Belgian1979vette

I have mounted dual electric fans instead of the factory one. Now it seems that she want to run hotter during low rpm driving. It seemed that at higher rpm (3000) she cooled down better.
Meanwhile I mounted a third relay to have the fans also run at low speed contineously.

I searched for the parts from my donor car and started to compare the pulleys. It seems that the siamesed 2 groove crank pully is smaller on my car than that of the donor. In my car it's the same size as the pulley for the PS which seems to be the same size on both cars.

Would this help with extra cooling due to the increased water pump speed ?

mrvette

IF your crank pulley is smaller than stock size, for sure you are slowing down ALL the accessories, and yes that can cause lo speed heat problems, gotta keep that water moving....

you maybe try drilling about 3 3/16" holes in the skirt of the thermostat itself, that bypasses the stat hole and of course increases the flow a bit....years ago, factories decreased the size of the hole, no matter what temp the stat was rated at, for instance 180f state had a larger opening than 195 rated stats, that is no longer the case, so I just drill the holes and forgetaboutit, but on really COLD winter daze, the engine maybe not warm up so good, can't win some daze....

CanadaGrant

I don't think a small diff in crank pulley size would cause an overheating problem. It would slow down the circulation but would also give more time in the rad to cool. I would be looking at a rad problem. I had something similar with my 69 427 and found it was rust/deterioration/ and straight out blockage. I stuck in a new Dewitts rad with a 160 stat and it runs 160 all day long.

Belgian1979vette

Well, what is in there is a 6.70" crank pulley and the other one is 7.75. So the difference is substantial. I think what I have now is a 1/1 and the other pulleys are an overdrive 1.24/1. Looks like it would increase the flow 24%.

On websites like Stewart (which is the pump I have) they say that there is no such thing as reduced absorption of heat due to increased speed.

I'm not sure how this would work on higher rpm however.

Belgian1979vette

Gene,

I had a Stewart thermostat with the holes in it, but in winter (and it can get cold here) she would hardly reach proper operating temperature. I since then switched to a Stewart without the holes but with a tube from under the thermostat to the top of the waterpump.

mikem350

For low speed cooling the fans have to be in a shroud that seals to the rad core. Idea is to pull all the air thru the core, not leak around it.

If you can, post some pics of the new fan setup

CanadaGrant

I don't think it's a matter of how fast you move the coolant but how you cool it. So, if what you say is true, then there would be no reduced absorption of heat if you slowed it down either...
C3's have a pretty good cooling system. GM learned that with C2 427's at the stop light. My 69 runs dead cool right on whatever thermostat I have in it. I'm from Canada but it still gets to well over a 100F here. When I replaced the rad the drain was plugged with debris, so bad it wouldn't drain, and I still can't figure out how it still worked. Guys spend a fortune on underdrive pulleys and other junk to try and get two more horsepower but still have the same old rad. Then install a sound system and can't figure why the battery is dead...
Look for the real problem first.

Belgian1979vette

It's a dual fan setup similar to the Spals but they are not Spals.

The car cooled fine with the mechanical fan, so this may be a fan issue as well. I haven't had the fans running at low speed either. So it was kinda all or nothing.

Solid LT1

Cooling system water circulation rates can and do have an effect on cooling performance. There does come a point where either you cavitate the water pump or circulate the coolant to fast in a system but, your probably OK at 24% increase as long as you don't plan on 6000RPM Autobahn runs. I just fought this problem with a Jeep and we had to buy an aftermarket Flowkool pump to get the lower RPM emissions NOX readings in specification with a better water pump impeller design.

We used to install a 5/8" (16mm) water restrictor in the upper return hose in our old Trans Am race Vettes to restrict water flow out of the motors, if we didn't do that they would run hot at 3500-7400RPM race speeds on the track.

cardo0

Umm, mike was describing the need for a good shroud that doesnt leak air into or out of - just pulls through the radiator not from any side through leaky seals. Whether your shroud worked for the mech fan doesnt relate to what u are using with the elec fans unless u somehow stuffed 2 elec fans inside the stock mech fan shroud.

If your cooling well at >3000rpm at same car speed then your pump flow would look to be low other than your statement the mech fan seemed to do the job with the same pump (and pully). Reads like the shroud used with the elec fans is not pulling the right air but u dont post whether the car is moving or not above and below 3000rpm so it kinda hard to diagnose for this.
Just guessing here but w/elec fans i think u could do a leak check with a smoke source just by energizing the fan w/engine off. U would need a smokey source to pass around the shroud and i dont think a cigar would be enough.

A pulley change should be easy to verify but i realize your overseas and cant get to the local pick your parts for a different pulley.

Belgian1979vette

OK, couple of decent replies.

This engine is a high rpm unit. It usually runs at 3000+ and regularly trips to 7000 rpm. I have been pondering the same cavitation problem as well, since the pump will turn 8.680 rpm at that speed.

I happen to have a pulley set from a donor car, which is how I found out I have small crank pulleys.

As for the electric fans and their shroud. This is a unit similar to the spal dual fan setup. I have made supports on the top and the lower parts that cover the shroud and connect it to the radiator. The sides are also sealed.

When feeling the front of the radiator while the fans are turning, I can feel the air being drawn. Something didn't feel with the stock fan at idle temps.

The fans cool the engine down fairly easy when at idle. This problem seems to occur at 2000-3000rpm and sub 60 km/h speeds. I haven't tried a different ign timing setting yet.

cardo0

I would suggest to look at your lower air dam if cooling is poor at low car speeds. But it still doesnt make sense that this wasnt a problem when using the mech fan. The lower air dam should be forcing undercar air up to the radiator. A lot of owners remove the air dam for one reason or another.

A lean condition or retarded timing condition could make it hotter but again that shouldnt change when changing fans.

Solid LT1

You might want to take a look at Canton oil pans......they have a great selection of pulley systems.

Belgian1979vette

I have a pace-car spoiler. I think this is one of the best to direct air flow into the engine. Nothing has changed from the air flow side and all of the rubbers are in place around the rad and support.

It almost looks as if the cooler air that I'm now using instead of hot underhood air has something to do with it.