rjdawson

Ok I've read the dozen or so 455 overheating posts and I'm stumped as to why I'm
still overheating at idle. If you could STAND IT, could you please see
if anything sticks out at you here?

-68 442 - Freshly rebuilt 455, I believe it was a '72. Bored .060 over, Edelbrock 750
and intake, old C heads from the 400, HEI, I don't think anything really crazy in the way of mods.

New aluminum radiator installed when the car was restored with the 400, but the 400 was not built correctly
and had to be immediately scrapped. I'm starting to think the rad COULD be undersized afterall now with
the 455 or was even too small for the 400?

The problem: Especially at idle or even at up to 30 mph, the temperature creeps up to full
temp, but get to 45 mph or above and it immediately cools right down to about 3/8 on the gauge which is
where it always was before.

I was really buying into the theory that if it cools at speed, it's not the radiator. But looking
closely at it just now, it appears to have an overall depth of 3" to fit into the original mounting but
the actual cooling surface is recessed at least 3/4" on front AND back, making it only 1.5"
thick. See pics.

Also, looking through the fins, I don't see any pipes running around inside, just thin metal vessels running straight
across. Appears to have plastic sides. Maybe that's all normal for a modern unit.

Here's what I've done so far:

-Timing set at about 16 degrees initial before advance, with plugged advance. Idle about 750-800 in Park but
have experimented with up to 1000

-To set mixture I leaned it out til it wanted to die then let out the screws until I got maximum vacuum
reading of about 19.5. It really drove great after doing that and putting in the HEI so I think that was fairly
close to being correct.

But, no change on temp including before and after HEI install.

Latest experiments:

-I read here that advancing timing = less heat, so I advanced the initial
timing even further to about 20-22 degrees with vac advance plugged. Engine still seemed to
run fine and didn't knock. Also learned that this engine might require a temperature vac advance switch
that gives full manifold vac at high temp, so I just plugged into manifold directly to simulate that. At this point
it was at 30 degrees+ at idle judging by marks several inches behind it, and it didn't advance much further when I revved
it to perhaps 2000 RPM.

-Others mentioned that too lean can lead to overheating. So I unscientifically let out the mixture
screws a couple turns each to make sure it wasn't running lean. The exhaust aroma let me know
that leanness was no longer an issue for the time being...

-To put a cherry on top I put "Water Wetter" in the radiator and octane boost (was worried about
the extreme advance causing detonation, I probably just reversed the effect of advancing the timing
by doing that now that I think about it).

Under those conditions it actually idled for about 1/2 hour last night when it was about 70 outside, before
it crept past 1/2 on the temp gauge. So it made a huge difference (2 long lights is enough to make it rise
steeply usually) but it still got to 3/4 eventually, and held there until I got too bored to see if it would go
higher. Outside temp has never made a difference at idle in the past anyway.

Then I took it out and it ran very poorly, not surprisingly. It was obviously set too rich and timing
was too advanced as it was difficult to turn over when restarting.

-Today at the car wash I was at 3/4 temp and sprayed water at the radiator for about
1 minute and temp went down to 1/4. That seems like a very good sign to me but I don't
know what that would suggest.

I just don't understand how it could be airflow. I have the original non-AC fixed blade fan and pulley
with shroud, and there's crazy heat blasting out of there at idle.

Misc: Fan measures 17", fixed blade, original from car. Pulley 7". See pic for shroud.

Here's what I'm down to now:

-There is a 16 lb pressurized radiator cap installed (I thought they all were?). It has a lever on it
which I haven't seen before. There is a nozzle coming out of the neck for the coolant overflow, but it
NEVER gets any overflow in there, still looks like new.

Also, last fall I I topped it off completely with 50/50 which I know now may have resulted in it
being overfilled. Now it's about 1 inch below the top. Other posts I read suggest these items could be problematic.

I wonder if they could have accidentally put way more than 50% antifreeze in when intiailly filling it? Looks NUCLEAR
green in there. I'll test that.

-Could a bad water pump provide enough flow at fast speeds but not at low speeds? That's
actually my #2 suspect now (or until someone here sets me straight). But doesn't explain how it cooled down from
3/4 to 1/4 with a 60 second spray of water earlier.

-Still something with timing / carb. But problem has remained the exact same before and after HEI, and anytime
efforts are made to properly tune the engine/mixture.

The engine somehow seems like it's making too much heat at low speed because it dissapates a LOT of heat as it is.

-Air flow - I REALLY don't want to do the electric fan route. Seems like that's masking the problem.
How to get more flow? I figured a fixed blade fan would provide the most possible. Smaller pulley =
faster fan speed? Try another fan just to eliminate the current fan as the problem? I really don't care about
power drain, I have more than I know what to do with now.

-Radiator itself undersized? I hear some people say the 455 needs a lot more cooling, and others say it doesn't.

-Someone asked if it has ever "boiled" - I assume that would mean steam being emitted
somewhere. It hasn't, but I'm very careful to head for open roads when I get to 3/4 temp so not sure if it would or
not given the chance.


Thanks, let me know if I won this year's longest post award!

Pics -
Cap and Overflow: http://virtualcourthouseriches.s3.am...m/101_1957.JPG
Radiator Thinness: http://virtualcourthouseriches.s3.am...m/101_1958.JPG
Fan/Shroud http://virtualcourthouseriches.s3.am...m/101_1959.JPG
Fan/Shroud 2 http://virtualcourthouseriches.s3.am...m/101_1960.JPG

Nilsson

This long post you never state what the max operating temp is in degrees, unless I missed it.

rjdawson

Not really sure what is meant by operating temp. How high would it go before it leveled off if I just let it idle?

Or what temp thermostat is in there? Not sure about that. I'd know a lot more about everything if I'd been a part of the rebuild, etc but unfortunately I wasn't.

I've just been going by the factory gauge which I know is not accurate but it IS consistent at being at 3/8 for the last 20 years I've owned the car and at highway speed, vs creep up to "H" at low speed.

ah64pilot

Sure he did, 3/4.

Hey man, I just had the same problem on my car. I couldn't figure it out. I changed the thermostat and radiator cap. I even did the water wetter thing...but you know water wetter doesn't work in a 50/50 mix? Anyway, I found my problem...and let's hope yours isn't the same thing.

I have an idea of what it may be, but let me ask you this first. When you open the radiator cap and look inside, how many rows do you see? Do you have two elongated holes? Or do you have 3 smaller round holes? Or do you have 4 round holes? This will give us an idea of the size of your radiator.

oldcutlass

Basically what you are decribing above is the normal operation of an engine. When they sit still and operate they get warmer, due to the lack of air and water flow at low rpm's. As you drive faster the air and water flow increases and cools everything down. Your temp gauge will fluctuate from 1/4 to 3/4 depending on speed and ambiant outside air temp.

The aluminum radiator is more efficient than the old styles because it disapates heat easier. If you feel there is still an issue you can install a mechanical gauge so we can see what the actual temps are.

rjdawson

To tell you the truth, when I look in the radiator I can't see anything but the coolant. And when I look through it I don't see anything except thin vessels going straight across.

The net size of the radiator is definitely 28X17X1.5 or so, the dimensions are identical to what AutoZone lists as the "non-AC" radiator for the 400 engine for my car.

Similar if not identical to this: http://www.oreillyauto.com/site/c/de...1386&ppt=C0331

They DO recommend it here for the 68 with 400 engine non-AC, which is what it was purchased for I guess.

Do you figure it's just not up for the job of the 455?

oldcutlass

Without actual temps in degrees, we can't actually tell you if its suitable or not. I run a similar radiator with my BB in the 67 with a flex fan and no shroud. It seems to work fine, it's been 100 here for the past week. If I let mine sit and idle the temp will slowly creep to almost 220, it maintains 180 all day long driving from 20 mph up.

rjdawson

OK sounds like that's the first thing to nail down then. Will post that.

oldcutlass

You can purchase an inexpensive 3 gauge cluster, oil pressure, temp, volts. It's easy to install!

Lady72nRob71

This is seems to indicate low airflow. The 7 blade A/C / HD cooling fan will move a larger volume of air and could help your issue.
Check to see if the seals are in place around the radiator so the fan is pulling air only through the rad.

We really need some degree numbers to see what it is really doing.

Infrared thermometer - much easier and faster - cheaper, too! Measure on the manifold next to the sender unit.

rjdawson

You guys really know your stuff.

I did not return the car to correct timing and mixture yet - but the temp gauge was reading "3/4" and I hit every water way I could with an IR thermometer.

And the temperature was....180-195. By the sending unit on the intake was about 200 even.

Sorta feel a little stupid now. Will tune up again now and report back.

I did notice one thing that I'm concerned about - I was "shooting" the headers and they all returned back about 250-325 except for cylinder 6 which was almost 450.

Double checked and all others were over 100 degrees cooler.

Hoping I'm off balance on my fuel mixture or something - if you've ever seen this I'd love to know what might be going on there.

Thanks a lot, I wish I knew more to help out too. Although after this I might know something about something.

ah64pilot

Is the car warmed up yet? Sometimes headers or manifolds will heat unevenly until the engine is warmed up due to the 4-6 and 3-5 exhaust ports being "shared" at the center of the head.

Also, get your timing and mixture all set up again and report back your temps. It could be that the sending unit is bad giving you the "3/4" reading. The 3 gauge pod from Autogage is a great idea to keep an eye on everything. Get the water, oil, and volt unit for ease of installation.

oldcutlass

The gauge clusters are about $30, I've got the autoguage set on my car. Based on your quick temp check, I really don't see anything out of whack. Ahpilot is correct, return all your settings to what they are supposed to be, and recheck.

rjdawson

OK, so I retarded the timing back to where it was before, about 16 degrees with plugged advance. Put the vac advance back on the carb again instead of manifold.

I also put the vacuum gauge back on and by adjusting mixture I was able to get a reading of 20 which is the highest yet.

It still didn't want to turn over at first when I started it so apparently more retarding the timing is needed.

Anyway, the temp shot up very fast after that while idling.

Here were some IR temp readings I took, not sure which are useful:

Bottom Hose: 195-218
Radiator: 190
Water pump body: 220
Neck at front of intake (thermostat?): 230
Small hose from neck to water pump: 220
Temperature Sending Unit: 235
Heater hoses: 220
Top hose 185-200
Top of Manifold near carb: 260

Could this indicate the thermostat is not opening all the way?

This is where temp gauge in the car was past max so I got it out on the road. It cooled off much slower that usual, I had a hard time getting it to come down much.

Any thoughts much appreciated!

rjdawson

This also appeared at the front of the driver's side head today, behind the power steering pump...

http://virtualcourthouseriches.s3.am...968%5B1%5D.JPG

oldcutlass

It looks like the sending unit is leaking. BTW what was the outside ambient temp when you were letting it idle for a long period of time? It looks to me that possibly you may have a sticking thermostat. The reading at the carb is where the exhaust crossover is, so it will be high.

If it's really hard to start, back your timing off a degree or 2. On your carb a/f screws, turn them both equally ccw 1/8 of a turn to richen it up a tiny bit.

ah64pilot

You can try changing the thermostat if you don't know how old it is. If that doesn't work I'd be thinking the radiator is too small...we'll see though.

As for your oil leak, that is coming from the intake manifold rubber end seal...at the corner. If you decide to replace it, don't use the rubber seals...just put a bead of RTV on the block and be sure to set your intake straight down on it. This works much better than the rubber.

compedgemarine

looking at the pics my first issue would be that the fan and shroud are mismatched. there should only be 1/2 to 3/4 inch between the shroud and the fan blade tips. if there is too much the air will tend to go in a loop from the engine bay to the front of the fan back to the engine bay. it would be hot as it picks up hot air around the engine and a small amount through the radiator.

ah64pilot

Thanks for the pictures! Yeah, that fan is WAY too small for that shroud. You need to measure the shroud and get the biggest flex fan (if that's what you want to run) to put in there. No wonder it's getting hot at idle...you might as well just take it off and blow on the radiator with your mouth.

66luvr

I was taking pics and you posted exactly what I was going to say.
I had the same rediator in my car. It never overheated as it never boiled over and puked coolant, but I wanted it to do better at idle. I bought an Alumitech with 2 rows of 1.25" tubes, and a shroud, put my fan back on (which looks a lot like his, mine is 18"), it didn't produce the results I wanted. The car was perfect when going down the road but at idle it would creep up. So now I knew it was definitely air flow. In order to get a fan which fit the shroud I had to get a clutch fan ( 19" ). I bought a "severe duty" clutch from Autozone, pic of box with number attached. The difference in the air movement at idle with the hood up was dramatic, it moved a lot more air. So far this year it has done what I wanted it to do, run right where the thermostat opens, 180*.
So I feel you need a fan which fits the shroud. The fan shoud fit inside the shroud about half way. It should not go all the way into the shroud.
Hope yours works as mine has.

RetroRanger

I third the fan shroud mismatch

it doesnt cool enough w low rad airflow (idle) but cools fine with rad airflow (45mph)

Lady72nRob71

x2. I did not even look at the pics before. Get a fan to fill the shroud so air is not pulled in from around that big gap.

miked

Be sure lower hose is not collapsing (missing spring)

Octania

That is a good idea, but would show as the opposite problem- poor cooling at higher engine speeds, not at idle.

If you need more airflow at idle, which appears to be the agreed solution... the factory had a fix for that- huge *** fan with many blades and a thermal clutch. Grab the clutched fan off an AC/HD Cooling vehicle and install that. Remember, the factory had VAST resources and many years of experience, and managed to make cars that did not misbehave like that.

A couple more things....
You may well find, depending on your cam and whatnot, that running your distributor vacuum with a manifold source is preferable. I just found a GREAT article explaining all that on the internet- from a Corvette forum. If you chose to run ported [carb] vacuum, you should have the factory Thermal Vacuum Switch in place, which transfers vacuum source from ported at low temps to manifold at high temps, to alleviate overheating at idle, as explained in the factory chassis service manual. Also, the '68 442 is supposed to have an air dam under the radiator support- plastic piece about 4" high [low? it hangs down]... from frame rail to frame rail. Part of that item's function is to help prevent hot air that just exited the radiator from being drawn right back in the front of the radiator. Pretty sure I read that in a Technical Service Bulletin of the era. So, make sure that part is in place as well as all the other radiator enclosure side pieces- which you may have to FABRICATE now that your radiator is non-std in size and shape.

rjdawson

rjdawson

Update - I installed a cheap 19" flex fan from autozone and it made a huge difference. So I will get a HD / AC fan with the as much cfm as possible. Thanks all who helped me figure it out!

35mastr

Post the part numbers for the HD/AC Fan and clutch as I am having the same issue at idle. Creeps up then will boil over.

rjdawson

I just bought a 7 blade clutch fan from a 68 Toronado, which I haven't installed yet - if it has a part number on it I will post it. Also will let everyone know if it is more effective than the cheap flex fan, as that new fan will occasionally let the temp go higher than I want (but much much better than before).