302 overheats at low RPM

Hi all,

I just bought an '89 fiberglass Austin Healey 3000 replica with what I think is an '84 Ford 302(5L) engine, a C-4 transmission and a Ford 8- inch rear end. Cooling is handled by a 3-core aluminum rad, an electric "puller" fan and a stock water pump. Driving it home from Toronto to Ottawa after buying it, it ran between 193 and 197 degrees at speed. When I slowed down however and was in stop and go traffic, the temp gauge went through the roof burying the needle at least twice (althought the engine didn't shudder, knock or stall). As soon as I sped up, the temperature went right back down to the mid 190s. I wasn't sure if the problem was due to the fan or water pump since I didn't know if it was the faster turning of the water pump due to higher engine RPM or the greater airflow through the ran caused by the higher rate of speed that cooled the engine down at higher speed. Easy enough, I just revved the engine when I was stopped at a light. I found that, even stopped, if I kept the engine RPM over 2000, that kept the temp down. I think that indicates that the water pump is the culprit (since electric fan speed is not tied to engine RPM. So what should I get? My choices seem to be between an new stock pump, an aftermarket mechanical pump from vendors like Weiand, Edelbrock and Flow Kooler, or an electric pump for ProComp, Proform and others. Right now, I'm leaning toward an electric one (35 GPM) since they are not tied to engine RPM like the mechanical ones. I am looking for advice with respect to this problem. Which way should I go? Will I have problems with things like mounting my alternator or with the alternator belt (since the alternator will be the only accessory driven by a belt if I go electric)? Any help would be greatly appreciated. Thanks.

Richard

Reply to
lxixboss
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Before you start swapping pumps, take a look at the rest of the engine first. The austin healy has a decent sized radiator opening, so air flow should be good. A close to stock 302 doesn't produce that much heat. And you have a large radiator. That combination should idle all day and not overheat.

First, make sure the fan comes on when it's supposed to. And make sure it's actually pulling air. It may be wired backwards and pushing air instead.

Second, look for all the reasons an engine would overheat: running lean, timing incorrect, clogged cats/exhaust, etc. If you have underdrive pulleys, get rid of them.

Third, check to see if you're building up pressure in the coolant system - a symptom of a blown head gasket.

Finally, make sure the radiator is full of water. It should be about the same temp from top to bottom. If it isn't, then it has too much air in the system. Needs to be burped better.

If all that checks out, then it's time to change parts. Start by changing the thermostat. If you have EFI, use a 195*. If a carb, you can go down to 180*. Be sure and drill a 1/4" hole in the base plat so the system will burp on it's own.

If all that fails to correct the problem, then change the water pump. A standard stock replacement from Autozone (or where ever) is inexpensive, works fine, and has a lifetime warrenty.

Reply to
.boB

he could have a poor radiator, I got a performance one from the west coast, and it ran hotter, because it has some scale in it, went and got another, and it was OK.

Sounds like the Fan is wimpy. they draw too many amps, I like the non-electric kind. Could be water pump too.

bottom or top? of the thermostat plate

Reply to
Mas Plak

Mas Plak wrote: Be sure and drill a 1/4" hole in the base plat so the system

I place it at 12 o'clock.

Reply to
.boB

".boB" wrote in news:47018259$0$24904 $ snipped-for-privacy@news.usenetmonster.com:

1/4" is too big. I changed the temp rating of a thermostat by 10 degrees once with a hole that big. 1/8" is plenty. All you want is a hole for trapped air to escape through.
Reply to
elaich

Question: My water inlet/thermostat housing has a hole in the atop fitted with a bolt (recessed head for a socket or whatever) Is this what you are discussing regarding drilling a hole. Mine (cast iron) came this way from NAPA.

Reply to
Spike

No, they are talking about drilling a SMALL 1/8 inch hole in the thin metal thermostat, ) (on the flat rim, not through the working parts) to allow air/super tiny flow through the thermostat at all times, weather it is open or closed...

Reply to
My Name Is Nobody

Spike wrote in news: snipped-for-privacy@4ax.com:

No. That is a hole for a temp sensor. We are talking about drilling a tiny hole in the thermostat plate itself.

Reply to
elaich

Got it. Thanks for clearing that up.

Reply to
Spike

Overheating problems require as a first step a proper radiator inspection by a competent technician. Until that is eliminated further steps will be a waste of time.

That said, I am not sure of your configuration, but often times over heating problems in "Ford Exotics" are due to limited air flow and improper shrouding or ducting. Often a very inexpensive solution is a cheap plastic 6 bladed fan. Other solutions may require a larger radiator or additional sheet metal work to reconfigure the ducting or shrouding. I doubt that the water pump is your problem. The water of course absorbs heat from the engine and dissipates it thru the radiator. In any "heat exchanger", there is a optimum flow rate for maximum efficiency. Too great a flow and the water may not have time to dissipate heat thru the radiator. At least, that is the way it was explained to me.

Ron Patterson First time on this list

Reply to
Ron Patterson

"Ron Patterson" wrote in news: snipped-for-privacy@corp.supernews.com:

Agreed. Here's something I forgot.

A perfectly normal appearing radiator can be defective, if it was overheated before. The excess cooling system pressure balloons out the copper tubes, and decreases airflow through the core.

Reply to
elaich

I saw a site for foreign cars with American engines (don't remember what it was called though) that said that the car you are talking about needs a stock fan and a good shroud that is not hacked apart. Look on google and search Triumphs or MGs with American engines. there was a link on the site to solve cooling problems with those cars. And BTW they said the stock water pump works best in this application.

Reply to
Les Benn

Take a look at the original posting. He has an AH replica. (Probably from Classic Roadsters, but doesn't say.) Stock pulley mounted fans don't work well, because you'de need such a long shroud. And he already has an electric fan.

Reply to
.boB

".boB" wrote in news:4703ad4f$0$24891 $ snipped-for-privacy@news.usenetmonster.com:

I don't trust electric fans. A stock fan moves much more air. And, his descrription of the car overheating when stopped in traffic, but being fine on the highway sounds exactly like a problem with the fan.

Reply to
elaich

Depends on the fan. I have an electric fan and have no over heating trouble even in the summer with the AC running and under drive pulleys.

Reply to
WindsorFox

Auto zone used to have them years ago, had a small loose rivet in the hole also, helped to open the valve, but they don't have them anymore.

Reply to
Mas Plak

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