Is my carb too big for my 383?

[Strawdawg]

Be very easy to by pass the box and try that first, I think

[Bluemonster71RT]

Be very easy to by pass the box and try that first, I think

I cant with this setup. This MSD distributor only works with the box

[734406pk]

That's the bad part with the MSD ignition, you have to change components to test them. Start out with some simple (and free) tests like: check for full power and ground to the MSD box, coil connections etc. remove the spark plugs label which cylinder they came from and inspect them. (may have some fouling due to the previous carb issues). Post some pics of the plugs if they don't look right. Check the cap/rotor/plug wires for signs of arcing etc. After that, I think you may need to start swapping out components, unfortunately. Is it fair to say that this issue happens at full engine temperature and/or when the base timing is less than 20 deg BTDC?

[Bluemonster71RT]

That's the bad part with the MSD ignition, you have to change components to test them. Start out with some simple (and free) tests like: check for full power and ground to the MSD box, coil connections etc. remove the spark plugs label which cylinder they came from and inspect them. (may have some fouling due to the previous carb issues). Post some pics of the plugs if they don't look right. Check the cap/rotor/plug wires for signs of arcing etc. After that, I think you may need to start swapping out components, unfortunately. Is it fair to say that this issue happens at full engine temperature and/or when the base timing is less than 20 deg BTDC?

With this carb it is now happening at full temp. The edelbrock didnt matter.  I have had poorer drivability at anything less than 19 deg BTDC it's at 22 now with the 18 deg bushing and I went back to the heavy silver springs thinking I had too much advance too fast. My coworker said to back off a 1/4 turn on my lifter preload. He is convinced that its a tight valve. Thats free to do. Even if the rockers are noisy again if the problem gets better I go from there. From there I guess new fuel filter and a coil. My coil is the only thing not new. Lol its gotta be 30 years old.

Thank you for taking the time to help me out. I'm trying to do everything everyone is suggesting in order of easiest and cheapest first. It's gotta be one of these things.     

[734406pk]

I would highly recommend replacing your 30 yr old coil with a matching MSD Blaster coil. The old OEM type may not be compatible. You may have a tight or hanging valve, but i didn't want to go there yet until the ignition system is 100% But removing the preload is easy and cheap. Good idea!

[Bluemonster71RT]

I would highly recommend replacing your 30 yr old coil with a matching MSD Blaster coil. The old OEM type may not be compatible. You may have a tight or hanging valve, but i didn't want to go there yet until the ignition system is 100% But removing the preload is easy and cheap. Good idea!

Yeah going to get a coil right now. I did the 1/4 off turn and problem is still there. Didn't even get past my house before I noticed that it wasn't right.

[Bluemonster71RT]

Put the new coil in and no change.  At about 1/4 throttle I can get up to 100 mph without a hickup. Any more throttle than that and it starts with the chugs. Fast stab or fast deep throttle brings on the pops. Its gotta be timing of fuel at this point No? I guess I'm at a loss here. Fuel pump, filter, sending unit? Unless something mechanical is bad but if so, it would show it at high rpm even with the low throttle right? Do I just start jetting this carb now? Retard the timing? Put 110 in it? It has to be something stupid. Usually always is.

[734406pk]

Ok well its not lifter preload. Readjust the preload to .040-.050" so we don't forget and check the MSD box for full 12 volt power input and ground. Then check your distributor cap, rotor, plug wires and finally spark plugs. When you describe engine "chugging" i'm thinking you are dropping cylinders. When you describe engine "popping" is that backfiring through the carburetor? If so, these are also the symptoms of high voltage arc flashing over to the wrong cylinder(s). The engine timing advance is relative to R.P.M. and not engine load if the distributor is a mechanical advance only, (no vacuum advance MSD Pro Billet?) Does the engine still seem to run ok when cold then act up on full temp?

[Bluemonster71RT]

Ok well its not lifter preload. Readjust the preload to .040-.050" so we don't forget and check the MSD box for full 12 volt power input and ground. Then check your distributor cap, rotor, plug wires and finally spark plugs. When you describe engine "chugging" i'm thinking you are dropping cylinders. When you describe engine "popping" is that backfiring through the carburetor? If so, these are also the symptoms of high voltage arc flashing over to the wrong cylinder(s). The engine timing advance is relative to R.P.M. and not engine load if the distributor is a mechanical advance only, (no vacuum advance MSD Pro Billet?) Does the engine still seem to run ok when cold then act up on full temp?

Cap looks good, rotor looks good. The plugs look as I just put them in. The "chugging" is the sound like if you were to hum at a low register and then give yourself a tap to the chest with your fist. The popping sounds like its through the carb. Not entirely 100% on that. The car is so loud its hard to tell. Yes MSD pro billet mech advance. Today it ran like crap right out of the gate. So I guess that kills the temp idea. I have about 200 miles on this build so I have only what it used to be like (headers, carb and intake were only mods) as a base line. Ill check voltage for the 6al and see what we have. (edit) just pulled some more plugs now and they have brown deposity film on them. Chitons book says thats a rich condition, weak ignition or wrong temp plugs.

[734406pk]

"just pulled some more plugs now and they have brown deposity film on them". That's interesting. Can you post a pic of all the plugs noting which cylinder they came out of?  Also measure the plug gaps for reference. Remember to place the BLACK (very stiff) spring in the secondary vacuum pod for now. It will make carb tuning easier. Do you know the current jet size and power valve number in the carb?  That's a great description of the chugging sound! Later I'll hum a low E and have my wife Kung Fu me in the chest to see if it sounds like a 383 dropping a cylinder. She will be happy to help. I'll let you know when I'm out of I.C.U. LOL! 

[Bluemonster71RT]

Nice, I was thinking B on my 7 string. LOL!  I cleaned all the plugs already. They were all the same except #5(3rd lh side) was wet. 72/75 are supposed to be the stock jets and 6.5 stock power valve.   

[734406pk]

Just a little humor... Ok, all the plugs  are clean and have white electrodes except for #5?. What brand and number plug do you have? Did you happen to check the plug gap? Are you running a single or dual plane manifold?

[Bluemonster71RT]

Autolite AR3933 gap is at 38. PERFORMER RPM 383 dual plane intake. Performer RPM heads   

[734406pk]

Ok, so all the electrodes were white except for #5 cylinder? And also, what is the octane rating of the fuel you are running now?

[Bluemonster71RT]

93 octane