Do they ALL overheat?
02-10-2019, 02:49 PM
#1
Do they ALL overheat?
Seriously, I am on the verge of just giving up.
If driven slowly enough or simply idling for more than a few minutes anytime the ambient temperature is 75-80 degrees this '67's 300/327 engine temperature will creep past 210 to 230.
The fan clutch is new and 'correct', fan is correct five blade, the radiator is virtually new and yes, flushed, as well as the block, thermostat is 180deg. Stant Superstat. vacuum advance is a B20 direct vacuum(non-ported), and initial advance is 8 deg. When driven at speeds over 30MPH the temp shows is constant at a tad over 180. I removed the splash shields in the engine compartment and that did help somewhat.
Yes, I have checked the temp at the thermostat housing with an IR gun and it closely matches the gauge.
The owners manual says that 210 deg. is ...'normal'. ....really? It also says that IF the temp exceed 230 when driving slowly, I should stop and let the engine cool down. Duh.
I KNOW that I can not be the only one with this 'problem?'.
I'm tempted to consider the water pump, but not really interested in the "try this and see" approach.
If driven slowly enough or simply idling for more than a few minutes anytime the ambient temperature is 75-80 degrees this '67's 300/327 engine temperature will creep past 210 to 230.
The fan clutch is new and 'correct', fan is correct five blade, the radiator is virtually new and yes, flushed, as well as the block, thermostat is 180deg. Stant Superstat. vacuum advance is a B20 direct vacuum(non-ported), and initial advance is 8 deg. When driven at speeds over 30MPH the temp shows is constant at a tad over 180. I removed the splash shields in the engine compartment and that did help somewhat.
Yes, I have checked the temp at the thermostat housing with an IR gun and it closely matches the gauge.
The owners manual says that 210 deg. is ...'normal'. ....really? It also says that IF the temp exceed 230 when driving slowly, I should stop and let the engine cool down. Duh.
I KNOW that I can not be the only one with this 'problem?'.
I'm tempted to consider the water pump, but not really interested in the "try this and see" approach.
Popular Reply
02-10-2019, 11:10 PM
Former Vendor
Trust me when I say I have solved this HUNDREDS of times because that's what I did for the last twenty years. The forum will throw dozens of ideas and suggestion on how to solve this issue, the problem is where do you start? Well, the natural reaction to slow speed and idling problems is to suspect air flow. Air flow is vital to a cooling system but the symptoms of idle overheating are almost always a timing issue, and by timing I mean the distributor map and advance function. Of course you want to make sure your engine driven clutch is working and going the right way and all the obvious stuff but don't let that get you off track and onto special mods and stuff. I just posted this comment on a C3 thread, so I'll cut and paste it.
This problem is real easy to check....
A: Get set up with a timing light and check the timing as specified in the manual. Before disconnecting everything, plug the vacuum hose back onto the distributor and the timing will jump an additional 15-18 degrees over the static timing. If it doesn't, you have a problem.
B: This overheating problem is real easy to prove...
If the timing does not increase 15-18 degrees, then simulate the advance function by turning the distributor. Add the 15-18 degrees manually but do not drive the car. Let it idle and see what happens then. You should be able to idle for 45-50 minutes with no issues. Again, do not drive the car like this. Change the timing back to the static setting before driving and get a new vacuum can and/or fix the problem.
You might have a good vacuum can, it might just be the wrong one. The difference between these timing issues and all other cooling problems is that this one MAKES heat. Well, it actually transfers it from going out the exhaust and into the coolant. All the others just limit the cooling function whereas you run 10-20 degrees hotter, not 30-40.
I am still not sure you have a good radiator in there. It should be some form of aluminum, either the correct 3155316 or a good replacement aluminum. See DeWitts 1249063M as an option. I like this one because it is equal in performance, Black color, and only cost $825. Not show correct but a real good performance radiator.
This problem is real easy to check....
A: Get set up with a timing light and check the timing as specified in the manual. Before disconnecting everything, plug the vacuum hose back onto the distributor and the timing will jump an additional 15-18 degrees over the static timing. If it doesn't, you have a problem.
B: This overheating problem is real easy to prove...
If the timing does not increase 15-18 degrees, then simulate the advance function by turning the distributor. Add the 15-18 degrees manually but do not drive the car. Let it idle and see what happens then. You should be able to idle for 45-50 minutes with no issues. Again, do not drive the car like this. Change the timing back to the static setting before driving and get a new vacuum can and/or fix the problem.
You might have a good vacuum can, it might just be the wrong one. The difference between these timing issues and all other cooling problems is that this one MAKES heat. Well, it actually transfers it from going out the exhaust and into the coolant. All the others just limit the cooling function whereas you run 10-20 degrees hotter, not 30-40.
I am still not sure you have a good radiator in there. It should be some form of aluminum, either the correct 3155316 or a good replacement aluminum. See DeWitts 1249063M as an option. I like this one because it is equal in performance, Black color, and only cost $825. Not show correct but a real good performance radiator.
02-10-2019, 02:53 PM
#3
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no they don't over heat. what kind of radiator do you have?
02-10-2019, 02:55 PM
#4
Le Mans Master
Is it a 15# cap? 8* of initial timing sounds a bit low. You can try increasing the timing slowly and test drive. If no pinging, you can advance a bit more. Is the vacuum advance functioning? How have you checked it? Does your lower radiator hose have the internal spring inserted to keep it from collapsing? Have you thoroughly read John Hinckley's article on this exact issue? And, to answer your initial question...no, they don't overheat if set-up correctly. Especially, at 75-80* ambient. I drive mine with the A/C on here in Texas when it's over 100* and she doesn't overheat.
Last edited by leif.anderson93; 02-10-2019 at 02:58 PM.
02-10-2019, 03:05 PM
#5
15 lb cap. I have had the timing at 10 and set it back to 8deg (closer to the 6 the book says). The hoses are new and wouldn't be collapsing at the low speeds where I have the problem anyhow. I reduced it to smooth out the idle and reduce the popping from the side pipes when backing down from 55 -60 MPH.
No, I haven't read John Hinkley's article on this. Where can I find it?
Thanks,
Bob
No, I haven't read John Hinkley's article on this. Where can I find it?
Thanks,
Bob
02-10-2019, 03:08 PM
#6
Is it a 15# cap? 8* of initial timing sounds a bit low. You can try increasing the timing slowly and test drive. If no pinging, you can advance a bit more. Is the vacuum advance functioning? How have you checked it? Does your lower radiator hose have the internal spring inserted to keep it from collapsing? Have you thoroughly read John Hinckley's article on this exact issue? And, to answer your initial question...no, they don't overheat if set-up correctly. Especially, at 75-80* ambient. I drive mine with the A/C on here in Texas when it's over 100* and she doesn't overheat.
02-10-2019, 03:13 PM
#7
Melting Slicks
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I don't blame you for being scared and worried about causing engine damage and costly repairs. Not to mention being stranded on the road and lost of driving time.
You can do all the above what was recommended or purchase an electric fan radiator with it's built in thermostat.
Good Luck in what you decide.
You can do all the above what was recommended or purchase an electric fan radiator with it's built in thermostat.
Good Luck in what you decide.
02-10-2019, 03:14 PM
#8
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02-10-2019, 03:15 PM
#9
Le Mans Master
John posted the PDF of his article in post #76 of the below thread...
https://www.corvetteforum.com/forums...problem-4.html
https://www.corvetteforum.com/forums...problem-4.html
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02-10-2019, 03:27 PM
#10
Safety Car
15 lb cap. I have had the timing at 10 and set it back to 8deg (closer to the 6 the book says). The hoses are new and wouldn't be collapsing at the low speeds where I have the problem anyhow. I reduced it to smooth out the idle and reduce the popping from the side pipes when backing down from 55 -60 MPH.
No, I haven't read John Hinkley's article on this. Where can I find it?
Thanks,
Bob
No, I haven't read John Hinkley's article on this. Where can I find it?
Thanks,
Bob
Last edited by Robert61; 02-10-2019 at 03:34 PM.
02-10-2019, 03:28 PM
#11
Hmm. I just assumed my radiatior was copper. Anyhow, this is a non-AC can and I can drive all day(and have) in 95 -100 degree weather and the temp stays rigth in the 185 -190 degree range and NEVER gets hot until I'm stuck in traffic for more than a few minutes or have to creep along at 20 MPH ..or less and then I always am in 2'n or 3rd to keep the revs up above 1000-1200 or so.
I will look at John's post.
I will look at John's post.
02-10-2019, 03:30 PM
#12
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John posted the PDF of his article in post #76 of the below thread...
https://www.corvetteforum.com/forums...problem-4.html
https://www.corvetteforum.com/forums...problem-4.html
The answer to "do they all overheat?" is contained within.
02-10-2019, 03:35 PM
#13
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Hmm. I just assumed my radiatior was copper. Anyhow, this is a non-AC can and I can drive all day(and have) in 95 -100 degree weather and the temp stays rigth in the 185 -190 degree range and NEVER gets hot until I'm stuck in traffic for more than a few minutes or have to creep along at 20 MPH ..or less and then I always am in 2'n or 3rd to keep the revs up above 1000-1200 or so.
I will look at John's post.
I will look at John's post.
02-10-2019, 03:43 PM
#15
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You only describe the radiator as a Harrison. Is it new or old? If you do not have a new aluminum radiator from DeWitts, that is part of your issue. Do you absolutely know the vacuum advance works? Does it actually change the idle speed when disconnected? Do you have the correct jetting, if too small, you will run lean and that creates extra heat. What plugs are you running? 
Dennis
Dennis
02-10-2019, 03:51 PM
#16
No this is not a new problem. It's always been there ....or at least in the three years that I have owned the car. It could be the radiator afterall, but it has been flushed and is not leaking. It looks new ....on the outside, anyway ans was supposedly replaced with the 'correct' one. I don't know of anyway to see if it is clogged, but since I can't think of much else to try ....maybe it is the radiator, but I would hate to drop $1000 to discover that the radiator wasn't the problem. A water pump, perhaps? ....although I have not experienced or heard of a water pump being at fault. Oh, and by the way, the bottom hose is new and does NOT collapse. That was among the first things that I checked.
02-10-2019, 03:54 PM
#17
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A temp of 180 going down the road indicates your radiator and basic cooling system is fine. A 230 temp at idle means you are not pulling enough air through the radiator core to get rid of the engine heat. Simple as that. You need to pull more air through the radiator core to solve your problem.
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02-10-2019, 03:54 PM
#18
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Is it a 15# cap? 8* of initial timing sounds a bit low. You can try increasing the timing slowly and test drive. If no pinging, you can advance a bit more. Is the vacuum advance functioning? How have you checked it? Does your lower radiator hose have the internal spring inserted to keep it from collapsing? Have you thoroughly read John Hinckley's article on this exact issue? And, to answer your initial question...no, they don't overheat if set-up correctly. Especially, at 75-80* ambient. I drive mine with the A/C on here in Texas when it's over 100* and she doesn't overheat.
Last edited by dcamick; 02-10-2019 at 03:56 PM.
02-10-2019, 04:08 PM
#19
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A temp of 180 going down the road indicates your radiator and basic cooling system is fine. A 230 temp at idle means you are not pulling enough air through the radiator core to get rid of the engine heat. Simple as that. You need to pull more air through the radiator core to solve your problem.
By the way, any chance your fan blade is installed backwards?
Is your fan clutch really working or is it just "there"?
02-10-2019, 04:23 PM
#20
OK, so I went and dug out my owner's manual. It clearly states that "Under normal operation, the gauge will indicate around the 210 degree mark. ....heavy traffic with stop and go, or prolonged idling in hot weather will produce a gauge reading around 230....." "Whenever the gauge reaches around the 250 degree mark, stop and ....."
It seem that possibly that I don't have a problem after all. Maybe I should have RTFB (read the .... book) before I started looking for a problem that didn't really exist.
By the way, vacuum advance works correctly and vacuum at the port in the carb at idle is 16" +. ...and U was mistaken, ALL small block radiators through '68 were aluminum.
...and Yes, m I feel a bit foolish about worrying about a bout problem that doesn't seem to be.
Bob
It seem that possibly that I don't have a problem after all. Maybe I should have RTFB (read the .... book) before I started looking for a problem that didn't really exist.
By the way, vacuum advance works correctly and vacuum at the port in the carb at idle is 16" +. ...and U was mistaken, ALL small block radiators through '68 were aluminum.
...and Yes, m I feel a bit foolish about worrying about a bout problem that doesn't seem to be.
Bob
