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1968 Solar red GTO
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Discussion Starter · #21 ·
A new engine can run a little hotter because it has to "loosen up" a bit, but not much hotter.

What oil weight? Oil is also a means to cool and engine. Thicker oil may not transfer heat as well as lighter oil. Just a thought.

Yes, you want 1/2 in and 1/2 out as the typical positioning. You can get a spacer to move the fan closer toward the radiator and into the shroud. That may be all you need.

Radiator should do the job at the specs you have.

Get a hand held laser temp gun and shoot the radiator at the top and the bottom to confirm radiator temps and there should be a noticable difference. This will also verify your gauge and can save a lot of head scratching and time if it is a gauge/sending unit issue/mismatch.

Your belts could be slipping and not know it. I have had that experience. The pulleys have a specific V angle and some of the replacement belts are close, but no cigar. They can be too skinny and not grip well, or even drop too deep and ride on the pulley center rather than the sides of the pulley. The belts that seem to be correct are the Dayco brand Top-Cogged belts.


Other things are the amount of slip from the clutch fan unit. The HD units will slip less at lower RPM's, but drag more into the upper RPM's - so pro's and con's for the real HD units. Hayden is the brand that most seem to use and I myself have used them with no issues.

The fan blades can be made at different pitches, More of a pitch/angle will cut more air at the lower RPM's.

Again, get the timing dialed in to eliminate that.

Definitely using way too much gas, in my opinion. Not good because you could be "washing down" the cylinder walls of oil and not good when breaking in a fresh engine. If you had a real healthy engine, or 3.90 gearing, I can see 10MPG's. I think you should be doing a little better.

So get that squared away as well.

(y)


I’m running the recommended 20/50 ( with zinc) frost least the break in period

Ill get that spacer- good idea, it needs to be further into the shroud i think

Ill check the belt too, that’s an easy thing to check

It’s geared at 3.55- it did a lot better before on mileage, ill check the oil for gas too

My friend recommended a straight (non clutch) flex fan, what do you think there?
 

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I’m running the recommended 20/50 ( with zinc) frost least the break in period

Ill get that spacer- good idea, it needs to be further into the shroud i think

Ill check the belt too, that’s an easy thing to check

It’s geared at 3.55- it did a lot better before on mileage, ill check the oil for gas too

My friend recommended a straight (non clutch) flex fan, what do you think there?
20/50 is too heavy unless you are road racing the car. 15W-40 is better, but 10W30 might be best. The factory used 10W-30. The RA IV used 15W-40 as it had bigger clearances and was in essence a factory race engine.

I have used the non-clutch flex fan on my last 400 build. Helped with cooling. The complaint is that they do make a "whirring" sound that some feel is annoying or loud. Never bothered me. The pitch of the blades really pulled the air and then flattens out as the RPM's increase and forward motion pushes air through the radiator. They can have an RPM limit as stated by the maker, mine was rated to 6,000 RPM's - which my engine didn't see to often as power dropped off around 5,600-5,800 RPM's.

Also used the water wetter which can be bought at most auto parts stores. It did drop my temps down a few degrees, but that was my experience with it.
 

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1968 Solar red GTO
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Discussion Starter · #23 ·
20/50 is too heavy unless you are road racing the car. 15W-40 is better, but 10W30 might be best. The factory used 10W-30. The RA IV used 15W-40 as it had bigger clearances and was in essence a factory race engine.

I have used the non-clutch flex fan on my last 400 build. Helped with cooling. The complaint is that they do make a "whirring" sound that some feel is annoying or loud. Never bothered me. The pitch of the blades really pulled the air and then flattens out as the RPM's increase and forward motion pushes air through the radiator. They can have an RPM limit as stated by the maker, mine was rated to 6,000 RPM's - which my engine didn't see to often as power dropped off around 5,600-5,800 RPM's.

Also used the water wetter which can be bought at most auto parts stores. It did drop my temps down a few degrees, but that was my experience with it.

After break in, ill look at using the 15/40 for sure

I ordered a 1” and 2” spacer for the fan to put the fan closer to the radiator in the shroud

I have a container of water wetter from another project that didn’t get used, ill throw that in too
 

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DO NOT USE A SPACER WITH A CLUTCH FAN! They are only intended for the flex fans.
OK, good point and had to do some research on the fan spacer. I found some posts were the poster was going to add a spacer, but these were 3/4" to 1".

However, on the whole, it was recommended NOT to use a spacer with the clutch type fan set-up. Several reasons came up. Many of the fan spacers do not have the pilot pin to keep the clutch fan centered and any slight off set can lead to vibrations that could take out the water pump bearing or even crack the cast iron housing of the water pump. (I also think other reasons for vibration destruction is an unbalanced/damaged fan and/or loose or sloppy bolt holes that don't center a fan)

Here is the best explanation for not using a spacer: "I would be a tad worried about the forces on the bolts, which would be extra long to deal with a spacer. On a normal fan, there are no torque differences between the fan and the pulley (through the spacers) thus no differential sheer forces on the bolts. However, a fan clutch has the fan rotating at different speeds than the fan pully, thus places sheer loads on the bolts and now those bolts are longer. The different rotational speed of the fan/clutch will try and twist the assembly in relationship to the spacer and twist the spacer in relationship to the fan pulley."

I have, and have used, Pontiac spacers on non-clutch fans. They had the correct pilot pin and receiving pilot pin hole on the back side which went over the water pump pin.

Since a longer drive on the clutch fan is available and would give you the extra length to move the fan deeper into the fan shroud, that would be a better way to go. However, if I only needed to move the fan forward another 1", I would use a Pontiac 1" spacer and grade 8 bolts/studs. The above mention of sheer loads would not solely be placed on the 4 5/16" fan bolts, the sheer loads would also be applied to the solid pilot pin of the spacer. If that can be sheered off, then the clutch fan would have sheered off anyway without a spacer.

This is my opinion and is what I would do if I only needed to move the fan in 1" to get it correctly positioned into the fan shroud. May not be correct, may not be recommended, might even come apart on me. I run with scissors, grind metal without safety goggles, sand without a dust mask, drive in the rain with streaking wiper blades, and listen to loud rock & roll music without ear plugs.

Bicycle part Font Rim Circle Auto part
 

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I have no tech advice on this but am at similar miles and set up as you on a new engine. My old engine had the same temperature creep you described, the new one does not. Other than when I did the cam break in, mine has not gone above 185 with a 180 thermostat. I'm running the same radiator as you with the original fan clutch and shroud. The old and new engines both ran the 11 bolt water pump. I have a Flow Kooler pump on the new engine, the old one was a factory style with a cast impeller. I think the fan fits a bit closer in the shroud on the 70 than what I'm seeing in your picture. I've attached a couple pictures (please excuse the fact that I didn't paint the fan, ran out of time).
 

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I know Im the oddball-out here, but I live in hot, humid, congested state and my car is a driver. I don't have radiator gaskets, a shroud, or fender flaps. Which further bolsters the proof that a well designed and maintained system works much better.

Some day Ill add those other parts.
 
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