. Also the advance thing works. Just don't overdo it. Also don't forget to then take out the unneeded timing at full advance or you'll be predetonating. Shoot for mid 40 degrees total in before 3000. The 20 initial seems high, but works for some of the bigger cams. I'd try at least 16+ to start with. Should perk up your low end too. If cranking is hard, a start retard is avail. from Summit. Different engine combinations like different timing curves. You'll need to experiment. Good luck! JS Quote Link to comment Share on other sites More sharing options...
Guest mattrp Posted May 3, 2000 Share Posted May 3, 2000 Well, I also have a 305, but out of a camaro in my z. I am using a 260z radiator, and with only a engine fan was getting some overheating on hot days. I have since changed to an electric fan from a ford taurus, late eighties i believe. The newer ones are even better with two speeds. I just leave it running all the time. Its great. No overheating, no matter what. All it took to install the fan was some cutting of the fan shroud and some nylon tie wraps. Matt 72 500Z Quote Link to comment Share on other sites More sharing options...
Guest Anonymous Posted May 3, 2000 Share Posted May 3, 2000 quote: Originally posted by Pete: If anyone can help please jump in. I have a 81ZX with a 78 305 from a FireBird (rebuilt, vatted the block, stock heads, flat top pistons, roller rockers, mild cam) and 700R4 trans....3" single exhaust, Holley ProInject, and 4core radiator with 165 degree thermo. When the car is moving it runs cool but the minute I come to a stop the temp climes. I have added a pusher electric fan...no help, Cool taped the exhaust back to the cat....no help, 7 blade clutching fan....no help, HD flex fan....no help, tried two different radiators ...no help, used two quarts of "40 Below"....very little help, Full shroud....no help. I just can't seem to get enough air to move across the radiator when stopped....anyone have an Idea? Oh yes I have adjusted the timing from 0 degrees up to 12 degrees advanced and no help. I also have an "air/fule" meter and have run rich and lean with no change. Also have changed the water pump......HELP! Pete, You said to put on our thinking caps. I think your radiator is too big. Or really too thick. It is hard to move alot of air through a 4 core at low speeds. Some of the adds I have seen for big radiators state this fact and mention that their equipment is for high speed driving read (super speedways) I have heard of Nascar car overheating on pace laps and in the draft. Even at this reduced speed they would be moving more air than most any fan. These cars also use squirl cage fans, mounted to the grill, in the garage area to keep their engine cool when tuning. I am running a new stock replacement radiator from advanced auto and running an independent trans cooler. I have a 350 sbc 10.5:1 compression and iron heads. I used an electric fan from a junk yard ford taurus and mounted it to the stock shroud. I have not had cooling problems. Thank God for that. How hot is your car running anyway. Mine will idle at 170f. Also is the radiator old. They can wear out. By this I mean that the metal will loose its ability to dissapate heat after so many cycles. Also is it painted black. This will also help the radiator dissapate heat. This does make a difference. So how is this for "off the wall" thinking? Bubba Fett ------------------ He sent me to get the Jedi [This message has been edited by bubafett (edited May 02, 2000).] Quote Link to comment Share on other sites More sharing options...
Ray Posted May 3, 2000 Share Posted May 3, 2000 Check all the other stuff first. If everything checks out ok, check the radiator cap. Most caps are 16lb but when they get old they will vent sooner. You can also get a 22lb cap that is used on most of the race stuff. It will raise the boiling point a little. The 22lb cap is only a band-aide, if the other stuff isn't working properly you will still have problems. Good luck Ray [This message has been edited by Ray (edited May 02, 2000).] Quote Link to comment Share on other sites More sharing options...
Mikelly Posted May 3, 2000 Share Posted May 3, 2000 Not only is the 22# cap a band aid, but it will cause problems with the heater core as I found out. I would recommend what Pete recommended and go with an aluminum radiator from Griffin. I use one. Keep in mind that people get mis-lead by multi core radiator designs. It has nothing to do with the number of cores, but how big the tubing daimeter is in the core. My Griffin is 1 1/8 inch diameter and is only a two core unit. However, because it is so large, it flows much better. Also, get rid of the electric fan, remove it all together from the front of the radiator. Now try and see what the temp reading is... Reason I say this is when I had two 10 inch pushers in front of my radiator they actually blocked more air than they pulled. They worked against the clutch fan on the back side of the radiator, obstructing more air than the clutch fan could pull. Interesting side note... This months Car Craft claims an added 45HP by getting rid of the watrpump driven fans all together and going with a puller style electric fan like the Flex-alite Black Magic electric fan.... interesting in deed... Mike ------------------ "I will not be a spectator in the sport of life!" mjk Quote Link to comment Share on other sites More sharing options...
pparaska Posted May 3, 2000 Share Posted May 3, 2000 Electric fans. The nice thing about them is they rob power (through the alternator) only when needed. The bad thing is it takes quite a motor and a good fan blade design to get them to pull enough air through the radiator. The OE fans I think are better than most of the aftermarket ones. Think about it. ALL new cars have electric fans, and they are usually oversized to provide a margin of safety for the worst conditions. Do you think the OEs would skimp here and risk a ton of overheating problems? I think not. Do you think the aftermarket guys have anything to lose if your fan doesn't cool well enough? Not much, IMO. The Ford fans seem to be used alot by engine swap people. JTR recommends a few. I'm using the 19" 98 GT mustang two speed fan. It does not have a shroud that completely covers the radiator, but I hear the Taurus one does. I do know that at high speed it is fairly quiet and really pulls the air through the radiator. At low speed it pulls fairly well (8.5"x11" sheet of papar on the front of the radiator test.) Supposedly the low speed of these Ford fans is equivalent cooling wise to the Flexlite 150 fan. The mustang fan pulls 20 amps on 12V at low speed and a whopping 35 amps on 12V at high speed. That coupled with efficient blades (somewhat evident from the low noise) and the relatively high amount of suction through the radiator (compared to the two 10" electrics I used to have) would lead me to believe that it will cool well. Food for thought... Another cooling issue with the Z swap. Make sure that the incoming air to the radiator support doesn't easily bypass the radiator. There are alot of holes around the radiator and the radiator may not fit tight to the support. I made sure that everything was sealed well with aluminum duct tape. And I'll close off some of those holes, possibly using a ram air box and a hose to direct all the other air through the support to the carb . That way the radiator gets the most use of the air forced through the grill and the engine will use what it can. I also made sure the the A/C condensor was ducted directly to the radiator core so that the fan would not suck around the A/C condensor. Hopefully, these efforts will have the engine running cool with no waste of the electric fans efforts, and the A/C will actually cool. ------------------ Pete Paraska - 73 540Z - Marathon Z Project - pparaska@tidalwave.net">pparaska@tidalwave.net - Quote Link to comment Share on other sites More sharing options...
Corzette Posted May 6, 2000 Share Posted May 6, 2000 Pete, I had this problem and I took out my thermostat, it runs real cool now and much better when at idle. Quote Link to comment Share on other sites More sharing options...
Guest Anonymous Posted May 6, 2000 Share Posted May 6, 2000 No T-stat,, hummm,, I would watch it closely now,,It will still overheat, it will just take a little longer now. You need to a t-stat to hold water in your rad to be cooled. Without it , Once ALL of the water gets hot , your done! You will need to find a way to cool your car with the t stat in it to really say you have solved your problem. just 2 cents worth. Tony ------------------ 74 260, early 350,K.B.pistons,edelbrock manifold,carb,and cam,202 cast iron heads.Let the transformation begin. Quote Link to comment Share on other sites More sharing options...
SpeedRacer Posted May 6, 2000 Share Posted May 6, 2000 Hi CorZette, you might want to think twice about running without the stat. However, it will work OK if you put a restrictor in place of the stat. The problem with running without a stat or restrictor is the water travels through the engine to fast and does not have enough time to pick up the heat. So, although the guage reads lower you end up with hot spots and uneven cooling of the block and heads which leads to other problems including warping. Up to you but just a suggestion. Quote Link to comment Share on other sites More sharing options...
Mikelly Posted May 6, 2000 Share Posted May 6, 2000 I agree with the last few posts. Do not run without a thermmostat. That is an old hotrodders tail. If your car overheats with the thermostat but not without it, then your problem isn't the Thermostat... Playing with fire there B-I-G TIME! Mike ------------------ "I will not be a spectator in the sport of life!" mjk Quote Link to comment Share on other sites More sharing options...
Guest Anonymous Posted May 6, 2000 Share Posted May 6, 2000 To all, Thanks for all the advice....I have not had time to employ any but hope to find time this weekend or next week. One more question.....I am running a 8" drive pully off the crank and ~6.25" pully on the fan drive......could I be underdriving the fan at idle which then would not turn the pump fast enough to circulate the collent....any thoughts on this? Also what is the advance timing going to do to my emmissions testing.....thus far I have passed twice with just a cat and nothing eslse.....runing about 8 degrees advanced. Thanks again and a great forum Pete Quote Link to comment Share on other sites More sharing options...
John Scott Posted May 6, 2000 Share Posted May 6, 2000 If your car doesn't pass then re-tune for emmission day. 8 degrees!! Get your timing up! Try 16 degrees and see what happens. You'll have to set your idle back down, and maybe take some advance out of the mechanical, but I bet it runs lots better. Colorado is experimenting with roving emmission vans. Set up on on ramps and other busy roads. Yes its the emmission police! Still experimental, but works like photo radar. If it "sees" a bad polluter it zaps the licence #. Bummer for some of the big cammed hotrods. Good for the air. I'm all for getting the oilburners and really gross polluters off the road. Most of us should have pretty effecient engines....WAIT A MINUTE! did I read that right. Your pulley size should be a 7 1/8" diam. for the water pump and 6 3/4" for the crankshaft pulley. Those are the standard sizes for the smallblock. Hmmm... JS [This message has been edited by John Scott (edited May 06, 2000).] Quote Link to comment Share on other sites More sharing options...
pparaska Posted May 7, 2000 Share Posted May 7, 2000 If the fan pulley is smaller than stock and the crank pulley is larger than stock, then you'd be turning the water pump and fan faster than stock, not slower. The smaller driven pulley is turning more revs for each turn of the larger diameter driving (crank) pulley. I'd think this would help the fan pull more air through, but would it help or hurt the woter flow rate? It'd be faster, but is that good or bad? Might it cause some cavitation in the pump? That's not good. Quote Link to comment Share on other sites More sharing options...
Modern Motorsports Ltd Posted May 7, 2000 Share Posted May 7, 2000 Nothing wrong w/ the parts you tried, has to be a fundamental problem IMO. water pump/thermostat/block plugged/rebuilt built too tight (seen that) let us know what you find out, I assume flow through rad seems fine? Hose squeeze test etc? If you do buy a rad I'd have to recc'd the Griffin's, love my 2 row 1.25" setup. Quote Link to comment Share on other sites More sharing options...
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