Join Date: Jun 2004
Location: Moxee Washington State
Some things I have had experience with.
Overheating: Usually caused by either insufficient coolant flow or improper coolant flow routing. Since you have had the radiator cleaned, and it's a 3 row radiator that's probably not the issue. If you are sure the head gaskets are on right we need to move on. Air locks are a very real issue and can be very difficult with a 289 unless you know the trick, which is to loosen the heater hose clamp on the hose that goes into the intake manifold to let any air escape. When you get a trickle of coolant, there is no more air in the system. (do this on a cold engine)
Another thing that I have seen is a faulty head gasket letting compression leak into the radiator. The engine seems to get hot in a hurry and blows the coolant out of the system.
Camshaft: The 268H Comp Cams cam is a great cam but it really likes a 4V carb. The 2100 Autolite can be made to work but the internal passages, accelerator pump and main jets and off idle circuit need to be correct. It takes a good carb guy to straighten one out. The 2100 is also very limited in air flow so another carb would work a lot better.
Timing: These engines like a total ignition timing of usually 34 to 36 degrees before top dead center at 2000 to 2400 RPM. It would be a really good idea to have a competent engine builder check that the TDC mark on the balancer is really true TDC when it's lined up with the pointer on the timing cover. The outer ring on the balancer is rubber mounted, if it slips, which I have seen them do, it will retard the timing. A competent distributor shop can adjust the advance curve in the distributor to arrive at the proper timing. The same shop can also check the vacuum advance unit. (Briefly, the distributor has around 14 degrees centrifugal advance internally, which equates to 28 degrees at the crankshaft, setting the initial timing at 8 degrees gives 36 degrees total. The rate that this internal advance comes in is adjustable. Bringing it in a little sooner than stock is desirable)
One thing you can do before spending any money is to measure the diameter of the balancer and figure out how much distance is 36 degrees. (simple math) mark the balancer with a piece of masking tape, spin the engine up with a timing light connected and see where the timing marks lines up.
Chasing this problem can be exasperating, everyone has an opinion, what I have listed here are things I have seen in the past.
1965 AC Cobra CSX2580
1967 410HP 427 Fairlane