Over heating
 

John Z-ANYONE
I have a 1967 conv. 327-300 hp.4 spd. 336 posi. All stock. I have owned the car for 17 years. It has 66,000 miles on it. I am a member of NCRS 29634. problem with overheating when in heavy traffic. Some history, about ten years ago, car had a mis, put in new tune up kit, plugs wires,points,rotor. Car still not right. Took car to local hot rod shop. Guy said that vacuum advance was not working We could get one at the time. He blocked the vacuum line off, and put a ACCELL spring and weight kit. Later that week I put a new vacuum advance on and hook vacum line up to stock location. Car runs super good, but driving in the woodward cruise ,after a short time car starts to over heat, I have to turn off woodward and get moving and then car will cool down. John I have read Beatin THE HEAT,NCRS summer 2013. I have set timing at 8 btdc. total timing,i do not know. 180 thermost,original radiator,no problem at highway speed. thanks George ?????????????

Is your clutch fan working as intended? If the answer is yes, how did you confirm?

Did you check your clutch fan?? There is a good article in the tech section on testing it.

If this just started after changing out the vacuum can, most likely has something to do with timing changes that were made. If he just stuck the spring and weight kit in without tuning it to the motor and determining the spring and weight combo needed to get total advance, you don't know what you have. You need to find out. A timing tape and timing light are all you need. Then make sure you have the right vacuum can and it is working properly.

Threads by LARS and others on timing will help you out.

The first two suggestions were the clutch fan because its an air flow issue and its easy to check. With diagnostics its easy to overthink things.

When diagnosing anything you want to check the simple stuff first so you don't self emolliate later.

And when old cars overheat its almost always one of two things, lack of coolant flow or lack of air flow. Start with all the easy stuff, coolant, clutch, belt, shroud(s) collapsed hose, bad T Stat, radiator flow, pump and so on as invariably that is where the trouble will be found.

Dan

My feeling is the radiator is old but it's just a guess, how old is the radiator and what type of radiator. If/when the top hose is hot and the lower hose is hot the radiator tubes could have build up deposits and heat is not being transferred to the aluminum and then to atmosphere.

Start by going back to make sure the tune up is good, dwell, timing etc. Post any markings on the vacuum advance control you changed, did this change stop the miss? It could very well be two different problems and not related to each other.

The 1967 300hp engine should have a vacuum advance control part number ending with #355 and the specs are something like 0*@7" vacuum 15*@12" vacuum. The stock engine should idle with approx 17-19" vacuum so the control should be pulled full at idle providing a total idle timing of approx 21* (15* V/A + 6* initial).

You need to tell us the number stamped on the VAC mounting bracket. Also, you need to map out the centrifugal curve. Installing a weight and spring kit without knowing what is does is a mistake. The OE '67 centrifugal curve is lazy, 30@5000. Using the silver or gold springs in the Mr. Gasket 928G spring kit will bring is all in at 3500 with the OE weights, which should be retained.

And please quantify "overheating". What's the highest temp you are seeing on the gage and what was the ambient temp at that time. Understand that slogging along in a parade in hot summer temperatures is one of the worse abuses an owner can subject his car to.

If you really do have the original radiator, it's now over 50 years old and suspect, although high operating temperatures only during slow speed driving are usually caused by a weak/inop fan clutch or a spark advance map that is not suited to the engine configuration and having a proper spec VAC is critical, but even the engineers screwed the pooch on this one a few times.

Duke

As others have said, I would verify that the Fan Clutch is working properly. Perhaps someone can post a link to the Tech info on this, I can no longer find the Tech Section here on the Forum.

Here are a couple of PDF's one Hayden put together that does a very good job of explaining the proper operation and how to troubleshoot a Fan Clutch. The second is an article that explains how to adjust the Fan Clutch you might find useful.

Good luck... GUSTO

My '67 Coupe has the original 300hp/327 in it. It has factory air and an automatic transmission which means in that front of the radiator is the A/C condensor and in front of that is the transmission cooler. In heavy traffic the temp starts climbing toward the 250 mark and the A/C has to be shut off. That was until I installed a SPAL 16" puller fan in it like I did my '62. I refuse to fight overheating and risk damage to the original engine, and I refuse to shut off the air conditioner because I want it turned on.

When I got the Corvette it had a Be Cool aluminum radiator in it. Be Cool makes a bracket kit for installing an electric fan. After I installed it I let it get warm with the fan off (heading for the 250 mark). At that point I flipped on the fan and let it run. The temp gauge took a just a couple minutes to head down to the mark below 180. It was over 100 degrees outside, and we had plenty of those kind of days last Summer here in So Cal. Now I don't give the water temp a second thought and I do enjoy my A/C.


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Isn't there also a "water additive" that will bring down the temperature. I've kept a bottle/can or two around for adding into the radiator during the summer months and it seems to work pretty well. Just a thought.

Randy,
Your top rubber radiator seal is installed backwards. If you look at the part of the seal that you have in front of the radiator support, you will notice a cut out area that will go around your radiator shroud bracket. This will allow the seal to do it's job the way it was intended:thumbs:
P.S. I agree with those that are suggesting the fan clutch. A new, correctly functioning fan clutch from K&B was the final piece to fixing my overheating problem at idle.

It's called "Water Wetter".

I think the consensus is that it works somewhat with pure water, but is not very effective when used with an anti-freeze mix.
Lots of discussion on the C-6 forum.

Do the easy stuff first: Pull your vacuum advance hose off the stock "ported" vacuum location and run it off manifold vacuum. The additional timing at idle will most often solve any overheating problems. More info from me, Duke and John about this in our Timing Papers, available from me via e-mail request. :thumbs:

Lars
V8FastCars@msn.com

NO. The marketing-hyped water-wetter additives are nothing more than surfactants, which are already blended into every coolant/anti-freeze on the planet, factory fill and aftermarket. The water-wetter additives are made to be used with plain water as the coolant, as it states on the back label on the bottle (but nobody reads the labels). Cooling fixes come in boxes, not bottles. :thumbs:

Another thought...don't forget the pressure cap on the surge tank. This little guy gets overlooked (a lot) but can cause and/or help to cause your overheating issues. The article below by John Hinckley is the "bible" when it comes to solving/maintaining your cooling system. I followed it to the letter, having to replace many non-original items. Overheating problems can become a lot like electrical problems...you can chase them forever if you don't have a guide to help you through. I HIGHLY recommend you read this article and follow John's sage advice.:thumbs:

http://www.camaros.org/pdf/corv_cooling2.pdf

Easy to remember. Just like my buying of wine---"Boxes not bottles"! (lol)

Good advice; and, you are 100% correct. I did not read the back of the bottle--print was way too small for my old eyes!

Exactly right. In some racing organizations they don't allow anti freeze because it's difficult to clean up of the track if you have a problem so people use it with straight water. Some swear by Water Wetter. I never saw a difference, but it made you feel good about yourself for using it.

OP check the FAQ thread on C1/C2 page sticky, page 3.... all things to check are there

https://www.corvetteforum.com/forums...aq-thread.html