More detail about cam, pistons, head gasket, etc. would be useful.

My knee jerk without knowing more detail of vehicle and engine is the new Champion radiator isn’t big enough. Or possibly there are some mixed components between V-belt and Serpentine belt drives. Fan or pump for example are sensitive to belt drive type and can be mixed up.

Bogie

 

It has a clay smith 264 cam. 110 lsa. Very mild. I used cometic mls gaskets .025, in and also .025 in the hole with hyper 4 valve relief pistons. Heads are flotek 64cc flat tappet heads, only thing I did with those was put z28 springs in them to because my machinist was afraid the doubles would be too hard on the cam break in. The champion radiatot is supposed to be for my chevelle. Maybe slightly bigger than the stock brass one I removed, plus an extra row. I reused all pulleys from the engine. Anything else that you think would be helpful?

 

timing.
Base timing is 12?
what is your all in timing ?
It acts and sounds like a plugged rad but we know that is not it.Thats is why I suspect timing Your rad setup /fan etc looks good

 

All in 32°

 

The fan has the right pitch for the V-belt, what about the coolant pump, where does it come from?

So far nothing leaps out at me. An independent check of the gauge and sender is in order, the wandering gauge might reflect something wrong in that stream.

Another simple thing is the coolant recovery tank, it should never be totally empty. Two things going on where some systems depend on that as a source to complete venting and filling, also, the level of coolant in the reservoir needs to keep the end of the connecting tube submerged to prevent drawing air into the system.



Bogie

 

The fan has the right pitch for the V-belt, what about the coolant pump, where does it come from?

So far nothing leaps out at me. An independent check of the gauge and sender is in order, the wandering gauge might reflect something wrong

The pump is an AC Delco from a local Federated auto store. The temp gauge is a mechanical and i will test it this weekend with some hot water of a known value. I think it may be getting some heat soak from the headers. I plan on replacing the lower radiator hose also which came off the old engine. It is a bit spongy and does not have any metal spring in it. As far as the coolant reservoir, it is basically an overflow. You can use it for washer fluid or an overflow. It does have a tube going from the cap into the coolant though. So far it hasn't been utilized. The level was already in there before i rebuilt the engine and hasn't risen at all. I am really hoping the lower hose is causing most of this. I will pick one up this afternoon.

 

verify the gauge with an IR thermometer. the gauge could be reading high

how far away is the fan from the radiator core? (should be OK based on the pic)

how much clearance do you have between the fan and the shroud? It looks a bit large of a gap, as maybe a 20" fan or larger. too large of a gap and you loose blade tip efficiency

do you have any better pics of the fan/radiator/shroud?

 

The fan is probably a couple inches away from the radiator. The fan is a 17" with a 19 3/4" hole in the shroud. I ordered the one that fit the radiator and car. So maybe 1.25" or so between the blade tip and opening. I had a 19" that i was going to reuse but it was rubbing inside the shroud so that wasn't going to work. I don't have any more pics but can get some. I also reused the radiator hoses. I am thinking the bottom one seems a bit spongy. It also doesnt have the metal spring i hear some talking about.

 

I am thinking it is the fan/shroud. I am thinking with the new set up, the fan is blocking air flow while cruising because it doesn't slip and that old set up with no shroud, enough air flow would get around the fan at cruise.

I think your idle temp is acceptable, but that might get better with a clutch fan set up.

https://www.opgi.com/cooling-heating/fans/fan-clutch-fan-blade13/fan-blade-18-chevroletbop-ch25854.html

 

I did run it with the old setup (19" fan and no shroud) during break in and down the road since my fan was too big for my shroud. It was 200 at idle but the temp was 235+ down the road. So the new shroud and fan has lowered it by 10 degrees or so.

 

Certainly could be the lower hose if it is soft the suction from the pump can collapse it.

Bogie

 

Be wary of that plastic fuel filter. I don't trust them for long term exposure. Could be just me.

 

I agree. I had a glass one on before but was afraid of the glass busting. I think i will switch it over to the metal one soon.

 

Out of curiosity what kind of heads were on it before? Temp sensor relocated with the new heads?

 

882 cast iron heads. Temp sensor same location though.

 

I would verify that they didn't sell you a reverse rotation water pump.

 

I haven't pulled it off to check but I called my store (federated auto) and they looked up the one I bought and said it is not a counter clockwise pump. I know what you're thinking now though... still isn't ruled out.

 

Simple test , you'll need an infrared heat gun , at operating temp , top rad hose temp vs bottom rad hose temp ( remember that you need to be within 1" of the surface being measured to get an accurate reading ) , less than 20° difference , its the rad. / Fan combo that needs attention .

 

I'll try that. Thanks

 

It seems that the first serpentine belt on the SBC was 1986 but it drove the pump in the standard direction of clockwise. This was also used into 87 production but some late 87’s started to use the 88-91 which had a troublesome stamped accessory mount these use a different routing for the serpentine and use the counter clockwise rotation pump. 92-95 mount accessories on aluminum brackets, these, also, use the counterclockwise pump. These pumps are identical in outside appearance to the earlier clockwise pump and they do get mixed up in packaging now and then. The 96 up pump is also counter clockwise and deletes the internal bypass but has more hose connections directly on the pump so it looks a lot different from 95 and older pumps.

But at this point since you note the lower hose feels soft, I go there first before doing a pump.

Bogie

 

In my mind, an engine should never run but a few degrees hotter than the thermostat setting, If the radiator is adequately sized and there is plenty of coolant flow. if it's not lean and retarded, a mild 350 with aluminium heads, aluminum radiator and headers, should have more heat dissipation potential than stock steel stuff. I use a Champion in my truck and am thoroughly satisfied with it.

 

I'm assuming this is a high output engine.! I don't like the 180 degree thermostat. That engine after warm will constantly be above 180, therefore the thermostat will never close. Meaning coolant won't stay radiator long enough to cool. I suggest a 195 thermostat. Also, I just started using Keyser 40 below as per instructions -as of now it helps.

 

Finished building and installing my old 350 now 355. New flotek heads, new champion radiator, new shroud and flex fan. 180° thermostat (tested in hot water). Timing 12°. Seems to like that the best. I previously had the 19" flex fan with no shroud and was getting 200 in the garage at operating temp, 215 with the heat on and 235-240 down the road with it off. Now with the new fan and shroud I get 190 idling and 208 with the heat on circulate but bouncing between 220 and 230 with the heat off. I know a new motor will put out a bit more heat but just wondering if it'll get cool enough to not have to put the air on heat to keep it cool. Keep in mind the blower is not on just the lever to heat instead of cool to circulate.
Oh before the build it was 200 all the time with a 19" flex fan and no shroud. Mechanical temp sensor in drivers head between 1 and 3. Any help appreciated. View attachment 634464

I feel for ya, it can be frustrating trying to pin point the cause of the overheating. I chased the same problem for several summers. I have a 406 sbc 550hp in a 57 Chevy. I run a 195 stat 34 * total timing in 110 degree summer temps in Phoenix. The car will idle in driveway at 195* for 30 minutes and run 195* around town, highway 185*. So I believe the radiator is the key to solving overheating As long as you have eliminated any other cause. I bought a DUAL pass radiator With dual 14” electric fans. In the winter months 65* -75* outside temps the car would run 160* on highway so I installed a 195 * stat. No more worrying about getting into the 220* ranges around town in summer. The hot summers here can cause lots of over heating issues. Good luck and let us know how you solved the problem !