Overheating issues
 

Sorry, it's a long post. But I figured I'd give you all the info I thought you may need to help...

I have had a heck of a time trying to figure out the overheating issues in my truck. I've replaced & upgraded several parts trying to figure it out but now I need professional help (with my truck too).

I bought the truck (basket case) back in '05 and finally got it on the road in '12. From that point till now it has over heated. Engine is a 86+ HO GM crate motor. It runs great at lower temps but once it starts going above 210+ it starts to feel like it's going to die and I need to have my foot feathering the throttle at idle. Once it dies it will not start again for another 15 minutes, at which time it will fire up and run until it gets around 210+ again then it acts up again. No steam or white smoke so it's not a head gasket.


Engine is a 86+ HO GM crate motor
TH350 (soon to be stage 2 200r4)
3:73 posi rear
Mallory Unilite electronic dist
Edelbrock 1406 Electric choke
Sanderson shorty headers
Edelbrock high volume water pump
Edelbrock 2101 Performer manifold
Aluminum 2 core (1" tubes) radiator
Dual 12" electric fans w/Aluminum shroud
180 Thermostat. Dakota Digital sensor in the front of the manifold.
Dakota Digital VHX gauges and a DD fan controller
Timing 11 degrees, 38 degrees total


I replaced the oem style 4 core copper radiator with an aluminum 2 1" tube radiator - still overheats. All air removed from radiator and mixed half distilled water & half antifreeze. Overflow attached and filled.

Changed the factory clutch fan with dual 12" with aluminum shroud - still overheats

Added a polycarbonate 1" spacer under the carb because it seems I was getting vapor lock, not as bad but still does when it gets hot.

Could it be the carb? I am at a loss because it all of the cars & trucks I've ever owned I never had issues keeping them running cool with just the factory components. In the cooler (low 70's) times of year it runs great and really has no issues. But once the temps get around 80+ I always have issues...which is what the temps are most of the time in Southern California. Anyone have any ideas that I may not have tried? I've researched for hours and hours on the subject and everything I have found was either already done, or I tried it and it didn't work. The other option is taking to someone that knows all about cooling and tuning and have them see if they can find the problem.

Thanks...

Re: Overheating issues
 

At what rpm are you setting your low initial timing?
You could need about 16 initial.
You also likely need a fuel regulator set at 5 psi.

Re: Overheating issues
 

Edelbrock fuel pump factory set to 6psi, suggested pump for the carb. The RPM was in the 850 range.

Re: Overheating issues
 

Two negatives!
Eddy carbs don’t like more than 5 psi. With your pump you might be flooding just enough when it gets hot to cause your idle problems.
Also at 850 rpm you’re likely already kicking in the mechanical timing in the distributor. That means your 11 initial might be actually 3 or 4 or less degrees. You need to get the idle down under 750 rpm, then set your initial to 14. Lack of timing is a heat builder.

Re: Overheating issues
 

I just checked real quick online and both videos I watched said the same thing for the 1406, 5psi! Okay, I'll order up a regulator and gauge right now to get it at 5psi. Once I get the regulator installed I will try the timing at 16 initial and then see what that does.

Thanks for the help.

Re: Overheating issues
 

Don’t buy a liquid filled gauge if you can. They don’t like heat either.

Re: Overheating issues
 

I agree with this . If you do get one only set the pressure when the gauge and engine is at room temp at first start up . After that you will get a false reading when the heat starts to warm everything .

I do agree to get you timing correct .

Are you sure you got the proper rotation on your water pump . If I remember correctly those come in both standard and reverse rotation . It sound like you have covered all the bases . Just something strange going on . I would verify the water pump part # to rule it out .

Just something to check off you list since your are beyond common problems .

Also has the heads been off . Head gaskets can be a problem if not correct .

Re: Overheating issues
 

Does your Mallory have a working vacuum advance?

Re: Overheating issues
 

I made sure the water pump was correct rotation and not a serpentine setup when I bought it. I had a no name high volume pump in it when I first got it running but swapped it out in my quest to lower the temps. I hope the fuel pressure is the problem, along with the timing being off. I have seen videos of fuel dripping while idling and mine does the same thing.

Having a heck of a time trying to get a regulator though...I guess the idiots in CA deem them the devil and won't allow Amazon to ship here? So sick of the morons that make the laws here, but I digress. I can't even find one in local parts stores so I will have to order through eBay.

I've owned just over 100 vehicles in my life and have never had the issues I've had with this thing as far as over heating goes. But this is also only the third Edelbrock setup I've owned. So tempted to switch to Holley but I have thrown so much $$$ at it already to fix the problem. I feel with your guys input I may be getting close to fixing it.

Also, heads have never been off. Motor has about 45K on it

Yes, Mallory has a vacuum advance on it

Re: Overheating issues
 

Go shopping at summit racing or jeg’s to find a regulator.
I always buy one that has a max output of 5.5 psi. Easier to control pressure that way.
Your local parts emporium might even have one. Plus a gauge too.

Here’s a couple that are rated to 6 psi.
I’ve used one like it to run my dual quad at 3 psi.
https://www.summitracing.com/int/sea...illocation=int

Re: Overheating issues
 

I just picked one up on Amazon. I guess as long as it is C.A.R.B compliant they will ship it. I have braided lines with AN fittings that go from the pump to the carb and aluminum line & AN from the tank to the pump. Bought Russel AN fittings and some aluminum fuel line to replace the Edelbrock "kit" that's on it now. I've read about issues with the Mr Gasket style regulators so I wanted to stay away from them. Will have everything by Saturday :metal:

Edelbrock 8190 Fuel Pressure Regulator 4.5 - 9 psi
https://static.summitracing.com/glob...8190_sn_ml.jpg

I will let you guys know what the outcome is once I get everything setup and adjusted. I REALLY appreciate all your input. I have only been able to drive no more than about 20 minute outings in my truck since 2012 because of this issue. Can't wait to drive it further to truck shows and whatnot without having to stress about getting stuck on the side of the road (happened more times than I'd like to say). With the new stage II 200r4 trans (with stage III shifting) I can actually drive it on the freeway too. Just have to take the time to install it.

Re: Overheating issues
 

I see you have a 180 thermostat listed . Is this the same thermo that has always been in there or did you change it . I did not see where you have replaced it .

If it has not been replaced I would pull it out and replace it . What type and brand of thermostat is in there .

Re: Overheating issues
 

Yes, it was replaced with a Mr Gasket high flow 180

Re: Overheating issues
 

Was it replaced after your heating problem and still had the problem .


Just for the record , I have no faith in Mr gasket stuff .

Re: Overheating issues
 

I swapped it out to try and fix the overheating...did nothing to help

Re: Overheating issues
 

Vac Advance actually working? Some times those things go out in less than a month.

New water pump have a cast impeller or stamped steel type. The cast ones are not that good at getting water moving when you need it.

Clogged up heater core? Check by disconnecting the unit with a bypass. Are you seeing any signs of rust in your coolant? You have to drain it to tell. Most all new radiator flushes have an ingredient called sodium citrate. I am sure it does not do a really good job.

A small layer of rust internally can cause big issues.

Re: Overheating issues
 

I don't see where you said the conditions under which it gets hot. Does it go over 210 while sitting idling in traffic? Cruising? Pulling a hill on the freeway? 210 isn't bad, but with a 180 t-stat you really should be running right at 180-190.

Re: Overheating issues
 

Yes, vacuum advance works good. The water pump was a high end Edelbrock high volume stamped prop.

No heater core, it's bypassed. Eventually I'll get a vintage air unit but not until I get the overheating issue resolved.

If I am cruising at 45+ it will get around 200-204. Anything under 45 and it starts to get hot. I did have the fans come on at 185 & at 195. I recently changed the 2nd fan to come on at 186 but it didn't help any.

Re: Overheating issues
 

With the bypassed heater core do you have the line off the intake plumbed back into the water pump or do you have both plugged.
Sometimes that can create a heat problem.

Re: Overheating issues
 

I just went and looked at the specs of the 350 gm ho crate motor . A couple things that I noticed . One was they recommend pump prem gas . What gas are you running . Looks like gm recommends a 93 prem octane . The other thing is they also recommend a total timing at 32 degrees total at 4000rpm , 5100 rpm max .

One thing that can contribute to overheating is a engine running to lean . If you are running a 87 octane gas this can cause it to run leaner . Also the 38 degree timing is to high in my opinion as well . This high timing can also cause high cylinder temps especially with 87 octane gas .

Just something to think about .

Re: Overheating issues
 

I have not run anything lower than premium fuel in any of my cars in over 20 years. So that's not a problem. Interesting about the 32 degrees total, everything I have read has stated between 36-38 total. But what the hey, I'll try any trick at this point.

I will have all of the components necessary to add a fuel regulator by this Sunday. Once I get the final piece I will start the process of adding it, then once that is on I will re-time it with the recommended specs. I will also re-check the mixture to make sure it's not too lean. I set it up a few years back with a vacuum gauge. Not sure if it changes a lot with the timing but I'll check anyways.

I have a hose connecting the water pump to the manifold.

Re: Overheating issues
 

Heres what I was looking at . I think this is the engine you have . You can verify . At the bottom of the page is what I was looking at .

http://www.chevrolet.com/performance...l-block-350-ho


That carb could still be running lean . Be nice to have a Air fuel gauge .

I dont know if you had seen this but on page 4 of the install instructions is there recommendation for the timing .

http://www.chevrolet.com/content/dam...e-19210007.pdf

Re: Overheating issues
 

210° in NOT an overheating problem. Fuel line touching a heater hose or near a header?

When it won't start for 15 minutes after dying does the accelerator pump in the carb squirt a good stream when hand operated?

What does the spark look like during this no-start period? Solid blue or orange and weak.

During the no-start period after dying, does it start if you tip in a little gas into the carb?

What is the vacuum reading during idle and how does the needle look? -BA

Re: Overheating issues
 

have you tried a normal t--stat? i dont understand the whole high flow tstat deals if your coolant is moving to fast though the radiator it will not cool off enough and just keep building heat

Re: Overheating issues
 

I ran an edelbrock carb on a couple different motors, 2 were 454s, and they didn't over heat. I think one had an issue of flooding because the fuel pressure, but swapped for a Holley. I'd try tuning the carb, lean of course can make a motor run warm.

Re: Overheating issues
 

Couple of questions, about when does it overheat:
1. does it overheat when sitting, or when moving (or both)?
2. if it overheats when sitting, does it go down when you start moving?
3. does it overheat below 45mph, above 45mph, or both?
4. does it overheat when driving on the highway?

Each of these things can tell you more info about the possible culprit. Once you reply we can start looking at what may be causing it.

Re: Overheating issues
 

How is 210° overheating? The Thermostat on my 350 is set to 195° as a minimum operating temperature which is less than 1/3 of a gauge. I think overheating is something like 265°. -BA

Re: Overheating issues
 

My response is in red ^

Re: Overheating issues
 

Yes, had a standard thermostat in it before trying the high flow. Thought the high flow would help since I have a high volume water pump. Made no difference.

Once I get all the parts to hook up a regulator I will re-tune and adjust the carb

The few colder days we get in Southern California it runs awesome! As long as the temps stay under 210 it does awesome. When it starts creeping over that then it's no fun anymore. Last time I drove it after having both fans come on at low temps it seemed like over 45 it did fine, but I got in slower traffic and had to drive at 40-45mph and it started getting hot again. The fan controller is set to turn off the fans at 45. It gets hot fairly quickly if I am just sitting in traffic and not moving much (again, result of living in SoCal) Both fans are pullers.

I have nothing but issues if the temps here are 80+ (which is most of the year) no matter what speed I drive

I really wish I knew the answer to this, if I did I wouldn't be here asking for help. I've owned muscle cars and trucks for nearly 40 years and have never had this problem on any other vehicle. Or if I did I was able to fix it easily. I have been fighting this for several years. I built my son a 72 Nova for his 17th birthday. We put a 350 in it & he has nearly the exact same setup as I do with the intake, carb, radiator and fuel pump. We put in a single 15" fan and it never overheats. Why I am having so much trouble with the truck is beyond me.

Re: Overheating issues
 

This may sound like a stupid question but is the fans running in the right direction . Check air flow to be sure when fans are on .

Also did you buy the radiator and fans and shroud together . If so check between the shroud and radiator to be sure there is no packing/cardboard to block airflow .

Just thinking out loud . These are simple things to check of your list . Its got to be something simple . You have covered most of the bases .

Re: Overheating issues
 

Already covered that, but yes they are both pullers and both come on & off at the selected temps

Re: Overheating issues
 

Post some pictures of your engine and your fan setup. Pull the plugs and post some pictures. From your description and what is going on it is lean, the float level may be low and it is vapor locking. On your fans is one set to run all the time and the second one set to come on at like 170? I went through this with my edelbrock and with the heat around here in the summer it would do the same thing. We fattened it up, added a heat shield spacer and ran the fuel level in the bowls up. It did better but never was able to completely stop it in the spring when it would get hot and we were still on winter mix fuel. It also never liked more than 4 psi fuel pressure. It has a holley on it now.
Jimmy

Re: Overheating issues
 

It's a bit dusty...

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Re: Overheating issues
 

Initially I had it setup for one to come on at 195 & the other at 210. That didn't work from the get go so I changed it to 185 & 195. Ran that way with the same issues so I never drove for more than about 15 minutes at a time. I recently changed it to 185 for the first fan & 186 for the second fan (although I have relays and 12 gauge wire I didn't want too much load at one time so I staggered them coming on). No difference, still gets up in temps.

I really think it is too much fuel pressure, combined with timing being a little off and it more than likely a little rich. Once I get the regulator mounted and the psi at 5 I will re-time it and re-adjust the carb. It is not a daily driver.

Re: Overheating issues
 

Delete.

Re: Overheating issues
 

I was a dealer mechanic when the mechanical fans (without a freewheeling clutch) were the norm and if there was a suspected alternator or water pump slipping i would grab the fan blades and see if i could turn the engine over. If i couldn't the belt was not tight enough. I noticed your alternator looks like it is at the end of the adjustment slot, so try this trick and see what happens. Obviously engine turned off, take a big screwdriver or prybar and wedge it between 2 of the fan bolt heads at the face of the water pump and try to turn the engine over and see if it slips. Good luck!!

Re: Overheating issues
 

There is a remote possibility that your lack of inner fenders is contributing to your problem.
The air trapped in the wheel wells doesn’t allow the hot air to escape behind and below the rad.
That’s just a theory developed from when I ran a set up like that with fender well headers on an L-88 in a 56 210. It ran hotter and the lack of inner fenders was thought to be the culprit. I did use a 7 blade fan and shroud which helped somewhat.

Has your truck always been without inner fenders?
Nice lookin’ engine bay btw!!

Re: Overheating issues
 

I think it is time to go through the carb, blow out all the passages and put in a "rebuild" kit. Then change the fuel filter and also the air cleaner.
Forget any talk about fans or overheating because this is CLEARLY NOT the issue.
You should think about losing that air cleaner that sucks up hot air that has gone through the radiator. Even the stock air cleaner was designed to pick up air that had gone AROUND the radiator. Why run hot air into your carb? I know it looks cool and sounds cool but it robs tons of power and I'm sure it contributes to your carb problem. Run a cold air intake or even a stock one for testing, and go through your carb.
If it was running rich from too much pressure you would have sooty plugs and black smoke.

Re: Overheating issues
 

This all sounds like a radiator problem to me. The radiator is new so here we are. I run a 400 sbc in an Impala with a wimpy thin radiator and a flex fan 6 inches behind the radiator with no shroud. My nice temp gauge shows me the temp going up to 210 before the thermostat opens and drops to a perfect 195 and stays there all day. Up here in Maine we get lots of 80 degree days but not a lot of 90's. It runs fine on any hot day we have though.

Nobody wants to change a new radiator so that causes us to do everything else under the sun first. It's like the tire balance threads where nobody wants to hear that it needs new tires but finally new tires will cure it. The only answer that makes sense here is the one nobody wants to hear. Something is not right with that radiator. A good radiator should be able to sit in traffic on a hot day without overheating. If they work fine at 50 mph but not in town, it is usually the radiator. I hate to say it.

If this was happening to me I would have a known good radiator that I could swap in there to try.

Re: Overheating issues
 

Radiator has been swapped out twice from the original oem style one I started with.

Installing a fuel regulator definitely helped. It is running a lot smoother now and no more dribbling fuel at idle.
I think from everyone's help as well as researching more into carburetor and fuel I think I have narrowed it down to fuel boiling in the lines. When I run it and it starts acting up I cannot touch the fuel filter because it is way too hot. Then it starts running really rough and wants to die, which it eventually does. All of my lines are far from headers and other direct heat sources but I think that is the issue. I always felt like the engine compartment got super hot so I always assumed it was getting too hot. I think I will try a return line back to the tank. After seeing several videos on the subject it makes sense to me now. I will eventually get rid of the carb and go with an EFI setup so I will need a return line anyways. Another (added) option is to put in an in tank fuel pump that I can either run with the current carb setup and eventual EFI setup. I have seen where that helped the problem further.

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