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Yet another over heating thread

2K views 26 replies 10 participants last post by  johnsongrass1 
#1 ·
I've read so many of these over the past week it's enough to make my head spin. Hoping you guys can see something that might help out here, to make things more clear.

I'm working with a 70 Chevelle SS. 454 with a Dyer's 6-71 blower. I can provide more detailed info if it will help but don't want to clutter the thread up right now.

So when I start this thing it goes up to about 200, then you can tell that the thermostat opens, it goes back down to 185/190 and stays there for a few minutes. I let it idle this way in the garage yesterday for maybe 5-10 minutes, and it began to rise. I shut it down at 220. Had I let it go, it would have gone more. It happens constantly.

Some things that might be helpful to know about the car:

The distributor has no vaccum advance. It's sitting at about 18 degrees of initial timing when idling ~800 RPMs. I do not know what total timing is yet, because I have not installed the timing tape that is sitting on my bench. What I *do* know is that at very low RPM's (under 1500) and light acceleration, it does stumble a bit. Get over 1500 it runs smooth.

The radiator is 4 core. It appears to be stock. It's the same exact color and faded finish as is the rest of the metal under the hood.

I have the coolant bypass for the water pump plugged. I did this because the intake manifold only had one port in front and I wanted to use it for the sensor for the electric fans. The thermostat has 4 small holes drilled on the outside ring of it. Also, it has dual electric fans with a 190 turn on point.

I can dig up the specs on the cam if it will help, but it has an aftermarket cam in there. I believe the heads are stock and the bottom end of the internals are forged from what the previous owner has stated. Although after digging into this car my trust for him has faded.

That being said.......where do I even begin? I had thought about putting the water pump bypass back on there, and disconnecting the heater portion of the coolant circuit from the water pump and using that for the temp sensor for the fans. I have 0 plans to ever use the heat in this car.
I would of course remove both hoses and plug the radiator side of this as well.

Can the timing being where it's at effect this all that badly? Seems like it shouldn't - but never know. The lack of vacuum advance perhaps?

Also, it has dual Holley carbs on the car. I have a feeling that if these guys are not dialed in right I may be beating my head on a brick wall. However, I have not the slightest idea of how to tune these for a blower car. That is something I still have to research. Are there any good resources known out there to start with this?

I would think the stock four core radiator would be sufficient, but maybe not? Should I change it out to aluminum?

So many options that may or may not fix it. What to do?!

Any help would be appreciated!!
 
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#4 ·
Hmmmm....I was guessing the fans were pulling enough through but I'll have to test to see. I should also add, this does happen while driving as well. If I'm going down the highway it stays a steady 190 most of the time. But the instant I slow down or get into town, it begins to climb. I'll see if I can dig up a picture of the fans and how they are mounted.
 
#5 ·
When an engine overheats at low speeds but runs cool on the highway the problem is usually the fan(s).
The fact that at speed there is enough capacity in the radiator to cool more power than you use at idle says that your problem is air flow and not the size or build of the radiator. Look at the shroud and make sure the fans are pulling air through the entire radiator. Then look at your fans - consider getting fans that will pull more air.
 
#7 ·
Something that Old Bogie (very knowledgeable Member here, doesn't seem to post anymore) told me when I was setting up my Hilborn was that if you plug your Bypass it doesn't "bypass" anymore (meaning that the water in your water jacket deadheads at the Heads as it has nowhere else to go-btw, bypasses on small Blocks are cast into the Block)-this is a needed function-

This can have an seriously adverse effect on your Heads/Gaskets/Piston/Ring seal-if I were you I would hook up your bypass-
 
#8 ·
Fair enough, I had thought about hooking that back up anyways.


Is it bad that I'm thinking about using one port on the water pump for the bypass and one to connect the temp sensor at and just getting rid of the heater core circuit all together?
 
#20 ·
What are you saying here? You don't use the water pump to connect the temp sensor. Usually you use the port in the intake manifold for the temperature gauge and use the port in the driver's side head for the sensor for the electric fans. In your case with the blower you don't have a port for the bypass. Another option you could do is run a bypass hose to the port in the manifold, use the port in the driver's side head for the electric fan sensor, use the port in the passenger side head for the temperature gauge sensor. See if you can find out the name brand of your fan and how many cfm's it puts out also measure the overall height and width of your radiator.
 
#12 ·
I'd like to see your setup as far as your Thermostat-if you have room how about using one of these? I think if you put your Sensor at the Water Pump you are checking your Temp AFTER the Radiator-


https://www.summitracing.com/parts/mez-wn0028b

It's actually mounted flat on the front of the intake rather than on the top. It's a tall intake manifold. That is a great idea though, thank you for the link! I bet that would work well.

how many amps do your fans pull?? what kind of fans??

does not sound like the problem but,
the heater circuit is a recycle too
if it goes from the front intake crossover to the heater core and back to the pump??
do you have a heater control valve in the hose?? open it..
or bypass the heater core and valve, just tie the hoses together..

you also have some bypass/flow thru the t-stat with the holes.. how big are the holes??

I'll have to grab the model number off the fans tonight when I take more pictures. The heater goes from port on water pump, to core, from core to radiator. No control valve as far as I know. The holes on the T-stat are probably 1/16". They are tiny. Four of them. At 12, 3, 6 and 9.

If you are OK on the road but not when at low speed or idle your fan setup is not doing its job. You have proven that your radiator is capable of cooling because it is OK on the highway. Make sure your fans are pulling air through the whole radiator.
I'm hoping it's as easy as just getting a different / new shroud to make sure these things are doing their job.
 
#10 ·
how many amps do your fans pull?? what kind of fans??

does not sound like the problem but,
the heater circuit is a recycle too
if it goes from the front intake crossover to the heater core and back to the pump??
do you have a heater control valve in the hose?? open it..
or bypass the heater core and valve, just tie the hoses together..

you also have some bypass/flow thru the t-stat with the holes.. how big are the holes??
 
#11 ·
If you are OK on the road but not when at low speed or idle your fan setup is not doing its job. You have proven that your radiator is capable of cooling because it is OK on the highway. Make sure your fans are pulling air through the whole radiator.
 
#13 ·
The heater goes from port on water pump, to core, from core to radiator.
need a pic to be sure but,
if the top port on the WP and the radiator port are both on the inlet/suction side of the pump??
if one has more suction, it may be recycling from the pump to radiator?? maybe
I don't know what that would do??

as a test
pinch the heater hose off, and see if it cools any different at idle..
 
#15 ·
Update - with some pics.


No fan shroud......gonna have to get one of those......I honestl 100% thought it had one on there. Must be loosing my mind. The fans are dual 14" fans, doesn't seem to be a lot of shrouds out there for them but I'm going to get ahold of customer service at Jegs to see if they can hook me up. I bet this fixes my issue.......


Cray. Happy Friday!
 

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#17 ·
I don't know if this will help you or not but I was having trouble with overheating on my 454 engine too. I had the 4 core radiator with dual electric fans like you. At first I didn't have any problems until I went to the drag strip and ran a couple of passes and after that it started overheating. I changed thermostat and mixed anti-freeze with distilled water with no help. I finally purchased a high flow water pump. It comes in natural or polished. https://www.summitracing.com/parts/wnd-9242/overview/make/chevrolet https://www.summitracing.com/parts/wnd-9242p/overview/ This made the difference for me and my temp stays around 185-190 all the time at idle or on the highway. Another member was having the same problem and went thru the same things I did. He purchased an Edelbrock high volume water pump that fixed his problem.
 
#19 ·
As an update to this thread.


I first tried this product:





It would have worked, had the neck been clocked in the right direction when it was installed. I tried flipping it around, which made it even worse.


So I then went with this:











So this thing worked, but it took some doing because of how my housing sits on the front of the intake rather than the top. It made the dome of the original housing stick out 1" farther, which interfered with the heater core hose running from the water pump to core. So I eliminated the heater core out of the equation completely by plugging the one port on the pump, and the other port on the radiator.


This also changed how my top radiator hose ran from the thermostat housing back to the upper radiator connection. It is closer to the supercharger belt then I'd like, but it does clear it. I have it held back by some thick wire tied back to a valve cover T bolt right now, hoping that if it heats up a few times like this the hose may give just a bit even and hold that form. Fingers are crossed, but I'm not betting on this one.


Anyways, all back together now. Shop is cleaned up from the inevitable spillage of coolant. I let it idle last night for probably 15 minutes in the garage, max temp of 195 sitting there. Granted the weather is cooler now than it was when I first started looking into this, but it's a good sign I think!
 
#21 ·
In my scenario (earlier on) I had one port open on the front of the intake manifold, and the thermostat housing. The port on the manifold was connected to water pump for bypass. The other port on the water pump was connected to one connect on the heater core. The driver side head was being used for internal temp gauge.


I attempted to use the port in the passenger side head but that plug just refuses 100% to come out. I tried heat, I tried impact, I tried a BFBB....nothing worked.
 
#22 ·
I had to get rid of my 4 core copper (stock) radiator and get an aluminum radiator for my 67 big block Camaro. The aluminum radiator I have is a 2 row with 1" tubes and the core is 18" x 24". These are the fans I have mounted to my radiator. https://www.summitracing.com/parts/bci-75007/overview/. I have a 195* thermostat installed and my temperature run around 185*-190* in the hot summertime. (mid 90's). I was tired of messing with my car running hot. You can choose from 2 wiring harnesses https://www.summitracing.com/parts/bci-75104 https://www.summitracing.com/parts/bci-75117 I couldn't do with out them, they have everything included.
 
#23 ·
I believe I'd probably re use the existing wiring on the fans that are there today as long as they met the electrical needs of new fans.


But, if this doesn't seem to help that is coming next. I'm just going to do it all while I'm in there next time by replacing the radiator, fans with a shroud and high performance water pump. The radiator and water pump are stock so I have no problem replacing those. It's good to buy toys. :)
 
#24 ·
Yeah, that is what I did too. I kept looking in Summit Racing's catalog and came across this radiator module. The more I read about it the better I liked it. I mean it was a direct-fit aluminum radiator for 67-69 big block Camaros. The overall height and width is 19" x 29" with 2 rows of 1" tubes. It came with dual 11" electric fans with the wiring harness included. It also came with a 13# Billet Radiator Cap and a 1 pint Billet overflow tank. All mounting hardware was included too. This module cost around $1095 back in 2002 and it took about 4-6 months of looking at it before I pulled the trigger. I glad I bought it back then because now it cost $1285. Summit Racing has another Radiator Module for the Chevelle https://www.summitracing.com/parts/dwr-4149003m/overview/year/1970/make/chevrolet/model/chevelle
 
#25 ·
Chevrolet Chevelle 4-Row Champion Radiator (68-77)

See site above. With a blown big block this is what you need with a full shroud whether you use 2 electric fans or a mechanical fan. If you can use a mechanical clutch fan with full shroud, that would be your best set up. Electric fans are ok but they put a tremendous load on your alternator. Both electric and mech clutch fans only draw power from your engine when they kick on.
 
#26 ·
Just as an update to this thread, the over heating problem is officially fixed. I was able to take it out for a long drive this weekend with a steady 190 temp at idle and on the highway both. A 55gpm meziere water pump fixed things up! Still using the stock radiator.


As a note to anyone that may come across this thread in a search - if / when you decide to change to an electric pump consider your alternator and power steering. Each of these are going to need different brackets for mounting. It certainly extends the project. :)
 
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