Thread: Rad Grill Question

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The Walker Tech guy says a shroud will lower the temperature about 20 degrees, but how many '29 roadsters have a shroud? Is that necessary?

Don Shillady
Retired Scienitst/teen rodder

I do not know how to start a new thread and it may not be necessary. If a shroud only lowers the temp 20 degrees do I need a shroud on a '29 Model A with a Zip water pump riser on a 355 SBC which is almost stock? I tried to find an old thread where someone said they could run in a parade with a Zip water pump riser on a SBC but I do not know whether that car had a shroud. I have a shroud but it is a hassle to install and looks tight in the available space. Before I try to install the shroud I would like to hear from some of you as to whether or not it is necessary to have a shroud on a mild 355 SBC.

Don Shillady
Retired Scientist/teen rodder

Don, you are going to get opinions all over the place on the subject of cooling, so here is my contribution. I prefer electric fans for several reasons. First off all, they put out much more cfms at idle than a mechanical fan, and idle is when you need the fan to be doing the most for you. When you are going down the road the airflow is sufficient in most cases to keep the car cool, but when you are sitting at a traffic light you need an artificial airflow, ie an auxiliary fan. If your car idles at lets say 800 rpms, that is all the fan will be spinning if it is a mechanical one. But an electric fan spins much faster and pushes more air. The second reason I like them is safety. I have been whacked by a spinning mechanical fan more than once, and have seen ones that have gone through car hoods like butter.

Shrouds I feel are absolutely needed because without one you are only pulling air through a circle the exact size of your fan. With a shroud it acts like a vacuum cleaner and pulls air from all across the core. Even with a mechanical fan a shroud is needed because the fan can draw air from other places than through the core, like air going around the radiator.

There are many aspects to cooling, but two of them are water flow and air flow. Your Zips pump will probably do a great job of moving the water, but you still need air going across the fins to extract the heat from the water.

So, that is my opinion, and you KNOW what they say about opinions.... I know some will say electric fans aren't traditional, but I build my cars to drive, and I hate sweating bullets at redlights.

Don

Itoldyouso, Thanks for your response. I guess I will have to install the shroud but I am reluctant to put screws into the sides of my Walker Cobra radiator. The Walker Tech guy says the outer tubes are blanks and that gives some added safety for screws into the sides of the radiator to mount the shroud. He says 5/8" metal screws will not pierce the tubes that hold coolant. I really hate this stuff where a mistake is so costly since it often takes me three tries to get it right and I don't want to ruin the expensive radiator but I guess with careful planning I can get it done. If I mess up the hole cut in the shroud that is less of a problem since the shroud is cheaper but if I pierce a water tube in the radiator that is a problem. As discussed earlier, I wanted to avoid the electric fan because of the amp spike when the fan turns on but I do see the advantage for an electric fan at idle where you need it most. Also in my discussions with several mfgrs. of electric fans it seemed to me that either they were underpowered at low amp draw or needed a high amp spike to get realistic flow rates. For instance the Brookville Tech guy recommended a deceptively low amp fan but it really looked like inadequate flow to me. Maybe I missed the point that only low amp fans are needed for the idle case and at highway speed the car provides it's own increased flow. Come to think of it the few rods I have seen with high water pumps had no hood so I can only hope that using the stock Model A hood with the many tall louvers will let the air "out". I will have to get in a rested positive mood to put those screws into the side of the radiator; if I am tired or work late in a hurry I almost always make a mistake and this time it could be costly!

Don Shillady
Retired Scientist/teen rodder

Sorry I missed your earlier question on the shroud.

My experience with a shroud doesn't show a 20 degree drop in engine temp.

In fact, I had the 32's shroud off for something and left it off for a while.
Temps didn't seem to change.
Even so, I put the shroud back on.
Doesn't hurt and like Itoldyouso says it's a help in the safety dept.

The stainless fans I use are like razors on the edge and will cut you badly when they're sitting still.

Ignition timing probably has the greatest impact on engine cooling, but I'm fairly sure we've been over that before.

My pal's shroudless 29 roadster with SBC and T-350 ran cool enough that he could get through most days without a problem, but now and then it would get warm, but not too bad.
That due to he's a bit of a cheapskate and likes the look of the no-got-no-vacuum-can Race-O distributors that don't cut it on the street as far as I'm concerned.

His 29 is full fendered and runs a stock Ford hood.
It does help that the hood sides are on, otherwise air - which always takes the path of least resistance - will stack up in front of the radiator and flow around it into the mechanical fan.

I respectfully disagree with Itoldyouso's comment about an electric fan pulling more air at idle.
I have yet to see one that pulls more air than my 6-blade Hayden 17" fan.

I don't care for electric fans and the problems they bring, but they are a good answer when there's no other way to do it.

Originally Posted by Don Shillady

I do not know how to start a new thread
Don Shillady
Retired Scientist/teen rodder

Don, you can start new threads by being in a particular forum.

Look on the right side between the Sub-Forum at the top and the forum proper just below.

Far be it from me to argue with Don, as I totally respect his experience and building ability. HOWEVER---I am not running a fan shroud on my small block powered model A---nor did I run one on my smallblock powered T roadster, nor on my 31 Desoto coupe! I never experienced cooling difficulties with any of these cars. They all ran an electric fan between the snout of the waterpump and the rear side of the radiator, with a heat sensitive sending unit in the cylinder head that pulled in a relay and started the fan when the temp got above 180 degrees. The engine in the 27T was modified with a hot cam, 4 barrrel and headers. The 305 in my current model A is a stock 305---the engine in my Desoto was a lightly modified 327. I do not think you need a shroud.---Brian

Don, With that big Walker radiator - even in the HHH Richmond area I wouldn't expect that you would need a shroud - and especially if you have a nice big diameter fan (NEVER one of those SS Flexlite{?} butcher knives). Do a web search and you will find that there are quite a few horror stories - they flex, they break via high cycle fatigue. I currently have an electric fan, but that might change as there ends up being more room then I expected between water pump and radiator and since I bought the Walker radiator and the CCS fan as a nicely priced package, decided to use it. Try it without first - it wont take long to tell if you need a shroud.

Gentlemen, Thank you all for the collective experience. I think IC2 said it best as to trying it without a shroud at first and then adding it later if needed; that will avoid the hole drilling for now. Several warnings about the flex fans helped me realize the flex-fatigue aspect which I did not expect. Gee Brian did it three times without a shroud, but he is in Canada while Don recommends a shroud down in Florida and C9x can run without one in Arizona; that is a real test! I am going to put up a sign in the garage to remember the idea that the timing has a lot to do with cooling, that is an important idea! Thanks again!

Don Shillady
Retired Scientist/teen rodder

Don, I am running a 330 HP 350 SBC in my 29 without a shroud. I have not encountered any cooling issues. I do however have a remote electric fan to cool my trans and a walker three core radiator to cool the engine.

29arod, thanks for that data. I have a Derallye cooler pan on my trans and an external cooler but I have not put it in series with the bottom part of the radiator yet. There are so many things to do on the car that I just do something whenever I can and not messing with that shroud saves me some time. It is really neat that your 29 is running, sometimes i wonder if mine ever will but I keep chugging along.

Don Shillady
Retired Scientist/teen rodder

Originally Posted by brianrupnow

Far be it from me to argue with Don, as I totally respect his experience and building ability. HOWEVER---I am not running a fan shroud on my small block powered model A---nor did I run one on my smallblock powered T roadster, nor on my 31 Desoto coupe! I never experienced cooling difficulties with any of these cars. .....---Brian

Nor do I think a shroud is absolutely required. If you are having problems it would surely be worth a try, otherwise, keep it simple. An open car with no hood will shed a crap load (technically speaking ) more heat than an enclosed engine. Ventilation under the hood is definitely a factor. Finally the shroud will actually impede air flow a bit at cruising and highway speeds; it all depends on what your set-up likes.

Kitz

I just got back from the nearby NSRA Richmond Nationals and paid special attention to details on the motor regarding shrouds and fans. There were a lot of electric fans with shrouds but of the cars I looked at I would say 5/8 had electric fans while the other 3/8 had low mechanical water pumps with flex fans. I also had a live chat with the Walker guy who said that out of 10,000 flex fans he sold maybe 50 disintegrated. So for the time being I will keep my 17" flex fan which is rated to 10,000 rpm since it is unlikely I will rarely go over 5000 rpm and the car will not be driven a lot anyway. The Walker guy did say that the 17" fan would help. I did not see any Zip water pump risers but indeed most of the electric fans were high up on the radiator. Here is a picture of a Deuce which had a flex fan and a low water pump but maybe the open sides help?

Here are two pictures of the Zip installation showing possible problem areas. The first is that the fan belt is pretty close to the indentation in the six-cyl water pump snout and it is the slack side of the fan belt cycle so it may rub; better carry a spare fan belt! The second shot is also difficult to see but I positioned a tip of the 17" fan near the nut on the snout of the alternator. I actually used about 1/4" of shims to move the fan toward the radiator so as to give more clearance with the alternator. You can see the total thickness of three shims as the gray thing behind the blue fan. The tech guy at Walker recommended 3/4" clearance between the fan blades and the inner side of the radiator but now I am slightly closer due to the need for clearance between the fan and the alternator. I could reduce the shims slightly but want to avoid contact between the fan and the front of the alternator. I still need to hook up the heater hoses and add the bottom radiator hose.

Don Shillady
Retired Scientist/teen rodder

Keep in mind the fan blades will move forward when the engine is running.
That'll give some more clearance between V-belt, pulley, whatever.

Fwiw - the fan blades on my 17" Hayden fan are about 1/8" in front of the V-belt and almost as close to the crank pulley when the engines not running.

The blades probably pull forward 1/4" when the engine is running.
When I say pull forward, I'm talking about the rear edge of the fan blade.
The front stays where it was when the engine was off.


Another fwiw, the Derale fans have the blades mounted on center to the hub - when viewed from above or the side.

Hayden fans have the blades mounted with the front of the blade even with the hub center when view the same.

That gave me a little more room between lower radiator tank and fan blades.
The Derale fan will not fit here.

Far as trans cooling goes, the 32 has a Derale vented trans pan and a home-made skin effects radiator with about 120 square inches of radiation area.
Works well.




Only place the trans ever got warm was climbing tight turns on a twisty and steep mountain road in 2nd gear.
The 2400 rpm stall converter allows slippage at those low speeds and slippage = heat.

20 minutes stopped at the view site allowed the trans heat to come down enough to finish the trip.