I have a 5.3/4l60e swap in a 74 c10 truck. It has a sns stage 2 cam Fti 3200 converter. I've been having a coolant issue lately. I have the stock c10 radiator 2 perma-cool e-fans rated at 1600-1650 cfm each. 190 thermostat. The fans come on when it reaches a certain point no problem. It's just when I'm in stop n go traffic for a long time or in a drive thru my temp reaches up to 230-250 and I have coolant spewing out of the overflow cap with or w/o a/c being on. But as soon as I drive off my temp goes all the way down to 180-198. NOTE: I do have the coolant lead from the head on the driver's side tied into the over flow hose going into radiator. Since I'm not running a ls swap radiator in the truck. What do anyone suggest could be my problem?

 

If it's cooling well once you take off, your fans aren't cutting it.
Make sure they are actually coming on, and are pulling air thru the radiator instead of blowing forward.
It could be they don't pull the rated air flow.
How are they wired and activated?
What's the sensor temp setting?

 

The temp setting is at 190. The fans do come on and they do pull air

 

I bet they aren't pulling ENOUGH air or they would keep things cool enough in traffic. Are they fully shrouded so all the air they pull IS coming thru the radiator? If so you might need bigger fans. The ones you now have aren't doing the job.
Are they wired thru 2 relays (one per fan) or a single relay?
Are the wires at least 12 gauge, preferably10 gauge?

 

The single core factory rad in my c10 could not handle slow traffic and idling in hot weather in traffic. I had a crap ton of fan going, like to the point it the fan sound was all you heard. Went to a 4 core. You can put more fan to it or you can put more radiator in it. But I had two puller fans and two pusher fans all drawing 100amps in total and it wasn't enough.

Some times you just need a bigger radiator and the factory ones in the c10's are very small compared to what a factory LS comes with now. 1" thick and single core is what the factory had in them, rated for like 200hp max.

 

Can you post a picture of how you have them mounted???


I ran basically the same drivetrain combo as you for years with a Windstar fan setup...It is 4400 cfm total, But. I rarely if ever hear the second fan kick on...

 

Yeah, what size rad do you have???


Nice thing about your setup is, you could get that old squarebody with a 454 and AC. The factory 4 core big bock rad will fit right in with 0 modification...

 

I'm not quite sure..just the stock c10 radiator. It doesn't seems like it's doing the job

 

both fans are wired through a heavy duty cycle single relay.. 12 gauge wire. Both fans come on when temp gets 200.

 

As said above, there are more than one stock C10 radiator.
You need a larger one for the higher heat load your engine puts out.

 

I'll give my setup, its a 1971 GMC, but similar parts should work for you.

1) My engine is a heads/cam 6.0, likely 475-500 HP, so making decent power
2) Stock LQ4 water pump and factory thermostat, which opens at 187-190
3) I have a coupler in my upper rad hose, which the two front steam ports are tied into. Rears are capped from factory.
4) I am using a modern $150 auto parts store radiator for a big block truck of my era. The GM trucks for my gen had 2, 3, and 4 core options. This is a replacement for a 4 core, but it's only I think 2x cores, aluminum 1" wide tubes, with plastic end tanks.
5) Late 1990s Ford Windstar dual e-Fans, with minimal trimming/sealing around the shroud
6) 4L60e with 3200 stall, typical plate cooler in front of rad.

This works amazingly well, and only about $300 total investment for all new parts. Driving steady state, I will sit at 190 degrees. In stop and go, it will cycle between 208 and 195 (low speed fans on at 205, off at 195). It has never turned on the high speed fan setting, which I have kick at 215. Never once in 4 years.

How is your timing? You can generate a lot of heat if your timing is off, during an idle situation. If its too retarded, the peak burn happens after the piston starts going down, this leaves heat in the cylinder. Too advanced can also sometimes do it. But a good cooling system should be able to handle it.

Can you post a pic? The front steam vents need to be tied into the pressurized system somewhere, not into an overflow line to the overflow bottle.

 

Very vague... You could potentially be using a single core radiator for a 6 cylinder without A/C, which, like the others have said, is vastly different than a big block with A/C radiator. Also, since you don't know what it came from, I am going to assume it is used, so it could be plugged up inside where you can't see it. My vote is new radiator.

 

I've solved my problem. Come to find out I had my steam line from the head tied into water reservoir line going into the outlet on the radiator above the cap. There was a peacock I was enable to thread a barb npt fitting and run the steam line to there which was located below the radiator cap but above the lower radiator hose. Plus I bled out the coolant system and drove in traffic no hot temps and stayed in temperature range as you mentioned for your setup.