302 Engine Runs Hot

[frainsg]

I have a 302 2bbl engine in my mustang II. It's bored 60 over and currently has an edlebrock performer 3721 4 bbl intake and a Holly 4010 carb. The rest of the engine, cooling and exhaust is stock. I've gone thru the cooling system extensively and I think everything is new and works properly. However, when the outside temperature passes 90 degrees I quit driving due to the temp guage hot reading needle deflection - especially at idle in traffic. It goes down driving around 40 and heats up a little at 60. I have the shroud, lower chin air deflector etc for good air circulation. I open the hood and can feel that the engine is hot so i don't suspect the guage.
I think the source of the problem is the rear water passage on the edlebrock manifold has a water passage that the stock manifold doesn't have. This water passage keeps hot water in the back of the engine longer. This would be a water flow problem that didn't come with the original engine design.
My winter project is to replace the cam shaft with a similar spec cam. I am going to put the original equipment 2150 carb and oem manifold back on. I'll post an update in 6 weeks or so.
Does anyone else have a similar experience??

[Administrator]

Have you thought about putting in an electric fan? This could help with the heat especially in traffic on hot days.

[frainsg]

I have been collecting parts to get the engine compartment stock, and would rather not put in an electric fan. I've looked at the fans in the Summit catalog and am keeping it in mind since it'll get hot soon. I wonder if the problem could be as simple as a clogged air conditioning condenser mounted in front of the radiator. I haven't taken it out ever in 33 years. I thought I'd get the A/C working after I nail the engine hot problem. I'll review the condenser when I replace the cam.

[GEE TEE]

You didn't say what year your car is or whether or not this is the original engine. That's important because the manifold you have is for EGR equipped cars. The Edelbrock Performer 2121 is for non EGR cars and doesn't have the water jacket crossover at the back. I haven't looked into what possible effect that may be having on your cooling situation, but it could be a problem.

You said that you are collecting parts to return the engine bay to stock. Are you trying to achieve concours correctness, or just a stock appearance? If you just want a stock appearance, then doing things like putting in a better 3 or 4 row radiator can help in the cooling department. What fan do you have? You said there is an A/C condensor, do you have a 7 blade clutch fan? Have you checked/replaced the fan clutch? Have you tried adding Redline Water Wetter coolant additive? It's usually good for a few degrees of cool.

You said you will be putting on the stock 2V intake manifold. Is that to achieve a stock appearance? You'd be suprised how stock an engine can look if you just paint your aluminum manifold Ford Blue. No one will notice unless they look carefully.

[frainsg]

GEE TEE,
It's a 1975 with California emissions engine. The short block and heads are original. I have the original accessories attached with the exception of the AC pump disconnected. The stock engine had EGR and currently has EGR. The 3721 has EGR and it also has the cross over water passage in the back. I pulled a correct cast iron manifold, numbers matching and dated 1975, with EGR passage, from a mustang II and it doesn't have the cross over water passage. I'm collecting parts to return the engine compartment back to concours stock. Fortunately, I never went far with mods (carb and intake, only) and kept most of the parts I removed. I actually recored the stock radiator with a 4 row and got no improvement. I have water wetter and again, no improvement. I think I'm supposed to have a 16 lb radiator cap, but had on a 14 lb cap. I put on a 13 lb cap and it seems a tad hotter. I think I'll get a 16 lb cap! The engine comes with a fan clutch which I took off to see if running the fan faster helps. Can't tell a difference.

Maybe I just need to yank the engine and give it a good flushin'.

[GEE TEE]

Frainsg,

Sounds like you have pretty well gone through the cooling system, although you didn't specifically mention the water pump. As for the radiotor caps, they won't make a difference in how hot the engine runs, only whether or not it boils over. Seems that each PSI pressure increase raises the boiling point of the coolant slightly so that it won't boil over, even though it exceeds the normal boiling point at atmospheric pressure.

Here's something else to check. Ignition timing too far advanced can also result in overheating. In addition to checking timing with a light, make sure your vacuum advance (and vacuum retard if you have a dual diaphram unit) are working properly and their vacuum sources are correct, i.e. manifold or ported vacuum. There may also be devices in line with the vacuum source such as a coolant temp vacuum switch that varies vacuum application based on engine temp. I hope you have a vacuum diagram for the car, you're gonna need it. On a related note, you said you will replace the cam. Does that mean that you currently have some sort of performance cam? Do you have low vacuum at idle? That could also impact ignition timing, especially with a dual diaphram vacuum advance unit.

If all checks out with the ignition timing, maybe your fuel mixture is too lean. That could result in heating up at speed, although I'm not sure it explains the problem at idle. With the Holley, that means removing the float bowls to change the main jet sizes; a messy operation at best.

One other thing. Do you have the correct thermostat installed? If so, when the engine warms and coolant starts to move through the radiator, does the temp gauge read in the normal range? Does it stay at that same reading other than when it starts to overheat? A nice cool day would be a good time to test this. That would give some idea that the gauge and sending unit are providing reliable information.

Good luck with the troubleshooting.

[frainsg]

GEE TEE,
Back in 2004 I pulled the heads off and got a valve job including all new valves of the same size. The old valves had a ton of carbon deposited on top like black hard whip cream. The engine has more pep now. I replaced the water pump then and the "new" one has about 4K miles. I do not have the correct thermostat. The one I am running is 160 degrees. The master parts book says I need 195. When I put a 180 in it seems to be a little hotter running. I have a new temp sender and tried to grounding the wire, opening the wire, measure sender resistance, and am not 100% sure but think that the sensor and guage are telling the truth. I have the shop manual set, the master parts book, the illustrated parts book, and wiring manual. I bought them from a guy in New York who gets them from places typically switching over to CD. They really, really help. I also have the vaccum schematic for my california car. It's very messy with mid 70's spagetti routing. You mentioned the timing. I forgot to include that the distributor is replaced with an aftermarket mallory with a single diaphram vice the stock motorcraft with dual diaphram. I can't seem to get idle vaccum above 19 inches and read in a recent MCA monthly "good carbs" that a healthy 302 engine should produce 20 1/4 inches. The cam is the original and has 240,000 miles. With an engine rebuild at 180,000 the cam mic'ed okay. I suspect its worn and may be contributing to lower vaccum.

One thing to note, and I drove the mustang into work today seeing this, when the temp needle rises off of cold it moves a little hot then settles back down to less hot. This happens consistently from a cold start. I think it supposed to mean there is air in the cooling system. I have an overflow tank which has helped a lot with purging air. I've driven it a couple thousand miles and no more air is pushing out. That's why I tried a 13 lb cap, to see if any air would come out, and check if the 14 lb cap was stuck. I still suspect there is air in the cooling system trapped. Trapped in the cross over?