383 mystery hiccups

[70NPORT]

Cruising down the Interstate...sped up to pass lumbering truck, put foot down a bit on the 383...waited to feel familiar surge forward....got the sound of marbles in a coffee can and intermittent backfiring up through the carb instead...now under normal load 383 feels like its lost some power...and will backfire up thru carb under heavy load.

Slowly replacing everything, but All ignition stuff brand new: Accel 8mm wires, Mopar dist.cap w/ points, MSD Blaster coil, Mopar 13.5v reg (still have same ballast resistor). Plug wires on nice and tight. No previous issues.

- 2bbl carb starting to bail? (original 40+ yr old piece). Time to swap out?
- dead cylinder? -timing problem?

guesses?
:eusa_doh:

 

[Kernel Sanders]

It may be some junk in the carb or perhaps the little pump shot plunger in the carb is in need of replacement... vacuum leak? Check to see if the vacumm advance can on the distributor is still good and is not leaking.

 

[Kernel Sanders]

I just noticed you may not be using electronic disty, if so when was the last time the points and condenser were replaced? check for pitting and set gap and check dwell

edit: sorry just reread... your points are new

 

[70NPORT]

It may be some junk in the carb or perhaps the little pump shot plunger in the carb is in need of replacement... vacuum leak? Check to see if the vacumm advance can on the distributor is still good and is not leaking.

Hadn't thought of that, thanks!

 

[polara71]

It ran fine after you did all of the replacing now all of a sudden its not? I'm not buying it, something moved. Timing, points, plug wire........something.

 

[azblackhemi]

Marbles in a coffee can sound like pinging to me. Does it idle smooth or does it miss? If it idles smooth but pings under acceleration it could be timing too far advanced. If it idles rough you could have a carb or ignition issue. Did the problem start right after you gassed up? If so it could be bad fuel. I guess what I'm saying is with a problem like this it could be alot of things so you need to eliminate one thing at a time. Start simple like maybe a fuel filter and work up from there. Good luck.

 

[70NPORT]

Marbles in a coffee can sound like pinging to me. Does it idle smooth or does it miss? If it idles smooth but pings under acceleration it could be timing too far advanced. If it idles rough you could have a carb or ignition issue. Did the problem start right after you gassed up? If so it could be bad fuel. I guess what I'm saying is with a problem like this it could be alot of things so you need to eliminate one thing at a time. Start simple like maybe a fuel filter and work up from there. Good luck.

She idles smoothly, with no misses and only pings under heavy load (acceleration). My first thought was shitty, low octane fuel got into the tank as well b/c I had just fueled up (gotta watch the gas attendants like a hawk) but I don't believe that is the problem. This behavior only happens under mildly heavy acceleration, under normal conditions she hardly makes a whimper.

 

[polara71]

Wawa fuel...plus shes mad she got hit

 

[70NPORT]

Wawa fuel...plus shes mad she got hit

Yeah, I'm hoping she'll forgive me today.... promised her I'd be more observant.

I messed around with the vacuum advance this morning and I think the culprit is the vacuum canister itself. Instead of further fooling around with it Im gonna go for the nuclear option: swap out the entire distributor. I think I have another 383 distributor in the ol parts cabinet......throw that in and see what happens.

 

[polara71]

Go electronic for a few hundred and you'll never look back

 

[70NPORT]

Go electronic for a few hundred and you'll never look back

Yeah, I think I'm gonna go ahead and do that, makes the most sense. The extra 383 distributor I thought I had was really a 440 distributor and was too long so that kind of put the kabosh on doing the swap. Looking for my Jegs catalog.hyes:

 

[70NPORT]

Go electronic for a few hundred and you'll never look back

Well I have the Electronic ignition w/orange box on order from Jegs; and also an Eddy Performer intake manifold as well (going to switch my Newport over to 4bbl set up). I have an old Carter AFB 600cfm 4bbl carburator that came off my 440 a few years ago I'm going to use for the 383.

The Carter carb is a "spread bore" type (it is a mirror image of the Eddy Performer carb). However, I cannot find any spread bore carb gaskets, just square bore. Does this mean I'll need a phenolic adapter plate (adjusting to square bore configuration) to use between the carb and intake manifold? I don't recall needing that on the 440, years ago. It also had a Performer intake manifold.

Ugh. Nothing worthwhile is easy.

 

[Aquaman]

Two of my cars have the Mopar electronic conversion. One still has point. When I replaced the points and set gap / dwell using a dwell / tach guage (still available for about $35 at Sears, Auto Zone, Advanced etc.) it runs like a top! Starts runs just as well as the electronic. Just will have to adjust and replace time to time.