Misfire Head Ache...

[Mopar-Charger]

360 sb, electronic ignition, new plugs, wires, coil, distributor is about a year old. It has its days, started with a severed ignition box pickup (from factory) to a vacuum advance canister problem (factory as well). Replaced the vacuum advanced canister with new one.

Rebuild carb last weekend (600 eddy)


Symptoms:

Starting - starts fine accept it will sputter and die, If i attempt to hold it at 2000 rpms to warm up, it drops in rpms till it dies. then it idles fine after two tries (when it warms up) I live in hilton head so its like 90+ everyday.

idle to light acceleration - hesitation/erratic sound with barely any throttle (moving it a hair from idle)

Misfires randomly while constant speed (1200-2000 Rpms) fine after 2000 under light acceleration

When I go WOT hesitates (like idle ^) then misfires randomly throughout acceleration, gradually worsens as it climbs to 5500 rpms

I had this problem early on while I had points (hence why i swapped to electric). Because this is my daily driver, I need a quick response.

I'm low on funds so I can just buy $400 racing distributor :icon_neutral:


360 distributor maybe? ProFrom?

Thanks,

Jake

 

[Xp29h]

How's your timing? Misfiring and/or backfiring usually means out of time. My thought.

 

[Mopar-Charger]

Initial is at 10, tried working on it this morning and it wont run. No matter how much throttle I give it it sputters and dies.

 

[super-bee_ski]

What do the spark plugs look like?
(Burn pattern?)

Are all cylinders firing?

 

[Mopar-Charger]

It ran very rich prior to carb rebuild, so they had some carbon on them but that's about it. Pulled each one out and wire brushed them.

I'm almost positive each piston is firing, plugged the timing light up to each and didn't see a miss.

 

[Cranky]

Is the engine basically stock? Cam change etc? Have you tried moving the timing up and are you sure the timing marks on the balancer are true? When was the last time the engine was running good and do you know what changed to make it start running bad? Are you using the same timing now that you were using with the point system? One of the first things I do when having a problem like this is to move the timing around to see what difference it makes and go from there....

 

[Mopar-Charger]

I had it timed perfectly prior to it sitting at a shop for 3 months for a 2 day framerail repair, but after the timing was f'd with firing order was off by two.

When I finally got it back to a good timing, the carb was dying so i had to compensate (retard it). But since the rebuild of the carb it's just not ran like it should. Mis-fire here, mis fire there. Never perfect.

I've head the harmonic balance can slip? A while back when I put the Purple Stripe cam in (509 lift) I couldn't even see the TDC Line. So I put a peice of tape from the line (close to 10 degrees) to the -10 mark. When it's running good I'll see the bottom of the tape around 0, so that means 20 degree initial?

I've been meaning to look for a vacuum pressure tester, but the shops around here don't carrier it. I was told just to plug that it in a adjust the timing for the most vacuum?

 

[super-bee_ski]

Well,
it could be numerous things (as you know) ...
From a cracked dizzy cap to a intake manifold leak to a poor performing carb or timing issues.

Interesting to note: It happens under acceleration/load...correct?

 

[Mopar-Charger]

I thought about swaping the cap and rotor (pretty cheap) nice if it worked.

The mis fire happens at all times, when I idle it stutters with any throttle then revs fine (When youre driving that first bit of throttle feels like you're running out of gas)

Since cutouts are off and neighbors are gone, let me take a video of the idle see if you guys can notice anything.