[Hotrodjohn71]

This post is not for the faint of heart. After trying everything I can think of and after hours and hours of searching through this forum, HAMB, Hotrodders, and many others and after trying everything I can, I still have a creep to overheat and boil over problem in about 5+ miles in 100 degree weather. Shouldn't a 326 Firebird be able to operate in 100 degree weather?

I will not give up so I am reaching out. Please dont fall asleep. I would like to converse with folks who have Firebirds that actually run in 100 degree weather like we have here in California today.

The engine is freshly rebuilt (stock bore) and mostly new/original/stock with a 2 barrel Rochester 2GC carb, stock exhaust manifolds and a new GM HEI distributor.

Anticipating cooling issues that I have heard about Pontiacs, I installed a new 8 bolt Flowcooler water pump 1622. My water pump is an 8 bolt, not 11 bolt.

The impeller plate is within less than the thickness of the water pump gasket to the impeller, probably about .030"-.040" or less.

I have a new 180 degree thermostat and my radiator is a new 3 core aluminum Champion CC370B which has 2 electric fans. The fans come on as they are intended to.

It just happens that I got to where I can start and run the new engine about mid July when it is about 90 to 100 or so here on a regular basis(cooler in the morning).

Every time I have run the engine, it has eventually overheated. When I was breaking in the flat tappet hydraulic cam, it overheated in the 20 minute break-in and boiled.. On the 3 times I have taken it out and driven it (under 50 mph for break-in), I just travel about a 5+ mile tour around town (averaging about 40 mph) and as I watch the temp, It just keeps creeping up and up and up till it gets to 230 and I pull it in and its boiling over again.

I'm pretty sure I burped all of the water out of the system by filling it, squeezing the hoses till the bubbles stopped in the radiator fill hole, then running the motor a couple minutes, shutting it down and filling until it was full. I am using a little less than 50% coolant to water.

When I run the engine with the radiator cap off above 180 degrees, I can see a nice flow of water in the radiator.

Engine pulls about 19 inches of vacuum at idle.

I am using Manifold Vacuum (not ported) to my new GM HEI distributor. I set the initial timing (vac disconnected from distributor vacuum canister) at 10 degrees. then the vacuum is connected to the distributor, I am idling at about 34 degrees. That seems to be the sweet spot.


The vacuum canister seems to pull a total of 15 distributor degrees (30 degrees crankshaft) by itself. The mechanical advance on the distributor seems to pull a total of 25 degrees by itself. 10+15+25= 50 Total advance(?)

The engine runs great. it starts great and idles great and when I turn it off, it does not diesel. The only time it acts bad is when the temp goes to 230 then it will ping a bit and loose power.

When I run the car in my garage in idle, I watch the temp gauge and I see that at about 185 or so, the thermostat must be working because then the temp goes down a few degrees, then cycles back up again after a couple minutes

It *seems* to stay cooler a little longer just idling in the garage as strange as that may seem but when I take it out to drive, it just creeps up to boil over.

I am a machinist by trade and I cant seem to get this right. This is a gift for my wife. I need serious help. I can answer any of your questions in detail as it seems im self training for a PHd in Pontiacs these days. Thanks

[leeklm]

You have probably confirmed this already, but make sure you have a spring installed in the lower hose to prevent collapse.

Looking through your post, one thing that could be suspect is your electric fan setup. Some of those units do not pull enough cfm, and could even be worse at highway speed because enough air cannot get through the radiator. The fan and shroud could actually be blocking air.

If you have the parts available, I would install an oem type 7 blade clutch fan and properly fitting shroud. This will pull way more air vs your current setup. Once you get things figured out, you can go back to the electric setup as desired.

I had a similar electric fan and shroud setup on my 66 gto, was fine around town but terrible on the highway. The clutch fan took care of the issue. When building my bird, I installed the Cold case "HD" radiator and Lincoln/Taurus electric fan and it works great. The Ford fan pulls a lot more air compared to my old cheap aftermarket setup.

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[JLMounce]

Get rid of that metal shroud. It’s blocking airflow through the radiator when the car is in motion.

If you look at factory shrouds, even on modern vehicles with electric fans, the shroud angles outward from the radiator surface acting like a funnel for airflow. Having a flat wall right behind the radiator core almost completely stops airflow when the car is moving and reduces the pull from the fans.

The way your system is setup it’s only got airflow through the areas of the radiator that the fans cover.

Check out the Flex A Lite black magic fan if you want electric. It has a properly designed shroud that produces airflow across the entire radiator core.

You can also try a stock fan shroud and clutch style fan like the car would have had from the factory.

[ID67goat]

Have you tried running a stock shroud and fan setup? While the dual electric fans and sheet metal mounting looks nice, I think it is limiting airflow while driving.

Otherwise everything else looks good in my opinion.....vac advance, timing, pump clearance, etc.

[Hotrodjohn71]

Thank you guys.
I do not have the big spring in the lower radiator hose. A while back I called Napa and asked them for one but he said they dont sell them anymore because they dammage aluminum radiators so I just left it at that. I would think a stainless steel spring would be just fine.

The reason I went with this particular radiator and fan setup is because I saw a post on First Generation Firebirds where someone recommended the setup by part # and said it worked well, but the points being made about that aluminium shroud blocking so much radiator area actually make alot of sense.

Actually thinking about it, that shroud really does seem to be defeating air flow at driving speeds .

Now that I think about it, the kit that came with the new radiator/fan setup had a bag with those through-core zip ties and padded feet for the fans to be directly attached to the core without using that shroud.

I just tossed those zip ties aside wondering why they were included because in my minds eye. I was imaging that shroud being correct.

I'm going to remove that shroud and reinstall those fans to the core and try that.

I'm just not quite ready to go with the stock fan, clutch, shroud and radiator. But I will if I have to.

[Hotrodjohn71]

JL Mounce, are you talking about a flex-a-lite fan like this one? It has 3300 CFM.

https://www.flex-a-lite.com/electric...ctric-fan.html

I just discovered that the two 10" fans on my setup only pull 1700 CFM's.

[leeklm]

If you end up needing to purchase a new electric fan, take a good look at a Ford Taurus or Mark8 electric fan. They fit nicely on the first gen radiator and again, move more air than most aftermarket fans. I used some aluminum flat stock to adapt the M8 shroud to the radiator, and makes for a nice looking fit.

You will want to purchase a purpose built fan controller as well. There are a few to choose from. I have had good luck with one from "Auto Cool Guy"..

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[tom s]

How much timing are you running?Int and total without the vac adv installed?Tom

[tom s]

Sorry just read the timing.Tom

[ZeGermanHam]

There could be multiple factors at play here, but the first place I'd start would be to ditch the electric fan setup you currently have and go back to a traditional heavy or severe duty mechanical clutch fan with stock shroud. With the setup you have currently, the air is essentially hitting a brick wall when you're driving at speed, and isn't letting much air get through the core of the radiator.

Note that if you zip-tie electric fans directly to the radiator, they are only pulling air through the core where they are placed, and not through the entire surface area of the radiator. This will hamper your cooling ability at low speeds and in traffic in comparison to the stock clutch fan & shroud setup. But you may get some meaningful data if you remove the current "shroud" you have installed and see better temps at higher speeds.

[Hotrodjohn71]

Tom, I think I confused myself on my timing description. I will have to verify tomorrow but my notes say I set initial timing at 6 degrees. Plus the 30 degrees from the manifold vacuum advance canister on the distributor yields 36 degrees at idle in park. I came up with 36 by finding the best and smoothest idle timing in park. Then the mechanical advance ads 25 fir a total advance of 61.

[tom s]

I always set my timing with no vac adv hooked up.On my stick shift cars I run 12 int with 36 total all in at 2000.My 69 bird has a 350 auto radiator with shroud and flex fan.I have had almost every engine in it from 366 short deck to 455s and now a 428 and they never run over 190 even in high 90 weather.I have never checked clearance on my 11 bolt water pumps.If me I would check the temp drop thru your cooling system.Temp going into the radiator and temp going out.There should be a substantial drop in temps.I use one of those laser temp guns.I also check temps on both sides of the Xover and at the thermo housing.Good luck with your issue.Tom

[grivera]

You can buy the lower hose spring from our host- as stated it needs to be in there to prevent hose collapse at cruise rpm. Install a sacrificial anode in place of the draincock to mitigate potential corrosion issues. https://www.amazon.com/Camco-11533-A...87688973&psc=1

[leeklm]

As Tom mentioned, disconnect the vacuum advance when checking initial and mechanical advance numbers.. Primary job of the vacuum advance is to apply additional timing at light throttle cruise speed.

As long as the engine is not turning over hard when starting hot, I do not worry too much about initial timing. The critical number is your total mechanical advance, somewhere around 32-34 running the engine up to 4k'ish for most iron head engines.

Once that is set, reconnect the vacuum advance, which is likely adding about 15 degrees of advance on top of the 32 degrees mechanical when checking in park at cruise rpm around 3-3500 rpm. Not uncommon to see a 48-50 degree number here.



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[Gator67]

We have a 68 Firebird 400 that’s driven year round here in Phoenix. OEM water pump, clutch fan & shroud…never overheats, even with A/C on in the middle of the summer.

[Hotrodjohn71]

Are the potential corrosion issues related to the hose spring caused by the metal of the spring touching the aluminum of the radiator hose fitting while the hose is connected, or is it just the metal of the spring being in the same water stream?

["QUICK-SILVER"]

That thumbnail says "reversible "S" fan blades". That tells me the fans could be front mounted for "push" with the zip ties, Or rear mounted for "pull" in the shroud.

How are the blades mounted? Flipped the wrong way, is way less efficeint.

What are you using to turn the fans ON and OFF? Seen core mount sensors work sitting still but not with the car moving. Wind from moving kept the sensor cool even though the radiator was hot. Had to block part of the core in front to keep wind off the sensor.

Just thinking
Clay

[JLMounce]

Originally Posted by Hotrodjohn71

JL Mounce, are you talking about a flex-a-lite fan like this one? It has 3300 CFM.

https://www.flex-a-lite.com/electric...ctric-fan.html

I just discovered that the two 10" fans on my setup only pull 1700 CFM's.

Yes I just installed one of these. I’ve always had an issue with temp creep at idle or in traffic with the stock shroud and a factory flex fan.

I can let the car sit and idle for 30 minutes in near 100 plus temp and it won’t go beyond 195. Cools the same as I always have seen from the car once moving.

[Hotrodjohn71]

Jason, I just bought one of those Flex A Lite 180s.
Everything I've seen about it looks great and theres a long list of great reviews.
Every point that's been made here about my existing shroud being an obstruction make good sense and the 2 fans together only make 1700 CFMs.

It looks like the seller I got my Champion Radiator from coupled it with the small fans and shroud from another source

So when I saw good reviews on the Champion .radiator from the gentleman on First Generation Firebirds Forum, his endorsement of the radiator was probably not including the fan/shroud setup I got.

Clay, my fan controller came with the Champion and it's made by them. It has a temp switch that goes in the manifold and switches a relay with a 40 amp fuse.

[Sport69]

What leeklm said:
Looking through your post, one thing that could be suspect is your electric fan setup. Some of those units do not pull enough cfm, and could even be worse at highway speed because enough air cannot get through the radiator. The fan and shroud could actually be blocking air.

If you have the parts available, I would install an oem type 7 blade clutch fan and properly fitting shroud. This will pull way more air vs your current setup. Once you get things figured out, you can go back to the electric setup as desired.

You need to setup the regular 7-blade fan (you can use a clutch fan if you don't want the fan roar at highway speeds) properly spaced to a properly fitted shroud, and with your 3-core aluminum radiator you shouldn't have an overheating issue.