454 Backfiring issue

« **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

che77y

jimpen

GT Jets

jimpen

GT Jets

jimpen

GT Jets

Brad @ SCJB

GT Jets

rush1

quick olds

Hoofy

Brad @ SCJB

quick olds

GT Jets

jyeager

81sprint

Hoofy

Brad @ SCJB

tunnels

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Bigblockchevy1691

Flusher

Flusher

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