SoCal Jet Boats

Tech Talk => Engine Mechanical / Electrical => Topic started by: Brad @ SCJB on March 24, 2015, 07:29:05 PM

Title: 454 Backfiring issue
Post by: Brad @ SCJB 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.
Title: Re: 454 Backfiring issue
Post by: Riverlife_ on March 24, 2015, 07:32:46 PM
Maybe carb gummed up? From sitting in the off season?


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Title: Re: 454 Backfiring issue
Post by: Brad @ SCJB on March 24, 2015, 07:33:31 PM
Just had the carbs rebuilt.
Title: Re: 454 Backfiring issue
Post by: Brad @ SCJB on March 24, 2015, 07:33:39 PM
Forgot to mention that.
Title: Re: 454 Backfiring issue
Post by: Brad @ SCJB 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.
Title: Re: 454 Backfiring issue
Post by: eliminator18 on March 24, 2015, 07:39:44 PM
Check plugs


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Title: Re: 454 Backfiring issue
Post by: mobboss 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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Title: Re: 454 Backfiring issue
Post by: mobboss 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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Title: Re: 454 Backfiring issue
Post by: Brad @ SCJB 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.
Title: Re: 454 Backfiring issue
Post by: mobboss 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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Title: Re: 454 Backfiring issue
Post by: mobboss on March 24, 2015, 08:26:08 PM
Could be 2 valves one on each head


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Title: Re: 454 Backfiring issue
Post by: Riverlife_ on March 24, 2015, 08:26:13 PM
Re check plug wires / firing order, maybe some crossed plug wires


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Title: Re: 454 Backfiring issue
Post by: GT Jets 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 ?
Title: Re: 454 Backfiring issue
Post by: jyeager 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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Title: Re: 454 Backfiring issue
Post by: Brad @ SCJB 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.
Title: Re: 454 Backfiring issue
Post by: GT Jets 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
Title: Re: 454 Backfiring issue
Post by: mobboss on March 24, 2015, 10:10:15 PM
What happens when you rev it up???


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Title: Re: 454 Backfiring issue
Post by: 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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Title: Re: 454 Backfiring issue
Post by: JBASHAM 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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Title: Re: 454 Backfiring issue
Post by: Brad @ SCJB on March 24, 2015, 10:17:51 PM
Compression test is 120 across the board
Title: Re: 454 Backfiring issue
Post by: GT Jets on March 24, 2015, 10:19:45 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  :thumbup:


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
Title: Re: 454 Backfiring issue
Post by: Riverlife_ 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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Title: Re: 454 Backfiring issue
Post by: 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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Title: Re: 454 Backfiring issue
Post by: crewchief22 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.
Title: Re: 454 Backfiring issue
Post by: crewchief22 on March 24, 2015, 10:25:46 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.
Title: Re: 454 Backfiring issue
Post by: che77y on March 24, 2015, 10:30:42 PM
Perhaps a few lazy lifters since she's been sittin?
Title: Re: 454 Backfiring issue
Post by: jimpen on March 25, 2015, 06:23:11 AM
Brad does it clean up at higher rpm's?


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Title: Re: 454 Backfiring issue
Post by: GT Jets on March 25, 2015, 06:31:11 AM
Brad does it clean up at higher rpm's?


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Nope.

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Title: Re: 454 Backfiring issue
Post by: jimpen on March 25, 2015, 06:39:41 AM

Nope.

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. Just having the carb rebuilt sounds kind of fishy.


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Title: Re: 454 Backfiring issue
Post by: GT Jets on March 25, 2015, 07:01:01 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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Title: Re: 454 Backfiring issue
Post by: jimpen on March 25, 2015, 07:10:42 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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Title: Re: 454 Backfiring issue
Post by: GT Jets on March 25, 2015, 07:16:07 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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Title: Re: 454 Backfiring issue
Post by: 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.
Title: Re: 454 Backfiring issue
Post by: GT Jets on March 25, 2015, 07:35:05 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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Title: Re: 454 Backfiring issue
Post by: rush1 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.
Title: Re: 454 Backfiring issue
Post by: quick olds 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?
Title: Re: 454 Backfiring issue
Post by: Hoofy on March 25, 2015, 12:08:13 PM
The swap is 4 & 7
Title: Re: 454 Backfiring issue
Post by: Brad @ SCJB on March 25, 2015, 12:09:10 PM
Thanks for the help but as stated the firing order has been checked a dozen times.
Title: Re: 454 Backfiring issue
Post by: quick olds on March 25, 2015, 12:13:21 PM
Ok wasnt sure if maybe it was forgotten that it was swapped
Title: Re: 454 Backfiring issue
Post by: GT Jets on March 25, 2015, 04:01:00 PM
This Fukker running yet?  Lol

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Title: Re: 454 Backfiring issue
Post by: jyeager on March 25, 2015, 04:20:09 PM
I got my money on some bent pushrods 👍


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Title: Re: 454 Backfiring issue
Post by: allfiredup on March 25, 2015, 04:36:13 PM
Not yet we will be working on it again tonite so fingers crossed
Title: Re: 454 Backfiring issue
Post by: 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.
Title: Re: 454 Backfiring issue
Post by: Brad @ SCJB on March 25, 2015, 06:39:44 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.
Title: Re: 454 Backfiring issue
Post by: tunnels on March 25, 2015, 06:47:54 PM
could there be moister in the distributor or a cross feed between wires?
Title: Re: 454 Backfiring issue
Post by: allfiredup on March 25, 2015, 07:50:42 PM
Still doing it with a new distributer.  Checking float levels now
Title: Re: 454 Backfiring issue
Post by: Bigblockchevy1691 on March 25, 2015, 08:05:13 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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Title: Re: 454 Backfiring issue
Post by: Flusher 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?
Title: Re: 454 Backfiring issue
Post by: Flusher on March 25, 2015, 08:15:10 PM
Did the plugs get checked?
Title: Re: 454 Backfiring issue
Post by: allfiredup on March 25, 2015, 08:41:02 PM
I think we got it :)
Title: Re: 454 Backfiring issue
Post by: Brad @ SCJB on March 25, 2015, 08:41:35 PM
I think we got it :)

spill the fukkin beans! this is killing me!
Title: Re: 454 Backfiring issue
Post by: allfiredup on March 25, 2015, 08:46:21 PM
 Dizzy a tooth off and adjusted floats.
Title: Re: 454 Backfiring issue
Post by: crewchief22 on March 25, 2015, 08:49:47 PM
You heading to the lake for some evening testing?
Title: Re: 454 Backfiring issue
Post by: Brad @ SCJB on March 25, 2015, 08:50:05 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.
Title: Re: 454 Backfiring issue
Post by: allfiredup on March 25, 2015, 08:51:29 PM
Hmm didn't you stab it in there last night there b-rad????
Title: Re: 454 Backfiring issue
Post by: Brad @ SCJB on March 25, 2015, 08:53:53 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.  :screwy: ;)

and like I said, it was popping before then. and that 'stab' was the same one that it was running on back in October.
Title: Re: 454 Backfiring issue
Post by: allfiredup 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
Title: Re: 454 Backfiring issue
Post by: jimpen on March 25, 2015, 09:00:17 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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Title: Re: 454 Backfiring issue
Post by: GT Jets on March 25, 2015, 09:05:43 PM
Hmm didn't you stab it in there last night there b-rad????

Anyone else see it?  Lol
Title: Re: 454 Backfiring issue
Post by: GT Jets on March 25, 2015, 09:06:27 PM
Hmmmm.
Title: Re: 454 Backfiring issue
Post by: Flusher on March 25, 2015, 09:10:57 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
Title: Re: 454 Backfiring issue
Post by: Flusher on March 25, 2015, 09:15:51 PM
#1 is on the other side of the engine?
Title: Re: 454 Backfiring issue
Post by: Flusher on March 25, 2015, 09:16:54 PM
Okay, I'll shut up now
Title: Re: 454 Backfiring issue
Post by: TrollerDave on March 25, 2015, 09:21:02 PM
Okay, I'll shut up now

No, please, go on.

 ;D
Title: Re: 454 Backfiring issue
Post by: FordLover on March 26, 2015, 06:12:12 AM
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
Title: Re: 454 Backfiring issue
Post by: GT Jets on March 26, 2015, 06:14:06 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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