Eight new spark plugs make for a happy Shelby

[deathsled]

https://youtube.com/shorts/Tvx_beLXg8g?feature=share4

Eight new Autolites fixed the backfire and smoothed out the idle. Still running rich so I need to work on the idle mixture screws. Big duh to myself for not replacing 10 year old spark plugs much sooner even though they were low mileage. I set the gap at .054 for a 302 roller rocker setup that currently resides in the engine bay (no worries as the original 289 block is in my closet quite literally). Seems to be running right but hope the gap is appropriate.

[98SVT - was 06GT]

HEI type gap. If running a regular coil go for about .032. The engine in your closet liked BF32 plugs on the street and BF22 at Willow Springs.

[deathsled]

HEI type gap. If running a regular coil go for about .032. The engine in your closet liked BF32 plugs on the street and BF22 at Willow Springs.

Coil is a flamethrower. Had to look up meaning of HEI. High Energy Ignition. The distributor is a pertronix. Gap is still too much? Seems to be running much better.

[Side-Oilers]

Richard, the main reason that late model (after 1975  ) cars have HEI and large plug gaps is for emissions.

I've found that older cars do best running the gap the engine was designed for.  Compression ratios and major mods aside.  And yes, even with platinum plugs. (Actually, I like the standard plugs much more than platinums in older-design engines, like ours.)

I'd run closer to .035-040 in your engine, or even tighter to what Brett recommended.  Pertronix and that coil you have aren't a full-boat HEI system.  Better than stock, but the gap doesn't need to be increased much, if at all. 

Others may have different opinions, but .040 is what ran best in my KR with its aluminum 482-inch side-oiler, 10.75:1 compression.

[deathsled]

Looks like I better pull the plugs and re gap them. I should have asked here in the forum before proceeding. I therefore made two mistakes.

[deathsled]

Adjusted the mixture screws by sound and what a difference it made to the running of the engine. Maybe should have used a vacuum gauge? I wasn't sure if it connected to the carburetor outlet or the intake manifold so I ad libbed. Did I screw up? I already gapped the plugs wrong.

[deathsled]

289 views. Lol. Looks like this post ruins it and makes 290

[Side-Oilers]

All those views and only a couple of suggestions?  The usual SAAC Forum contributors must all be in jail this weekend.

[TA Coupe]

I've been in next-door jail for 8 years.

      Roy

[chris NOS]

i wish i could help ! but air/fuel mixture tuning is unknown to me !!

[deathsled]

i wish i could help ! but air/fuel mixture tuning is unknown to me !!

It was heretofore unknown to me but I am learning. It appears to have worked out well for me. I need to re gap the plugs though.

[rhjanes]

A vacuum gauge hooked up to the port on the underside of the carb, or intake.  Adjust the gap first,  Then set the timing.   Then worry about the idle screws.  And yes, start by lightly seating them in.  Then out 3 turns.  Start the car and watch the gauge as you adjust the two idle screws.  Finally, reset the idle RPM and do that as the manual states. 
And you stated it's running rich.  You know this because of black soot on the old plugs and perhaps out the tailpipes?  So the idle isn't really the issue for running rich.  That's because it might need to be jetted down.  Easy on most of our Fords.  Remove the front bowl and see what the jet size is.  Go down 2 numbers.  So they have 74 stamped on them?  Try 72's.  Clean the plugs between each jet change. 

Hope that helps. 

[deathsled]

A vacuum gauge hooked up to the port on the underside of the carb, or intake.  Adjust the gap first,  Then set the timing.   Then worry about the idle screws.  And yes, start by lightly seating them in.  Then out 3 turns.  Start the car and watch the gauge as you adjust the two idle screws.  Finally, reset the idle RPM and do that as the manual states. 
And you stated it's running rich.  You know this because of black soot on the old plugs and perhaps out the tailpipes?  So the idle isn't really the issue for running rich.  That's because it might need to be jetted down.  Easy on most of our Fords.  Remove the front bowl and see what the jet size is.  Go down 2 numbers.  So they have 74 stamped on them?  Try 72's.  Clean the plugs between each jet change. 

Hope that helps.

It does. Carb is a Holley 650 double pumper. Need to re gap the plugs again. Ho hum