missing/sputtering at speed

[Zorm]

Hey all,
Ok finally got the stang running after new exhaust manifold, and carb (1bbl for 6cyl) So now, she starts right up and won't try to die when I step on the gas while parked. If I drive her around the neighborhood, she's fine, now that’s only going about 15-20mph.
Well today on the way to get her leagal (tags) she was sputtering like mad, she also died then was a bear to keep running . I finally just stomped on the gas and she ran. :x
I think that was bad gas issue, put 10 gal in and she's a little better but still, when I am getting up to speed 40-45 and while at speed, she still sputters or maybe misses, when I let off the gas, she's smooth. Could this be a timing issue? points issue? dizzy cap/rotor issue or plugs and plug wire issue? She has a new fuel pump and filters from the P.O. that is why I am leaning to the ignition side of things.
Please advise
Thanks

 

[wallaka]

Accelerator pump maybe? Take the air cleaner off and pump the throttle manually. You should be able to see gas squirt if you look down the carb. If not, you need a new accelerator pump. Could also be trash inside the carb, but the only way to really check is to tear it down and rebuild. Good news is rebuild kits are cheap and come with instructions.

 

[MustangSix]

Test the vacuum advance. If it's bad, the car will sputter at higher speeds from lack of timing because the only advance on your distributor is in the vacuum canister (see Load-o-matic sticky above).

 

[Zorm]

wallaka: its a newly rebuilt carb, I am assuming I should not have any problem with the carb

mustang6: So, if I got a bad vac advance, now might be a good time to switch to the D II dizzy setup?, I can still use it with the stock carb right?

 

[wallaka]

wallaka: its a newly rebuilt carb, I am assuming I should not have any problem with the carb

mustang6: So, if I got a bad vac advance, now might be a good time to switch to the D II dizzy setup?, I can still use it with the stock carb right?

His answer was better than mine anyhow

The '66 carb and dizzy are designed to work together. Yes, it's possible to use the DSII with a SCV-equipped carb but it won't be optimal. The SCV sends a specially modified vacuum signal to the dizzy.

 

[73GreenMachine]

Something similar happened to me and it turned out that a rich carby setting had caused excessive carbon buildup in the cylinder head, causing major preignition and sputtering. The motor barely ran. I fixed it by putting in some fuel system cleaner in the fuel and pouring a little down the carby while it was running in neutral at about 2000rpm. It got rid of the carbon quickly, leaned out the jetting a bit and the car was flying again! Give it a go anyway it might save you some trouble.
73GreenMachine.

 

[jahearne]

Same thing happened to my Ranchero. Rebuilt carb, but they didn't replace the SCV. I replaced the dizzy instead of missing with the load-o-matic. Go for the DSII upgrade.

 

[Zorm]

went to a junk yard Saturday and got all the DII stuff from a 81 Futura wagon, cool thing is cap and rotor look brand new as do the plug wires (8mm) got it all for $23.50. I did not take the coil, just the coil holder. I then ran to A.Z. to get the control module checked out, its bad, got a new one for under 20.00. I'll take the bad back to the yard and get at least 1/2 of the cash back.
So, next question, should I get a better coil?, (got the peice that slips onto the top of the round coil from the yard) should I use my MSD 6 with all this or stand alone? do I also need to regap the plugs once everything is in?

 

[jahearne]

Nice score on the used parts. I couldn't find them anywhere in my area so I opt'ed for the DUI, which was expensive but it'll be worth it in the long run.
Definitely go for a better coil. Personally, I don't have experience with MSD6, but a lot of the other members have had great results; do a search for MSD. With a better/hotter coil, you can increase your plug gap to 45 - 50 thousandths.

 

[nachoman]

i had a similar problem. Turns out the wire clip on the condensor was just barely shorting out against the distributor housing when the breaker plate moved. Took me about a month to find.

kevin