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Sorry I am new here, I will introduce my self and apologize for my stupid first question. My 1977 L48 new to me 2 weeks ago, is running 140 to 160 on the gauge. It never goes into the red but in my mind It is too hot. I have never had a V8 before so I though I would thow it out.
From: At my Bar drinking and wrenching in Lafayette Colorado
Yes, you should be concerned. Your engine is running too cold. It should be 180 - 200. Thermostat temp should be 190. If you're running 140-160 you need to change your defective thermostat to get your temp up where it belongs. I recommend you "shoot" your engine temp with an IR gun to verify that your gauge is accurate - it is unusual for an engine to run that cold, so you may have other problems.
Lars
I also have a 77 Vette, but unlike you my biggest issue over many years was trying to get it to run cooler.
Yours is clearly not coming up to temp.
Running spot on. Your temp guage should be pointing just a fuzz below the 200 mark. anything below 215 is OK.
Anything above 190 is OK. Below 190 the engine is COLD. it will not run properly until it comes up to temp.
This I know from many years of experience with this car and many others with a gen 1 chev V8.
As Lars stated, get the proper thermostat in there to start with. Then go from there.
jbnb77,
If you ever wrote a book on How To keep Your C3 Temps Under 200
You would sell 10,000 copies.
Unless you still have all the emissions crap still on there, such as sensors at the waterneck, the lower temps will do no harm.
It's still hot enough to remove condensation from oil and cast-iron parts.
However, I suspect you are either misinformed about what the dash marks on the temp gauge represent.
Or, the sending unit is suspect. If the wire to the senders terminal is loaded with grease, there is the poor GRD or poor reading.
If you have ever been to a drag strip, the staging lanes are NOT used to bring coolant temps up to 200 for better performance, hint-hint.
From: At my Bar drinking and wrenching in Lafayette Colorado
Verify it with an IR gun. You can "shoot" an accurate temp on the water crossover on the forward intake manifold just below the thermostat housing gasket. You can also use the IR gun to "see" when the thermostat is opening by "shooting" above and below the thermostat as the engine comes up to temp: Make sure the thermostat is actually opening at a temp between 180 and 190. Always keep in mind that the thermostat only controls minimum engine temp, and has no control over maximum temp. Temps up to 220 are not unusual, and are marginally OK. Temp should not go over 230 on a properly functioning car (for reference, on the early C4 Vettes with the standard Gen 1 small block, the engine fans do not come on until temp hits 230, and they shut off at 217).
If all checks good, the first thing to check is your timing. Most out-of-tune Corvettes are severely retarded, and this is the biggest contributor to high engine operating temp. Make sure your timing is set up for 36 degrees total with resultant initial timing in the mid-teen range. Make sure your vacuum advance is functional and hooked up to manifold vacuum, which should make your actual timing at idle about 30 degrees.
If this does not solve the issue, you need to start looking at radiator condition, capacity, and airflow through the radiator, which includes assuring that the car has the correct, stock fan with a functional fan clutch. Many cars have been "modified" with POS "flex fans" and other horrible aftermarket components. The integrity of the seals around the radiator, and the position of the fan in the fan shroud are also very important aspects to Corvette engine cooling. Inspect everything - most of these cars have been modified and messed with over the years, and simply bringing them back to the stock, correct configuration does a remarkable job of making them run right.
Lars
My error guys. It is running 240 - 260F on gauge under load. and 220 at idle.
That is scary hot. I think you need to get a heat gun as suggested to rule out a faulty gauge. Then go from there. Stuck closed thermostat or other issues would then need to be eliminated 260 is a crazy number and will result in serious engine damage.
From: At my Bar drinking and wrenching in Lafayette Colorado
260 won't actually cause engine damage, but it should be boiling over at that temp with a stock radiator cap. The fact that the OP indicates it's running at 260, but does not indicate a boiling-over issue, indicates that his numbers may not be accurate. NASCAR engines operate "normally" at 260 all day long, but use high pressure cooling systems.
Lars
they are also machined to live at those temps are street cars arent
Harbor Freight sells those temps guns they are super cheap.
These cars suck up every bit of debris from underneath. Do you have the airdam underneath?
On any vette, once a yr i remove the fan/shroud and from the backside blow out the fins with a garden hose (not apressure washer or youll flatten the fins)
Youll be amazed at how much crud comes out..take your time. Works great on other coolers, condenser for ac etc I do the condenser at home the same way it really helps.
Lots flush, change coolant but I never see guys do this. Buddy loaned me his Expedition last week...that radiator has to be over 3 ft wide
90k mi and plugged solid. Ac now get super cold right now fans run way less
First make sure your timing is correct that can have an effect on temps..then adjust carb if need be, ck your cap etc.
In warm climates I like to use the Milodon 160 hi flow stat. A std stat Ill drill 3 1/8" holes around the outer ring to prevent air pockets
The IR temp gun arrived today. I took car o to highway to put under load and ran it up to 245 and confirmed with gun. I am now working on timing but before I started with dist cap and rotor and new plugs. I dont like these Napa caps, there is barle lip and getting it to seat with notch lined up is a PITA. Is there a better cap out there or do they all seat this way?
What cap did they sell you?
The ECH RR171 IMO is the better of the 2 Napa brand caps they sell.
The ECH RR171 has the Brass terminals.
The MPE RR171SB has what looks like tin plated terminals.
Either of the 2 caps should fit correctly.
Is your L48 77 equipped with A/C?
You will see (2) Items #1s and (2) items #2s
There is a difference in the thickness of these seals.
Make sure all the radiator support seals are there.
Last edited by bmotojoe; Aug 20, 2022 at 10:16 PM.
I use these Stant caps with the red valve lever. They are rated to the same pressure, fit my radiator, and provide a useful pressure release which helps debug issues.
The also don't require channellocks to remove, like the original one did (pictured, left). The box on the right is the current ACDelco replacement. This was for a 79 L48, so the part numbers may be different for your car.
Please post some pics of your setup! For a start, is your vacuum advance connected?
My error guys. It is running 240 - 260F on gauge under load. and 220 at idle.
Take a look at the attached file for understanding the basics of the Corvette Cooling System.
Water boiling point is 212F, at 15 psi that boiling point is increased to 249.8F. A 50/50 mix of water and antifreeze will add 11F buffer to those number so in reality the car pukes out the overflow when the water temp is 260F or higher.
If your car is truly running at 240 - 260F I would expect to see some level of boil over at shutdown, all that aside 240 - 260F on gauge is too hot for an L48 to run so you have issues to sort out.
Owning a Corvette is a special thing! Having your High School Dream car is even better!
My Uncle had a 1969 with side-pipes and I knew back then I would have to have one someday. I have been lucky as I have had my 1968 BB Convertible Corvette since 1991 and my 1988 since 1994. Corvettes are special and require more tender loving care than many older cars. Here on this Forum you should find plenty of experts to help you out with your "New to You" Corvette! Take your time and be sure to buy the GM Factory Service Manual (FSM) as well as the Assembly Information Manual (AIM) for your year Corvette. The factory manuals are better and more accurate than any aftermarket books. They have better troubleshooting guides and schematics in them.
On my Corvettes I run 70/30 mixtures where I have 70% Distilled Water and 30% anti-freeze because we don't get that cold very often and cooling is more important and that works better when you use more water. Having a infrared thermometer is a very handy tool as you can check your wheels when driving to be sure that they are all close in temperature, with a bad wheel bearing or stuck brake caliper it would show up quickly. I also check the exhaust manifolds in roughly the same place over each cylinder to ensure that all 8 plugs are firing and everything is working right. There are plenty of uses for the thermometer.
Having a good working radiator cap with an overflow bottle is also very important because as the coolant gets heated up it expands and needs to be collected, stored and drawn back into the radiator as it cools off. So often a broken hose or defective radiator cap can allow air to get into the radiator and that impedes the cooling to have a big air bubble inside the radiator.
Good luck with your Corvette and be sure to get it up to date and as "safe" as possible. Replace the belts and hoses and check the brakes to be sure that you are in a safe car. Brake fluid should be flushed every couple years at most as older brake fluid can cause lots of trouble rusting through the lines and damaging the brake calipers. There are lots of places that need attention on an older Corvette but the guys here are here to help you in any way they can. There is a lot of experience here on the Forum. Just be sure to put as much as you can on the profile so people can look up your Corvette and see what you are talking about. Any Modifications are very important as we need to know about them to help you more effectively. Be sure to check the tires and don't drive fast on tires over 10 years old. Corvettes are a lot of fun and are fairly easy to work on and take care of.
Sorry I did not mean to abandon this thread. I have been side tracked because of a fuel leak at the fuel inlet of the Carburetor. I was trying to start by checking timing until I found the leak. So Once I get that leak fixed I will be back on the heating issue.
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L48 engine temps
