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Running Hot at high speeds
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Author:  sandy in BC [ Fri Mar 21, 2008 12:16 pm ]
Post subject:  Running Hot at high speeds
The Valaint is running well and should be ready for intergalactic travel with one exception. It runs hot at high speeds.

Im running premium fuel ....and a fan. The timing is initial 14....mechanical 15....and have 45 at cruise. No ping has been detected. It will idle for a week and never go over the centre of the gauge.

In 5th gear at about 80-85 (no speedo) it heads to the top of the gauge and steadily climbs till I chicken out....slowing to 60-65 cools it down in a couple of miles.

I managed to flip the belt over with high revs (rubberizing the bridge) and wonder if the belt is slipping at high speeds.

Is my cruise advance too much at 45 degrees?

Any other ideas?
Author:  argentina-slantsixer [ Fri Mar 21, 2008 12:23 pm ]
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my car did the same when I pushed her too far (above 100 mph steady after more than an hour of high speed mercyless driving)
Author:  LUCKY13 [ Fri Mar 21, 2008 2:09 pm ]
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Belt slippage can be a problem and should be looked at closely. Most of the time when I see this problem it is because of a restriction. Either the rad is to small, partly stopped up, or the lower rad hose is collapsing from the negitive pressure the water pump is greating ( needs a spring inside of it) . The hardest one to prove is when there may just be a few of the core tubes stopped up and the rad looks like its flowing but still is restricting. Look for cold spots up & down the rad when the engine is warmed with either a infrared temp gun or by hand ( becarefull of fan blades and getting burt).

Sometimes I will find a water pump problem, but most of the time it will get hot at other times if this is so. (bent or rusted blades, incorrect blade to block clearances).


Jess
Author:  Doc [ Fri Mar 21, 2008 2:17 pm ]
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Also test the thermostat, sometimes they do not open completly.
Author:  emsvitil [ Fri Mar 21, 2008 2:53 pm ]
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Everytime I've had a high-speed cooling problem it's been a radiator problem................
Author:  argentina-slantsixer [ Fri Mar 21, 2008 8:21 pm ]
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pulled my notebooks on my car. Happened that at WOT it didn't like lots of ignition timing, but when cruising at steady high rpm, the cam would make excellent vacuum and this caused te carburetor to lean out a bit intermitently (when Pow valve closed and/or open marginally according to fluctuating vacuum reading) I had to A) replace the power valve or B) change jets making the primaries a little richer (any of those) in conjunction with using a really stiff vac pod that would only open on steady high vac (relatively, my car idled at 16 but cruised at 11.5 @ 110 mph if no load such as sudden acceleration or clmibing up was present)

I also had this problem: since I had electric twin fans, if I used no t-stat it would be hotter than if I used a hi flow tstat. A "normal" t stat also caused to run hotter. I ended up with mylodon hi-flow t-stats in 165°F and that worked as a charm)

edit: my cam was installed ALL WRONG like 10 degrees off on the retarded side. I can't blame anybody on taht since I put together my engine... didn't know better at the time. Just took it to a racing cams regrinder who said it was "ok to line up dots and that would do it, no degreeing neccesary" :roll:

I had other issues back then when running an auto transmission but you have a T5... I'm curious, what final ratio do you get when using your OD? I guess that if the final ratio is too low for what would be "balanced" for your car frontal area and such, it could help to the overheating condition...
Author:  sandy in BC [ Sat Mar 22, 2008 7:05 am ]
Post subject: 
Final drive ratio 3.55 x .70 OD = 2.48 ....with 25" dia tires.

Problem is worse in 4th at 90 mph

I disconnected the vaccume pod and the problem remained.

I have always wondered if aerodynamics caused the air to flow around the grille at high speeds.

The rad is a stock 65 round tank......the only rad I have for replacement right away is a brand new aluminum 4 row Suburban rad....too big.

Thermostat is a good stock style 185degree 14 lb cap....no leaks ...good pump. The rad hose has internal wire.

I may have to cruise slower than I had hoped......
Author:  argentina-slantsixer [ Sat Mar 22, 2008 9:08 am ]
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Quote:
The rad is a stock 65 round tank......the only rad I have for replacement right away is a brand new aluminum 4 row Suburban rad....too big.
I don't think that rad is too big. I had (just before the teardown) a custom made 5 row big V8 rad and it helped a lot with the cooling.

The fact of this getting worse in 4th gear, talls me "something's wrong with revving up high". I'd check if this problem gets better or worse without tstat, and if it gets better with no tstat I might give those hi flow tstats a shot.

Now, not related, but with that .7 OD I'd use at least 3.81 gears, (to tell you the truth I'd be all over a set of 4.10 for a final ratio of 2.86) mmmmm.... I can feel the slant pulling thru alll the gears like a banzee screamer... :D
Author:  Doctor Dodge [ Sat Mar 22, 2008 9:36 am ]
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Sounds like a flow problem, either water or air.
You are (we are) running out of time... MATS is next week... no time for major "brain salad surgery", like saws-alling a "berb" radiator into the car...
Here is something I have done. Do you have some extra heater cores, trans / oil cooler or AC condenser laying around?

I have used heater cores, plumbed into the air path with the heater hoses, to get me some additional MPH before overheating. It's not "pretty" but doing that got me where I needed to go... faster, with-out overheating.
DD
Author:  AnotherSix [ Sat Mar 22, 2008 9:48 am ]
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If the radiator is ok, I would suspect the airflow like you already do. What kind of fan are you using?

Does there seem to be pressure under the front of the car, like lift at high speed? Maybe trying a simple air dam, just something flat attached to the radiator support that hangs down a few inches. It can put more pressure in front of the grill and less under the car.

The other thing that comes to mind, you must be spinning a few rpm at speed. Maybe the water pump is cavitating? I have used flow cooler disks and they do help. I think one of them made for the LA engines will fit the slant pump.
Author:  emsvitil [ Sat Mar 22, 2008 12:06 pm ]
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Collapsed lower hose????

Can you make it overheat at same rpm in lower gear?
Author:  slantzilla [ Sat Mar 22, 2008 1:02 pm ]
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Maybe the car is asking for some red ale? :lol:
Author:  sandy in BC [ Sat Mar 22, 2008 5:04 pm ]
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We lowered the car another inch on the front today to even it up with the lower rear and to help get the alignment where we wanted it. I think it will hlp put more air through the car. It seemed a little better on the way back from town. I may lose my front license plate once Im over the border. Its "in the way"

Tomorrow I try a new 180 Tstat....and no Tstat to see what gives.....and mebbe a ll red ale.....mebbe 1/4 bottle (3/4 for me)....and a rad flush.

The water pump has a plate/disc...the lower rad hose is fine.

It only overheats above 75mph....worse in 4th than 5th.

The Sub rad really is too big....both width and height.

I know I can just slow down.....but I cant take the extra days off work.
Author:  slantvaliant [ Sat Mar 22, 2008 7:07 pm ]
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A collapsing lower radiator hose is possible, as is inadequate airflow through the radiator.

A lot of modern cars have a deflector hanging down below and in front of the radiator, which helps force air through the radiator. Think "vertical chin spoiler", with the airpath sealed to the radiator support, to increase air pressure in front of the radiator and decrease it behind.
Author:  Aggressive Ted [ Sat Mar 22, 2008 8:45 pm ]
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Sandy,

Are you running the stock 4 blade fan?

The last two years I have been running the MOPAR clutch fan that Summit sells. It is a offset 5 blade. It really cools well on my engine, too much! I finally ditched it for an electric fan which gives me more heat. I can run over 75 mph just fine. No difference in temp with the stock radiator.

Maybe once your engine breaks in some more it will cool down. I am running 5-30W oil, maybe try some "wetter" in with the antifreeze????

The stock cap is 16#, maybe that will help a little.

Could you drop down to Seattle or Everett on the way? I will loan you the MOPAR setup to see if it makes a difference on your trip. It is in excellent condition. :D
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