Coolant temp control

[Doorkicker]

Several things pop out at me.
1-Have you verified the temperature readings you are getting are accurate?
2-Belt tension? It looks deep in the alternator pulley groove. Is it slipping?
3-Radiator size. You should have a 26 inch core if you are making that much HP.
4-Fan, I hate flex fans. I doubt that fan is pulling enough air.
5-Timing what timing are you running at idle and low speeds?
6-Was that radiator designed to cool that much HP.?

I really appreciate lists! Thanks for taking the time... all great questions. Here's my first pass...


1-Have you verified the temperature readings you are getting are accurate?
Yes. I used a digital thermostat and a laser thermostat, both we're very, very close to the reading on the sniper.

2-Belt tension? It looks deep in the alternator pulley groove. Is it slipping?
Hmmm.... I will double check that. I did take note yesterday the power steering pump belt seemed not as tight. I just finishing building this engine, so I bet things are still settling in. Good catch.

3-Radiator size. You should have a 26 inch core if you are making that much HP.
Ok... so you're onto something, IMHO. I purchased this rad for the first engine I built for the car last year. (Yes, I build a motor and then rebuilt it again... I wanted more power, who doesn't?!). It was not stroked, slightly modified stock heads, and not as big of a cam with low compression - about 350 hp+. However, the opening was limited and I thought about going to a 4 core... this is a 3. I don't disagree a bigger rad is probably the better decision, but 26" is much larger than the opening in the rad support... are you suggesting cut it and open it up more? Because I've been contemplating just that.

4-Fan, I hate flex fans. I doubt that fan is pulling enough air.
I'm not married to it. I honestly only care about performance... please share a recommendation on a better fan.

5-Timing what timing are you running at idle and low speeds?
I'm going to double check the static timing, but at the moment it's reading 16-17 degrees at 980 idle.

6-Was that radiator designed to cool that much HP.?
Frostbite says 450-750 HP.

 

[diesel_lv]

Amazing... ok. I will say this, I looked for a repo factory shroud and couldn't find one... AT ALL... I call everywhere and several junkyards. So I made one.

Your tapping into my other thought... my fan might be too small.

Way too small. Factory fans were 17-18" rigid 7 blade for stock big block, much less 600+ hp. If it's good cruising, then it's not getting enough air at slow speeds, fan size to start. Other variables out there, but start w fan. Mancini sells a factory authorized 26" shroud.

 

[64 Sportfury]

Are you running a hood to radiator support gasket/seal? Is there a stone guard attached? For the best airflow through the radiator fins it is important that the airflow coming through the grille has nowhere to go but through said radiator fins.

 

[Geoff 2]

You need to p*** off the elec fan & get a 19" clutch fan & severe duty clutch, plus a factory shroud. You also need a separate trans cooler.

Everything about your coolant system says...blockage. The elec fan blocks a lot of the rad core. The shape of the shroud is not conducive to free air flow.

If the engine has a sizable cam, it needs a LOT of timing at idle & cruise to run cool.

A properly designed cooling system has excess cooling capacity, with the t'stat controlling temp. Your system is under capacity.

 

[Doorkicker]

Hi All - Just wanted to close out this thread with an update and status as promised.

BLUF:
The main culprit turned out to be timing. Long story short, I was off (retarded) about 12-13 degrees at idle, hence the temp spiked at idle. Thanks @pnora! Your #5 was the killer.

I also found that my trans cooling lines were pretty much right up to my headers. Not sure how that happened or how I missed that, but there they were nice and hot.

Fixes/Changes:
The first major change was fixing the timing and I made a lot of other tuning changes at the same time - for example, I was running a touch rich. As a result it stopped spiking from 170-180 to 200+ at a stop sign. In fact, it hadn't gone over 195.

The second change was installing a 10x10 with 10" fan trans cooler with new lines running up and over through the side away from the exhaust. The trans was running fairly hot IMHO. So now the fan kicks in at 175 and is keeping that managed.

Finally, I made sure the rad was filled and without an air pocket. Not sure if that was an issue, but I did it anyway.

Results:
Car running down the road hums perfectly at 180-181. I took for a 45 mile run yesterday. When I would stop at a light it would creep to 188 max. I let sit idling in the parking lot at the end of the run and it made it up to 196 after about 10 min.

I'd call that fixed.

 

[Demonic]

I'd suspect airflow is a bit low when parked/idling.