Bust a Cap
I have an '00 Toyota RAV4 that's completely stock, mechanically. It has approximately 60,000 miles showing and, in general, runs very well. The problem is the Check Engine light comes on without any noticeable provocation. Everything seems fine; it runs fine; gas mileage is the same as always, but the light keeps going off and on. I took the RAV4 to the nearest Toyota dealership, and they said it was probably a defective gas cap. They replaced the gas cap and, of course, the check engine light didn't come on when the RAV4 was in the shop. Later, the light came on again. There isn't any logical pattern to this problem, but I'd sure appreciate it if you could help me solve it.
Joseph Martin
Richmond, Kentucky

You could have a minor leak in the EVAP system. Newer trucks and SUVs equipped with OBD-II (on board diagnostics) are somewhat prone to problems with the evaporative emissions system. A leak or crack in any number of places among the many hoses, canisters, and valves can cause the engine warning light to illuminate. A loose or defective gas cap is another possible source and one that's quick and easy to fix. We surmise that the dealership went for the quick fix, which obviously wasn't the cure. An OBD-II diagnostic system performs multiple tests on the EVAP system. Driving conditions can dictate the amount of time it takes to perform the tests based on varying driving conditions. The Check Engine light should only come on after the OBD-II system has noted repeated failures. In the case of evaporative emissions, they need to exceed federal standards by 150 percent before the light is supposed to illuminate. When an emissions problem is either repaired or goes away on its own, the OBD-II system again has to make multiple checks before it turns off the warning light. We think you still have a minor or sporadic problem with your EVAP system. There's also a very slim chance that you got two defective gas caps. Try another service department or an independent tune-up shop. We bet they'll find the problem.

I have a high-mileage '85 Ford F-150 two-wheel drive that's been given the prerunner look with lifted suspension and big 33s on wide rims. It's been a good truck, but the engine is really pooping out. The odometer reading was suspect when I bought the truck, and the only accurate odometer reading now would be lots. The engine smokes badly, uses a quart of oil every couple hundred miles, and has some pretty noisy valves. I thought about rebuilding the existing 351ci engine, but then I scored a strong-running early '70s 351 Windsor engine on a trade for an old scooter. The 351W heads were supposedly rebuilt. My question is whether I'd be better off swapping in the whole early engine, swapping cylinder heads, or trying to rebuild the existing engine? I'm looking for the best choice, but saving money is also good.
Dave Hulteen
Phoenix, Arizona

You could install the early engine in your truck, as long as that's within smog regulations in your area. The problem with the early 351 is that it's balanced differently, and you'd need to change some external accessory items. You'd need a correct flywheel or flexplate, matching harmonic balancer, and related balancer pulleys. The water pump, front cover, and oil pan from your current engine would need to be installed on the early 351. Swapping the early cylinder heads onto your current engine would involve installing hardened valve seats and different rocker arms. The old heads were designed for leaded gas. Another possibility would be to rebuild the short-block that's in your truck and add a pair of Ford Motorsports cast-iron GT-40 cylinder heads, headers, and a free-flowing exhaust system. The beauty of the GT-40 heads is that they perform like early cylinder heads, and they're designed for unleaded gasoline.