I finally got my 50 Chevy on the road, but she's running a bit warm at speed. The fan won't turn off while im driving at speed, even on a cool 80 deg afternoon. I'm sure I have an air flow problem but I'm not sure how to solve it. Around town it's ok, the electric fan will cycle on and off even with the a/c on Pontiac 350, 400 heads #13, no egr, 12 deg base timing, vac advance to manifold. 5" wp pulley 8 crank, 180 deg stat that I just tested. The fan switch is in the intake manifold 200 on 185 deg off. The radiator is a newer 28" x 18 brass cross flow, 16 lb cap (it hasn't puked yet) I do have the radiator tipped back a bit at 18 deg to try and clear stuff. The Taurus fan covers the whole core except for 3.5" on the drivers side. I added a filler piece to the hood brace to try and keep air from flowing over the top of the radiator. Friday night I whipped up an air dam under the radiator that hangs 3" below the bumper. This helped a little bit. I'm working on filling up the 2" gap on the sides of the radiator. Do you guys have any other ideas for me to try? Posted using the Full Custom H.A.M.B. App!
You are on the right track by filling in the top and sides. Incoming air is always going to take the path of least resistance and go around a radiator if possible. your goal will be to MAKE all of the air go through it. if it isn't a new radiator, have it pulled apart and rodded out, as I have seen what looked like otherwise pristine radiators plugged to the gills.
What I tell customers with hot running problems is that the air pushing through the rad at 40 mph is waay more than any fan can do. Your car isn't technically overheating, it isn't barfing green stuff on the ground or exhibiting any of the usual overheat symptoms. I'm old enough to have worked on that engine when those cars were new. One I had that ran warm turned out to be a timing problem. Have you stopped to check that initial and centifugal advance are spec? It takes a timing light and a clean timing scale and pointer on the engine. A loose timing chain can retard the cam and ignition timing causing weird overheating problems, as can a jumped tooth on the timing gear. My shop we always start with pressurizing the rad with a cooling system tester. No doubt the Chinese make these now and you can buy a cheap one. We also have the advantage that we do smog check and can use the infrared tester to check for blown headgaskets by sniffing the radiator coolant hot.
Not real sure the radiator is sufficiant for that thing. If it is a wrecking yard pull out, it is probably restricted.... I only say that because you said it was a "newer" radiator. WHat did the radiator come out of???
Hit the radiator with a temp gun. If its plugged up the temp gun will show you. The center of the radiator will be cool. Are the fans running while its on the highway? They Probably shouldn't be. Posted using the Full Custom H.A.M.B. App!
Hot at speed usually indicates inadequate coolant flow. Hot when slow usually related to air flow. How hot is hot???
By hot I mean over 185 deg, the fan won't turn off when running 50 to 70 mph. As soon as I stop it will run for a while then cycle off. It's definitely not overheating. I've hit the thermostat housing and the radiator tanks with my little infrared gun at idle, 180 and 140 respectively. The radiator is out of a friend of a friend's wrecked 72 Impala He got it new and ran it for 2 years before parting it out. It looks brand new inside the tank. If I can't get this solved this year, I'll pull it and have it cleaned out. I didn't verify the cam timing, but it pulls 16" Hg here in Colorado. Can too much advance cause it to run warm? I recently installed an adjustable vacuum can to keep a bit more advance idling in gear with the A/C on. Here are several pictures to show you what I'm up against. 1st is the hood brace filler, then the lower hardboard air dam LOL, the lack of clearance then my next test is to really try and seal up the top of the radiator
I installed an electric fan on my 400 Pontiac that does 12 seconds in te 1/4 in a 3810 lb car. It sucked at cruise if I turned it off. There was no damned way that the air was going through the radiator. It was a Mark 8 Lincoln 2 speed fan. Even when on it didn't cool. I went back to the factory power flex fan and it stays at 160-175 with a 160 stat. I'm guessing that most of the air is slamming into the face of the radiator and not going through it. With a mechanical fan, it always pulls air through it. The tighter the fins on the radiator, the harder it will be for just a natural airflow to push through. I have 4 Pontiacs and they all run nice and cool. I run 160s in all of them and have been ever since reading the old Pontiac Performance books that you gain 1/10 in the quarter from going from a 185 to a 160. If aat all possible I'd run a 160 stat and a mechanical fan with the blades 1/2 way in the shroud. Also the water pump divider plates need to be clearanced for the pump to work efficiently. What stat ar you running as the temp usually will run 10-15 degrees hotter that the t-stat number. This number is when the stat just starts to open and will open all the way in that 10-15 degree's. The only reason I went to an electric was just to try and gain a bit at the track by freeing up some Horse power. It wasn't worth it and I never did try it at the track. To me I'd rather have a cool running engine than to gain maybe a .10 sec at the track. I did put a pusher fan on and it proved my theory about air hitting the radiator and not going through. The air would part your hair above the radiator and you couldn't feel it through the radiator. It didn't have a shroud so I built a small one . I used it only while sitting in the staging lane to get my temp to 160 continuously. All my cars run 10.5 compression on pump gas and run cool! with no electric fans. Just the factory stuff.
180 deg stat. Isn't 160 a bit cool for a mild street engine? I wish I had room for a mechanical fan. Tell me more about this spacer plate! I'm a Chevy Buick guy. I haven't pulled the water pump off this yet. I'm off to google right now Posted using the Full Custom H.A.M.B. App!
As TRW said, the electric fan might actually be inhibiting air flow. Take it off and take a test drive. If it's better, you know that's at least part of the problem. If it doesn't help, I'd say you have a coolant flow problem rather than an air flow problem. Leave the radiator cap off and view down the filler neck when the thermostat is for sure open. There should be a torrent of water flowing by. If not, it's probably a coolant flow issue. Or the timing is too far advanced...at speed.
160 is not too cool. I have had them in my cars since 1980. I had one with 260,000 and when I sold it, it was running good but I stepped up to a bigger higher HP engine. the guy didn't want the valve covers and so we yanked them off. The guy said, are you sure it has 260,000 miles on it as the cast iron still looked like brand new. Even in the winter, the heat will blast you out of the passenger compartment if you leave it on. Try a 160 stat and see what happens. The electric fan won't come on until it reaches the sending units temp on the fan anyway but at least your fan may not run when heading down the road. I have 2 electric fans on my 1936 Ford . One pusher and one puller as room like you is non existent. I run a 160 stat and a 180 sender of the fan. It never gets hotter than 180 and usually runs at 160 on the freeway. I think you may be on the right track with blocking the air so it goes through the rad. The divider plates usually end up way off the impellers as there is no quality control on the rebuilds. So you need to look at the clearance between the impeller and water pump fins. I set mine to .020 and they have been as far off as 1/4 of an inch. You just tap the divider to get it closer to the impeller. I have heard tht people will get down 15-20 degrees just with this correction but...... I believe thats at idle. Another thing that it could be is that you are running way lean but aagin, I think its the air hitting the radiator and sliding up over the top. Oh and my car that I was talking about is a mild street driven car. Only raced at the track a few times a year but always driven on the street.
Nope I had it as a puller. And the factory fan shroud from the Lincoln Mark 8 fit the radiator like it was made for it. By all accounts, this thing should have cooled global warming!! It would fricking blow air!! But it just didn't work. So I went back to the tried and true factory set up and temps went back down to 160-175 max. sitting in 100 degree traffic for hours. I swear if I looked down and saw the temp at 180, I would freak thinking something was wrong!! LOL!!
Also if the cooler stat doesn't work, take the water pump off and check the divider plate. The water pumps that work the best also are the cast Iron impellers, not he stamped ones. You can still get the cast ones but its a hit and miss at the auto parts stores.
I also buy the high flow 160 stats.They open way more than standard ones. http://www.jegs.com/i/Mr-Gasket/720/4363/10002/-1?parentProductId=744369
If it doesn't overheat in traffic or stoplight driving but it does out on the highway the radiator is plugged or two small. This may or may not pertain to you but water jackets are hard to clean. When engine get rebuilt the hot tanking will loosen up up crud but not get it out. The person installed the fresh rebuilt engine and immediately wants to put a new radiator in. The crud starts flowing through the system and starts slowly plugging the new radiator. The person will chase everthing under the sun except the radiator because its new and extra capacity and aluminum etc. etc.. Long story short if you rebuild an old core engine its a Good idea to run it with the old radiator for a few hundred miles before you install the new one. Obviously your tune has to be correct, but if cars that overheat at speed but don't overheat during spotlight to stoplight type driving have radiator issues.
Here's a link to save me from trying to detail pictures and post them. http://www.wallaceracing.com/water-pump-mods.php The way his radiator is slanted makes a natural slide for the air to hit and flow off the top and not through. Also he is running a 180 stat and the temp gets only to 185 and the fan doesn't turn off. It's actually not overheating. After reading your posts again............... The engine is working harder and the air flow doesn't go through the radiator at speed so the fan stays on but still only gets down to 185.( Heres the problem) It isn't overheating but the fan sensor and the T-stat are too close. At 180 the T-stat just starts to open but at 185 I doubt it is open all the way and the fan keeps trying to cool it but the T-stat keeps closing and restricting flow. Get a cooler stat to start!!!!
Thanks guys. And thanks whippet, I found that site also. I don't think it's running lean, it's not surging at speed and I haven't changed the metering rods for my altitude yet in the 1404 500 cfm edelbrock carb. Since the stat is out right now, I'll pick up a 160 to try tonight. I'll also get a pump gasket to take a peek at the divider plate if that doesn't work. Thanks guys Posted using the Full Custom H.A.M.B. App!
One more thing that caught my attention while I was reading about the pump plate. Could air trapped in the upper rad hose cause this? I've got the radiator mounted quite low so it will clear the sides of the hood. The top of the cap is really close to the same level at the thermostat, so the upper hose would have air in it. I've run it without the cap on to try and purge it.
that 500 Edelbrock is sort of small for the 350. You should get a stock Q-jet or at least a 650 Holley. I had a 650 Spreadbore double pumper on a 350 Pontiac and had to richen the jets bigtime. It hauled for a little 350. This is the one that I put 260,000 miles on and sold it as a good runner.That thing would see 6500 RPM every day and loved it. The 400 I have in its place is a non ported 400 that was built as a stock rebuild in 1991 and does 12.5s at the track, 0-60 ft in 1.60s and 0-60 mph in 3.8 seconds. I even added a 150 shot of nitrous to it and am now at 11.75 with a real poor nitrous shot. That poor motor puts out 408 HP and then another 150 nitous shot. So thats not too bad for a $999 rebuild that was built in 1991 and still kicking ass. The rest of the car has a used TH 350 that cost $150, a sock 8.5 rear end and has a weight of 3810 lbs. The carb on it is an 800 Dbl pumper. Pontiacs like bigger carbs even though their ports are small. The rear wheel dyno showed a 13.1 on the wide band throughout the pull untill I hit the nitrous that ran it below 10 on the wide band. I just have too much fuel pressure on the nitrous circuit. ( Seperate pump). I'd change the stat and see what happenes before any other changes. And by the way, alot of people have their temps run around 200 -210 and say that its fine. Its way too hot for my liking but some people do run these temps. Also I'd run the vacuum off a ported source.
I think you may be working a solution for which you have no problem. 180 to 200 is a pretty good heat range for a pressurized system. Are you sure your gauge is accurate? If it says 190 but reads 180 at the therm housing, you might want to consider that you have an optomistic gauge. What part of colorado are you in? At 8000 feet, your readings may be a bit off because of that. Where is your timing set, that can have an effect on running temp. And remember the thermostat will only have an effect on when it opens not how hot the system will eventually get. As an aside are you familiar with the Tommyknocker Brew Pub in Idaho Springs??? One of our favorite places in Co.
My Dart was running hotter on the Highway than around town...went thru all the cooling stuff..cause it needed to be done anyway. I was running to lean..rejetted the carb and now it runs the proper temp on the highway...so make sure it's not running lean.
That engine is sitting way to high in comparison to the radiator... besides that, I wonder about the 400 heads.... Your carb is the same one I am runnin. I have no problems, but my engine is way lower. you have trapped air
Or in rare cases, to much coolant flow, not allowing it to cool before leaving the radiator. At idle the coolant has slowed enough to cool off. At highway speeds the pump is pumping faster/harder and moving the coolant to fast through the radiator. Just a thought. I have seen it happen.
THIS! Running fine around town w/AC on but hot at speed usually indicates not enough (or clogged) radiator
You all can laugh all you want....Is the spring still in the bottom hose? More than once I've seen the water pump suck the bottom hose shut at speed and restrict flow. When I worked behind the parts counter we had a customer chase his tail for awhile until he replaced the bottom hose just because "he wanted a better looking hose." No other changes, cooling problem solved.
Unless you have a filler on the thermostat housing there is no way to eliminate air in that top hose. You don't want air in the system. I have found that unless a radiator is well flushed when removed any deposits will harden if left for very long. Cooling problems at speed are usually due to not enough capacity or a clogged radiator.
I'll bet if you remove that fan shroud, your engine will run cooler at speed. I just cured the same problem on my 47, after chasing it for 5 years. Your electric fan is right up against the rad core, and air from the corners of the core, has no way to go through, or around the fan. Fan shrouds only work when the fan is mounted on the engine, space between the fan and the core.
I indicates 15 degree hotter than measured. I'm at 5600' along the front range area. The only problem is the fan runs continuously. I believe it's running right at 190 ish on the highway, right above the off temp of the switch. So either cool it down a little more, or get a hotter switch. I'm going to try and cool it down a bit first. YEZZZIR! been there, done that Agreed! I tried burping it again after putting in a 160 t-stat last night to no avail. It shows turbulence in the radiator tank once the stat opens. The internet says an air pocket in the upper hose is worth up to 20 deg. One of those in hose fillers is on order. That way I can burp and fill it better. The heads do bump compression, but besides that why? The block is a 75 350" and the heads are '70. my research shows no compatibility issues. If the hose filler and air management doesn't fix this, that will be next along with pulling the water pump to check the condition of the divider plate. The radiator is a 3 core cross flow and has a 28" core width. I'm pretty sure they don't come any bigger No spring, new corrugated universal hose. Thanks guys, I'll keep you updated as I work my way through this.
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