carb tuning?

JohnnyC

JohnnyC

Member
Ok so heres the layout:
77 Scout II
rebuilt 304 with minor mods: gasket matched ported heads, bored .040 over stock, new stock cam/lifters
prestolite electronic distributor: set about 10 deg
holly 2300: 58 main jets, 6.5 power valve which I switched from a 4.5, float bowl set to just seeping over threads, 31 shooter.

The problem is that at partial throttle it seems to surge. At first it was hesitating real bad so I changed the pv from a 4.5 to a 6.5 and that seemed to help the off the line hesitation, but it doesn't want to run smooth when the throttle isn't over the halfway point. It feels like its slows then quickens but pretty subtle.
Also does anyone have a picture of how the throttle linkage is supposed to be hooked up?
 
What's the list# on your 2300? Hopefully not a 4412. What you're describing sounds like a lean surge. You need to take a plug reading. Find yourself a stretch of road where you can cruise along for a bit at 40-45 mph. Shut the thing down while at speed and coast to a safe pull off. Get under the hood with your plug wrench and pull a couple plugs randomly. Optimum afr at part throttle cruise should leave a light, tan residue on the plug electrodes. A lean condition will show as white to non-existent residue. Overly Rich will show a sooty black residue. If the plugs look lean, then you ought to look at #61 main jets to see if that helps.
 
Hesitation at mid-range is normally an indication of main jetting that is too lean.

Even at your nominal operational altitude (I was there last week!!), a 58 jet is going to be too lean.

I'd install a pair of #62 and go see what happens.
 
Thanks guys for the quick response but the carb tuning is going on stanby for a bit. The piece of crap tranny won't stop leaking for nothing so I have to sort it out. Thanks for your guys help.
 
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