Mercury 410 Overheating

[Porkchop]

Hello,

I am new to the forum, but I have been reading on here for a while and been a member other related forums.

I have a 69 F100 with a Mercury 410 that is overheating. I've had the truck for 22 years, and it had a 360 until last summer. It never overheated with the 360, and it never overheated with the 410 until I did the work below:

-Built engine myself. Installed August, 2023.
-Ran great for <500 miles. No overheating. Have both the stock temp gauge and an Autometer gauge. Then I started here a tick/knock I didn't like
-Removed intake manifold to inspect lifters/cam (everything looked good)
-Decided to replace the stock S intake with an aluminum intake. I know this won't be popular, but I decided on the Chinese knockoff that you see on Amazon/ebay/etc.
-New 180 deg thermostat (smaller diameter to fit new manifold)
-New upper radiator hose

After doing the above lifter inspection / manifold swap, it is now overheating.

Engine details:
410 bored to 416
Stock style cast pistons (new),
Original rods and crank
C6AE-R heads w/ CJ valves
Chinese aluminum intake
Felpro factory style head gasket
Mild Howard's cam
Stock distributor with Pertronix
Stock exhaust manifolds
Estimated compression: 9.6 static, 7.9 dynamic

Base timing is about 12 degrees, however I have tried a variety of timing trying to find a balance between cold start and detonation. Regardless, it never resulted in running hot.

Boiled the new thermostat and swapped in the old thermostat from my 360 (which I also boiled). There is no issue going to the smaller diameter thermostat, right? The original 1966 S manifold that I took off had the larger diameter thermostat.

There is no mixing of coolant and oil.

Maybe the problem is that Chinese manifold? But I can't think of how? I can not find any feedback on those manifolds whatsoever. I do feel guilty buying it, I won't pretend I made the moral choice. But allow me to be the guinea pig if it is the issue. Is there some common issue when going to an alunimum intake that I am missing?

Thanks for any help!
 

[1964Fastback]

Is it overheating at idle or driving down the road or both?  What temps are you seeing on the gauge now, compared to before?

Pat

[Porkchop]

It will overheat both at idle and driving. I can't go 2 miles down the road. It is not hitting a steady temperature. The gauge has every intention of going all the way, but I am shutting it off before that can happen. It is also dieseling when I shut it off.

Prior to the overheating issue, it was running at about 190 F - whether driving or idling. Now it is hitting 230, but like I said I am shutting if off. That is a bit of an estimate because I don't have the Autometer Gauge connected with this new manifold - it doesn't have 2 ports. I am going off the factory gauge and temperature sensor which I do know work well, there just aren't any numbers on the gauge.

I will work on getting the autometer connected.

Also, it is quite cool outside - highs in the mid 60's.

[70tp]

Sounds like radiator May be plugged ? Or something blocking the water flow?

[1964Fastback]

Yeah, that's all I can think of is something blocked at the two faces of the intake (gasket problem?) or the thermostat area if the basics are in place (full radiator, fan and belt okay, etc).  There must be other people running these intakes that would have mentioned if the water passages were blocked.

Pat

[FrozenMerc]

Is the thermostat opening?  New stat, smaller diameter, it may be defective, or there may be geometry in the new intake that is preventing it from opening, perhaps installed backwards?

When it gets hot, are the rad tanks hot too?  If the rad is cool, you definitely have a blockage.

[jayb]

If it gets hot that quickly the thermostat should be opening, so if you start the engine cold with the cap off the radiator you should see some flow in the radiator once it hits 180 degrees.  If you don't, there is some blockage.  Thermostat installed backwards maybe?

[WConley]

You may need to pull the intake and check the coolant passages.  Since that's the one major part you changed, I would be very suspicious.  There could be a big chunk of slag in there.

[Porkchop]

I have the same radiator, fan, and water pump as when it was not overheating.

Thermostat is definitely in correct direction. I boiled the first thermostat to confirm it opened at 180F. I then took the known good thermostat from my 360, boiled it (it opened at 180F), and then installed it.  It actually opened wider than the first thermostat so I thought that was going to be it. Nope.

I was wondering if I blocked off flow, but I don't see how. I used a Fel Pro gasket set with water passages on both ends so even if I could manage to install them backwards it wouldn't matter.

Perhaps the water passage in the manifold is blocked as mentioned? Maybe I could try to fish a coat hanger through the thermostat hole? I am not yet ready to rip the manifold off. 

I will start it cold and watch for flow in the radiator as suggested. I'm 99% sure the radiator tanks are getting hot, but I will check that too. Maybe later today.

The manifold does not have an exhaust crossover. I did not cap the holes on the head, but from what I'm told that is ok. Is this correct?

[WConley]

The manifold does not have an exhaust crossover. I did not cap the holes on the head, but from what I'm told that is ok. Is this correct?

You should be fine if there's no intake passage.  The intake gasket can typically handle sealing that.

[driveamerican]

Could it have trapped air does the stat have a bleed hole

[Porkchop]

I was wrong about there not being coolant in the oil. The dip stick was reading a bit high today so I drained the oil, and the first bit was water/coolant. Trying to separate it to see how much.

Obviously, I will have to remove the manifold to figure out the problem. Perhaps I messed up the gasket install or maybe there's an issue with the manifold. We'll see how motivated I am.

[Porkchop]

The driver's side coolant port in the manifold is totally blocked off. It's not even slag, it's 100% blocked off. It's not flush with the gasket surface, but inset. I will see if I can post pictures.

Do not buy these manifolds.

Given that these things are everywhere, I'm surprised nobody has reported on this.

I do not know yet how the coolant was getting in the oil. Upon removing the valve covers I saw coolant resting at the very back of the manifold by the rear most bolt holes. After removing the manifold there was coolant in the lifter valley. I can't say for certain that this didn't happen when I removed the manifold. I drained the block, but I know that doesn't 100% clear the manifold of coolant.

[jayb]

Looking forward to the pictures.  What I suspect is that the sand core for the water jacket cracked or broke when the sand mold was assembled.  This will leave a "fin" of aluminum in the water passage after the manifold is poured, blocking the flow. If that's what the problem turns out to be, the fin is usually pretty thin, and you should be able to take a punch and break through it, and clear out the passage.  Then the manifold will be usable.

[Stangman]

How about head gaskets on backwards if the intake port doesn’t fix it.