I have a 1977 Ford F-350 Dually crewcab with a 460 V-8 4spd manual. The engine is from a 1973 Lincoln. The engine is not running very smooth. The idle is eratic and when warm you shut it off and try to restart it turns over like it is out of time. I have set the timming dead on I beleive 10 BTDC if I remember right. My question is The 460 was rebuilt and bored over .10. Would I need to time the engine different due to the incease in displacement. It has a new carb, fuel pump, sparkplugs, points, cap, rotor. Also there are 2 holes in the intake that used to supply the choke with Heat? Do they have any Vaccum to them will they need sealed up.

 

You don't need to change timing because the displacement is increased, but you might need to because the new pistons have a different compression ratio. I'd check the choke on the new carb. If it's not right she'll run like that.

 

It's always better to plug holes in the manifold to be sure there are no vacuum leaks. Vacuum leaks can causes your motor run rough. The change in CID or compression will not change the initial timing spec.

 

Ah but compression does. My Ford ran at 20 degrees advanced when I had 8:1 Comp Ratio. Now that I'm around 9:1 comp I only run 12 degrees advance. It knocks and occasionally misses if I run more advancement.

 

If you have the EGR spacer check to make sure it isn't stuck open also.

 

The initial can be run higher with the lower compression because the fuel detonation limit isn't reached. You should not run more than a total mechanical advance of 36° to 38° for any of these engines and if the lower compression lets you cheat the initail a little higher it still isn't recommended. If you insist on running the 20 degrees initial then recurve the distributer and shorten the advance curve. BTW high initial timing is really a race motor thing because their idle speed is much higher to start with. In a street engine the high initial is ill advised because of problems cause with proper idle speeds. Initial time is irrelivant in most cases, it is the total mechanical and mechanical + vacuum advance that matters.