Carb And Timing Problems.

[fords2live]

The last couple of weeks my car has been really pissing me off to the point I'd rather take it to the crusher and throw away all the money I just put into it, then just sell it. So here's what going on.

Couple weeks ago my car just started acting really ing picky with tuning and performance. It started with a little miss here and there in between 1500 and 3000 and progressed all the way to what it's doing now which is holding at 4000 under load and the car missing and sputtering like crazy. Before you could just barely kinda hear a miss and now you can feel them. If I get it out and try to put it to the floor it has a bad back fire out the exhaust and bad lack of power. It'll pull, then backfire and lunge forward. Several times. All the way through the whole rpm range. From 1500 to 6500. But when It's in neutral you can't even tell theres a problem until I try and bouce it off the rev limiter. Which is 7200. Then it'll make it sound like a backfire limiter instead of MSDs spark drop limiter. And last night I turned my distributors advance back down to the quickest curve with all my timing in by 2000. Started running like trying to get on the highway almost couldn't make it up to speed, but then I kept it in 4th and held it at 3000 for a few miles then all of a sudden it was fine then stuck it in 5th an cruised for another 5 miles real smooth. Stuck it in 3 and pulled to 4500 then open throttle to 6800 without a problem. Got on my street put it to the floor in first at 3000, grabbed second and went for a ride. Keeping in mind it got up to full temp before I even moved from my spot. So it feels like more of a work through the kink more than a get warmed up kinda thing.

Spec.

302 Performance build 9.6:1 comp. 91 octane engine.

MSD Ignition System E-Curve Dist. No ign box (24* initial - 10* advance, all in at 2000 - 34* total) I've tried 34 total all the way to 40 total. Nothin

Quickfuel Carb 4160 Vac sec. No choke body (.68 in the primary & .73 in the secondary) No clue what the air bleeds are. Never touched them. 6.5 power valve.

 

[CarMichael Angelo]

I'm just gonna wing out a guess here,... but unless you've been having problems w/ the carburetor,.... or its really crotchedy, and in need of some serious work, the carb isn't your problem.

It sounds ignition related to me. Wires, plugs, cap, coil, and the internal distributor itself are all where I'd be looking.
Load related misfires stem from the ignitions inability to light the mixture, or light it at the right time.

7200 rpm huh?.... When was the last time you replaced the valve springs? You also might wanna look there. A weak, or tired spring will just stop doing the job, and you could also get some popping there as well.

 

[fords2live]

Springs aren't even a year old yet. But if its the wires, distributor or coil that's gunna be manufacturers defect because its all about 6 months old. It's an inconsistent miss so I know its not valvetrain. The thing with incorrect timing tho is that the other night it was terrible even when it was completely warmed up and then holding it at high rpm it just stopped missing and backfiring. Then it ran like it should. Really good.

 

[84Ttop]

Might behoove you to check the grounds in your car. I always run a heavy ground cable directly off the engine to the frame and also make sure that your batter ground is clean and of sufficient size. May sound trivial but I have seen stuff like this before all caused soley by a bad ground.

 

[jrichker]

What year car? Is this a EFI car converted to carb? Are you still using the EFI distributor? Did you do all the work or buy someone else's project?

The backfire out the exhaust is unburned fuel from a malfunctioning ignition system. It collects unburnt fuel in the ehaust pipes or mufflers until it gets a flame or enough heat to auto ignite it.

MSD (May Suddenly Die) needs to be removed and a mechanical advance distributor should be used in its place. Use a stock coil, with a DuraSpark setup or GM HEI module in place of the MSD ignition junk.

Copied from pikapp33 I researched, and found the best stock type distributor to use was from an 83 Bronco 5.0, which is a Duraspark (magnetic pickup, and also has a steel gear to work with the EFI hyd roller cam.

I chose to use a Richporter FD30 ($85). Then added a BWD C194A Cap Adapter ($12) to use the Fox style dist cap/wires (the Richporter comes with cap/rotor, which I didn't use; other brands come without and are cheaper, but have a core as well; no core on this one). And then a BWD D166 rotor ($6) to match the cap adapter. All together about $125, much cheaper than the MSD billet dists, and am very happy with the quality of the the dist and the way the setup worked out.

The Richporter FD30 distributor is available at Advance Auto Parts ($90) & O’Riley’s ($81)

DuraSpark diagram courtesy of /www.billwrigley.com

See http://webpages.charter.net/1bad6t/duraspark.html for more help.
Note the ballast resistor shown in the diagram: you’ll need that too

OR

See http://www.carbdford.com/tech/HEI/hei.htm to use an inexpensive GM HEI module instead of a DuraSpark system

 

[Hawkeye_306]

You have a restriction somewhere in the fuel supply.

 

[vfast]

change power valve to 6.0 and what were the spring installed at?