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My car has been running hotter than normal at highway speed. This past winter I replaced the intake manifold, distributor and carburetor. I have re-tuned the car. I believe the timing is correct. If the carb is too lean could that cause the engine to run hot at highway speed. My car is running slightly below 210, in the past it would never be that high. I have a 50/50 mix in the radiator. I am thinking the carb should be a little richer and maybe add a little water to the radiator. The engine is a 327/300.
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Re: High Temp at Highway Speed
You mention a new distributer. Is the timing adjusted correctly and is the vacuum advance working correctly? -
Re: High Temp at Highway Speed
I believe the timing is correct. I will be rechecking today. How do I verify the vacuum advance is working correctly?Comment
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Re: High Temp at Highway Speed
DIsconnect the vacuum hose with a timing light on the damper. Timing should drop (retard) when disconnected and advance when reconnected. You really need a dial back timing light or a degree tape on the damper to tell if it's advancing when it's supposed to and the proper amount. However, if it isn't working at all, you can tell with the disconnect test. You should have 50*+ of total advance on one of those engines at cruise settings when everything is right.Comment
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Re: High Temp at Highway Speed *Thanks* *NM*
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Re: High Temp at Highway Speed *Thanks*
As Ed suggested, proper functioning of the vacuum advance is the first thing to check. At idle with the vacuum can connected, the total timing should be initial plus full vacuum advance. You didn't state the year of your car, but most 300 HPs have a vacuum can with 15-16 degrees of advance, but the specs changed a bit over the years.
If the vacuum advance is okay, the next thing to check is the radiator. What is its history? If the date code indicates it's original, it is probably well clogged with deposits, which have significantly reduced its heat transfer capacity, and since they are not reparable, the solution is a new DeWitts.
DukeComment
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Re: High Temp at Highway Speed
Ralph:
I believe the first thing I would do is confirm if the reading of the guage is correct. If you changed the manifold, you either changed sending units or you re-installed your other sending unit in your new manifold, both of which can lead to discrepancies from past readings.
The second item would be checking the stiff wire in the bottom hose. Make sure it is good from the pump, all the way to the radiator.
This is assuming your cooling system is full to start with.
MikeComment
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Re: High Temp at Highway Speed
The gauge would, indeed, be the first thing to check.Comment
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Is High Temp at Highway Speed Normal
I checked the gauge with an infrared tester. It appears to be accurate. I did reuse the old temperature-sending unit. Upon further examination this is what I found. During low speed driving 45 MPH or less the engine temperature is about 180F. During higher speed highway driving, 2500 RPM plus for extended periods, say over 15 minutes, the engine temperature elevates to 190-200F. It seems to maintain 190-200F for as long as the RPM’s are over 2500. When I return to normal or low speed driving the temperature continues to elevate to close to 210F+. After an extended period, say 20 minutes, the engine temperature will begin to cool down to about 180-190F. Since putting my car back together a few years ago the engine had always ran in the 180-190F range regardless of type of driving or out side temperatures. I should add today’s ambient temp was 90F+
Could this be normal and I'm concerned for nothing???Comment
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My opinion
Normal "new" is 180. Your radiator is no longer "new". Nor is the rest of your cooling system. Your symptoms are normal for a car like yours. The archives are loaded with info.
Water boils at 212 at sea level. A 13# cap will raise that to 238. I wouldn't run one that hot but that would give you a large margin of safety for boil over. My '63 runs in the same temp range as your car under the same conditions. It has the original radiator. I haven't messed with it. It has never boiled over even in the heat at Bowling Green last week.
You can try all the tricks others recommend. I would spend time and resources on a new radiator if I was worried about fixing it. Which I wouldn't, yet.
You may have something else wrong. Just my opinion.
MikeComment
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Re: Is High Temp at Highway Speed Normal
You never did mention what year car you have, but if it has a 35+ year old aluminum radiator, it's probably near time for a new one. Check other things like timing, vacuum advance, and radiator hoses first, since they are quick and cheap. If everything checks out, you may want to give Tom DeWitt a call. If you don't want to spend the $$ on a faithful repo, he has some good alternatives as well.Comment
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Re: Is High Temp at Highway Speed Normal
The car is a 67 Corvette with the original rebuilt 327/300 engine. The radiator is not original, but it looks like an original aluminum. When it was replaced I don’t know. Tomorrow I will recheck the timing. After I set the timing to 36 degrees with the centrifugal advance springs removed I replaced them. However, I can’t remember if I gave it a few quick rev’s past 3000 RPM to verify if the advance was coming in. If I am not getting enough advance could that be causing the temperature increase? I did squeeze the lower radiator hose. Not sure what I looking for. It wasn’t stiff and it wasn’t soft. It is only a few years old. A radiator replacement my be in the future, as a winter project.Comment
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Re: Is High Temp at Highway Speed Normal
Ralph - you should be able to see the date code on the top left of the radiator for an age check....CraigComment
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Re: Is High Temp at Highway Speed Normal
Craig, no date code. I just checked.Comment
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Re: Is High Temp at Highway Speed Normal
Ralph, a couple of things. You are looking for about 36* total advance WITHOUT the vacuum advance. In other words the initial + the mechanical advance. The vacuum will kick in another 15-16* at full vacuum, or where ever your can is set to kick in. If the radiator has been replaced, is it actually an aluminum radiator? If it is, whether it's a DeWitts repo or a Griffin look alike it's probably ok unless it has been abused by running without coolant or any anti corrosion protection.
On the lower hose, you are looking to feel a spring inside that will prevent the hose from collapsing under suction. You can squeeze the upper hose together. The lower you should not be able to.Comment
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