Big Block guys... How do you keep 'em cool?

I'm running a 400" Pontiac engine in my model A. I know this isn't technically a 'big block' but these Pontiacs are notorious for heat problems. So how do you guys running big inch engines cool them off. Especially in harsh traffic. What kind of fans, what size radiators, high flow pumps etc . . . Thanks!

 

I know my '70 GMC has a big 4 core radiator,180 thermostat, and it;s got a 396ci motor... in heavy slow traffic it gets up to about 210 a buddy recomended I install an electric pusher fan on the outside of the radiator with a toggle switch to turn it on when the temp rises. might consider something like that on yer model A.

 

MAC-

first thing is to make sure you are properly tuned up. timing and AFR can have a big effect on temps.

also, with the pontiac motor, there is a divider plate just prior to the impellar. make sure that the plate is properly clearanced from the impellar, or else the impellar loses it's ability to pump effectively. this is covered in Jim Hand's book on the Pontiac motor which is a great reference if you don't already have it.

the stock configuration from radiator, water pump, thermostat, fan should be sufficient to keep your 400 cool.

 

Main thing is, I'm concerned about the size of the radiator. It's a 2 row aluminum. 27x17x3. I'm running a 180 thermostat. I've got my timing dialed in, and it's running a tad on the rich side. I have the divider plate installed correctly. As of right now I'm only running a 16" electric fan pulling through the radiator. No shroud and no flex fan. If I add those two components do ya think that'll make the cut?

 

A shroud is one of the most important components in being able to control cooling temperatures. If you don't have one put it on the list of "must do" things.

Frank

 

Haha! I was actually just reading through some of your older responses to guys that were asking questions similar to mine. Sounds like you know your stuff. I'm working with minimal clearance so I wanted to draw a quick illustration of what I was thinking about.

As you can see by my lovely drawing, I'm working in a tight spot. If I made a shroud, it would be extremely minimal and it would only be about and inch deep. With both fans covering nearly the entire surface of the radiator, would a shroud even be necessary? Thanks for the input

 

400 Pontiac truly is a big block. Shroud is a must, otherwise the fan will "short circuit" and draw air from the path of least resistance. Sounds like you have a thermostat, that is important as the coolant needs to stay in the radiator long enough to cool. Your radiator size stikes me as borderline, but perhaps the shroud will help. You might try adding a wetting agent to your coolant.

 

I've read so many things about water wetter and the like just being 'snake oil'. Would a high volume water pump help? I've read that sometimes that pull water through the radiator TOO quickly and it doesn't have time to cool. True?

 

I put the biggest cross flow radiator I could in my 55, then put a big clutch fan behind it, and a full shroud. The radiator is the one for the early-mid 70s Chevy p*** cars with the 454 engine. It's ugly, but it does the job. Driving in Arizona is a good test of your cooling system.

 

Thanks for the replies. I can see that I need a shroud. You think my design will be adequate? What about the overlap of the flex fan and the electric fan. Would it cause any weird turbulence? What about mounting a smaller 'push' fan on the front of the radiator as well? 3 fans? Yikes. Would I be a lot better off switching to a 3 row radiator of the same dimensions as the 2 row?

 

Such a 'tiny' rad a HotRod usually has, with only 2 rows and a bigblock isn't the best setup IMO. I think you need a 3 row rad. at a minimum.
I'm running a 496" in my '60-NY with a 3-row, stock viscous-fan and half a shroud, no cooling-issues when idling.
The flexfan somewhere behind the electric fan doesn't do much good. A fan only works properly when it's no more than an inch away from the radiator, unless there's a shroud around it. So the flex-fan might as well be removed if you run the electric fan continuous.

Also, running your ignition as advanced as can without letting your engine ping under power is best for temps.
You could also work on the ignition advance curve for further finetuning.

 

I have a 454 and I never overheat. I run a 180* thermostat. Ya gotta have a fan shroud if you wanna be cool.

 

The age old hotrod problem! In a normal car you'd fit the biggest radiator you can and a fan shroud and shut the hood so no one will see it.
Hotrods though - big motors = cool.....modern electric fans = not cool.

 

Use a be cool radiator and a dual fan system- works pretty well.

 

Water Wetter works, I used it in race bikes for years, you're not allowed to used regular coolant in case you rupture a line or go down.

As for your dilemna, stock pump, mechanical fan in shroud. Pusher fan in front if needed. Your radiator would be the weak point right now.

I cool the 425 in my Buick with the stock radiator from 57 a flex fan and a shroud. Stock pump as well.

 

462" Buick engine in a 32 roadster.


Here's what works for me:

Isolated T-400 trans cooling system.
No trans fluid introducing excess heat into the radiator.

Walker 4 row radiator.
Does the job.
My 31 on 32 rails roadster has a two row aluminum radiator built by a local.
He says it will do the job and so do several experienced builders at the Saturday morning donut run.
I have yet to try it, but it should do the job considering how well the teensy radiator on my 88 Mustang GT did in 105* + summer heat in Central California with the A/C on.

The tubes in the 31's aluminum radiator are fairly large and have a lot of surface area exposed to airflow.

17" Hayden stanless flex fan.
This fan moves a lot of air.
The narrow bladed fibergl*** 'flex' fans leave a lot to be desired imo.

These pics show a 15" Hayden stainless flex fan in my 31.




Note the width of the blades.

Since the 31 is also on a 32 frame and the 455 Buick engine in it is mounted in the same place as the engine in the 32 a 17" fan will probably fit and I'll swap to that later on.

One reason I mention the fan brand name is that the Haydens have the fan blades mounted almost flush with the fan blade hub.
A Derale I have and others I see have the fan blades mounted central to the fan blade hub.
That means the Haydens fan blades sit to the rear and have more clearance to the front than other fans and may help in making things fit.

I do have a shroud and it may help, but I ran it without a shroud for a few weeks in a summer heat wave and the engine ran about the same without it.
However, keep in mind the Buick fans sit low and the bottom of the shroud is open.

A 180* thermostat.
I'm guessing a Pontiac thermostat is like a Chevy in that it doesn't plug a byp*** port when it opens like Ford Clevelands do.
Make sure your stat is for a Pontiac.
Drill one 1/8" hole in the stat flange to relieve any potential air locks.
One hole is sufficient, the engine will warm up like normal in 16* F mornings and two holes will extend the warm up period four-fold in the same temperatures.

The hood is liberally louvered, both top and sides.


Your sketch shows a lot of tilt to the engine.
Regardless, I'd remove the electric fan - which is nothing more than an obstacle to air flow in this case - go with the biggest stainless flex fan you can get in there.
Both of mine are 6 blades.

If you do have as much engine tilt as indicated, build a shroud and run it.

Most importantly of all, run a vacuum advance distributor, source it to full time manifold vacuum so that you have advance at idle.

Generally a racing style no-got-no-vacuum-advance distributor doesn't cut it in traffic on hot days.
I have guys I know tell me that they work fine, but I also note that so far, all of them later complain of overheating problems.

My personal record of running around Las Vegas one hot summer day (109* F) had the car running hotter than normal, but it did ok on the freeway and in light traffic.

 

Thanks for all the input guys. I think I'm in for a lot of trial and error. I'll let you know what happens. Thanks again.

 

Someone will say it sooner or later, so it may as well be me...Pontiacs aren't big blocks or small blocks, they're all (except for the late 301) the same size.

Anyway, to elaborate on what The Monkey said they shouldn't run any hotter than any other engine if set up corrrectly. Take a look at this discussion on how to make sure the clearances between the pump impeller and the divider plate are set: http://forums.performanceyears.com/forums/showthread.php?t=411256

 

I would avoid flex fans.....ran one on a 454...it let loose on the 1-2 shift at about 5grand. Threw those blades ALL OVER the engine compartment and cut up every hose, ****** cooling line, AC lines, fuel line, radiator core, etc. There was an interesting puddle of guts on the highway including ****** fluid, prestone, and fuel sprinkled with a few small chunks of aluminum flex fan and a cloud of R-12 hovering over everything...

It sounded like someone threw a chainsaw into a jet engine.

 

Really? Maybe you missed this part...

Reading is fundamental.

 

^ that's a very interesting read. Guess I'm gonna pull the pump off and check the clearances. That'll make 3 times I've pulled the water pump off and I've driven the car up and down the driveway twice. LOL

 

or, if you do run a flex fan, make sure it's a good one...which means no aluminum! it will have a thick steel center, and wide, curved stainless steel blades held on with lots of rivets, and with reinforcement plates over the thin blades.

 

Yes, but maybe you missed this part:

Reading is fundamental.

 

Like the others said, with a Pontiac you MUST be absolutely certain that you have the divider plate timing cover and water pump set up correctly and in good condition.
Also water pump pulley size is important on Pontiacs. Over the years there was different diameters and they tend to get miss matched by people.
That is some of the Pontiac specific stuff I can remember (its been awhile) others here im sure can remember more.
There just like flatheads in that the ”notorious” stuff is mainly ignorance
The rest is the basics for any motor.
big radiator
bid fan
shroud
timing
correct flow speed

 

Ran a 502 in my 33 highboy and had the same problem. The trick is airflow more than radiator size etc. Finally ran a 3000 cfm Spal fan with a home made shroud which wasnt more then 1 1/2 deep.In the worst traffic[louisville nats] it never got over the thermosat. Must use a 40 amp relay. Water wetter ****s, The way it works is by descaling the inside of the block and cooling system. Its acidic, and does eat aluminum radiators over time. Buddys replaced Griffins after one year, bottom tanks shot. Run green antifreeze with distilled water only.

 

I guess technically a Pontiac V8 is neither "small", nor "big" http://www.onpedia.com/encyclopedia/Pontiac-V8-engine
not worth an arguement, either way

 

I haven't read all the responses here, but I'll throw my hat into the ring. If you're running an electric as mentioned, keep in mind some of the cheap ****, pancake motor powered ones only make noise, and do NOT move any air to speak of. I had a short, aluminum radiator (painted black) in my green flaked Deuce I posted here last summer with a 389 Pontiac. A steel fan from Speedway about an inch from the core with no shroud, and the hottest it ever got in traffic was 200 on a 103 degree day. It would come down to about 180 in 2 blocks of driving after traffic let up

 

Big blocks tend to heat soak. meaning that once they get hot it takes forever to get them cooled down. What we did on our 70 Chevelle super-pro car (it has a 15to1 496 in it) was install an RCI electric water pump combined with a GM electric fan off a Buick Regal. The radiator is a stock 88 Caprice.
The car will run a steady 170 degrees with the fan off as long as you are moving. Like any other big block with a lot of compression, it will eventully get hot. With the engine off and the electric water pump and fan on for three minutes the temp will drop from 230 degrees to 160. Shut everything down and the engine will hold at 165 while not running. I've had several big blocks and never had one that you could really cool off quick once it got hot.
I don't know if the RCI water pump is a continous duty pump or not. A lot of racers use them and ours has held up well so far.
There are electric sprint car pumps out there that actually mount in the lower radiator hose that are continous duty. The name of the company is Meisure. (The spelling is probably wrong). This pump is a good choice when space for a full sized water pump is prohibitive.

 

Wow. I just pulled the pump and the divider off and there was a good 3/8" gap between the impeller and the edge of the opening on the divider plate. So I hammered that thing down and I've got to within 1/10". Hopefully that'll make a difference. Thanks!

 

Did it have a stamped or cast impeller? Go get a pump with a cast impeller , that will help also.