454 Backfiring issue

« **on:** March 24, 2015, 07:29:05 PM »

Working on a friends boat.....ran great last year. He put a new cap/rotor/wires on it....and it is now backfiring out of the exhaust on both sides at idle. Put the old cap/wires back on and it's still happening. Triple checked firing order....swapped the coil......we are stumped. Only thing hes changed since last year is the cap, rotor and wires.

« **Reply #1 on:** March 24, 2015, 07:32:46 PM »

Maybe carb gummed up? From sitting in the off season?

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« **Reply #2 on:** March 24, 2015, 07:33:31 PM »

Just had the carbs rebuilt.

« **Reply #3 on:** March 24, 2015, 07:33:39 PM »

Forgot to mention that.

« **Reply #4 on:** March 24, 2015, 07:35:20 PM »

The backfire is rhythmic going from one side to the other...which point to ignition in my book.

« **Reply #5 on:** March 24, 2015, 07:39:44 PM »

Check plugs

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« **Reply #6 on:** March 24, 2015, 07:42:48 PM »

When ever I get back firing like that . I pull the # 1 plug and and get it to blow.
It sounds like 180 out.

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« **Reply #7 on:** March 24, 2015, 07:47:24 PM »

Could also be a stuck valve. If all else fails pull the valves covers and make sure all the valves go up and down.

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« **Reply #8 on:** March 24, 2015, 08:04:57 PM »

Pulled the distributor... Checked the teeth on both sides. Set it at TDC....same thing.

I would say stuck valve as well but its back firing on both sides.

« **Reply #9 on:** March 24, 2015, 08:25:28 PM »

Well you did say it has been sitting for a year??? Stranger things have happened!

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« **Reply #10 on:** March 24, 2015, 08:26:08 PM »

Could be 2 valves one on each head

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« **Reply #11 on:** March 24, 2015, 08:26:13 PM »

Re check plug wires / firing order, maybe some crossed plug wires

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« **Reply #12 on:** March 24, 2015, 08:38:21 PM »

I would run the valves real quick like. If you have to, back them all off a turn and see if it still pops.

Try the damp towel trick too, take a couple of damp shop towels and start to block off the carbs creating a rich condition.

Do you have the right carburetor base gaskets? Are the floats set right ?

« **Reply #13 on:** March 24, 2015, 09:28:36 PM »

Is it possible that you guys didn't put the wires on right???

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« **Reply #14 on:** March 24, 2015, 09:35:09 PM »

Checked the firing order a million times...put in a brand new battery....been on the phone with Glenn (gt jets) and hes even stumped.

« **Reply #15 on:** March 24, 2015, 09:42:10 PM »

Almost has to be a broken ground wire or something just wrong enough to allow it to run.

Have you tried removing the alternator belt?

I am grasping at everything I can on the way down.

GT

« **Reply #16 on:** March 24, 2015, 10:10:15 PM »

What happens when you rev it up???

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« **Reply #17 on:** March 24, 2015, 10:13:07 PM »

Carbon build up on the heads??? Try a little water down the carb when reving it up. Like a tea spoon!

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« **Reply #18 on:** March 24, 2015, 10:13:09 PM »

Compression test and or leak down could verify or weed out a sticky valve.

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« **Reply #19 on:** March 24, 2015, 10:17:51 PM »

Compression test is 120 across the board

« **Reply #20 on:** March 24, 2015, 10:19:45 PM »

Quote from: mobboss on March 24, 2015, 10:13:07 PM

Carbon build up on the heads??? Try a little water down the carb when reving it up. Like a tea spoon!

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LOL we used to pour like a liter down em....LOL

Ensure the pick up wires are not backwards......

Green from the 6A to the black/purple and purple to the black/orange... Also too grounding the box is muy importante...

Just out loud for the listeners...

GT

« **Reply #21 on:** March 24, 2015, 10:22:51 PM »

Maybe pulled the plug wires away from the boot?! Bad connection? Cap on right? Lol I'm just fishing here

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« **Reply #22 on:** March 24, 2015, 10:23:11 PM »

Are you guys running a 6al box?

If so try to disconnect it. I have herd of them going batty and doing shit ilike that.

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« **Reply #23 on:** March 24, 2015, 10:23:58 PM »

Check exhaust temps to see if you have a cooler cylinder. Will at least help you identify what cylinders are the problems.

« **Reply #24 on:** March 24, 2015, 10:25:46 PM »

Quote from: mobboss on March 24, 2015, 10:23:11 PM

Are you guys running a 6al box? If so try to disconnect it. I have herd of them going batty and doing shit ilike that.

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Maybe change the rpm chip as a test.

« **Reply #25 on:** March 24, 2015, 10:30:42 PM »

Perhaps a few lazy lifters since she's been sittin?

« **Reply #26 on:** March 25, 2015, 06:23:11 AM »

Brad does it clean up at higher rpm's?

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« **Reply #27 on:** March 25, 2015, 06:31:11 AM »

Quote from: jimpen on March 25, 2015, 06:23:11 AM

Brad does it clean up at higher rpm's?

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Nope.

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« **Reply #28 on:** March 25, 2015, 06:39:41 AM »

Quote from: GT Jets on March 25, 2015, 06:31:11 AM

Nope.

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. Just having the carb rebuilt sounds kind of fishy.

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« **Reply #29 on:** March 25, 2015, 07:01:01 AM »

Quote from: jimpen on March 25, 2015, 06:39:41 AM

. Just having the carb rebuilt sounds kind of fishy.

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Sort of kept trying to go down that road. ...

I think so too.

I'm thinking stupid lean somewhere.

GT

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« **Reply #30 on:** March 25, 2015, 07:10:42 AM »

Quote from: GT Jets on March 25, 2015, 07:01:01 AM

Sort of kept trying to go down that road. ...

I think so too.

I'm thinking stupid lean somewhere.

GT

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. That's what it sounds like I would have the carb rebuilder have another go at it or find a new one.

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« **Reply #31 on:** March 25, 2015, 07:16:07 AM »

Quote from: jimpen on March 25, 2015, 07:10:42 AM

. That's what it sounds like I would have the carb rebuilder have another go at it or find a new one.

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There are two on a tunnel ram. Twice the opportunity for a slight boo boo.

GT

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« **Reply #32 on:** March 25, 2015, 07:18:37 AM »

The thing is that the backfire isn't a lean pop. It's a loud bang with 6" of flame shooting out. To me thats unburnt fuel getting into the header and burning.

The other thing is that its rhythmic. If I wasn't standing in front of it and checked the firing order maybe 5-6 times myself, I would bet it was a crossed plug wire, but its not.

Hal is bringing over a ready-to-run distributor today and they are gunna give it a go. If it still does it after that, I'm starting to wonder if the timing chain went bad.

Also, its a MSD 6a box, no rev chip in it.

« **Reply #33 on:** March 25, 2015, 07:35:05 AM »

Quote from: Brad @ SCJB on March 25, 2015, 07:18:37 AM

The thing is that the backfire isn't a lean pop. It's a loud bang with 6" of flame shooting out. To me thats unburnt fuel getting into the header and burning.

The other thing is that its rhythmic. If I wasn't standing in front of it and checked the firing order maybe 5-6 times myself, I would bet it was a crossed plug wire, but its not.

Hal is bringing over a ready-to-run distributor today and they are gunna give it a go. If it still does it after that, I'm starting to wonder if the timing chain went bad.

Also, its a MSD 6a box, no rev chip in it.

So the grounds were good and the pickup wires didn't get reversed?

I was sure that was a possibility.

It could be cross talking, but with two different caps, rotors and wires. It sort of all but eliminates it.

I would eliminate fuel stuff first. But trying the distributor cannot hurt.

GT

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« **Reply #34 on:** March 25, 2015, 09:26:07 AM »

Is an hei distributor make sure the metal ground strap is in the cap, I've seen those get left out.

« **Reply #35 on:** March 25, 2015, 12:01:15 PM »

Is it possibly the swapped firing order? I forget what cylinders they swap but maybe thats it. Or is it jumping spark. In the wires?

« **Reply #36 on:** March 25, 2015, 12:08:13 PM »

The swap is 4 & 7

« **Reply #37 on:** March 25, 2015, 12:09:10 PM »

Thanks for the help but as stated the firing order has been checked a dozen times.

« **Reply #38 on:** March 25, 2015, 12:13:21 PM »

Ok wasnt sure if maybe it was forgotten that it was swapped

« **Reply #39 on:** March 25, 2015, 04:01:00 PM »

This Fukker running yet? Lol

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« **Reply #40 on:** March 25, 2015, 04:20:09 PM »

I got my money on some bent pushrods 👍

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« **Reply #41 on:** March 25, 2015, 04:36:13 PM »

Not yet we will be working on it again tonite so fingers crossed

« **Reply #42 on:** March 25, 2015, 06:16:32 PM »

Popping out exhaust, cyl is firing with exhaust valve partially open. Pull one plug wire at a time when the popping stops you will know what cylinders are causing the problem. Sounds like incorrect firing order.

« **Reply #43 on:** March 25, 2015, 06:39:44 PM »

Quote from: Hoofy on March 25, 2015, 06:16:32 PM

Popping out exhaust, cyl is firing with exhaust valve partially open. Pull one plug wire at a time when the popping stops you will know what cylinders are causing the problem. Sounds like incorrect firing order.

not trying to be rude, but we checked the firing order a million times as stated above.

If I had not even checked it myself several times, I would agree with you.

« **Reply #44 on:** March 25, 2015, 06:47:54 PM »

could there be moister in the distributor or a cross feed between wires?

« **Reply #45 on:** March 25, 2015, 07:50:42 PM »

Still doing it with a new distributer. Checking float levels now

« **Reply #46 on:** March 25, 2015, 08:05:13 PM »

Quote from: jyeager on March 25, 2015, 04:20:09 PM

I got my money on some bent pushrods 👍

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I have to agree or a couple stuck valves. Seen this a couple times. Has there been valve covers pulled yet??

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« **Reply #47 on:** March 25, 2015, 08:12:53 PM »

X2 on pulling the valve covers.

Could you put a timing light on each wire to verify each cylinder is consistently firing?

« **Reply #48 on:** March 25, 2015, 08:15:10 PM »

Did the plugs get checked?

« **Reply #49 on:** March 25, 2015, 08:41:02 PM »

I think we got it

« **Reply #50 on:** March 25, 2015, 08:41:35 PM »

Quote from: allfiredup on March 25, 2015, 08:41:02 PM

I think we got it

spill the fukkin beans! this is killing me!

« **Reply #51 on:** March 25, 2015, 08:46:21 PM »

Dizzy a tooth off and adjusted floats.

« **Reply #52 on:** March 25, 2015, 08:49:47 PM »

You heading to the lake for some evening testing?

« **Reply #53 on:** March 25, 2015, 08:50:05 PM »

Quote from: allfiredup on March 25, 2015, 08:46:21 PM

Dizzy a tooth off and adjusted floats.

I call BS on the dizzy being a tooth off. That doesn't even make a difference - no such thing lol - and even if it was, the dizzy never came out between last October (when it ran great) until last night after it was already popping.

« **Reply #54 on:** March 25, 2015, 08:51:29 PM »

Hmm didn't you stab it in there last night there b-rad?

« **Reply #55 on:** March 25, 2015, 08:53:53 PM »

Quote from: allfiredup on March 25, 2015, 08:51:29 PM

Hmm didn't you stab it in there last night there b-rad?

There is no such thing about the dizzy being a tooth off. It just changes the position of #1. Even then, when I checked the timing, after I stabbed it, it was dead on. Your theory is invalid.

and like I said, it was popping before then. and that 'stab' was the same one that it was running on back in October.

« **Reply #56 on:** March 25, 2015, 08:56:30 PM »

Lol. We're not sure could have been the floats but whatever it was it's better now

« **Reply #57 on:** March 25, 2015, 09:00:17 PM »

Quote from: allfiredup on March 25, 2015, 08:51:29 PM

Hmm didn't you stab it in there last night there b-rad?

. Good to see you all picking on the Ford guy.

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« **Reply #58 on:** March 25, 2015, 09:05:43 PM »

Quote from: allfiredup on March 25, 2015, 08:51:29 PM

Hmm didn't you stab it in there last night there b-rad?

Anyone else see it? Lol

« **Reply #59 on:** March 25, 2015, 09:06:27 PM »

Hmmmm.

« **Reply #60 on:** March 25, 2015, 09:10:57 PM »

Quote from: jimpen on March 25, 2015, 09:00:17 PM

. Good to see you all picking on the Ford guy.

He must have as stabbed it in the front of the engine.

Just kidding brotherman.

Peace

« **Reply #61 on:** March 25, 2015, 09:15:51 PM »

#1 is on the other side of the engine?

« **Reply #62 on:** March 25, 2015, 09:16:54 PM »

Okay, I'll shut up now

« **Reply #63 on:** March 25, 2015, 09:21:02 PM »

Quote from: Flusher on March 25, 2015, 09:16:54 PM

Okay, I'll shut up now

No, please, go on.

« **Reply #64 on:** March 26, 2015, 06:12:12 AM »

Quote from: allfiredup on March 25, 2015, 08:51:29 PM

Hmm didn't you stab it in there last night there b-rad?

That right there looks like someones new quote to add to their profile! lol

« **Reply #65 on:** March 26, 2015, 06:14:06 AM »

Quote from: FordLover on March 26, 2015, 06:12:12 AM

That right there looks like someones new quote to add to their profile! lol

I knew I was not the only one lmao.

GT

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