New AMC 360 Installed - couple questions

[JR74CJ5]

Hi all,

So finally got the 360 finished up and in. She's running good and strong.

Two concerns - let me know your thoughts on these all. Like to bounce around some ideas...

1 - Still running a bit on the hot side. I have a new flex fan, 180 degree thermostat, new cooling hoses and "shouldn't" be anything wrong with the radiator. Now I'm not running a shroud, but never have and never had any problems with the temp... I am running the temp sensor that came in the new intake still, so not positive on accuracy yet. Next to check. Main question - is it normal for a fresh rebuild to run a little hotter than normal during break in? I assume with stuff starting to "clearance" itself out in there and piston rings seating it would be a little more friction than the old tired 304 had... It's running about 220 - 225 degrees F.

2 - At idle, when I advance timing to 12 degrees per the DUI HEI unit instructions, the engine "stumbles" intermittently... Not really a miss at all, but hard to explain. Shakes a second like a miss would, but thermo temp reading confirms at least not a constant miss, and at higher RPM, or increased timing advance it gets better. I think I have it set at 14 degrees advance @ idle. I'm slightly worried this is too much, though I know some high performance engines run much more than that...

Random mentions for both:

I am still running my MC2100 carb on a adapter to the edlebrock 4 barrel performer intake. Too little fuel maybe? Running lean causes additional heat right? Too little fuel at idle may stumble a bit? Haven't done the calculations, but the carb was right (maybe slightly high) for the 304 CFM - probably a bit low for a 360...

Haven't even re-adjusted carb mixture screws yet really. set them about a 1/2 turn richer than I was running them on the 304.

I do have the shroud for the fan / radiator, just needs adjustment for fitment again, and never needed it even while on rubicon on 100 degree + days before...

Let's see what you all think. Questions on set up etc let me know.

Thanks for looking

 

[Lumpy Grits]

Get the fan shroud installed.
You may also want to consider some hood vents at the back of the hood in-between the hinges.
Check you plugs color to be sure you ain't run'n lean.........
Take the t'stat out and see what you get in temps.
LG

 

[cglax6]

Need to make sure your temp gauge and sensor match up or you could get bad readings.

First, put that shroud on and see what kind of results you get.

If you're sure of your temps, you could be running lean.

Are you running headers or stock manifolds? You could just be trapping a crapload of heat under that hood.

Side note...you may want to look at a different carb. You say you have the performer intake...what cam do you have? Edelbrock recommends a carb in the 500-650cfm range for carbs with that intake. You'll be fine with a 500cfm carb seeing as you won't be running at high RPM.

 

[JR74CJ5]

I think it's a great start to put the old temp sending unit back in from the 304's intake to start and see what I get on temp readings...

Also ensuring the mixture is right is another good start for multiple reasons too.

From there - I do run hooker headers. However, remember they're the same ones that were on the 304, and it ran 210-215 all day with no vents, shroud, etc... The problem I have with the shroud is during water crossings the fan flexed and hit the shroud, which bent the blades and sent them through the radiator. Moot point as I "shouldn't" go through water that deep anyways, but you know.... It also needs a bit of work to reinstall, not impossible by any means, just annoying...

Not arguing, I want the feedback, just explaining my thought process before going too far down a rabbit hole you know?

 

[Lumpy Grits]

210*-215* is high with a 180* t'stat. That 'stat' is fully open at 195-200*.
Can you do a 'rod-out' to your radiator?
Really do feel you need to install the shroud.
How can the fan blade hit the shroud, if the body mounts and engine mounts are in good order?
How much blade tip clearance to the shroud do you have?
Also-Do you have a dedicated GND from your dash panel to the battery? That alone, can make all the difference in the world to gauge readings.
LG

 

[Posi]

If your running lean a vac gauge at idle will confirm it.

 

[JR74CJ5]

How can the fan blade hit the shroud, if the body mounts and engine mounts are in good order?

Hitting a mud hole with it spinning hard bent the fan blades enough to hit it somehow... I wheel this thing pretty hard sometimes, so it's always possible there was a loose body bolt etc around that point.

I'll need to reinstall it to see clearances etc. It's worth a shot to try to concentrate more volume through that radiator and increase cooling, but at freeway speeds the volume is pushed in from the airflow anyways and fan may as well not be on depending on it's flex out and engine RPM

If your running lean a vac gauge at idle will confirm it.

I'll text you later to confirm some of this - I have a vac gauge, and tried using it before for mixture setting etc, but didn't fully grasp the concept. I searched on it a while and got a lot of mixed information and started running down the ported vs manifold vacuum hole etc... I know at idle, my passenger side vac port from carb has very low vac until rpm's are increased then it's stronger. Will get readings. That is where I have vac advance on distributor hooked up.

What is everyone thinking on the timing setting for advance and intermittent "stumbles" at idle with lower advanced timing?

 

[JR74CJ5]

210*-215* is high

Is 210-215 degree damaging hot though on these v-8's? Or just a bit higher than normal?

I'm liking the ideas for cooling it a bit though. Starting with mixture settings, confirming engine is not running too lean, and checking the sending unit out and accuracy with a IR gun.

Then looking at that shroud again, seeing what it will take to get it thrown back on there.

Then I'll look at more options on venting etc if still needed.

I did read some about decreasing the antifreeze 50/50 mix down to more water than antifreeze and having good results. During the summer there is not much worry of freezing temps here. May research that a bit more. Does water cool more efficiently than antifreeze?

 

[JeeperChris]

You need the vacuum line to the distributor blocked off when you adjust your timing.

 

[JR74CJ5]

You need the vacuum line to the distributor blocked off when you adjust your timing.

Yep - got that - thank you though.

That's also when I noticed vacuum @ idle is near non existent...

With the line plugged, advance on timing is around 14-15 (hard to tell for sure since only ticks 10 each way on marker) - should be closer to 12 per the DUI instructions if I remember right from 5-6 years ago when installed it...

But if I retard timing any and raise idle with adjuster screw, the engine seems to run rougher at idle...

 

[Lumpy Grits]

Most have very good results with a 195* t'stat. A 195* 'stat' isn't fully open till 210*-215*. IF the cooling system is clear and flowing correctly. Your engine will even run better.
HINT-Seal off any gap in front of the radiator and the grill.
That will force the air to go through the radiator, and not around it.
The shroud helps a whole lot with that.......
I hope you only use distilled water to mix with the AF.
Tell us about your radiator.
Also-The stumbles your engine is having, could well be caused by a incorrect/unbalanced idle fuel mix.
Have you checked for carb and manifold leakage?
Stay with 50/50 AF mix.
LG

 

[JR74CJ5]

Most have very good results with a 195* t'stat. A 195* 'stat' isn't fully open till 210*-215*. IF the cooling system is clear and flowing correctly. Your engine will even run better.
HINT-Seal off any gap in front of the radiator and the grill.
That will force the air to go through the radiator, and not around it.
The shroud helps a whole lot with that.......
I hope you only use distilled water to mix with the AF.
Tell us about your radiator.
Also-The stumbles your engine is having, could well be caused by a incorrect/unbalanced idle fuel mix.
Have you checked for carb and manifold leakage?
Stay with 50/50 AF mix.
LG

School me on how a thermostat does anything different to the cooling system when fully warmed up at operating temp. If it was high enough to restrict flow intermittently to force more cooling to the fluids in the radiator before re-entering the engine, I could get that but I don't think it's realistic, is it? Mainly the higher thermostats are to warm up the engine operating temp quicker in colder weather correct?

Like the idea of a little sealing around the radiator front and grill - will look into that a bit for some more "forced air cooling" AND putting that dang shroud back on there

I did not use distilled water - yeah I know... I also still drink from the hose instead of those fancy bottles... :laugh: I understand though, but have never used distilled water in my cooling systems.

Radiator is 3 core steel replaced in 2011 when I stuck the fan through it's predecessor for mouthing off while I was mudding. It's name is Bob, and he's of dark complexion - not much more I can tell you about him Just kidding. Definite possibility it needs a clean out, especially since I do not use distilled water in the system. I may look into a new 4 core alum one day...

I'll be checking the mixture with vac gauges and will check again for any leaks around the carb or intake - all fresh built so "shouldn't" be any, but still worth the re-check. We did check the first time I had it all together, but not this time yet. This is kinda a preparation thread to see if I was missing something in my mind others may have thought of, like yeah JR the engine will run hotter when freshly built for X miles or so - keep an eye on this etc.

Will report more when I get it checked out a little more.

 

[lowcountry]

"Mainly the higher thermostats are to warm up the engine operating temp quicker in colder weather correct? "

No. A thermostat rating is meant to keep your water temperature at what ever the thermostat is rated at...nothing to do with cold weather.

To answer an earlier question, 200 - 210 is not going to be "damaging" to your engine,

 

[JR74CJ5]

No. A thermostat rating is meant to keep your water temperature at what ever the thermostat is rated at...nothing to do with cold weather.

So restricting flow until in-block temp is higher before introducing cooler fluids into it doesn't help with warm ups, or maintaining warmer operating temps in cold climates?

https://auto.howstuffworks.com/how-does-the-thermostat-in-a-cars-cooling-system-work.htm

https://auto.howstuffworks.com/cooling-system8.htm

And some of the hottest climates run no thermostats right? Why when a higher temp one would help keep their engines cooler? I'm not sure this is the most efficient idea (no thermo) but it's been done quite a bit.

Again, not arguing, looking for schooling there. I'm really only wondering how the increased temp rating of the thermostat would assist in maintaining a lower over-all operating temp. If what you said above was true completely, I'd just want a lower thermostat rating, all things otherwise considered...

 

[Lumpy Grits]

The t'stat is the main 'choke' point in your cooling system.
If you are running higher than the t'stat should run when fully open(usually 10-15* above it's rating)then you have a coolant blockage and/or airflow issues.
The temperature stamped on the t'stat is when it just starts to open........
I live in the Mojave, and would not for one minute run any water cooled engine without a t'stat.
No t'stat is bad all around for the engine.......
Be sure the t'stat is not in backwards-You want the temp sensor towards or in the block.
Check the color of your spark plugs to confirm correct fuel mixture.
LG

 

[JR74CJ5]

The t'stat is the main 'choke' point in your cooling system.
If you are running higher than the t'stat should run when fully open(usually 10-15* above it's rating)then you have a coolant blockage and/or airflow issues.
The temperature stamped on the t'stat is when it just starts to open........
I live in the Mojave, and would not for one minute run any water cooled engine without a t'stat.
No t'stat is bad all around for the engine.......
Be sure the t'stat is not in backwards-You want the temp sensor towards or in the block.
LG

Yeah I agree LG - no thermo isn't what I want to do either way - just asking the questions to try to make sense of how a higher temp rated thermo would be better for the engine / overall operating temp. I'll have to do some more research on that...

Yup - got it orientated correctly - good call on the checking though, I've done it before knowing better then too.

 

[JeeperChris]

Be careful on a 4-core radiator. I got one for mine with a 258 in it and the mechanic is putting it in for me this time. There ain't much room there. I have a 4-blade solid mount fan. You will have more room with the V8 but just know that it's a hog.

 

[Lumpy Grits]

You want at least 3/4" space from the front of the fan or fan-clutch, to the radiator fins.
Anything less, and you'll be 'eating' a radiator when the frame flexes.
LG

 

[JR74CJ5]

I've got the room if I go that route, but appreciate the heads up for sure bud - more available in the grill, and more available by removing and adjusting the spacer for the fan as needed if needed (my fan is about 3" out in front of the water pump +/- from memory...) Think I may be a bit over 3/4" off radiator, but not positive - haven't checked in a while...

Got lots of stuff to check in there now just for S & G's.

Thanks all -

 

[Lumpy Grits]

Make sure the grill's body mount(under the grill)is 100% GTG.
Even 1" clearance is good for the fan....
Can you post any pictures of your set up?
LG