Im running a 2 core rad, a flex fan and a 160 thermostat with my 350. When the car's rollin it runs at 165-170, but when it sits at idle it starts to heat up right away(I had to leave it running at idle for about 20 mins at a smog test the other day and it ran up to over 200). What do I need to change to fix this? More rad, electric fan or what?
radiator could be partially clogged. flush it and see if that helps. I don't think new radiators are too expensive..under $200.
cooling temp at 200 degrees at idle is safe . u may need to flush the rad & block . 3 years ago after i had just purchased my gs 350 , i had to replace the water pump . i removed the rad and flushed it from the top & then the bottom. u should have seen the crap that washed out of it . then with the water pump & thermostat housing removed, i flushed the block thoroughly. what a mess of sludge blew out of the block ! i do not know how the engine ever cooled . last spring, i installed a set of guages - temp, oil pressure, voltage . my car runs about 180 on the road & can run over 200 at idle . i replaced the aftermarket fan with a proper 6 blade which sucks far more air through at idle . the temp will still climb well over 200 if i let it idle for a period of time. the only other change i made when we performed a whole lot of work under the hood last winter, was to toss away a huge old tranny cooler that had been installed years ago & reconnect the tranny line to the cooler side of the rad . another problem that can occur, is that an air bubble/air lock can be formed when u refill the rad with coolant . u need to drill a small hole in the collar of the thermostat about a quarter inch in from the outside perimeter . one of the guys attached a picture of a thermostat where he had drilled . this allows the coolant to fill the block & stop an air lock .
You might want to go to a heavier radiator. A 2 core stock radiator will have a tough time keeping up with a 350 , especially modified. Mine did the exact same thing at every stop light. I flushed it and it hel[ed a very small bit. I replaced it with a new radiator and it cured it. Mike
ok, i have the same prob with my '66 300. on the road, it will cool down to 160 or so, with no thermostat, or a 160* one. I tried both ways. But no matter what, it can cook up to 230 at idle, even in 20* temps outside. i have new water pump, flushed block and replaced all hoses when the pump went on. So i figure the now 37 yr old radiator has bought the farm. I checked the summitracing catolag, and they have a aluminum radiator in the same size as my stocker. it is listed in the hardcore race parts and sold as a summit brand part. the 2 row tube alum. style rad. is supposed to be better than a 4 row copper/brass one. The best part is that it is CHEAPER ($169.95) than a stock replacement. The bad part is that it does not provide for transmission cooling, so i get to install the trans cooler i have been wanting to get. I got a cooler for a class "A" RV up to 24k lbs. and will run it in front of the rad. The next thing will be to install an electric fan, but since i ordered it today, the rad. should arrived by wednesday, and with summit, the shipping is free!!! Lets hope all cooling issues are resolved before those summer temps arrive. a conv. is not fun when it can't be driven in the sun!
Unless you don't have the room I would suggest staying with a stock fan and clutch. I had a 12.5:1 455 stay cool with a 4core and the stock fan. hope this helps
Stupid question, but have you checked the rad cap? If you're not at 15 lbs of pressure it'll heat up fast...
Over heating, thanks for the info hello all, and thanks. I just logged to ask the very same questions that 'grey' asked. I have a 455 in our 56 Buick, it too creeps up the scale in traffic/idle. I have fitted an electric, but this is not as good as the flex I took off. But I will go by your advice and obtain a standard clutch fan and shroud of an orginal car. This leads to the next question, where are the best places to buy a second hand fan assembly while I am in the states CA, LA mainly and a couple of days driving to and from Las Vegas. Is Memory Lane the best place? Ausie boy, Bruce
most of the time when you run cool down the raod with air being forced through the radiator, but the temp climbs from idleing sitting still. it is most likely a fan problem or a shroud problem. 99% of flex fans arent worth their weight in scrap. they flatten out at high rpm not puling much air when you are working your motor hard like when drag racing. at idleing they dont pull much air due to poor blade design. they rob you of a lil power at the bottom end because they are just more rotating mass that your crankshaft is being taxed with. its always amusing to see someone who has dropped major bux on lightweight connecting rods in their motor and then they have a one on the heavy stainless steel flexfans stuck on the front of their water pump. unless you are frequently turning more than 5500 rpm, use a stock clutch fan that is thermostat controlled with the correct shroud... it will spin firmer when your motor is warm and free up a little when your motor is cooler. it will let you accelerate good by not being a solid rotating mass problem. good shrouds are a must, especially when idling. no waterpump mounted fan is gonna help you idle cool without a good shroud. dont you think if flex fans were such a good idea that automakers would use them on cars .... so much cheaper to make. if you have room, properly installed electric fan systems work real well. rotsa ruk!
G'day Yuk, thanks for the info. Yep, agree, although not being a drag racer had never thought to the depth that you have outlined. I hated the flexi that came with the motor, and that is why I put the electric fan on. unfortunatly, this does not seem to be holdingup to the manufactures cliams. So, these things are hard to get in Australia, so I will be looking a good system when in visit CA next month. Do you have any preferences for a rad size 19"x19" for a 455 near standard rebuilt unit. I am mostly quite driving this with the odd ocassion towing a vehichle trailer. thanks for all your info Bruce
all electrics are not created equal... if you check the amperage they draw they not only vary from fan to fan but even when you have fans that claim to be reversible sometimes will have drastically different currents draws for each direction. i would like for someone (maybe me) to take a few fans and test how much cfm they move in each direction ... i bet most people would be surprised. as for you radiator, people might talk bad about you behind your back if you put less than a 4 core in front of a 455 that will be doin a lil towing. i would even add an external transmission cooler of a heavy duty nature. if you have winter temps under 0 degrees celsius for more than just a couple days per year, run the tranny cooler in series with the radiator's built in cooler. if you winters are mild. run the external tranny cooler as you only cooler. B&M, Transdapt, and others make some nice ones .... when you weigh the price of a good tranny cooler plus a good radiator plus a good fan against the price of a good tranny rebuild it is still money well spent.
Whats your timing like at idle? Are you running a vac. advance? I reconected my vac. advance at the problem was solved immediately, stays at 165 at idle. Stock rad, flex fan.
my motor compared to yours is like comparing apples to oranges for the most part. my 74 lesabres' new motor tranny combo is a late model throttle body injected chevy 350 with a factory roller cam and 700R4 tranny. if you have vacuum leaks on a motor, you can have all kinds of irregualities and a heating problem can be one of them. leaning out a fuel mixture can cause heating problems severe enough to burn a hole through a piston or head gasket trashing the motor. i have seen motors leaned out so bad that the center of a spark plug melted and blew out of the spark plug housing. inspection of all vacuum hoses and carb base gaskets could be time well spent.
Another insteresting test is to hit the radiator with a garden hose (well the water actually) while idling, and see if that brings the water temp down. It *should* bring the temp down drastically - if not, you probably have poor circulation, most likely a clogged radiator. If it does bring the temp down quickly, then your radiator is just too small. (The water gives you the effect that you have a very huge radiator, water will take a *lot* of heat away from the radiator as long as the coolant is flowing properly through the inside). It's kinda a subjective test, but may give you some insight. -Bob Cunningham bobc@gnttype.org
