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Out of ideas

2K views 17 replies 10 participants last post by  aquartlow 
#1 · (Edited)
I have a 1977 F250, 460. The thing shudders at idle. Runs like a champ otherwise. Aside from the shake, it has a very clean idle. It's not misfiring at all, smooth under load, plenty of power, no hesitation. Here's what's been done.

1. New distributor and cap
2. New plugs and wires
3. New carb
4. New harmonic balancer
5. Timing set up and checked twice
6. Motor mounts are good.
7. Ruled out vacuum leaks

Took it the local guy (known as the local classic Ford expert) who checked all my work, redid some of it, and did the balancer for me. All we can think of is to pull the engine and send it to a machine shop to get it re-balanced. Before I go that route, I am hoping for some fresh thoughts.
 
#3 ·
Cam specs?

Timing specs?

Compression and leakdown test?

Minor vacuum leaks?


S
 
#6 ·
what year is the crank from, flywheel have a counter weight on it? is there a weight behind the damper?
 
#7 ·
It's difficult to understand exactly what shudder means. If you could send a video with audio it would help. If you didn't do anything to it to upset the balance I doubt that balance is the problem. Since it probably hasn't been doing this since 1977 think back about what may have changed that could be associated with the shudder. If nothing, then check the ignition module. I've seen them do some strange things. Just swap it with a known good one and see if anything changes.
 
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