Question: I recently bought an '01 Ford pickup with the 5.4L engine. It seems to run really well, but coolant seems to just disappear, though I can find no leaks. Apparently, the first owner had the same problem and that's why I bought it so cheaply.
I pulled the cylinder heads looking for a leaking head gasket, as per information from my dealer's service department. There was no bad head gasket or visible cracks in the heads or the block. I put it all back together hoping for the best, and it still has this mysterious leak.
Marshal Spiek
Little Rock, AK
Answer: It took me a bit of research to find an answer for this one, but I like challenges. This is what I came up with.
First, it could be a crack in the cylinder head, not visible to the eye, which only opens up enough when the engine is warm. But I also found that there is the possibility of some very small pinholes in the head casting under the exhaust valve seat. The coolant leaks out here and is vaporized as it leaves the tailpipe. It's such a small amount that you never notice any visible vapor. It's too bad that when you had the heads off, you didn't have them pressure-tested-the leak would have most likely shown up.
There are three solutions, the best being to buy some new cylinder heads. Second best is to again pull the heads and remove the exhaust seats, weld up the hole and do the machining for a new insert. However, before I went to that much work, I would try a can of KN Block Sealer. I've had remarkably good luck using this for various mystery coolant leaks in the past. Be sure to follow the instructions as printed on the can. It just may work and if it doesn't, you're only out a few bucks.
Question: I've got an '83 Ford Bronco with a 351 Cleveland engine and C6 box. I'm rebuilding and modifying it until it's the truck I want. I've already fitted 35-inch Mudders, given it 5 inches of suspension lift and fitted a rear Detroit Locker. I'm currently rebuilding the C6 and making a reasonable amount of mods to the engine, such as an aftermarket carb, a Weiand Accelerator manifold, extractors, and a cam that makes power from 2,500 to 5,500 rpm.
My problem is whether or not I should fit a 2,500-rpm stall-speed torque converter. I'm not sure if the benefit of getting my revs into the correct power range will be outweighed by the problems caused by more traction loss. I'm currently running 4.11:1 gear ratios but plan on dropping them to around 4.55:1 in the future. I live in Carnarvon in Western Australia, which is about 500 km (310 miles) away from another town. Most people run stock four- or six-cylinder diesel Toyota or Nissans with standard manual gearboxes and minor suspension mods, so it is hard to find someone out here who knows much about real 4x4s with decent power/drivetrain combos that actually work.
Ben Jansen
via fourwheeler.com
Answer: That sounds like a nice mid-range cam with most likely a max rpm limit of about 6,000 rpm. Hopefully, it's not something designed for a circle-track racer that never sees rpm below that. If that is the case, and you're trying to build a trail machine, I would say reconsider the cam choice, or better yet, pick up the phone and talk with the manufacturer of the camshaft and see if this is really the cam you want to run. Most likely, they will also give you some clues as to what is the proper stall-speed converter to use. Just remember that the converter is going to be slipping at any rpm below that 2,500 figure, and most of the time on the trail you are going to be below that unless you make a point of keeping the rpm up, either out of necessity for power or to prevent excessive slippage. Slippage makes for heat, and heat is a destroyer of transmissions. For instance, I have seen a drop of over 50 degrees of fluid temperature at highway speeds between full lockup and non-lockup on a lockup-style torque converter, and that is only about a 200- to 250-rpm difference. With the 35-inch tires and 4.11:1 gears, you're just going to make the lockup point at 65 mph, so the 4.56:1s would definitely be a good choice to swap to.
Also keep in mind that just because the torque converter is rated at 2,500 rpm, torque characteristics of the engine can alter that rpm. Even the axle ratio will affect the load that the converter sees and change the stall speed. Under full-throttle acceleration, the stall speed will be higher under a heavy load, such as is generated by a heavy vehicle and a high gear ratio, compared to a light vehicle and a low gear ratio. For instance, this 2,500-rpm stall converter in your Bronco with the 4.11:1 gears and 35-inch tires may turn into a 3,000-rpm converter. However, in a lightweight roadster like a Cobra with 28-inch tires and 4.11:1 gears, it becomes a 2,000-rpm stall converter.
Picking the right torque converter is really a hard decision so my best advice is to spend some time on the phone with both the cam manufacturer and torque-converter manufacturer's technical department and go by their recommendations. You want to be sure to tell them the application, engine specifications, axle ratio, tire size, and vehicle weight.