I built a 355 that isn't overly powerful, but can't seem to get it to run below 220 or so degrees, either sitting w/ the fan on or cruising.
Its a 355 (old 69 block) w/ xe268 cam, about 8.7:1 comp, 882 heads, edelbrock performer intake, 600 cfm carb, manual trans, headers, griffin 2 row aluminum rad w/ stock single electric fan, 180 degree t-stat. Serp belt set up with reverse rotation water pump. Base timing is at 13, w/ total at 32 by 3000rpm. Even with vacuum advance unhooked it runs hot, so i know its not too advanced when driving.
It has about 200 miles on it and will fluctuate right around 220 degrees, I have to have the fan on anytime I'm stopped or it will climb. I have verified the gauge is reading correctly w/ an IR temp gun. I'm getting about a 20 degree drop across the radiator so I know the system is flowing properly. I'm not getting any pinging or anything so I know its not lean, I even retarded timing a couple of degrees anyway, just for confirmation.
Any thoughts?

 

You may want to make sure the thermostat is opening, I got a "190 degree" thermostat in a gasket kit for my truck and it only let the engine get to 130 degrees, so its possible that the thermostat isn't opening soon enough. If it is opening, it could possibly be a bad water pump or a blown head gasket/cracked head, or its possible that the single radiator fan can't keep up with the engine heat.

 

Did you properly burp the radiator?

Is your Air Damn intact?

 

I put the t-stat into a pan on the stove before I installed it and saw it open, I also verified its opening around 180 with the IR temp gun. The air dam it intact and in good shape. I have bled the cooling system a couple of times.

 

One thought, thermostats are directional...if it's installed backwards, meaning turned around, not upside down, they won't flow properly. You can also drill two small holes in the edges of it to permit some coolant to run through all the time.

have you replaced your hoses? It's possible the lower hose is collapsing with the water pressure, limiting flow.


It's normal for the temp to climb while at idle, the fan would normally come on with the temp switch, but if you have it on all the time, that's moot. The temp would rise, then fall till the fan turns off, then creep back up again. Very normal.

The fan should be off when you are on the highway over 45mph...at that point the fan is actually impeding airflow and the car should cool down to near the thermostat's opening temp unless your running the car hard.

Could also be the motor breaking in still but that's a long shot.

 

This is an old carbed engine, does that still apply for the t-stat?
The hoses (everything under the hood) is all new, the hose does not collapse when RPMs are raised.
The stock electric fan is wired up to a toggle switch so i can turn it on when I want, I usually have it running when the car is below 20mph or so and off above that.

 

I run a single fan in my 355 with no issues, the only heat creep I get is when I turn the AC on.

It is possible the Thermo stat isn't opening enough, is installed backwards or there is another issue as you've mentioned.

 

I don't see any markings on the t-stat indicating a direction. I did a lil searching but cant find any info on that either. Not doubting you, I have just never heard of a directional thermostat. Do you have a link to a photo or something about it?

 

The spring should face down

 

Ozz was stating that the thermostat is directional, meaning a front and back to it. He wasn't referring to it being upside down, i know it is in there the correct way (spring facing down), I just have never heard of a t-stat having a front and back side (one side faces the radiator, the other faces the firewall)

 

The last two thermostats I bought, the instructions indicated one part of it was "foward", it was based on how the center post inside the spring on the bottom faces.

 

Was it a high end t-stat or something? The ones I usually buy are a t-stat in a box, no instructions or anything like that. Just your basic t-stat from NAPA or advance auto, etc.