javella383
Member
383 with Holley 4150 750 MSD ignition, running her on the street in break in stage getting plugs foul,, best plugs? and best way to lean the Holley out a bit Thanks
Carburator too rich
- Thread starter javella383
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rklein71
Well-Known Member
Don’t rule out the ignition system as the cause of fouled plugs as a weak spark can do it too. MSD should be okay, but you never know. Do you have a good ground as that can mess up an ignition system.
javella383
Member
I will check ground good tip, This is a fresh Rebuilt too so I am thinking the jets may need adjustment. Pulled plug totally black not that wet but black
rklein71
Well-Known Member
Main jets really have no impact on fuel delivery until wide open throttle. Make sure your float levels are set correctly, to high a float level can cause the issues you are describing.
javella383
Member
Thank you novice here well it’s been awhile My 1970 Barracuda just came out of a 33 yr storage, we refreshed included rebuilding the original Holley750 , I have driven her about 200 miles not really opening her up but more crushing at 2-3000 rpm.
javella383
Member
I grew up in Westchester where I drove her in the 80’s now I live near Saratoga Springs,, not far from Lebanon Valley
moparleo
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A lot of missing info. Just a stock build 383 with a 750 Holley ? Or....
javella383
Member
383 .030 aluminum heads 425 Hydraulic cam 10-1 flat top pistons, and 3:91ratio .
Chryco Psycho
Well-Known Member
Holley type carbs are actually simple but you have to change the correct part in the correct order , for example @ 2-3000 RPM you are running on th main jets but if the vacuum is low the power valve could be open & bypassing the jetting .
Here is alink to an article I wrote about tuning Holley or similar tuning tips in Reference Material
Here is alink to an article I wrote about tuning Holley or similar tuning tips in Reference Material
DetMatt1
Well-Known Member
Nice car, welcome to the site from the Motor City!
340 Slapstick
Well-Known Member
Love the paint job!
Dodgeboy
Well-Known Member
Most aftermarket carbs are rich "out of the box", How adjustable is your carb? Press in or threaded jets/bleeds? When I got my 384 rebuild they installed a cold sparkplug (champion RJ9YC), it was black, I switched to the champion RJ12YC and with tuning the carb my plugs look just as good as the ones in my 07 Ram. I used to run a holley 750dp but now have a holley 850. General tuning tips would be check your timing, fuel preasure, take notes on carb settings, start tuning idle circuit first, then transition circuit, excellerater circuit and then wot. We would need more specifics to point you in the right/better direction, every combo is different
javella383
Member
Thank you, I am running the RC12yc in it for the break in period, fouled after about 200 miles and cruising primarily at 2-3k RPM, weather is cool now in Northeast so hot plug may work, I am also running an MSD 6A Ignition.
I will change out plugs back out idle screws 1.5 turns listen close and go from there. so, appreciate the feedback
Dodgeboy
Well-Known Member
If you have a vacumm gauge you can use that to set your idle mixture screws/idle speed. That should allow you to get the idle air/fuel ratio in the 13.5 -14afr range just be setting it to highest engine vacumm (using idle screws) and then set idle speed. If that doesn't work you can try lowering the fuel level in the floats (this will make it leaner). Try this before before messing around with jets/air bleeds.
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