A snorkel alone is only half the equation for crossing deep water. The exhaust system should be routed to allow the engine to push out exhaust when underwater. Relying on the exhaust pressure when crossing deep water can cause excess pressure in the engine, resulting in stalling. A sudden change in pressure can cause the water to back up into the exhaust and end up within the engine’s cylinders.
Cooling
A Jeep’s cooling system is subjected to harsh conditions off-road. Slow speeds drive up underhood temperatures, and trail debris such as dirt, rocks, and mud can end up in the radiator fins, potentially causing overheating. A factory Jeep radiator can be upgraded to a more modern aluminum radiator for increased cooling efficiency.
Novak Conversions makes a direct fit aluminum radiator for the CJ. In addition, a large factory-style engine-driven fan or electric fans running with a proper shroud are needed to pull enough air through the radiator.
The traditional style but increased capacity four-core radiator combined with a factory fan shroud and large engine-driven fan keeps my AMC 360 cool even on the hottest days on the trail. Good airflow and high-capacity systems are put to the test in Jeeps used off-road.
Flex-a-Lite makes a direct-fit, shrouded dual-fan system for the CJ. Note that these fans draw 19.5 amps, which can put a heavy load on a stock electrical system. A higher output alternator may be needed. Small flex-style performance engine-driven fans are typically insufficient for off-road use and should be avoided.
An old-school Jeep trick to help with underhood temperatures is the installation of 1/2- to 1-inch-thick blocks under the cowl side of the Jeep’s hood hinges. This props the rear of the hood up, creating a nearly full-width vent that can drastically remove engine heat. The functional look created by this is rather unique and can be a conversation piece to the novice.
Some companies such as Royal Purple and Lucas make coolant additive to help increase cooling efficiency. There has been mixed reviews on the effectiveness of these products. If cooling problems are experienced, it may be worth a try.
An old trail trick to keep the underhood temperatures down was to stick a block of wood or steel under the cowl side of the hood hinges. The 1/2-inch or so opened a gap that ran fully across that allowed underhood heat to escape. Slow trail driving drastically raises underhood temperatures; even placing your hand there allows you to feel the heat moving.
Finally, using a quality water pump with a proper pulley configuration is another important component to cooling in a Jeep. Spending some extra money in the area of cooling only lowers the likelihood of trail-related cooling issues.
PCV, Idle Mixture and Timing
The positive crankcase ventilation, or PCV, valve is designed to remove vapors from the inside of the engine. Most PCV valves draw engine vapors into the induction system to be burned with the fuel mixture. An old or defective PCV valve can hinder engine performance and cause excess vapor buildup within the engine.
Some carburetors and injection systems do not have provisions for adjusting idle mixtures but, if possible, adjust the idle mixture to proper specifications. A vacuum gauge is often the best device for adjusting the mix. Improper mixture, especially off-road, potentially causes the engine to run hot or have an excess fuel smell. An over-rich condition fouls spark plugs and leaves soot deposits in the exhaust system.
Proper engine timing affects many variables, including engine longevity, fuel economy, and engine power. Setting timing is a simple process using a timing light with the engine running. Rotating the distributor advances or retards the timing as needed.
Oil and Fuel Additives and Ethanol
Old Jeep engines have been left behind in the modern world. Most gasoline is unleaded and contains a mixture of ethanol. The early AMC era used engines designed to use the lead in gasoline to lubricate valveguides and piston rings. The removal of lead and the addition of ethanol can sometimes cause issues. Lead substitutes can be added to the fuel to slow wear.
In recent years, zinc dialkyl dithiophosphate (ZDDP), a zinc-based additive found in engine oil, has disappeared from most brands. This oil component provided protection against wear for older engines, especially in a flat-tappet camshaft. Most newer engines use roller camshafts and other modern components that do not require ZDDP. It is claimed that adding a ZDDP additive such as Lucas Break In Additive replaces the missing ZDDP and prevents wear in old engines run without ZDDP.
Determining the effect of ethanol mixed into gasoline used in an old engine can make your head spin from the possibilities. Some older engines run normally; others experience performance and fuel-efficiency issues. Finding non-ethanol gasoline is becoming more difficult and there are other ways of making your Jeep’s engine more tolerant of the mixed gas.
Most aftermarket carburetors perform well with mixed fuel and can be adjusted using mixture screws and jet changes. Both stock and aftermarket TBI and EFI injection systems typically perform well with mixed fuel, especially more advanced systems that run oxygen and MAP sensors.
Pretty, Shiny Stuff
Why not finish off your Jeep’s underhood with some items to show off your hard work? A set of aluminum or chrome valvecovers and a matching air cleaner dress up the engine a bit. Degreasing the engine helps keep the engine cool and prevents the possibility of the gunk smoking or catching fire from the heat. Once the engine is clean, a fresh coat of engine paint can finish the package.
Putting It All Together
Starting with the engine, I put together a recipe for a Jeep suited for maximum performance on- and off-road. As stated earlier, the factory engines provide for the Jeep in this capacity quite well. Retaining the factory engine, if possible, saves money and allows for upgrades to increase performance.
Based on that premise, this factory I-6 Jeep engine is equipped with the following.
• Aftermarket intake with a Weber carburetor or TBI
• Set of 3-into-1 dual-exit headers
• Performance Y-pipe running through a 2½-inch exhaust and a performance muffler
• HEI-style distributor, preferably a brand name or a conversion
• Set of performance spark plug wires and spark plugs
• Reusable air filter
• Factory-style engine-driven fan with a proper shroud
Based on that premise, this factory V-8 Jeep engine would be equipped with the following.
• Matched aftermarket intake and camshaft combination
• Off-road-friendly carburetor
• Set of factory exhaust manifolds feeding into a performance Y-pipe
• 3-inch single exhaust with a performance muffler
• HEI-style distributor, preferably a brand name or conversion
• Set of performance spark plug wires and spark plugs
• Reusable air filter
• Factory-style engine-driven fan with a proper shroud or a proper-size electric fan setup
Many of these elements would work well with a swapped engine, with the exception of a modern fuel-injected engine. Modern engines would likely not need any modifications because their out-of-the-box performance specifications are well suited for the Jeep.