What's wrong?

-

MOA

Well-Known Member
Joined
Feb 23, 2016
Messages
350
Reaction score
158
Location
CA
I realize it's hard to diagnose over the internet......

I'll try to give a much info as possible.
72 318, is making 365 hp on the dyno. Fresh build.
Crackling and explosions out the exhaust.

I thought it was too much fuel pressure, regulator didn't fix the problem. I don't have a gauge on it, I backed off enough to where it shouldn't even run, still runs and crackles, muffler explosions. Etc.

Checked firing order several times, timing is set at 16 deg. Has FBO ignition with advance limiter plate. Worked fine on the dyno. Did not use the FBO ignition on the dyno though.

All plug wires are sending current, checked with timing light.

Carb is new 1906 AVS2 650 cfm.
 
Is this when under load (accelerating) or decelerating, or all the time?

Ignition cutting off and on can result in raw fuel going into the exhaust and popping. So it could be erratic power supplied to the ignition, erratic ground, etc. If you can get it to do this sitting still, then you can put a voltmeter on various parts of the ignition system and watch to see if the power to it is steady.
 
18436572 clockwise..check 'em again and follow all the wires 5-7 tend to get swapped easily. Try stock box if you said FBO wasnt used on dyno.
s-l640.jpg
 
Well if it didn't do it on the dyno then now does with a different ignition then you found where to look. Is the box grounded good? What wires? Was the distributor used on the dyno run as is or was a different one used?
 
It does it idling or with the rpms increased.

Have not driven it yet.

I was thinking maybe the rev limiter was causing it, but it will rev up fine and still crackle and explode. I'd like to get this corrected before my mufflers are balloons.
 
Phista. 6 and 8 were reversed.

It sounds great now.

Many thanks.
 
18436572 clockwise..check 'em again and follow all the wires 5-7 tend to get swapped easily. Try stock box if you said FBO wasnt used on dyno.
View attachment 1715545370


Apparently you're diagram is a lot easier to read than the one in the Hanes manual.

I checked it twice, had my son double check it. It's one of the first things I Double checked.
 
Well, that rules that out; How's your cap condition and phasing?
 
It is a simple thing to overlook. I have made that firing order mistake that Pishta mentioned.
Its so easy to overthink it, loose sight of the basic steps, and then you start swapping parts and chasing your tail.
In the future you'll spot it as soon as you hear it.:thumbsup:
Good luck.
 
Been there, done that. They run a lot better with the plug wires in the right places.
 
Good to hear it's fixed and a simple one too. Never overlook the obvious. Go back to basics.
 
Shii....., I wired up a LA like my B's rotation when I went back to an LA, that doesnt work well.......
:rofl:

wonder how I missed that post #6? whatever, free fixes are good!
 
-
Back
Top