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Installing Headliner Insulation in a Truck


It's getting hot here in July and my 1990 Chevy truck's AC hasn't been converted to R134a refrigerant yet. And it's out of refrigerant. So I'm noticing all the ways in which the interior gets heated up. The other day I was sitting in the sun waiting for someone and I realized heat was radiating off the inside of the truck's roof. The front part was cool to the touch because it is double-layered metal, but the back part was another story. It was nearly too hot to touch and it felt like it was pumping out heat into the interior.

The interior headliner area before I added the insulation

That's what it looked like before I added the insulation. I used a roll of insulation I found at Home Depot. It was $10 for a 2 ft x 10 ft roll. I cut it down to 18 inches x 45 inches to fit the area I wanted to insulate. I then used 3M spray-on headliner adhesive to make it stick to the metal.

Insulating material and adhesive that I used

The interior headliner area after I added the insulation

I wish I would have measured the temperature before and after. It's a drastic improvement. I left the truck sitting in a parking lot in similar conditions for about the same amount of time as the day I noticed the heat. The interior insulation was barely warm to the touch when I came back out.

The stock headliner would have accomplished this insulation, but it's made of pressed cardboard-like material and had fallen apart over the years. I plan on adding an aftermarket headliner from LMC at some point, but this insulation will just add to the affectiveness of the headliner when I get it.

New Seats in the 1990 Chevy Truck


New seats from a salvage vehicle for the 1990 Chevy Truck

I finally got some "new" seats. These came out of a salvaged 1994 Chevy truck, but they were originally from a 1990 model. Either year would have fit. It took me about 6 months of watching and waiting to find some decent condition, blue seats for the truck.

Before installing the seats, I thoroughly cleaned them with Shout Auto Dirt and Stain Remover (you can get it on Amazon here). They came out very clean and smelling fresh.

Here are the old seats for comparison:

Old seats out of the 1990 Chevy Truck

I would say it was a worthwhile upgrade :).

New Exhaust on the 1990 Chevy Truck


1990 Chevy Truck Custom Y-Pipe

I finally took the plunge and got the exhaust replaced on my 1990 Chevy truck. I went with a simple one-in, one-out magnaflow muffler with a turned down outlet pipe. It sounds great, but the star of the show is the custom Y-pipe I asked my exhaust guy to make. It looks like the one pictured above. I'll take a picture of the actual exhaust when my garage drops below 98 degrees F.

After reading in numerous places that the stock Y pipe on these trucks is very restrictive, I wanted to see if I could squeeze some performance and efficiency out of getting mine replaced. My exhaust also had holes from rusting throughout it, so it was time. Reading on, you'll find this:

GM intentionally made that Y pipe restrictive to increase back pressure and most have paid someone to spread a myth that back pressure in the exhaust is GOOD. Its NOT. Air velocity is good not back pressure. The reason for the back pressure was so that the EGR smog system would work better and the increased pressure would build up a lot of heat to keep the o2 sensor hot. A good free flowing exhaust does typically need a 3 wire heated o2 sensor conversion to maintain its temperature. To fix 90% of the exhaust issues, I recommend a Flowmaster Y250300 collector from your favorite vendor and replace that section of Y pipe where the 2 pipes merge. Dramatic improvement over that stock GM design.

Here's what the stock Y-pipe looks like:

Stock Chevy truck Y-pipe, 88-98

I showed the exhaust guy a picture of that Flowmaster collector/Y-pipe and he said "I can make a pipe like that, just not as pretty". So I said go for it. And boy is it awesome. The truck feels like it has more torque off the line, seems to have more power on the highway, and my gas mileage increased 17.5% (13.1 mpg to 15.4 mpg).

The whole system rang in at $196. Not cheap, but it was needed and I'll recoup some of that (or all of it, eventually) with better gas mileage. Thanks to David Jones at Extreme Muffler for building and installing the new exhaust.

The TBI Air Flow Enhancer, a.k.a. the Salad Bowl


I just installed the TBI Air Flow Enhancer from Jegs. You can also get it at Summit Racing under the name Hypertech TBI Power Chargers 4001. And you can also make your own for much cheaper. I had read mixed reports of the effect these bowls have on performance. Some say it doesn't do anything and some say you can definitely feel an increase in power.

TBI Air Flow Enhancer, a.k.a the Salad Bowl

TBI Air Flow Enhancer, a.k.a the Salad Bowl kit from Jegs

The tipping point for me to buy one was an old 1993 GMC 350 Pickup – Project Jake, Part III. This is about the only "proof" I could find that the bowl makes a difference. These guys actually have a before and after dyno run for the Salad Bowl mod:

TBI Air Flow Enhancer Dyno Results

TBI Air Flow Enhancer Dyno Results from Hot Rod Network

They show that the bowl gave an increase of 8 HP and 8 LB-FT of torque at the rear wheels. However, I've watched enough dyno runs (thanks Roadkill and Might Car Mods!) to know that pulls can vary quite a bit without anything changing on the vehicle. But I wanted one anyway, just to see.

This is the stock TBI collar for a GM 350

This is the stock TBI collar for a GM 350

At first I thought my air cleaner stud would be too short. I had read somewhere that you might need a longer one. Then I realized you can just back it out a bit. It will still have plenty of threads left in the throttle body, but you'll still be able to attach your lid, as well.

Air cleaner stud adjustment for bowl

Just unscrew your air cleaner stud a bit to make it stick up enough with the bowl.

And there it is, with everything buttoned back up:

TBI Air Flow Enhancer installation complete

TBI Air Flow Enhancer installation complete

So now for the big reveal: my very own opinion on the effect of the Salad Bowl mod with the TBI Air Flow Enhancer/TBI Power Charger. I definitely feel more power. Everything from taking off from a dead stop to accelerating on the highway seems to take less throttle. The truck feels like it has more "grunt". So if you're on the fence about getting a bowl, I'd say go for it. Or make your own.

Hopefully less throttle means more miles per gallon. I track the gas mileage of the truck here: Chevy K2500 Fuel Economy Log. I happened to fill up the tank the day before I installed the bowl, so this tank will be 95% with the bowl. We'll see what it does to the gas mileage.

Update 05/09/2017: Did the first fill-up after the salad bowl install. It was 14.4 mpg, which is about 1.3 higher than my average before of 13.09 mpg. I also got a free-flowing exhaust installed that raised the next tank to 15.4. I'll write about that soon.

And someone at Jegs got a little carried away with their packing:

Whoa there, Jegs