Sometimes, we get so caught up in the confusion of engine troubleshooting that we miss important details. We swap carburetors, change ignition points, adjust timing--yet fail to notice the obvious. What about proper choke adjustment when the engine is cold, with a steady pull-off as the engine warms? Is there a healthy accelerator pump shot when you work the throttle? Is PCV valve function what it should be? If you have ignition points, is the gap correct? Are contacts pitted? Does your Mustang have the correct ignition coil? Have you examined the distributor cap and rotor for cracks and proper continuity? Do your ignition wires pass the resistance test? Is your fuel pump long in the tooth and not delivering adequate pressure and volume? What about the fuel filter? Even if it seems irrelevant, check it.
Though the nimble Ford six presents its share of tuning and performance challenges, it doesn't have to be a poor performer. If you believe in this engine, there's plenty you can do to get its performance back on the beam. Your greatest friend in engine tuning is the desire to troubleshoot. There are no freak occurrences nor is there magic, just physical facts. If you cover the bases step by step and pay close attention to detail, you can super-tune your Mustang six and wind up with a reliable powerplant that will give you a lot of driving pleasure for years to come.
Help For Classic Carburetors
Last year, our hobby suffered the unfortunate loss of Jon Enyeart and, as a result, his Pony Carburetors. We are gradually becoming familiar with other classic carburetor rebuilders in the industry. In Pittsburg, California, Recarbco performs concours restorations on vintage carburetors of all types--Autolite, Motorcraft, Rochester, Holley, Carter, Stromberg, Edelbrock, Zenith, and a host of others. Kurt Praxl has opened his own carburetor restoration shop in Western New York as KP Carbs/Carbontooters. Kurt was trained and mentored by the late Jon Enyeart when Pony Carburetors was located in Western New York. Kurt's work is outstanding and on a par with what you would expect from Pony Carburetors.
10 Choke function should...
10 Choke function should be checked. When cold, the choke should be closed, but not tightly. When the engine starts, it should be partially open and demonstrate a steady pull-off with engine heat. Fast idle should come off with a light stab of the accelerator.
11 Look for the obvious....
11 Look for the obvious. Never use sealer on a carburetor base gasket or spacer. Always use appropriate gaskets making sure they're in good repair. Heater hoses provide hot coolant for good cold start performance.
12 Once Terry Simpson discovered...
12 Once Terry Simpson discovered the incorrect 1100 carburetor on a six-cylinder Mustang at the Restomod Shop, he decided to check ignition timing and found too much. Someone installed the wrong 1100 carburetor and never bothered to check ignition timing, which begs the question--didn't they notice how poorly this thing ran?
We keep beating the PerTronix Ignitor drum, but the darned thing works so well it's a no brainer if you drive your Mustang. PerTronix introduced the Ignitor more than two decades ago and changed the world for those of us who grew tired of fooling with ignition points. The Ignitor is super compact and hides inside your Load-O-Matic or Dual-Advance distributor. And if you bury the Ignitor's wires in heat shrink, this thing defies detection.
Once installed and properly gapped, the Ignitor never requires service or adjustment. Count on replacing your distributor cap and rotor when you change spark plugs while giving the Ignitor a quick once over. Your Load-O-Matic gets a #1266 Ignitor or #91266 Ignitor II. If you have a Dual Advance distributor, order the #1261 Ignitor or #91261 Ignitor II. If you decide to stay with ignition points, don't do it on the cheap. Opt for a Motorcraft or NAPA tune-up kit with heavy-duty points with phenolic rubbing block and vented contacts. Go with a cap and rotor with brass terminals.
Is Spark Knock Harmful?
Ignition timing is not only important to power and fuel economy, but also engine health. If you're running too much timing (advanced), your engine is at risk for spark knock or detonation--that rattling sound you hear under hard acceleration. Light pinging isn't always harmful, but any pinging is unacceptable.
Spark knock typically occurs when fuel ignites prematurely on the compression/ignition stroke. It can be caused by a red-hot piece of carbon or early ignition timing. It can also be caused by combustion chamber dynamics, such as the 351C-2V with its open chambers and poor quench, or a lean air/fuel mixture. You want the optimum balance of good timing coupled with air/fuel mixture in order to keep combustion temperatures conservative. Detonation can be considered a more violent form of spark knock with opposing flash points in the chamber coupled with an ugly head-on collision mid-chamber. Spark knock and detonation act violently on the piston dome, wrist pin, and rod journal.
13 Look for hidden elements...
13 Look for hidden elements like bad grounds, poor connections, and chaffed wiring. Sometimes distributors are rebuilt and never get their ground wire back, especially with mass rebuilders.
14 Secondary ignition wiring...
14 Secondary ignition wiring has its own share of gremlins. Start your engine and observe in total darkness. Do you see arcing among the ignition wires? Crossfire and arcing to ground robs your six of a healthy spark.
15 Good connections are everything...
15 Good connections are everything to performance. Ignition wire connections must be confirmed at each end and installed using a dielectric compound. And remember, ignition wires don’t last forever. Replace them every four years regardless of how often you drive your Mustang.
16 Distributor caps offer...
16 Distributor caps offer their own share of gremlins, including hairline cracks that you can't see. However, high-energy electricity finds them with ease. When in doubt, swap caps and see if that makes a difference. Choose a cap with brass terminals.
17 Timing marks are located...
17 Timing marks are located on the timing cover and are marked accordingly. At idle, you want 6-12 degrees BTDC according to Ford. Total timing should be 34-36 degrees BTDC at 2500 rpm. Road test and listen for spark knock under hard acceleration.
18 Checking valve lash should...
18 Checking valve lash should be an integral part of engine tuning yet few do it. Although 170/200ci Mustang sixes had hydraulic lifters, cam lobes and lifters wear down and proper valve lash winds up lost in the process. We’ve seen some Ford sixes with hydraulic lifters equipped with adjustable rocker arms. Most were non-adjustable, which calls for different length pushrods to take up clearances.
19 If you want your tuning...
19 If you want your tuning spot on, perform both a compression check and a cylinder leak-down test. With the data, you can ascertain engine health. A compression check alone isn’t enough confirmation because it is only static compression. Leak-down is more dynamic compression and real evidence.
20 Another barometer of engine...
20 Another barometer of engine health is blow-by. If you have oil around the filler cap, it's an indication of excessive blow-by from poor cylinder sealing. It can also be a dysfunctional PCV valve or plugged draft tube.
21 While you're checking...
21 While you're checking engine health, check intake manifold vacuum. At 500-575 rpm idle speed, you should see 17 inches of vacuum. A bouncing needle or low vacuum indicates a wiped cam, valve leakage, low compression on one or more bores, or intake manifold vacuum leak.
22 Some performance issues speak for themselves, like this fuel filter and rubber hoses, which are a fire hazard when positioned over a hot exhaust manifold. What's more, you are at risk for vapor lock and no start while hot. Fuel lines should be hard lined between the pump and carburetor where possible, with the fuel filter located away from a hot manifold.