Overall, electrical problems are something that new racers often struggle with. A lot of times, they are looking for a mechanical problem and missing the real cause because it's electrical. Often it's something as simple as a poor ground. We've had occasions when somebody brought an engine back, claiming that it didn't run like they thought it should, and it turned out that the engine wasn't properly grounded. You would think a race car with metal all over it would be a good ground, but nowadays, with the tough powder coatings that people are putting on the chassis and the zinc-coated motor mounts, it can be tough getting a good ground. We recommend running a ground from the back of the cylinder head to a rollbar. Before bolting it on, grind off any powder coat or paint so that you have a clean, metal-to-metal contact.
We've also had problems in the past with racers not getting their engines full of water. About everything that races on Saturday night these days is designed like a Chevrolet Monte Carlo that's low-slung in the front. As the radiator has been lowered over the years, it has become common for the highest point in the cooling system to be somewhere in the engine and not the radiator fill cap. If you simply fill the radiator with water, and if the top of the engine is higher than the fill point, you will trap air pockets in the engine and have serious cooling problems.
You can fix that by mounting what we call a surge system-basically an overflow tank-on the firewall a little higher than the engine. When you fill the coolant, fill from the surge tank. That will flow from the tank, to the radiator, and onto the engine. As long as the top of the tank is the highest point in the system, you shouldn't have a problem.
Cox Race Engines
Contrary to popular opinion, I believe that adjusting the valves should be done with the engine at room temperature whenever possible. We have run several tests, both in the shop and on the dyno, and we have found that adjusting valves on a "hot" engine isn't always ideal. During the time it takes to adjust the valve lash, or just check them, the engine cools off significantly. This change in temperature leads to a variation in component expansion and clearances. Allowing an engine to cool down for the few minutes it takes to check 16 valves can change valve lash significantly from cylinder to cylinder.
Because of this unpredictability in temperature and component expansion, I believe the best way to check and set the valve lash is with the engine at a constant temperature-and the best way to do this is with the engine at room temperature. The general rules of thumb for adjusting at room temperature are as follows:
Cast-iron block with cast-iron heads: Adjust 0.002 looser than specs
Cast-iron block with aluminum heads: Adjust 0.004 tighter than specs
Aluminum block with aluminum heads: Adjust 0.010 tighter than specs
This is just a baseline. With a new engine, I usually check the valves at room temperature, then bring the engine up to operating temperature and check them again to verify the difference between the hot and cold lash. Now I know the difference and can make my adjustments on a "cold" engine accordingly.
Also, on roller rockers, do not run the feeler gauge in and out in line with the roller. The roller will give you a false feeling of lash. Always run the gauge sideways when checking lash. And it's always a good idea to keep records of what valve, or valves, required adjustment during each check. This could be a telltale sign that something is about to fail.
If the valve lash is too great, a cam lobe may be failing or a roller lifter axle bearing may be worn. If the lash is too tight, it may be a sign that the seat is getting beat up or the valves are sinking in the head. All in all, it's a good way to catch a problem before it gets ugly.