All... my '62 has a Chevy 350 (Fastburn 385 crate motor) in it... I was battleing serious overheating... I put a new sender, new thermostat and finally a new aluminum Griffin radiator in it with an electric pull fan... having done all that... I was able to get it to stop overheating within a 1/4 mile from the house... BUT... and here is my dilemma....

Cruising= 180 degrees steady
Stop at a light= fairly rapid increase to 200+
Start cruising again= usually drops back to near 180 after a couple of miles of driving

Anybody have any suggestions on how to keep it cool all the time?

Thanks
Scott

 

What kind of overflow tank have you got? Is the system completely full? did you pop a couple small breather holes in the stat? these things have worked for me.

 

Is the fan shroud in place?
Clutch fan working properly?

 

Since it does not overheat while cruising, it indicates a possible airflow issue (shroud, fan, etc.). If the fan is a clutch fan, the clutch may be slipping excessively. I assume you have the shroud on, but are the seals around the radiator intact?

Also, overheating at idle can be lessened if you have full time vacuum advance (search previous posts on this subject). Vacuum advance really does help lower engine idle temps.

I have a healthy 350 CID (with a flex fan, older non-original copper/brass radiator, radiator surround is sealed, as is the gap at the top of the shroud), and frankly it never overheats.

Note that temp rise on stopping from a cruise speed is normal (since the engine has been "creating" quite a bit of heat, and now the airflow through the radiator has slowed down. However, it should not go up +20 degrees.

Do you have the stock shroud and fan?

Good luck,
Plasticman

 

All good items.. system if full... I have the shroud in place... I have a flex fan running as well as the electric pull fan attached to the backside of the radiator... I have an expansion tank... not sure what you are asking specifically about it... breather holes in the stat?

Radiator surround and seals arround the radiator... not sure I completely follow...

Agree with the airflow assessment... I am just at a loss for what to do to fix it... thought the new radiator would be the solution... disappointed that I am not running on temp all the time but happy that the new radiator allows me to get past 1/4 mile from the house...

Have read on other forums that the carb could be part of the cause... I have a Barry Grant Speed Demon carb on it... seems to be perfectly tuned at this point....

Thanks for the initial replies... any additional advice?

Scott

 

My car does the exact same thing. I'm going to try a few more things. Its got the clutchless fan.
a few questions..
1)how far into the fan shroud should the fan be?
2)should I seal off the gaps beside and underneath the radiator?
3)do the 5 bladed fans(used with clutch)or a flex fan pull more CFM than my lil "X" fan??

 

Sorry to hear you suffer from the same deal but happy to hear I am not alone... possibly together we can get a solution....

How do you intend to seal off the radiator... I certainly have large gaps on either side of the radiator as well as a gap across the top btwn the shroud and the radiator...

Scott

 

What type of dist. are you using, and what is the ignition MAP?

What is initial timing set at?

What is your manifold vacuum?

What is your TOTAL idle timing?

What vacuum can are you using?

Mark

 

Fan should be half and half inside the shroud. As far as gap, filling them won't hurt, but mine has a few also. ran 185 thursday on a 90 degree day.

 

Have you verified the temp with an IR gun ?

How far beyond 200 deg. ?

 

Check the Corvette Central catalog for seals around the radiator. They are (if memory serves) rubber flaps that are glued in place.

Also make sure the fan is the correct diameter. The larger the fan, the better (but of course, you don't want it to hit the shroud due to engine movement).

As for flex fans, there are some weak ones out there, and some great ones. GM has used flex fans on some cars in the 70's and 80's, and those are great because of the seven blade high pitch design (but they are noisy!).

In other words, every item you can "upgrade" will help keep the heat down. You may be looking for a magic bullet, but several small bullets
will help.

Plasticman

 

Oriondriver, first, I would get rid of the flex fan. In all my years, I've yet to find one that pulled as much air thru the radiator as the stock ones. Put the original five blade fan on with a new fan clutch or use a fan spacer. The correct depth for the fan into the shroud is approximately 50/50 on the blades. However, on my 59 I had an overheating issue at idle and I sealed the openings around the radiator on the front side with sheet rubber and black silicone sealant I bought from the hardware store and installed a 1-1/2-inch deep spacer behind the original 4-blade fan. Voila!! The fan is now fully within the shroud and pulls a ton of air thru the radiator( DeWitts type aluminum). The car runs very cool and doesn't overheat a bit. My 62 has a DeWitts radiator, the original fan and clutch at 50/50 spacing and doesn't overheat.

 

Carb has nothing to do with it. Your symptoms are classic, and indicate you have enough radiator, but not enough airflow at idle/low speed; that says you need to upgrade the fan/clutch/shroud (ditch the flex-fan), seal the gaps around the radiator and shroud, and make sure your ignition timing map is set up correctly with properly-functioning vacuum advance, connected to full manifold vacuum.

 

Well.. upon closer inspection I noticed that the lower shroud (left and right sides) are not there...nice size gaps on either side of the radiator and a nice 1" gap across the entire top edge of the shroud between the radiator and shroud... guess I will start there and see what happens if I can seal the gaps... sheet rubber and silicone, huh?

I am not a motorhead so I have to admit that most of the questions about vacuum advance and the like are above me... the car does have a MSD Corvette Pro-Billet Tach Drive with MSD Blaster and a MSD 6AL ignition control... I believe the vacuum advance lockout plate is on it as the vacuum advance is plugged...

As for the fans... the flex fan is as big as it can be to fit... the electric pull fan is pulling a lot of air... the problem is that it appears that the air is "leaking" out under the block or out the sides... a guy looked at it a couple of weeks ago at a gas station and told me to just remove the flex fan as the electric fan was much more efficient...

I have not verified the temp with an IR gun but I did change out the temp gauge just to verify that it was not the gauge...

Again.. thanks for all of the advice...

Scott

 

I thought 200-220 stopped in traffic on a hot day was normal? Mine runs 180 on freeway and up to 220 if I get stuck in traffic (100° F days around here...) doesn't puke coolant though - so every thing seems fine. Except my *** sure gets hot. And my shifter - that sucker is blazing hot some days.

I'm sure you could get better performance from your system by sealing up the rad but I'm not sure I'd worry too much about 200° -

pm

 

At what temp should I start to get worried... it has yet to spew fluid... any thoughts on running something like "40 Below" in it?

The other thing I noticed missing is the lower baffle forward of the radiator... worth the cost to put back in?

Scott

 

Oriondriver, The flex fan you are using, regardless of brand, WILL NOT move as much air as the factory fan. PERIOD. The flex fans are oversold to convince you you are going to have increased horsepower and less drag. Bulldooky!!! Put on the original fan with either the original fan clutch or use a spacer that will put the fan into the shroud.

Repairing the shroud is a must. The gaps around the radiator I was referring to are on the front side of the radiator, not the rear side. Also, is the lower radiator baffle (fiberglass) installed between the front fiberglass grille surrond and the radiator core? It is installed above the front license plate horizontal brackets that go back to the frame. If you have a large 6 to 8-inch gap between the front fiberglass of the car and the radiator core support, it's missing. I had to buy one from Eckler's and install it before I could seal the exterior gaps under, and on both sides of the radiator core support. It made a BIG difference in the cooling of the car. The sheet rubber I referred to can be had at any good hardware store. It is sold in 12-inch wide pieces from a roll. The silicone sealant (black) can be had at any auto parts store or Wal-Mart. It will adhere to the metal and rubber. Good luck.

 

just use water and antifreeze...that other stuff is a waste of money.. seal around the shroud...and make sure the complete shroud is there...I am not a big proponent of electric fans...a stock fan, possible one from an air conditioned model should help out, what temp thermostat are you using? you could also use a smaller waterpump pulley to make the pump spin more at an idle....little steps..one at a time..you will get that baby cool yet.

 

Any idea what thermostat your running if one at all? Recommended temperature range is a 180, not a 160.

 

I recently put in a new 180 degree stat...