[topdog1300]

Originally Posted by pontiacphil

I've posted several times in the past about my 67' GTO overheating at idle. It ran hot before my total rebuild this past Winter and it continues to do so after the rebuild. It's a stock 400 bored .30 over, forged flat tops, true 9.48 compression, 670 heads w/ 3-angle valve job, stainless valves, roller tips, Crower #60242, 3:36 gears, rebuilt Turbo 400, Pertronix HEI, Quadrajet that appears to be set correct (not too lean or rich) factory intake, 2 & a half in. exhaust, Ram Air exhaust manifolds with X-pipe, running 91 octane gas, 7 degree advance at 750 RPM idle with total advance at 37 deg. at 3,000 Rpm, Flow Kooler water pump tweaked the way George advised me to, 180 degree Mr. Gasket themostat, Ames shroud. 400 miles on the rebuild running Mobil I 5w-30 with a can of GM EOS and 20 qts. of Mobil I ATF in the tranny.
Before, and after the rebuild, the car gets hot at idle. Will run in the 200 deg. range on the hwy. at 55 mph but as soon as you drop the idle down to under 1,000 RPM it goes to 225 to 230 very quickly. I shut it down at 230 but think it would keep getting hotter if I let it run. I set the idle up to 850 but it didn't help. Had my Harrison 4-core recored and it didn't help any. I ordered a Rodney Red 8 wks. ago and got it last wk. Jerry, the owner, was a very nice guy to work with. Got it installed this morning, used a 50/50 water to antifreeze ratio. used foam to seal the gap around the shroud, went for normal 5 mile cruise route, outside temp. about 90, hoping for the best, and the damn car did exactly what it's been doing! 200 on hwy. and up to 230 in about 3 minutes when you get under 1,000 RPM. I was most surprised that the aluminum Rodney Red didn't lower my temps. any, whatsoever. If I'm setting still in the driveway and boost the RPMs up to around 1,800 it will start dropping the temp. quickly to about 210. My original fan was a 18 in. Flex Fan so I took advice from this site and installed a Hayden #2797 Clutch Thermal Fan and a Hayden #220618 steel fan about 2 months ago and it made no difference with the overheating problem.
So, where do I go from here? I don't know if my temps. drop when you increase the RPM because the fan is drawing more air through the radiator or is it because the water pump is turning faster? How can you tell the difference?
Needless to say I'm very frustrated and don't know what I should do next. I've read every post on this site about overheating and it appears I've done about everything there is to do. If lack of airflow at idle is causing my problem I'm tempted to order a 18 in. Derale #17018 Flex Fan because I've read a lot of good things about it here. Should I ditch the Flow Kooler water pump and try to find a cast impeller NAPA #58-299, 8-bolt water pump, tweak the divider plate the way George K. details, and hope for the best! I've read some positive posts about electric fans but there are some negative posts as well. I really thought, and hoped, that the Rodney Red would solve my overheating problem but it didn't. Sorry for the long post but I would certainly appreciate any help, advice, or suggestions any of you can provide with this matter. Thanks!

I have the same problem and now have ordered a anuminum radiator from Chevellecooling .co they guarantee to run 30 degrees cooler.