Question: What can I do to hop up my 4.9L 300ci straight-six engine in my '85 Ford Bronco?
San Antonio, TX
Answer: Six-cylinder engines respond to the same treatment as a V-8. That is, more gas in, more exhaust out, and better combustion all make for more power. With that said, the easiest way to make more power as a starting point is with an aftermarket intake manifold and carburetor change, along with a quality set of headers and after-cat exhaust system. Offenhauser (www.offyparts.com) has a four-barrel intake available; so does Clifford Performance (www.cliffordperformance.com), as well as camshafts and headers.
Most major cam manufacturers also offer cams for the Ford six. If you want to go all-out with a total rebuild, consider a set of high-compression pistons, a balancing job, and maybe some port work. If this is a trail vehicle, then keep in mind that to maintain some of that good bottom-end torque that the six is famous for, don't go too wild on the camshaft and follow the cam manufacturer's recommendations. Overcamming is a far worse sin than undercamming. Also, you want to keep in mind that the higher compression will require a higher-octane fuel to prevent detonation.
Question: Why does GMC say in the owner's manual not to run chains on my '01 Yukon XL? I called the tire company (BFGoodrich) and they were very nice but couldn't tell me about tire chains. They suggested I call GM, which I did, and a kind young lady checked and said that I couldn't run tire chains because there wasn't enough clearance. She couldn't tell me "clearance from what?"
I called the service department at my GMC dealership, which is 100 miles away, and he said he didn't know why GM recommended no chains.
Help! Sometimes a fellow has to run chains. The highway patrol sometimes requires chains where I live. I'm running the BFG Land-Terrains (sold only by Wal-Mart); they're LT275/75R16s, 31.8 inches in diameter. If the chains may hit the fender liner if loose or at speed, no problem. But, if the chains will tear up a brake or fuel line, that's different. I would want to run them only on the rear wheels.
Answer: Yep, there are times when the California Highway Patrol does require chains, even on 4x4 vehicles. They have this thing about trying to prevent accidents. Just because you have four-wheel drive doesn't make you a good driver or allow one to drive faster. Their main reason for chains on 4x4 vehicles is that it at least causes the traffic to slow down. And four-wheel drive doesn't really help all that much in stopping distance on ice.
The only reason I could see that GM would say not to run chains is the lack of clearance. Some chains, due to design, take up more room than others. The European V-type, with the ice-biter cleats, most likely takes up the most room, the so called "cable chains" the least.
I believe the body and frame design on your Yukon is similar to the present models and yes, it is a tight fit. In fact, I tried this, and couldn't get my hand between the shock and the tire, it's so close in the back. Take a look at yours and see what you think. There is definitely not enough clearance for any type of chain.
Up front, there seemed to be enough room for chain clearance as long as you remember not to turn too sharply, and even if you forgot, the noise of a chain against the body would quickly remind you. In some situations, it's better to run a single set of chains up front instead of on the rear. However, the vehicle should be in four-wheel drive. Duh! Gee, that stands to reason, right? Even more so because the front will now have more traction, a lot more traction than the rear, and there's a better chance of the rear of the vehicle sliding in a corner, so if this happens, you will have to learn to "drive out of the corner."
As you mentioned, most people run their chains way too loose because they don't want to have to stop and re-adjust them. There is also the factor of one size of chain fitting a variety of tire sizes. Instead of buying the chains at a discount store, I suggest you buy them from a tire store and have the service technician properly size them for your tire and vehicle.
It's nearly impossible to get a perfect fit and eliminate all slop, so this is where chain tensioners come in. Having lived in snow country for 30-some years, I've tried all sorts of tensioners. What I have found works best for me are tarp hold-downs. These are the heavy-duty black rubber units truckers use to hold the tarps covering their loads (kind of like an extra-heavy-duty bungee cord). They come in a variety of lengths. I usually use two on each tire, hooking one end in a chain link, running across about one third of the tire's diameter through a chain loop and back again, hooking the end about one third the distance apart again. I do the same with the other one, in just the opposite direction. They're easy to use and they do the job. If I know I am leaving the chains on for an extended amount of time, I've even resorted to using nylon rope to pull them tight.