trouble tuning mild 351c with holley 3310

[c9zx]

Mike,

   Thanks for posting the info on the Autolites now being made elsewhere. I agree with you on the NGKs. I used them for many years. Chuck

 

[Stanglover]

Interesting thoughts on the Autolites. I too have run those plugs in my Mustangs for years without any issues at all. The 25's I just took out and the 24's I just put back in, all look excellent and run well, no miss-firing. There are probably better plugs out there for our old-school engines, just a matter of finding what runs best. It's like the majority of us use BF Goodrich Radial T/A's as our go-to tire. Why, there are some excellent alternative tires out there, but we tend to stick with what we know.

Geoff.

 

[87fox72mach]

Ok so i drove the car a bunch more. Dialed back vacuum adcance. Bumped initial timing to 14 deg. I pulled half my plugs so far they all dont look to bad. 1 has some whitish frost on it. I replacing them with 24s gapped at 0.40. Before changing anything i did get the cat to run without rattle that i could easily hear

 

[Stanglover]

Ok so i drove the car a bunch more.  Dialed back vacuum adcance.  Bumped initial timing to 14 deg.  I pulled half my plugs so far they all dont look to bad.  1 has some whitish frost on it.  I replacing them with 24s gapped at 0.40.  Before changing anything i did get the cat to run without rattle that i could easily hear

 Sounds like you're getting close, good stuff!

 If you did not read my post, I am at about the same point. I did just bump the initial to 16 today, seems okay, but I have not run it too hard either. I think the trick was to set the heavy spring to 'just lose' by bending the tang outward a fraction. That alone seemed to slow the advance down to where it no longer pings on hard acceleration. You may also need to re-tune your carb with a vacuum gauge and the idle mixture screws, NOT the curb idle screw as most of us have either done or do. My tuning guy say he wishes they were not even there. The advice I got was to back the curb idle screw off until it just makes contact with the stop, then give it a 1/4 turn. The transfer slot should be about right at that point. If the transfers are open too much, the idle mixture screws will have no effect. That is based on his opinion, you may need to play with it to find the sweet spot. Tune for max vacuum at the desired idle rpm's.

I also need to change or reposition my accelerator pump cam as it is a bit sluggish if I mash the gas at low speed, but comes on strong if I'm cruising around 50mph and hit it hard.

Hope this helps, but it is advice from a relative novice too don't forget!

Geoff.