Big Bang

[hacmjim]

Hi all. I hope someone can help me out. Just finished my 69 RR, Had it out for about a 10 mile run recently. all seemed fine. Put it back in the garage and tried to start it 10 minutes later. Did not want to start. I pumped it a few times then just held my foot to the floor. Suddenly, there was a huge bang like I have never heard before. I shut it down. Tried again days later. It started, but runs very rough and is very loud. Seems like the noise is coming from the carb? Pulled the valve covers and all seems ok. Checked the plugs and they are fine too. Any suggestions would be most appreciated. It is a 383 with Edlebrock 600cfm card, headers, alum intake, comp cam with a 480 lift. Thanks.

 

[khryslerkid]

Did you check your timing?

 

[69roadr]

back fire may have blown out your power valve and exhaust, hence the rough running and loud exhaust

 

[Hemi Rebel]

Eddy carbs dont have a power valve

 

[65-440]

Maybe that bang was your muffler exploding ? Explain "running rough" .... misfire? hard start? .....

 

[Propwash]

Is it chugging out heavy exhaust? Those eddy carbs like to shell out accelerator pumps (especially after sitting for long periods of time-like winter storage).

 

[Xp29h]

I know I blew out a big hole in the muffler last year. Once the hole was there the back pressure the engine needs wasn't there and it ran rough as heck. Once fixed with new set of mufflers.. all good again. Check the exhaust for a hole, then go from there..

Good luck.

 

[hacmjim]

Is it chugging out heavy exhaust? Those eddy carbs like to shell out accelerator pumps (especially after sitting for long periods of time-like winter storage).

No heavy exhaust. Starts ok, but it misfires. The exhaust appears to be ok as well. I know the timing isn't quite right yet. I was planning on getting it back on the dyno but wanted to get a few miles on it first.

 

[mmissile]

I got my Charger 500 wet under the hood, and it cut the ignition for a couple seconds. It filled the exhaust with raw fuel, which ignited in the exhaust and blew the back of the muffler out.

 

[hacmjim]

Guys, thanks for all of your advice. While I think the exhaust is intact, I will double check it. I will update you on what I find.

 

[mopar 3 B]

Is the valley pan still intact? Checked oil for fuel contamination? Could also be dirt or metal in a carb float seat. A bad excellorator pump should not cause an explosion.

 

[Propwash]

Is the valley pan still intact? Checked oil for fuel contamination? Could also be dirt or metal in a carb float seat. A bad excellorator pump should not cause an explosion.

Sure it will.....especially if it's supplying an erratic fuel supply. Just about any carb problem that throws the air/fuel ratio, and/or delivery far enough out of whack can cause a big bang, rough running, or non-running condition when tossed against a range of RPM's. The problem with the eddy carbs is the rubber boot on the accelerator pump dries out and flips over upon itself, rendering it's metering capabilities useless. It becomes a free-for-all.

hacmjim.......In your last post you mentioned the timing being a bit off. Have you checked the basics of the ignitions system (plugs, wires, cap, rotor and where your timing is sitting)?

 

[Mopar_King]

I recently had a similar issue. She would start and run, but under heavy acceleration sometimes it would misfire. Or, she wouldn't start at all. Bad distributor coil or cap. My mechanic fixed it. I am not mechanically inclined so I might not have the terms right.

Good luck.

 

[mopar 3 B]

Sure it will.....especially if it's supplying an erratic fuel supply. Just about any carb problem that throws the air/fuel ratio, and/or delivery far enough out of whack can cause a big bang, rough running, or non-running condition when tossed against a range of RPM's. The problem with the eddy carbs is the rubber boot on the accelerator pump dries out and flips over upon itself, rendering it's metering capabilities useless. It becomes a free-for-all.

hacmjim.......In your last post you mentioned the timing being a bit off. Have you checked the basics of the ignitions system (plugs, wires, cap, rotor and where your timing is sitting)?

Just curious why would the lack of fuel cause an explosion? Usually went the accelerator pump goes bad in a Carter carb is just goes flat on acceleration. No pump no extra fuel. Or is the eddy built different?

 

[Propwash]

Just curious why would the lack of fuel cause an explosion? Usually went the accelerator pump goes bad in a Carter carb is just goes flat on acceleration. No pump no extra fuel. Or is the eddy built different?

Rightfully so 3 B........ If the air/fuel leans out enough to where it doesn't ignite consistently, it can allow unburnt fuel to enter the exhaust system. Fire the system back up....backfire This will also happen with a WOT and a bad accelerator pump. A lean burn condition on acceleration when trying to transition between circuits can also cause a backfire in the intake, a bad accelerator pump can also be the culprit of that. The OP stated he heard a big bang, so the car obviously backfired. He didn't indicate if it was a under the hood backfire or exhaust backfire. Lean conditions can cause backfires from both end's, but usually being rich will cause exhaust. The problem i've seen and have had with the eddy carbs, is not that the accelerator pump just completely fails, and zero fuel get's through. It's more of an issue of the boot flopping or deteriorating to the point where fuel supply becomes erratic. I had these issues with a few eddy carbs. Spent a lot of time researching my carb issues, and thought back then that I was really wasting my time, but now I'm glad I did. I do not run Eddy carbs anymore, being this isn't the only issues I had with them.

 

[patrick66]

I blew out the muffler on my wife's '78 New Yorker Brougham a few years ago, trying to start it. Turned out the timing was off just enough to do that. In the end, I had a sticking oil pump which caused the erratic timing problems. I replaced the oil pump, retimed the car, and have had zero problems with that since then

 

[66Satellite47]

Sure sounds like timing, which can cause a variety of symptoms other problems as discussed.

 

[miller]

Sounds like somebody needs to run a good compression check.

 

[The Horvaths]

With ethanol-laced and ready-to-boil-in-the-tank fuel, pumping the pedal before a hot start is a recipe for disaster. When I need to hot-start, the pedal goes down about 1/2" and holds there during cranking. Works every time.

 

[hacmjim]

Guys, thanks for for all of your help. Turns out it was a block off plate I had over the opening on the intake where the choke is housed. When it back fired, it blew that plate up, causing the noise and rough idle. A new plate and it runs much better. I am still going to get it on the dyno to get the timing and carb adjustment right. Still need to figure out the hot start issue. It simply will not start 10 minutes after I shut it down until it cools. Thoughts?