Running a Little Bit Hot Tonight!

Comparing a 20" 6-blade fan to a 19.5" 7-blade fan:

The GM (chevelle, Camaro, b-body, etc) 7-blade "19" fan actually measures about 19.5" . 7-blades vs 6-blades (all else being equal) is a 16.7% increase in bade area. 20" vs 19.5" diameter is only 5.2% more area (all else being equal) . The smaller, more bladed fan should have 10.9% more blade area than a 20" 6-blade

 

That assumes all other things are equal, such as blade pitch, size and profile.

 

Still haven't found a 20" fan at the Nats but will keep looking.

I did put my 180 thermostat back in and it heats up pretty quick and hits 200.

So, without thermostat, it won't run 150, with 180 thermostat it runs over 200? The thermostat does work in boiling water at the proper temp. I did put four 1/8" holes in the thermostat around the edge to see if that makes a difference.

I can't imagine it is a capacity problem if it won't get over 150. If a 180 thermostat makes it run too hot, does that indicate a flow problem? The thermostat is too restrictive or the water pump isn't pushing enough flow?

 

Something is certainly up with the thermostat (its not in backwards right??) or water flow. I'm sure it's one of the first things I asked in this thread, but the timing cover isn't corroded behind the water pump is it?

I don't recall ever seeing oversized water pump pulleys or undersized crank pulleys for BBB, but if there is such a thing could the pump be turning too slow?

 

Gauge accurate?
Point an infrared around yet?

 

Not to hijack, but on this same subject, I would like to see a pic of a gutted one or know exactly what to do to gut it so I can also do this. I only drive my car basically from June to November and occasional parades and am prone to temps climbing when sitting id;e for extended period. And I have a 160 stat. Can climb as high as 210 during parade with 160 stat. I do see the cooling/warming cycles on the temp gauge so I know it is opening and closing, but after a while it runs away.

 

Ken, that sounds more like an airflow or timing issue.
210* won't hurt anything anyways, just gets a bit closer to that runaway threshold.

 

Exactly. I need to take care of that on our Roadster as well. Fresh engine = a little tight as well.

 

Fresh engine = incomplete heat transfer from rings and valve seats, where a good % of heat transfer takes place.

 

So maybe the more I drive it the better it'll get.

 

Roadster runs cool when moving. Temp rises rapidly at idle. I think the wimpy flex fan has to go. The problem is that there is very little room between the water pump pulley, alternator, etc. and the radiator. Fan can't have much pitch.

 

Those flex fans can definitely do that!
(break your engine in good and hard)
Not saying that the only reason it runs warm is break in...just that you will see the temp gauge show less disparity from load related heat as it breaks in.
It won't creep up as far and then back down when it begins transferring heat more efficiently.

 

So, that explains mine getting cooler. Never seen it be that big of a difference between fresh and broken in before.

Also, the four 1/8" holes seemed to be about right. Hits about 190 then drops back to 180 pretty consistently.

 

If you get the "cheap" sheetmetal flex fans, you can stack them up (one on the water pump, then a 2" spacer, then another fan) and you will pull a LOT of air. It almost sounds like a supercharger under there.



-Bob C.

 

Adding the holes can make it climb up quite a ways before the thermostat opens and cools it back down.

 

That's exactly what is on the Roadster. Not enough room to stack them though.

 

OK, next issue. I finally got a 20" 7 blade clutch fan. It fits my old fan clutch but it is a little loose and has a slight wobble. Where the heck can I get a new fan clutch that works?

Every clutch I've been able to check locally is too big in the center and will not go through the hole in the fan. The hole in the fan measures less than 2.5" and the clutch flange is more like 2.6" in diameter.

They say it fits but it sure doesn't.

Here's an example that says it fits the GS but it shows flange at 2.6" - http://www.oreillyauto.com/site/c/d...260_911&keyword=fan+clutch&pt=03389&ppt=C0331

 

About 10 years ago, I got a new one at NAPA. for my wife's '79 Z/28.

 

NAPA doesn't have one. Checked Autozone, Advance and OReilleys, no go.

I guess I'm going to have to buy one of the too big ones and turn it down to fit in the hole.

 

Download the Hayden catalog, look through the clutch specs to find one with the proper pilot hole diameter and depth, water pump bolt circle, fan bolt circle, and overall clutch length, that is intended for standard rotation water pumps/fan blades.

www.haydenauto.com

Click on "Catalog", then on "2013 Hayden Catalog".

Specs start on page 342 on the .pdf.

The application guide shows a 2707 or 2705 fan clutch for the majority of Buicks (they're very popular numbers), both of which have a 2.6" flange. If they don't fit your fan...I bet you have the wrong fan.

I do see a 2710 listed for '68 Skylarks with 4.1L, and that does have a smaller flange. Might want to compare to your existing fan clutch. Does your fan have a 3" or 3.25" bolt circle?