popping and banging

[graham fury]

hi I've got a 66 fury 111 318 poly 2 barrel with petronic electronic ignition a couple of weeks ago it started popping and banging wouldn't run or ticker it only started after the car had done a couple of miles I called the Rac and by the time the guy got to me it started and ran fine the following day I changed the coil it ran with no problems on the Saturday I went to the ace cafe then up to Chelsea bridge with no problems I thought problem solved.
today I changed the plugs and took it for a spin about 1 mile down the road it started again this time it backfired so load its blown the exhaust apart I managed to get it home. I was just wondering if anyone has encountered similar symptoms or knows of a possible cause cheers

[John]

I cant explain the irregularity but popping and banging as you describe sounds very much like a timing issue

[graham fury]

I would have thought if it was timing would it not be constant as opposed to intermittent

[John]

Yes thats what I cant quite understand. Have you set the timing?

[graham fury]

no not yet but I'm wondering if the distributor is on its way out i.e. when its warmed up

[morgan]

Sounds like something is moving about when it shouldnt in the timing. Has it got vacuum advance ? Pop it off, block it up, see if problem persists.

[graham fury]

cheers will give that ago and check the timing

[Dave999]

mechanical or vacuum advance mechanism might be sticking.

Or

the phasing of the pertronix might be dubious see if the pickup can be adjusted a little
and check that the collar with the magnets in it, on the distributor shaft is not moving up and down or round and round.
those collars are fragile things the last thing you want to have to do is try to fit the 8 tiny magnets back in all the correct way round.... they all want to attract each other.... been there done that, had to make a little fixture to do it no fun

ot it could just be voltage drop to the coil when the wires get hot.

air leaks tend not to be intermittent they occur and get worse so other than a quick spray around the manifold and carb mounting with WD40 to see if the engine note changes i'd discount that

to blow up your exhaust would indicate

1) very late ignition
2) this ignition event setting off a bunch of fuel in the exhaust from a previously failed event
3) maybe a sticking valve !!! unlikely unless very bent or the spring has snapped.

or the pertronix is going bad
never had one go bad by half measures. work or fail as far as i know its a chunk of semi conductor that lets current flow when no magnet is near and stops current flow as the magnet passes. it either works or is totally burnt out. uses hall effect.... which is why the magnets need to go in the right way round if the collar falls apart. backwards magnets = backwards operation

Dave

[mopar_mark]

As said, popping & banging of unburnt fuel indicates a timing issue. A timing light will give you quick feedback on timing...

Some or maybe all, have a plastic coated gear for cam timing, the teeth wear & enable the cam timing to slip. Although, this problem would show up all the time, not just after a few miles.

As it’s a simple & cheap fix, I would also pull the rocker cover off & check rocker arms on Cyl #1 versus TDC, also in conjunction to Dizzy rotor arm position.

[graham fury]

checked the timing it was spot on the vacuum made no difference so have ordered a full electronic distributor conversion from the states my thoughts are start from scratch with all new components and take it from there at least it eliminates one small part breaking down so I've got a electronic ignition distributor coming it has the coil on the cap and does away with the ballast resistor so less to fail .....I hope thanks to everyone for tips and suggestions but for now I've just got to wait for the dreaded eBay global shipping

[Dave999]

sounds like an HEI clone

if it is all contained in 1 big chunk with just + and _



Dave

[graham fury]

it is a clone but its somewhere to start it might be a waste of money but then I'm good at that

[John]

checked the timing it was spot on the vacuum made no difference so have ordered a full electronic distributor conversion from the states my thoughts are start from scratch with all new components and take it from there at least it eliminates one small part breaking down so I've got a electronic ignition distributor coming it has the coil on the cap and does away with the ballast resistor so less to fail .....I hope thanks to everyone for tips and suggestions but for now I've just got to wait for the dreaded eBay global shipping

Out of interest Graham, what was the timing?

[graham fury]

im not sure it was set up by my mechanic I just put a timing light on it and the white lines lined up I've spoken to him and he's going to sort it when the dizzy arrives .... Im not much good with teccy stuff I put fuel in it goes when it stops I panic lol

[Dave999]

it is a clone but its somewhere to start it might be a waste of money but then I'm good at that

thats not a bad thing at all

if you had not said you had purchased something my next suggestion would be

see if a late model electronic distributor fits.
limit its mechanical advance.
buy a 4 pin HEI module. mount it on a chunk of aluminum
buy a low resistance 12 volt coil and wire it up with no ballast dlb198 off a jag /range rover

thus creating a HEI clone...

provided you don't drive at 6500 rpm all day you''d have no problems.

bang for buck there is no equal if you are happy to use none Mopar parts
won't beat a race set up but not all of us need a race set up, and although they can be better, their benefits are often over-stated.

i.e the spark power ratings mean nothing what the engine needs it gets, (you can't hold back a spark until more power builds) and that is wildly different from the maximum the coil and ignition can produce

my only concern with modern distributors is who made it and did they provide a sensible advance curve... dunno what a sensible advance curve is for a poly but i'd suggest with a combustion chamber much the same shape as my aussie hemi i.e open and semi hemi shaped it probably likes no more than 28* mechanical advance (but will work smoothly but less power with as much as 36) at 3000 rpm and will need more than "the book" states for initial advance maybe something like 8 -12 BTDC.

some fiddling may be necessary

Dave