I have a built 350, .040 over w/ 400 crank, Edlebrock heads, intake, dual quads- 500 c.f.m. each, hooker long headers into 2 1/2" SS pipes. Had it tuned and re-plugged, carbs adjusted,etc. Now it heats up when in traffic, temp low to mid 80s. when on the freeway it cools down. I have a alum high cap. radiator, and an Edlebrock water pump. When at a stop light the temp guage rises, but moving in town traffic it cools down. I put two electric fans and eliminated the clutch fan. I thought the timing was off, so had it checked again. It has a healthy custom built American cam. Could the water pump be going out? it's a high flow pump. The fans are running in the right direction, and are set to run 100% of the time the ignition is on. :DeadHorse: :givemebeer.sml:

I'm thinking maybe some air in the system?

How hot is it getting? And how many tubes does your radiator core have? Water pumps either pump or they don't, so I doubt you're having water pump trouble. If you have a 2 tube radiator, I would expect you'd see temperatures up to 230 degrees on a hot day. With a 3 tube radiator, expect 215-220 degrees, and with a 4 tube radiator, expect to see 200-210 degrees. I have a 4 tube radiator in my '82 and I rarely see temperatures climb above 210 degrees.

I'd be suspecious of the electric fans ability to pull enough air. For a short time I replaced my mechanical fan/clutch assy, with an electric, and it started overheating while standing still. Plus if you blow a fuse with the electrics, you're dead in the water, (like when my fan fuse blew while I was picking up a date!:doh:...I didn't even get into the ballpark on that one, let alone "First Base".)

My theory on why electrics don't work well with C3s is that the shrouds on electrics block too much air. Junk the electric and go back to mechanical, I'll bet your overheating problems will disappear.:thumbsup:

Metalkid:rockon6rk:

Four core radiator, and there appears to be some big blowing of a lot of air behind the fans. I have a 160 thermostat, and on the road it runs there. In traffic it is now climbing over 230+. The radiator is not new, perhaps the cores are in need of cleaning? It ran fine until the tune up and placing the correct length of plugs in it, adjusting the timing. Could it be the timing with a custom cam? I got the grind, 330 duration, .442 lift. down from a 315 and .473 :-)

What about a thermostat should be a 195 degree

When you say, "got the correct length spark plugs"..correct for what, a stock setup or the Edlebrock System you're running?

I've got a Holley SystemMax II w/Edlbrock Performer Manifold, Performer Q-Jet, Aluminum water pump, and a polished aluminum thrermostat housing. I had to change the stock plugs to ones that were recommended with the Holley SystemMax. Could be length and or temperature of the plugs, but I suspect it might be you mechanic!

If you've managed to make an electric fan system work, (like it was running fine before you took it to the shop for tuning), then I would start checking out your cooling system for crazy things like "dirt in the radiator"...seriously! I've got a buddy who had installed a new cooling system in his Jeep Cherokee, had a mobile mechanic come by to change out something, unrelated to the cooling system. As soon as he ran it it started boiling out, and he found that the mechanic had dumped red clay soil into the radiator! He's spent the last several weekends trying to clean it all out.

If this is the first time you've run the Vette with the new engine setup, and haven't tried the electric cooling system before (like before all the other engine mods), then I would try going back to the mechanical fan/clutch system first, to eliminate that as a cause.

As mentioned above, I tried an electric system, spent $, hassled it, lost a date, then went to a performance shop, where they told me the electrics (back in the day..maybe they're better now...but doubt it) don't work with C3s, the shroud and the framing used to hold the fan motors in place just block too much air, plus you loose the added benefit of the clutch/fan assy, freewheeling (when it's not needed), which reduces engine drag = better performance.

Think about it this way. Stock, you have nothing blocking the air going through the radiator.

Electric: Shroud reduces the avail surface area of the radiator to the size of the two openings for the fans, which is further reduced by the fact that the fan motors themselves are also blocking air. You're effectively taking the surface area of the stock radiator and reducing its effective working area to two donut shaped holes whose surface area is determined by the length of the fan blades. Doesn't really matter how fast the fans are moving, or how much air they're pulling, you're still effectively trying to "breath through a pair of straws". And that won't cool you off at all!


Metalkid:rockon6rk:

The heads had plugs for stock iron heads. The alum heads are thicker and needs a longer plug to fit into the chamber to fire on top of the piston. I didn't have any problems with the cooling system before, ran the system 3 years. I next will have the radiator checked. The block is new from GM, so no old rust kicking loose there. The two fans do reduce the surface of the rad. allowing air through, but it is a larger one, and alum. so felt it was enough. The last thing I'll try is a clutch fan, but it also had a shroud reducing the space of air flow. Is there any way to check if the timing is causing it to over heat? When moving, it cools down, stopped at idle, it gets too hot. I have a 165 thermostat because it normally runs hot. To go to a 185 or 195 may be taking it too close to over heating? I do live in So.Cal. and it do get hot here. The distributer went to an electronic one that connects to the stock casing, eliminating the points. Could I be running too hot or cold of plugs?

The heat range of a spark plug will not cause the engine to overheat.

A 195 degree thermostat will not cause the engine to overheat. It will just get it up to operating temperatures faster than a cooler one.
Reduced or restricted water flow caused by an incorrect gasket can cause an engine to overheat.

Engine timing can cause an engine to overheat.

Reduced air flow through the radiator will cause an engine to overheat.

A properly shrouded and correctly sized electric fan setup is perfectly okay in a C3.

A defective or incorrect radiator cap can cause an engine to overheat.

I have a built 350, .040 over w/ 400 crank, Edlebrock heads, intake, dual quads- 500 c.f.m. each, hooker long headers into 2 1/2" SS pipes. Had it tuned and re-plugged, carbs adjusted,etc. Now it heats up when in traffic, temp low to mid 80s. when on the freeway it cools down. I have a alum high cap. radiator, and an Edlebrock water pump. When at a stop light the temp guage rises, but moving in town traffic it cools down. I put two electric fans and eliminated the clutch fan. I thought the timing was off, so had it checked again. It has a healthy custom built American cam. Could the water pump be going out? it's a high flow pump. The fans are running in the right direction, and are set to run 100% of the time the ignition is on. :DeadHorse: :givemebeer.sml:
i run a 7 blade Stainless Steel flex fan on my 500HP stroker motor . never goes over 180 degree even with a/c on in traffic in 100 degree heat you got to move a lot of air at low speed in a vette elect fans just dont seem to do that

I'd be suspecious of the electric fans ability to pull enough air. For a short time I replaced my mechanical fan/clutch assy, with an electric, and it started overheating while standing still. Plus if you blow a fuse with the electrics, you're dead in the water, (like when my fan fuse blew while I was picking up a date!:doh:...I didn't even get into the ballpark on that one, let alone "First Base".)

My theory on why electrics don't work well with C3s is that the shrouds on electrics block too much air. Junk the electric and go back to mechanical, I'll bet your overheating problems will disappear.:thumbsup:

Metalkid:rockon6rk:
i agree , elect doesnt seem to work w/c3 body to much heat is trapped not enough natural in flow . you got to move lots of air ,i used 7 blade S.S. flex fan w/2 in spacer never goes over 180 even with a/c on

Just you telling my the car cools down while moving tells me you need to get a clutch fan back on that motor and put a 180 stat in the car and go from there. Electric fans do not cut it, especially with the motor/mods you have. If it still runs too hot, then time to step up to a big block rad (4 row). Also, before getting a new rad, check the fan clutch (after sitting overnite you should be able to hear the fan roaring at engine start-up and then slowly fade away, if not get a new fan clutch) clutch fans are very powerful they can consume as much as 8-10 horsepower when working properly. :burnout:

i see all these cars that run 210,220 or hotter, mine never runs hot it gets 110 heat index in louisiana, and my engine never gets over 180 even w/ac on max in traffic at a crawl in the hot sun

You might hava a too small throat opening for a thermostat. Also, if you have a long style pump w/ bypass hose eliminate it. Another trick is to drill 4 1/8 in holes around thermostat and if possible, install a bleeder screw at highest point of cooling system to bleed out all air from system Had this problem w/ my 68 big block and cured it.

I have a built 350, .040 over w/ 400 crank, Edlebroto 2 1/2" SS pipes. Had it tuned and re-plugged, carbs adjusted,etc. Now it heats up when in traffic, temp low to mid 80s. when on the freeway it cools down. I have a alum high cap. radiator, and an Edlebrock water pump. When at a stop light the temp guage rises, but moving in town traffic it cools down. I put two electric fans and eliminated the clutch fan. I thought the timing was off, so had it checked again. It has a healthy custom built American cam. Could the water pump be going out? it's a high flow pump. The fans are running in the right direction, and are set to run 100% of the time the ignition is on. :DeadHorse: :givemebeer.sml:


I am afraid to jack my 375 horses any furthern cause it runs hot also, Have tried every thing, airdam to flex fans hate it, spring in radiator hose missing but it is not collapsing. how about your rear end ratio did you beef it up?

I am afraid to jack my 375 horses any furthern cause it runs hot also, Have tried every thing, airdam to flex fans hate it, spring in radiator hose missing but it is not collapsing. how about your rear end ratio did you beef it up?
im running 383/500hp never goes over 180 degrees.even with a/c on

my trans is 4 speed manual, wonder if that affects cooling motor? art

my trans is 4 speed manual, wonder if that affects cooling motor? art
should run cooler w/4spd doesnt have to cool trans fliud w/radiator

Sorry about getting back to you on your suggestions, I'v been quite busy. You hit the problem on the head. I have a 350 block and heads, and the builder put 400 CI gaskets on, blocking the steam holes, thus blocking water flow to the heads. m Lucky I noticed it right away and was able to get it to the garage for a complete go through. New gaskets, no heating problems. Now I'm waiting for the new 5 speed trans to come in so I can have some fun in the sun. Thanks for your help.

I'm thinking maybe some air in the system?

May I ask what the color is of your Vette? Looks purple in some pictures. I own a '73 which has a custom paint and I'm thinking the color might be close to yours if its a purple, plum.