As far as header configuration goes, generally speaking, a long-tube design will make more power than a shorty, though we've had good results with some recent 31/44-length designs, such as those from Hedman.
Finally, the general rule for converter placement is that the farther a restriction in the exhaust system is from the exhaust port, the less impact it will have on engine performance. Therefore, placing the cats closer to the headers will make them more restrictive. Of course, to go back to the original point, converters must be close to the engine to function properly, which is why you'll find them either as part of the manifold or right after it on most late-model production cars.
Advance DebateI hope you can settle a little dispute for me. Friends of mine (Ford, GM, and Mopar owners) have asked me to help tune their cars; most are 11- to 12-second rides. We seem to constantly have a problem getting the vehicles to idle without the mechanical advance coming in. I keep telling them to lock out the mechanical advance, install a start retard, set the timing, and be done with it. Since these cars leave the line above 2,000-3,000 rpm anyway, with the advance already in, I don't see the need for functional advance mechanisms. They feel that not having a working mechanical-advance distributor just isn't right, and that the distributor has got to have the lightest springs possible. They also believe that if you set the timing at a constant 30 to 40 degrees, some type of major engine damage will result.Don GundersonWaterford, Michigan
Your method of locking out the advance mechanism is a common practice among drag racers and has been for decades. Before there were start-retard functions in ignition systems, most guys would rig up an ignition kill button so they could crank the engine without spark to get it spinning and then release the button to fire it.
You didn't tell us much about the vehicles in question. Are they race-only or street/strip? This is important, because race-only cars can make due with fixed timing settings and so forth, but street-driven cars were designed with advance curves for a reason: To cope with the varying engine load conditions a road-going passenger car regularly faces.
To answer your question, yes, you could lock out the distributor and have the performance you're looking for assuming that these cars do, in fact, maintain higher rpm from launch all the way down the track. It isn't the most sophisticated approach, but it could work. Of course, even with the start retard, there may be detonation issues on the street under part-throttle loads-this is probably what your buddies are concerned about. Detonation can indeed cause engine damage in the form of blown head gaskets and broken or burned pistons.
You mentioned that your friends want to run the lightest springs possible. This is really the obvious flaw in the tune-up. If you don't want the advance to come in too early, you can't use the lightest springs. It's that simple. Heavier springs exist to help you tune the advance to come in when you want it.
Our advice: Leave the locked-out distributors at the drags and experiment with springs and weights to produce the advance curve you want. If you really want to get high tech, have the distributors curved at a shop that has and knows how to use a distributor machine.
Poncho PressureI have a question for you concerning my Pontiac 400 motor. I am concerned about a very low oil-pressure reading. When in drive, at idle (870 rpm), and at operating temperature, the gauge reads 13 psi. At highway speeds (70 mph at 3,800 rpm) it reads 40 psi. Are these readings too low for safe operation?Fred AligDenver, CO