The 1970s were not kind to horsepower. That fact became abundantly clear when we ran my 1979 Chevrolet Blazer on the dyno at SMG Motoring in Hopedale, Massachusetts last week.
I posted a photo gallery a few months ago showing the Blazer in its current state. Brian Lohnes over at BangShift gave me free reign to post updates on its progress since last February. You can read all those updates here.
What I didn’t mess around with, though, other than regular tuneup stuff, was its performance. The Blazer always ran pretty well, but it was pretty pokey off the line, and you could really feel it wheezing at anything over 75 miles an hour.
Lohnes prodded me to do something about it. I’ve been thinking about it for a while. The thing I really liked about the Blazer was how bone stock and un-messed around with it was, and the idea of putting headers and all that stuff on it didn’t appeal to me. Plus, I’m not looking to make a drag car out of it. I’m just interested in making it more drivable.
Engines, as you’ve heard since the earliest days of hot rodding, are just big air pumps. If you can get the optimal volume of air in and the optimal volume of air out, you can have an engine that not only delivers good performance, but better fuel economy, too.
In the 1970s, though, engines got seriously restricted. What really killed performance after 1973 wasn’t vacuum canisters or catalytic converters (although they didn’t help). It was low compression. In the 1960s, Oldsmobile was squeezing out tremendous power thanks to its Ultra High Compression V-8s that developed 10.5:1 compression ratios. By 1979, when Chevrolet introduced the L48 V-8 in the Corvette, compression had dropped to a dismal 8.2:1, neutering Chevrolet’s “performance” car with just 190hp.
Luckily, the trucks were spared at least some of the compression loss. Luckily again, this is a 1979 and not a 1980, which used a 9.2:1 compression 305 instead of the 350.
Early on, the previous owner cut the catalytic converter off, which provided a lot more seat of the pants acceleration. I can only imagine what this thing felt like with the cat in place.
The first pull on the dyno was horrendous. In the early days, I should’ve gotten 165hp out of it, which isn’t anything to write home about. I got 125 depressing, OPEC-era, worn-out hp.
The good news is, the only place I have to go is up.
On the second pull, we used the old high school hot-rodder’s trick of flipping the air cleaner cover over.
That alone got us four free horsepower.
The problem here isn’t mechanical. The Blazer only has 61,000 miles, so I’m betting that all the spinning iron in there is in decent shape.
The issue is that (A) I’m not getting sufficient air in, and (B) as evidenced by the stream of exhaust flowing out of that electrical conduit-sized single exhaust, I’m not getting sufficient air out. The truck is seriously restricted on both ends, so our thought is that we can get halfway decent power out of it for short money.
The Rochester Quadrajet four-barrel is a decent carburetor, but it’s tired and leaned out as far as possible. Q-Jets suffer from bad throttle shaft bushings, so it would require a complete rebuild and probably run in the $300 range. Lohnes has a Holley 650 ready to go for me, for free, which is is like music to my ears. While we’re at it, we’re going to swap out the original cast-iron intake for a Weiand cast aluminum intake that I’m going to paint up to look as stock as possible.
I’m also not sure what I’m going to do about the air cleaner. I hate the idea of looking at an open-element air cleaner in something so stock looking under the hood. I may just opt for a freer-flowing K&N air filter in the stock housing.
At the back end, I’m going to completely change the exhaust. I don’t want anything obnoxious, so I think I’m going to opt for Flowmaster 70 Series mufflers, with a true dual setup. The 70 Series mufflers flow a lot better than stock, and read about 82 db at 3,000 rpm from 30 feet away, which is louder than it is now, but not enough to have my neighbors calling the cops when I fire it up at 5:30 in the morning.
Again, I love the stock look, so I’m going to have the pipes turn out behind the rear wheels just the way the original exhaust does.
This isn’t going to be any kind of fire-breather, but I’d like to be able to tow a utility trailer with a motorcycle on it with some authority. If I can get 185 hp out of it, I’d consider it a success.
I’m replacing the exhaust on Friday, and within a few weeks after that, we’ll get to work on the business end. Then I’ll run it back to SMG Motoring and we’ll see what we got out of it. We’ll run another contest to guess how much we managed to improve.
