383 stroker running too hot

[bstock1962]

Hello, I have a 1972 c10 that i recently had my 350 replaced with a 383 stroker. According to the mechanic it has a 9:1 comp cam but no other info is known about it. He also installed a vintage air system at the same time. Now, when the temp gets above 90 degrees outside the engine runs too hot (don't know actual engine temp is due to gauge is stock) but about 3/4 of the way to max. If I turn on the AC it gets even hotter before I shut it down. I've replaced the 180 degree thermostat with same, and coolant is flowing through top hose. TH400 has a cooler in front the the AC condenser and blocking air flow ( see attached picture)

I did check my timing after reading forums. With dist adv plugged and 1406 edelbrock driver side port capped, the total timing is 41 btdc. At idle it is 25 btdc. I thought these number were off so I verified the balancer mark using a piston stop. It was right on (does a radical cam produce these types of numbers???) So I tried moving the timing around to see what the engine temperature would do, and nothing seems to affect it (still runs hot). Also, vacuum stays below 10" at idle no matter where I set the timing.

The question is do I need a better radiator? It currently has a 3 row stock looking setup with stock fan. Is it assumed you need a 4 core alluminum radiator when running a 383 with vintage air? Looking for advice before purchasing a Champion MC369 radiator.

[sean1969c10]

I think the first thing to do is to verify that the truck is actually running hot. Pick up a non contact laser thermometer and see what the truck is really doing. Check at the thermostat housing, top of the radiator and the bottom of the radiator.

[Stocker]

Welcome. Seems to be a rash of running-hot threads here lately. I like Sean's idea of verifying actual temps first, as the old stock gauge -- or its sending unit -- may be off.

Other things you might check: it has a fan shroud (good) but what type of fan, and is the fan in the right location within the shroud? Good pressure cap? Coolant recovery tank can help a bit since it allows the radiator to stay full.

[RUN GMC]

In your picture there is a gap between your radiator and condenser.....seems like ambient engine air/temp is or would be getting pulled back through instead of pull through the condenser to help pull down the temp.....how is the a/c doing cooling the interior?

[bstock1962]

Sean, I have a laser thermometer now. It's only 87 degrees outside right now (and the stock gauge is now only going 2/3 way) so obviously my measurements are showing cooler. Therm housing is 220, top of radiator is 219, bottom of radiator is 192. I need to measure during the heat of the day tomorrow when it should be 100.

Stocker, The fan blades are positioned half way within the shroud. It's a 7 blade clutch type fan and pulls air into the engine area. Pressure cap is 14psi. I haven't been losing coolant so not sure an overflow tank would help? See attached picture.

Run GMC, the AC is working well until the engine gets too hot and everything starts to bake.

[snipescastle2]

Might have to "Burp" your cooling system, air pockets can get trapped in the heads causing the engine to run hot. Some people have drilled a 1/8" hole in their thermostat to aid in venting the air out of the heads. HTH,
Ben

[Stocker]

That all looks / sounds good. Maybe the fan clutch isn't doing its job well enough, possibly being stressed by the new stroker. Also just might need a different radiator as you first thought. Gonna be interesting to see what readings you get when in tomorrow's heat.

[bstock1962]

Snipescastle2, I've read about drilling that 1/8" hole many times on other posts. Any reason not to do it? If not, I'll try that soon.

Stocker, is there any way to test a fan clutch? Or do you just replace them when you suspect a problem?

[Stocker]

Originally Posted by bstock1962

Stocker, is there any way to test a fan clutch? Or do you just replace them when you suspect a problem?

Look for any hint of fluid loss, check for looseness in the shaft, and see if it freewheels after you rotate it by hand (it shouldn't). You should feel mild resistance, kinda like it's mired in molasses. Here's a couple sites with good basic info:

http://www.aa1car.com/library/cooling_fan_clutch.htm

http://www.haydenauto.com/featured%2...s/content.aspx

Note the differences in design (thermal / non-thermal -- always go with thermal), and standard duty, heavy duty, and severe duty thermal units. Aside from possibly being worn out, you may have a standard duty unit and your 383 might be happier with a heavy duty. Looks like severe duty is only needed on larger trucks, or ones that are working extra hard and need even more aggressive cooling.

[bstock1962]

OK, update: Ran it again at 95 degrees outside. Therm housing was 232, top of radiator 228, and bottom radiator 205. Seemed like it was headed higher too before I shut it down. It's definitely hot, and it sounds like fuel boiling in the edelbrock 1406 carb after shut down.

Also did the fan clutch spin test. Almost 2 turns while cold, then about 1 1/4 turns while hot. So fan might be a little marginal according to the links Stocker sent me yesterday.

[Stocker]

Originally Posted by bstock1962

Also did the fan clutch spin test. Almost 2 turns while cold, then about 1 1/4 turns while hot. So fan might be a little marginal according to the links Stocker sent me yesterday.

Are you saying the fan free-wheeled that much after you took your hand off? If so, that is beyond marginal..... it's definitely a bad fan clutch.

Your fan looks like mine, with a 2 1/2" pitch. Per the Hayden site that requires a heavy duty unit.

[garyd1961]

Sounds like you need a new fan clutch.
Also what type heads do you have? Vortec and some aftermarket heads don't have a place for the by-pass on the water pump. You need a bypass hose from the front of the intake to the top of the water pump.

[prodjay10]

I have an after market temp gauge as well as a laser thermometer and I noticed a 20* temp difference from the two when I measure temp at the thermostat housing. Someone else told me they experienced the same thing.

I think it's not the same measuring core temp vs surface temp. So if you are reading 232* at thermostat housing with the laser thermometer, the actual coolant temp is likely 20* hotter or 252*.

[67 chevelle]

Generally 36 is tops for timing , if you were running 41 it would sound like marbles bouncing around in the engine ,,unless,,, something else is seriously off ,, try some royal purple blue ice , it works well

[snipescastle2]

With regards to the 1/8" hole drilled in the thermostat, I can't think of any reason not to do it, as it's not large enough to bypass the flow,and it allows air to escape freely.
I'd say the clutch fan is definitely not up to par and causing more bad than good.
I'm not running a shroud on mine, (I should be) but that flex fan moves a crap load of air, and has a lot of drag on the engine, but, it's maintaining the temps.
Hope you sort it out soon!
Ben

[BugzC10]

Looks like you have a 2 core radiator. Now that you have A/C I would change it to a 4 core. When I tool around in slow traffic in 100 degree heat with my Vintage Air on the temp starts moving up to 200. If I driving at 50+ it stays at 185. I have 4 core and 185 stat. Without the A/C on it stable @ 185.

[leftybass209]

You jumped on the fan issue, which is good, but did you really look at that radiator? How old is it? They usually look worse inside, than they do outside, and just the outside looks to be past its prime. Also, you have an AC condenser, and what looks to be a trans cooler, double stacked in front of the radiator. One or the other is okay, but three is typically a no-go.

You never want your fan to have to work through anything to pull air across the core. Bent fins, dirt, trash, and mounting places like where your accumulator is attached to are all obstructions. AC condensers, and trans coolers are also obstructions if they have bent fins and trash in them.

You may have created a dead spot on your radiator the size of the trans cooler, which i'd estimate at maybe 25% of your surface area.

If you're lucky, the fan is the biggest culprit as it's the cheapest fix, and it sounds like it needed to be replaced anyway. However, i'd take a house fan and aim it across what you have now, and feel with your hand on the inside to find any points of weak airflow or misdirected air. The aluminum radiator covers do a good job of directing airflow through the core by eliminating the gaps between the core support and the radiator.

Best of luck figuring it out!

[davepl]

Just another thought - it looks like that fan has taken a hit or two in its lifetime. I don't know if they become dangerous when damaged, but it can't help. If you have access to a spare, replace it when you replace the clutch. Keep the same style and same or higher blade count, of course.

[snipescastle2]

Those auxiliary trans coolers are just that, auxiliary. You really want a liquid cooled heat exchanger for the transmissions heat, the air coolers help, but minimal.
Ben

[bstock1962]

Ok, another update and question. I went ahead and replaced the radiator with a 4 core aluminum. That took my temps down to 180-190 at the thermostat housing...very nice. I still have a little fuel boiling (percolating) problem in the carb but I have a spacer on the way to isolate the carb from the intake heat. There currently is no spacer.

Now, for a dumb question...my old radiator was painted black and probably the same way, but is the radiator supposed to tilt back a little at the top (instead of being mostly vertical) ? Actually it seems like the entire engine etc all tilts back a little (see photo). Is this pretty standard or do I have some sort of overall alignment problem? Thank you!

[snipescastle2]

The factory did that intentionally. As the engine/transmission is at an angle for the driveline alignment. The black paint on the factory radiator was probably there to prevent corrosion, in my opinion, it would effect the heat transfer, otherwise, I'd say you're set and nothing to worry about.
Ben

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[leftybass209]

Glad to hear you solved the issue!

Your radiator angle is fine. Any paint on a radiator is not a conventional paint, but rather a coating that doesn't inhibit the heat transfer of a radiator, and it's certainly not needed for aluminum.

[Stocker]

Originally Posted by leftybass209

Do some research on 4 row vs 2 row in regards to tube size. For me, a 2 row champion with 1 inch tubes was more effective than a 4 row. 4 row radiators require different top and bottom brackets. The bottoms are riveted, so it would be a little more difficult to do in the truck, but still doable.

On that note, here's something borrowed from a thread from a couple years back. Seems like a fitting time & place to post it again.

[bstock1962]

Ok, update: New fan clutch made a big difference. Thank you Stocker!

Temps dropped to 215 at the thermostat housing, 210 top of radiator, and 185 at the bottom. This is with the AC blasting too and 95 degrees outside. I attached a photo of the bad fan clutch. Notice the thermal spring is missing.

Now I want to get greedy and get rid of the transmission cooler blocking air flow. I'm tempted to strap it too the inside of the grill instead of attached to the AC condenser. That would look crappy! I think temps could drop even more with it gone though.

So I guess I would still need a new radiator with cooler built in. Leaning heavy towards a 4 core. Until then, I can drive in in the high heat now!

[Stocker]

That's great news, I'm glad you saw a big improvement! Your old fan clutch was a standard duty, not correct for your application. And with it out, it looks pretty grimy, and has probably been losing fluid for a long time.