Re: 383 backfires
[Re: 8urvette]
#2428697
01/04/18 02:51 AM
01/04/18 02:51 AM
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Joined: Jul 2006
Posts: 4,319 Puyallup, WA
StealthWedge67
master
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master
Joined: Jul 2006
Posts: 4,319
Puyallup, WA
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Years ago I had a cam go flat in a 318. The first clue I got was it started popping through the carb as soon as I put any load on it. If you’ve verified timing and believe the carb is in working order, you might want to pull the intake and put your eyes on the cam lobes. Good luck! 🍀 BTW: 274 & 282 duration at .050 would be ultra radical race only type of camshaft dimensions. I’m thinking yours would be seat to seat numbers.
LemonWedge - Street heavy / Strip ready - 11.07 @ 120
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Re: 383 backfires
[Re: 8urvette]
#2428714
01/04/18 03:21 AM
01/04/18 03:21 AM
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Joined: Jul 2006
Posts: 4,319 Puyallup, WA
StealthWedge67
master
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master
Joined: Jul 2006
Posts: 4,319
Puyallup, WA
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Well that’s good! Next thing that I’d look at is cap, rotor & plug wires. (That’s actually the first thing I should have thought of actually. Haha). Resistance in the secondary ignition would possibly cause misfires that may backfire through the carb. The coil could also be something to look at.
LemonWedge - Street heavy / Strip ready - 11.07 @ 120
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Re: 383 backfires
[Re: 8urvette]
#2428753
01/04/18 09:07 AM
01/04/18 09:07 AM
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Joined: May 2015
Posts: 1,134 Lost in Time
Iowan
super stock
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super stock
Joined: May 2015
Posts: 1,134
Lost in Time
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I think you need more timing if your cam specs are correct. Try 20 degrees initial and 38 total.
Have a great day Iowan
"obsolete is neat"
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Re: 383 backfires
[Re: 8urvette]
#2428832
01/04/18 12:57 PM
01/04/18 12:57 PM
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Joined: Nov 2003
Posts: 36,041 Lincoln Nebraska
RapidRobert
Circle Track
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Circle Track
Joined: Nov 2003
Posts: 36,041
Lincoln Nebraska
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Problem since day 1? started after a part or adjustment change? In addition I would do a compression test & for sure you need more initial. Holler how it goes.
live every 24 hour block of time like it's your last day on earth
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Re: 383 backfires
[Re: 8urvette]
#2429177
01/04/18 09:30 PM
01/04/18 09:30 PM
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Joined: Jan 2003
Posts: 14,506 So. Burlington, Vt.
fast68plymouth
I Live Here
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I Live Here
Joined: Jan 2003
Posts: 14,506
So. Burlington, Vt.
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I'm going to assume that since the OP has said he "degreed" the cam that it was done with a degree wheel and the person doing it knew what they were doing....... And it's not just a matter of verifying the dots are lines up.
I'd do a compression test.
How's the lifter preload?
Jetting in that carb?
Check for rotor to cap phasing.
Check the pick up coil wire polarity. I've seen both msd distributors and control boxes that had the polarity reversed from what it was supposed to be.
68 Satellite, 383 with stock 906’s, 3550lbs, 11.18@123 Dealer for Comp Cams/Indy Heads
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Re: 383 backfires
[Re: 8urvette]
#2429285
01/05/18 01:27 AM
01/05/18 01:27 AM
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Joined: Jul 2006
Posts: 4,319 Puyallup, WA
StealthWedge67
master
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master
Joined: Jul 2006
Posts: 4,319
Puyallup, WA
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While the heads are off, have the springs tested. I would think that bad springs allowing valves to bounce could cause what you’re describing.
LemonWedge - Street heavy / Strip ready - 11.07 @ 120
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Re: 383 backfires
[Re: 8urvette]
#2429306
01/05/18 02:26 AM
01/05/18 02:26 AM
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Joined: Jan 2003
Posts: 14,506 So. Burlington, Vt.
fast68plymouth
I Live Here
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I Live Here
Joined: Jan 2003
Posts: 14,506
So. Burlington, Vt.
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If the polarity of the pick up coil wires are backwards it puts the rotor phasing way off, and it can fire to the wrong terminal.
It can run like what you're describing.
If its a non-digital box, then the proper way for the wires to go is whichever has the timing retarded(compared to when the wires are swapped).
I have a jumper wire I use on the dyno that has the male/female distributor connectors on it, with bullet connectors in the middle of the jumper so I can easily swap the polarity. It's come in handy a few times.
68 Satellite, 383 with stock 906’s, 3550lbs, 11.18@123 Dealer for Comp Cams/Indy Heads
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Re: 383 backfires
[Re: 8urvette]
#2429561
01/05/18 06:52 PM
01/05/18 06:52 PM
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Joined: Jul 2003
Posts: 150 Indianapolis, In. area
BTBelvedere
member
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member
Joined: Jul 2003
Posts: 150
Indianapolis, In. area
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That would be too funny if that was the issue.
the MSD came from one car and went into this car. it ran fine in the other, in fact the entire motor came from that same car- prior to the cam fiasco the motor ran very well in the other car.
but the MSD was wired in at a later point- it was supposed to be a temporary thing. LOL. you know how that goes... I will have to check that out. I had a similar experience a lot of years ago.We took the engine going 11.20s right out of my car and put in in a friends gutted Duster hoping for a 10 second time slip. We used the engine as it was, including the dist and carb. We used the stock coil that was mounted in the Duster and didn't give it a second thought. Sounded good in the garage. Would not run a lick under load. Eventually put it back in my car and it ran just fine.
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