big block cooling

[knuckledragger]

What radiator are people running with a big block?The reason I am curious is that I have a new 3 row brass in my truck with a 402 and it runs 210-220 when hot.I have tried different thermostats and run without,no change.I am trying to determine if I have an issue with the cooling passages being blocked or just not enough radiator.The engine is a craigslist special that I purchased as a grenade engine.I really dont know anything about it.I have checked the flow from the water pump and it is working.Ideas?
Dan

[GCncsuHD]

Do you have a fan shroud? What kind of fan are you running? Faulty clutch if clutch fan?

[knuckledragger]

I am running dual 12" spal fans,no shroud.I have a pt cruiser fan assembly with shroud I might try.

[GCncsuHD]

How many CFM for each fan? I'm gonna go out on a limb here and guess 1200 or less per fan, it's on the low side of CFMs for just the big block alone, much less having to cool the TH350 as well, throw in the fact that you don't have a shroud and it doesn't sound nearly sufficient. Setting the fans back from the radiator a bit and building a shroud to take full advantage of the entire radiator core rather than just two 12" diameter circles of it would make a drastic improvement.

Just guessing your radiator core size is about 20"x24" (off the top of my head) you have about 480 sq in of available cooling area, with two 12" fans you are using less than 1/2 that at about 226 sq in when idling. If the truck is able to stay cool while running down the road, but not when sitting at idle, this is definitely your problem.

[knuckledragger]

That is what puzzles me.It runs cooler at idle than at highway speed.It has a 3.07 diff so rpm isn't the issue.

[GCncsuHD]

Weird, are the fans pushers or pullers? Engine running way lean?

[knuckledragger]

pullers and is running fat

[geezer#99]

Install an airdam under the rad. About 4" high so it's below the frame. This dam creates a low pressure area behind it. Result is air flows thru the rad instead of under the truck. Should help. I used one from a 75 nova on my big block chevelle. Dropped highway temp 15 degrees too.

[Rannos]

You may want to double check your timing as well. Timing can effect running temp as much or more then a lean condition.

[knuckledragger]

timing is at 8degreess due to the closed chamber heads.Thanks for all of the input.I have just about decided that it is sediment in the block or heads.
I had originally planned a 250 6 with some bolt on stuff when I found the deal on the bbc.I may still go with the original plan for the 6.I am fairly certain the 3 core radiator will have no issues with cooling it.

[Rannos]

What is you full timing? 8 degrees is not much for initial timing. My motor is just under 11 to 1 and I run 15 degree initial and 36 degree full. Motor produces roughly 425 hp and am cooling with with a single 14" spal fan with no shroud and a 2 core aluminum radiator and it stays 180ish driving and 190-195ish idling... I have a 195 stat. Running to little advance or retarded at all tends to cause more heat in my experience.

['63GENIII]

Mine runs anywhere from 195 to 215 while towing in 100 + weather. I'm running about 11 deg. initial, a 4 row brass stock rad, 195 thermostat, 19" fan from a '97 454, stock fan shroud replacement and a HD fan clutch. When the fan engages it sounds like an airlpane but it never overheats and never pings.