Mission Possible: A Boxy 1984 Caprice Classic

[101Volts]

Yesterday I changed the engine oil to T6 0w40 early. It's thinner at startup and operating temperature than the T6 5w40, so there's some marginal improvement.

I would have changed the gear oil at the same time but I'm going on a trip with the car tomorrow and don't have any limited slip additive which I don't know if I need or not. I decided to leave that for later.

Looking at oil specs, I see not all 0w30s and 5w30s are quite the same as stated on the bottle. Pennzoil Platinum 5w30 is actually thinner at startup and operating temperatures than Mobil 1 0w30, though Mobil 1's 5w30 is thicker than their 0w30. I'm not yet sure what oil I'll use next - P.P 5w30, RLI 5w30, Amsoil 0w30/5w30?

Edit/Update: Didn't feel like bumping the thread but that last oil change and using the Lucas ATF Thickener (leaky transmission) destroyed mileage, since the change I got 18.48. As of this time mid-march I'm draining the oil overnight and replacing it with Pennzoil Platinum 5w30, keeping the filter (It's an Amsoil EaO) and I'm draining it too.

[101Volts]

Differential oil changed with Amsoil Severe Gear 75w90, limited slip additive not necessary with this oil even though it's a limited slip differential (I tested it.)

[101Volts]

Gotta say I feel like a young wannabe here having not done much of anything to the car since we got it.

I got some of the floor mat to make an air dam. The changes I've done so far haven't done much if anything except make the engine run quieter considering I had to put Lucas StopLeak in the transmission after changing 2/3 of the ATF which was in the car; I had a leak.

I'm also looking into an electric fan again but so far I've not seen anything to the size of the stock fan, is that an issue? The stock one is about 19 inches in diameter and the biggest electric fan I've seen has blades going to 16. Amazon says these ones fit and I'm wondering how well they work (if at all.)

Flex-a-lite 116 Black 16" Trimline Fan (reversible):

https://smile.amazon.com/Flex---lite...s=electric+fan

This 16" fan has reviews saying the blades broke off. Ow.
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Flex-a-lite 114 Black 14" Trimline Electric Fan (reversible):

https://smile.amazon.com/Flex---lite...s=electric+fan

This one has no reviews of fan blades breaking off.
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Flex-a-lite 180 Black Magic X-treme 15" Reversible Electric Fan:

https://smile.amazon.com/Flex---lite...s=electric+fan

If I wanted to go to nearly $300 just for a fan this one could be had. There are also a few more that are even more expensive.

[ChopStix]

As a fellow Chevy guy. If you pull a trailer and or sit in a lot of heavy traffic on hot days. Then just buy 2 -16" fans. Mount one on the rear of the radiator and wire it to a thermo switch to auto turn on/off with temp needs. The front of the radiator fan wire it to a manual switch. That way you can use the front if you need the extra cooling. But a single 16" should easily handle your car under most conditions. I've used a single 16 on different vehicles for at least a decade without any drama.

Recently I spent $26 for a new 16" fan, then another $26 for the thermostatic switch on ebay. The fan is a generic brand. But the thermo-switch is a name brand temp adjustable model, as its more important for reliability.

The more expensive fans that I have purchased in the past were not more reliable, or note worthy better at cooling. The only difference that I saw was that they were louder than the cheap ones. Which I believe is a sign of them using more power to run faster. Knock on pc, I've never had an electric fan fail on any vehicle. If you throw power pulleys on while doing the fan, you should gain 2-4mpg collectively. That's my 2 cents.

[101Volts]

It's been a while but in the last two weeks I put an air dam on the front bumper which leaves a few inches' clearance. I have no data yet and haven't taken a photo but the dam is made from floor matting, perforated plastic and stainless steel hardware to hold it on just like on the Suburban.

The last few readings pre-air dam have been around 21.05, 20.56 and 20.11. I have no idea if those are accurate though as they're all extended tanks at multiple stations. All are on 87 grade "Up To" E10. I haven't rebuilt the carburetor yet, it needs done though. The car takes more than five pumps to start up when cold and may have not been worked on since the 1990s, if ever.

Why can't I edit the original post at this time?

[cosmick]

The most accurate way to get tire revs per mile is to use a cloth tape measure, used for sewing, to measure the new, mounted, inflated, unloaded circumference of the drive tires, use Pi to figure the diameter, then use 97% of that in all your calculations.
20168.0672268 ÷ diameter, then x .97, will also get the tire revs / mile.
Gm speedometer calibration is also super easy for the 700R4, and cheap, too. More accurate than GPS, by a lot. You need to know your axle ratio, then you can try it with all 4 of the available speedometer drive gears, to find the closest match. But then there are speedometer correction gearboxes out there, small enough to fit in your closed fist, to get it dead-nuts perfect.
I know the Caprice is boxier than a 78 Camaro with the 5" rear spoiler, but drag should be similar, because of that spoiler. One of my 78s had a 350, a 700r4 i swapped, a 3.08:1 axle, 235/60r15s, and returned 25.1 mpg at a steady 65 mph, including some hills.
It was one of the best combos i ever drove, and i am very strongly tempted to replicate it in my current i6 Camaro. I fe e l some tweaking could get it even higher, both in mpg and in performance, partly because i later discovered that my distributor's centrifugal advance hadn't been working.

[101Volts]

This air dam mod may have just given a significant difference. The latest tank reads 22.49 and I noticed I didn't have to push the accelerator down as far when hill climbing that long hill between Brockway and Rigway and I also saw the fuel gauge go down considerably slower over the course of the tank. However, I'm not sure if the gas amount is quite accurate as the pump kept shutting off too fast and then it overshot at the end. I won't go to this station for filling this car up with gas as long as it does that.

I'm thinking of using a Renewable Lubricants' gasoline additive too:



I've been getting a lot of pre-detonation in this car even nearly 10k miles ago. The spark plugs and wires haven't been changed since 2011 (108/109k) and maybe this additive will help with that. If not, I'm going to either slowly pour water down the air intake or soak the cylinders in Seafoam because not only do I have pre detonation but the emissions out the tailpipe stink even when the car's been on the road for hours.

I'll report if the additive works not only in this but in other cars such as a Grand Caravan I never put in the garage on this site which should benefit from it and be easy to tell as it has a digital MPG gauge. This fuel conditioner is supposed to keep valves clean too, it's not only for fuel injectors. That one gallon's supposed to treat 2k gallons of fuel.

Hey, I have a wild idea. Perhaps I could take the electric fans off the dead 3.0 Caravan I now have and use them on the Caprice? I may have to still buy the thermostat but if it fits...?

[101Volts]

Somehow my F.E. went down (temperature change is part of it, no doubt) and I decided to stop the pre-ignition issues we've been having which I never mentioned before. Most fuel I've run in this car is 87 E10 and over the last few thousand miles it feels like it's been losing power uphill so I got two bottles of Amsoil P.I. (I'm not over-treating the fuel) to hopefully clean out the valves and combustion chambers and I filled up with 91 Octane E0 today at the station I said I wouldn't fill at. It's one of the only stations that sells E0 near me, this pump is specially for E0 and it didn't have an overshooting problem when I pumped unlike at the other pump. It may be a bit early to tell but I haven't noticed as much pre-ignition even after hard acceleration since the fill. It's still there but it's not as bad.

I haven't changed the spark plugs or wires for five years and the carburetor hasn't been worked on since before I got the car at the very least, it's only been 13k miles since the spark plugs were replaced but considering I've mostly run 87 E10 they may have considerable deposits.

[101Volts]

Short reports:

1: I'm not convinced the RLI additive works much. Mistakenly overtreating it may have caused smoke to come out my tailpipe on heat-soaked hot starts. I'll continue using it at the proper treat rate now that I stopped using it as much these last few tanks.

2: The car starter's being replaced soon; the one I've been using turned over slowly and it finally died.

3: I removed the air dam in January; the plastic supports were junk after riding 70-80 MPH on I-80 for 250+ Miles. I plan to reinstall it with improvements.

Tips:

If you're thinking of making an air dam don't waste your time with plastic, just buy small metal corner brackets; they were 58¢ ea. at Home Depot when I bought mine.

If you want to make an Air Dam for an 84 Caprice Classic 4-Door Sedan the bottom of the bumper isn't flat; it goes sharply downward around the grille. I'm not sure if they kept the same bumper shape for all 1977-1990 Caprice cars, Coupes and Wagons included.

EDIT, years later: In case you went to the last post here instead of reading the first one, I have to report that this car was wrecked on September 3, 2017. Sad day, but I'm happy that my Dad survived not only the wreck, but also the "fallout" afterwards. He had an ulcer issue a month later.