[WeCruzin69]

I have a 350 small block in my 69... I never did have an overflow tank for my radiator (I don't think it ever came with one) so I installed one of those chrome cylinder looking overflow tanks. Anyway... for some reason, I overheat when sitting in traffic for a while - like say at a drive through or something... and it pours out of the overflow. I do have a temp gage installed, and at normal cruising - the temp stays around 190-200. When sitting still, and barely moving, after about 5 minutes, the temp starts to go up to 210-220 area, and then that's when it starts pouring out. I have installed a new thermostat... I have a new Eddy aluminum water pump... a new aluminum radiator... The timing is dead on from what the engine specs call for, so I don't think it'd be any of those... I'm wondering if it may have something to do with the radiator cap... should I be using a vented or un-vented cap? I believe I have a vented one on it right now. I think I'll try the un-vented and see what it does, but I'm just curious of any ideas I could check as well before I really do cook something... Thanks.

 

[Dean]

Are the fan blades part way out of the shroud?

 

[atle]

190-200 is pretty high for normal cruising. what temp stat do you have in there?

and when you did not have the overflow tank did the temp get up high like that?

 

[pnugene]

Are the fan blades part way out of the shroud?

Do you have a shroud? What type fan/clutch, what camshaft are you running, initial timing and advance mechanism? Retarded timing and lean mixture can really cause problems with temp.

 

[WeCruzin69]

I did have the problem prior to the overflow tank - it would just pour onto the ground instead, which is why I put it... but I have no idea what radiator cap was on it... so I just replaced it with a vented one because I was under the impression that's what I should have with an overflow tank. However, when I had the problems prior to the overflow tank being installed, I was also still running the bone stock radiator, and water pump. I do have a shroud (repro stock 69 shroud), also a steel bladed flex fan - not one of the flimsy light weight ones - and yes it is in the shroud and not part way out of it... If I remember right - I have a 185' thermostat.

Timing is at:
12' BTDC
34' Total BTDC

Camshaft is hydraulic flat tappet /
Camshaft Lift .450 intake/.460 exhaust
@.050 duration 222' intake / 222' exhaust

Here is the rest of my current engine set up:

4 bolt main 350 Engine
Stock 4" bore
Stock Cast Dished Aluminum Pistons
Cast iron Crank
Stock stamped (self aligning) Rocker Arms w/1.5:1 Rocker Arm Ratio
GMPP Vortec 060 cast iron heads (64cc)
Edelbrock Performer EPS Vortec Intake #2716
GMPP .028 head gaskets
Edelbrock Aluminum Water Pump
HEI Ignition
Proform 141-130 polished aluminum valve covers
Stock Fuel Pump
Holley 670 Avenger Carburetor
Heddman long tubed tuned headers (1 3/4" primary pipes w/3" collectors)
2.5" Magnaflow X-pipe dual exhaust

 

[pnugene]

By vented, I assume you're talking about a lever-release type cap. All radiator caps are designed to vent beyond their pressure ratings. Buy a 15lb. standard cap for it. Your fan blades should be halfway in the shroud, not all the way in. A shorter fan spacer may help a lot. Your engine will probably respond favorably to more initial timing, maybe 16-18 degrees BTDC. Make sure the idle mixture isn't leaned out. Several small changes can make a big temp difference.

 

[WeCruzin69]

The radiator cap I have doesn't have the release lever... by vented, I mean it is the kind that allows coolant to be sucked back into the radiator from the over-flow tank as the motor cools. I will take a look at the timing and fuel mixture settings and play with it a little more. I'll also take a look at the fan... thanks.

 

[bracketchev1221]

You are right that it doesn't have to do with the tank, but be sure that you have a tank to recirculate. Some OVERFLOW cans are just that, the fluid goes in, but can't come back out. A true reservoir system, will draw the fluid back in.

 

[WeCruzin69]

The fan does partially stick out a little from the shroud, and appears to be half in and half out... The tank is a reverse flow tank... I guess I just need to play around a little more with the timing and fuel mixture.

 

[Tom Mobley]

do you have a fan clutch? id so, is it any good?

 

[WeCruzin69]

No, the fan doesn't have a clutch. It's one of them flex lite fans with the steel blades.

 

[JJ'65]

I have a 350 small block in my 69... I never did have an overflow tank for my radiator (I don't think it ever came with one) so I installed one of those chrome cylinder looking overflow tanks. Anyway... for some reason, I overheat when sitting in traffic for a while - like say at a drive through or something... and it pours out of the overflow. I do have a temp gage installed, and at normal cruising - the temp stays around 190-200. When sitting still, and barely moving, after about 5 minutes, the temp starts to go up to 210-220 area, and then that's when it starts pouring out. I have installed a new thermostat... I have a new Eddy aluminum water pump... a new aluminum radiator... The timing is dead on from what the engine specs call for, so I don't think it'd be any of those... I'm wondering if it may have something to do with the radiator cap... should I be using a vented or un-vented cap? I believe I have a vented one on it right now. I think I'll try the un-vented and see what it does, but I'm just curious of any ideas I could check as well before I really do cook something... Thanks.

Cooling system with water/antifreeze mix that can vary in temperature from "room temperature" to 200*F+ ain't going to work well without pressure relief mechanism (vent)...especially if its "full to the brim"...read some here and enhance your knowledge

http://www.arrowheadradiator.com/technical_articles.htm

Good luck'
My$0.02