My newly built engine runs hot! I’m guessing it’s because of all the aluminum parts that it now has (heads, intake, aluminized headers, radiator). The Craig Davies fan controller I have suggests not using a thermostat as it’s supposed to control the cooling. So, I’ve tested that idea and there’s no difference in cooling; it’s still hot! The shop I just had my car at gave me the third degree about not having the stat installed. I’m putting it back in today. They also suggested higher cfm fans might improve the air flow. Mine are 1400 CFM each and they both run once they come on (10 second delay for 2nd fan start).

I’ve been thinking that it may have more to do with the fact that the factory shroud/mechanical fan forced more air over the engine than the electric fans do as they point downward due to the rad angle. So, as a test I was thinking about fabricating up something that can redirect the air low towards the engine.

I had some leftover fiberglass that I used to reinforce the holes in the fiberglass in the rocker area and used it to make a piece to cover that open area below the rad in the engine compartment.

I used the factory shroud as a mold by assembling it and flipping it over then laid the fiberglass over the lower part of the shroud. I had enough material to go about halfway over the shroud from the bottom. I just used one layer of fiberglass which makes it pliable enough to manipulate around the eBay CA’s, e-fans, etc.

The fitment was pretty good as the piece has all the dips and recesses like where it goes over the lower rad hose, CAs and such. I secured it to the upper CA bolts with washers and nuts and the lower part where it fits under the rad, I just taped it.

I tested it just running the fans and with the “hand test” and it feels like there’s more air moving upwards. Whether this makes any difference in cooling I have no idea, but it was easy to do and didn’t take that much time or effort. If it does work, I’m not sure how to make it a better more finished looking product. Some of you all that have better fab skills than I do could probably come up with a better-looking piece.

Pics attached.


Factory shroud used as mold for fiberglass shroud piece

Bottom of shroud used as mold for fiberglass piece

Fabbed up fiberglass piece from lower shroud placed

Fabbed up fiberglass piece from lower shroud placed view2

View from under car before secured

Fiberglass shroud piece secured to rad with tape

Fiberglass shroud piece secured to rad with tape view2

 

Sorry, I don't think I saw part 1 of your adventure, but I can tell you that air moving over the engine itself does very little for cooling compared to the rest of the cooling system.
What does make a difference is getting every bit of air possible going through the radiator, instead of around it. So you want as much of the foam seals in place around and on top of the radiator as possible to seal to the hood, etc. The chin spoiler/air dam plays an important role in scooping air up into the rad as well. To your point, the rad in C3's is laid back pretty far and underneath a "solid" front end, so it needs a lot more help getting air into the rad than your buddy's C10 pickup.

Oh, and the thermostat has little to do with the maximum temp your engine gets to, unless it is malfunctioning and sticking closed. Rather, it is intended to bring the engine up to operating temp faster by circulating water in the block instead of letting it go to the rad. So, keep the t-stat for street use, you can pull it out for racing if it makes you feel better.
Factory wants the engine to come to temp quickly to reduce the amount of emissions it produces. We want them to come up to temp quickly to promote oil flow and better drivability when its cold out.

 

I missed the first one also but how hot is hot. What temps are you running and don't rely on the crappy factory gauge either. They can be as much as 30 degrees off. Also check the timing on the engine. If it is off it can cause the engine to run hot. I ran a pretty modified motor with all the aluminum pieces you have, honestly that has little to due with temps also. As said above make sure you are getting all the air through the radiator. Missing or bad seals have been the issue of a lot of cooling issues.

 

Hi guys,
Thanks for the replies.
Yeah, sorry, the first part was buried within another post but after getting everything put together and fired up, I noticed how hot it was in the engine compartment vs. before when most everything was factory parts except for the aluminum intake manifold. With the factory shroud centered directly towards the engine I never noticed the heat like I do now I'm thinking? I'm surmising that is because that 7-blade fan was pushing much more air and directly towards the engine. The e-fans don't come on until 180* and it seems like everything is hot, intake, heads, headers, in particular. I installed a switch that I can turn the fans on manually with the ignition switch turned on, but their downward flow didn't seem to help much. The headers seem to be the hottest which I would expect, and I do have titanium wrap that I can put on them to help some.
Yeah, I've got the rad sealed up well with foam all around and as I said this is just an experiment so if it doesn't help it'll be scrapped.
My temps as I recall are like mid hundreds for the top side of engine and 230ish for the middle exhaust headers, 150+ish for the end tubes, once it's warmed up. The carb is about 10* to 20* lower than the intake which I expect is due to the phenolic spacer under the carb. The rad and rad hoses seem to be the coolest at around 114* +/-. I do have a good chin spoiler and I put the stat back in this morning.

 

okay...you need to make a determination about what you are talking about. When you say your motor is running hot, must of us are thinking your radiator temps is above 220 and climbing. You seem to be talking abouut the engine compartment.

You have non ceramic headers in a closed compartment with a giant iron heater that is pumping out lots of heat. Yes the aluminum sheds heat faster than iron so that will up the compartment temps, there isnt much air flow in there other than what comes though the radiator and its going to be 200 plus degree air. THere are threads about hood vents you can search for if you want to cool that area more but unless you get ceramic headers or wrap them then its just going to be hot in there.

For engine cooling the radiator being sealed isnt the only issue, its the whole radiator air box that has to be sealed. My 68 had a bunch of seals in front of the radiator that kept the air forced into that area in front of the radiator from escaping other than going through the radiator. If you want more air you need to have a good air dam. My 68 had a tiny plastic lip of an air dam. it want much bigger in 69 0r 70. In 71 they added a bigger rubber extension under it and it scooped more air into that box and it made a big difference and after that the dams grew. A bigger dam means more air through the radiator. Also if its low speed engine heat then check the lower radiator hose for a spring, without it the hose collapses and no water flow just adds to the heat

 

Forgot to mention that you did a great job making that lower fiberglass shield. If you want more air flow in there out a scoop in it so it forces air into the engine compartment and hopefully forces the heat out past the firewall and out the vents

 

a new tight eng will run hotter until
things "wear" in.
more power will create more heat.

 

Hi RR,
Well the digital display on my fan controller got over 200* and climbing when I shut it down. My main thought is that it's just hotter than what I recall with the old engine setup. But it is totally different with all the aluminum pieces. I'll double check the air box you mentioned, the rad is pretty well sealed with foam pieces all around. My temp gauge was showing about 210* but it was tuned for the old engine.
I've also been wondering if I may have some air trapped somewhere. I'll check that out tomorrow.
Thanks for the feedback and prophs on the fiberglass shield. It did seem like it was moving more air through the engine bay as I didn't feel as hot leaning over the fender.

 

The thermostat has just about zero bearing on how hot an engine will get. Its role is to delay any coolant circulation until a certain temp is reached to quickly reach fuel, performance, and emissions efficiency. Once that temp is reached, it's wide open and all limitations on the maximum temp of the engine fall to the coolant circulation, radiator, and coolant chemistry.

I think you should pick up an infrared thermometer and take accurate measurements of the thermostat housing, radiator inlet and outlet elbows, water pump housing where the lower hose attaches, and the forward walls of each head. Without this data, you are just guessing about any potential problems. 195°F to 230°F are typical GM original engine design parameters for C3s.

 

How much of a horsepower bump did you give the engine? Is the radiator stock or a newer bigger aftermarket one, i forget if you posted that?

 

67:72,
Yeah, I understand how the stat works and as an experiment I had removed it as I was concerned that maybe the new stat wasn't opening, and the fan controller vender suggests leaving it out as their claim is that their system controls that function. It made no difference whether it was in or out with regards to the heat. I posted here my temp readings, and they were from one of those IR guns but I'm not sure I trust it. But it does indicate that the heat is consistently rising over time to which I would think the point is that it would be cooling down as some point. Now this is done sitting in my garage and not driving down the road which I need to do but I am a little concerned that it will overheat and then I'll get stuck at the side of the road.
Most everyone I talk to about stats say you need to have it installed and I don't disagree, so it's been reinstalled.
Thanks for the feedback.

 

RR,
The engine builder thought it would be over 400 but so far seat of the pants is not that impressive, but I wanted to ensure the brakes were good before attempting to pound on it some. Also, it's an automatic and I put a shift kit in it and a new converter that supposedly stalls at about 2400. I think I'm going to wrap the headers next to help with the heat. The rad is a Cold Case direct fit supposedly, two row 1" tubes. I do have a condenser and trans cooler mounted in front of it and it look like there's some room on the driver's side that I could put a small pusher fan there to help if it becomes necessary.

 

400 hp could get the motor hotter and if its a small block your not going to see much torque until higher in the power band if its a 350 so that could be why your arent impressed yet if you havent gotten on it really hard.

Not sure it that radiator is just better than stock or if its good enough for a performance engine. I dont think a pusher fan is going to help your situation with any cooling since the fans are only for idle and slow speed cooling and all the higher speed cooling is just air flow through the radiator. Any more stuff blocking your flow could just make the heat issue worse

 

I put a 3 core in front of my warm (450hp)383 and it’s just enough on hot days in town. I would suggest a bigger radiator.

 

You stated your temp gauge was showing about 210* but it was tuned for the old engine, a temp gauge doesn't care what engine is installed so this doesn't really make any sense. The highest temp reading you have posted is 210* and no mention of the radiator boiling (puking) the water out at 210* so I will assume it doesn't.

1) The boiling point of water is 212 °F at 1 atmosphere of pressure (sea level).
2) For every pound of pressure increase the boiling point goes up 3°F.
3) Typical radiator cap pressure is 12 to 16 psi.
4) This raises the boiling point of the engine coolant to about250°F to 260°F.
5) Mixing ethylene glycol antifreeze with water in a 50-50 ratio increases the boiling point 11°F.

Your engine is not overheating.

My 65 427 car ran on the hot side of life and always indicated 210ish on a hot day and the gauge was reading about 10* high so I guess I was steady state at about 200F. While I always felt it was running hot it never boiled over.

 

Hey Mr D,
Thanks for the reply and science info.
I guess I should have been clearer regarding my comment old vs. new engine. The old engine's temp sensor that I installed but verified worked (via the heated water in pan w/thermometer) as advertised (180*) or close to it. I also installed one of Willcox's temp gauge adjustable resistors as per their instructions. The old sensor went with the old engine when I sold it, and the new engine got a new 180* sensor but I did not check its accuracy. I got a little nervous when the gauge got to 210* so that's when I shut the engine off. There was no puking of antifreeze. So, you're probably right that it's just the way it is, not overheating but it's still too hot for me. I don't recall not being able to touch components because they were so hot before so that's a new experience for me (one of the AC pipes next to the evaporator box was too hot to touch, makes me concerned about the starter motor heat soak) and one that I don't like and don't think is normal. But hey, heck, what do I know. lol!
However, fwiw, I've started wrapping my shorty exhaust headers with the titanium wrap material and as I had a 3/8" plug in the water neck I removed it and there was no coolant visible. So, I added coolant through the water neck hole until it reached the hole's threads and also confirmed the fluid level at the rad fill opening was to the top. And I added coolant to the recovery tanks to the cold line. I also did the squeeze the top rad hose to see if it created bubbles in the rad which it did not (YT video) so I'm guessing/hoping I don't have air in any of the passages (but the car wasn't on an incline so...).
BTW, the Cold Case rad came with a 16-psi cap. Another observation is that the water gauge seems to be working better than I recall how it worked with old engine. I don't recall seeing it move as much as it seems to be doing now.

 

This last statement sure seems like you don't know what the temperature is. Go get a cheap temp gun and get a reading. Since you installed a new sensor (what sensor? where did you get it?) then you really don't know.
You may not have a problem at all. I would suggest the temp gun first.

 

I don't know what radiator or water pump that you have, but from experience 2800 cfm is way too low on the fans. Fans ratings can be misleading because of the core air restrictions. I originally had so called 2800 and over heating problems.

My upgrade to Spal dual 12 inch draw something over 30 amps running and are rated at over 4000 cfm.

i tried a bigger water pump and biggest 4 core aluminum radiator as a fix with my 2800 cfm which was probably less than 2000 in reality

 

Fans actually can cause a air flow restriction as mph increases. The twin Spal shroud includes opening rubber flaps. Only stopped in traffic do I need two fans running. Even on 100 degree desert days I only have one fan running and free airflow through the other

My present water pump is a Team G aluminum driven faster with a smaller diameter pulley. I also have 6 inch damper pulley. So a stock 8 inch pulley would not require a small water pump pulley. Team g pumps probably have twice the water flow as a stock pump and use less hp doing it

Going to electric fans drawing 30 plus amps also requires a bigger alternator

As to hot rodded 400 hp claimed. It's TQ that you feel on the seat of the pants acceleration. 350 ci sbc is lacking on TQ when you have 20% losses with a automatic transmission

 

carriljc, Sorry I don't know what you mean regarding last statement... I have a cheap temp gun that's what I'm using and have posted as such for the temps I'm seeing. Water temp sensor like what one gets from the parts store that send info to the water temp gauge. Bought if from one of the Vette parts vendors, don't recall, prob Summit. Yeah, I may not have a problem it just seems too hot from my previous experience with mostly factory setup, and I don't recall things getting this hot such that you can't touch it.
Thanks the comments.