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dynamite sounding explosions coming from exhaust

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Old 02-03-2006, 05:08 PM   #1
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Default dynamite sounding explosions coming from exhaust

Here lately when I go to crank up the Nova it has been getting harder and harder to start (giving it more gas and more cranking tries than usual) but when it did fire up it would take the normal "warming up" to get a good lopey idle. But the last couple of times trying to start it the idle sounds terrible like it barely wants to idle. Keep in mind I haven't adjusted anything since I've had the car now for a few months and when I got it it ran fine. Well today again it took a longer than normal amount of time to crank it and when it did run (barely idleing) I would get these loud as almost dynamite explosions occasionally out of the exhaust. So loud it hurts your ears and then I just turn it off. I'm just getting into this and have no idea how to tune a carb so yea I plead dumb on my part. But what exactly is happening here? Here's the specs on the motor:

383ci sb
4 Bolt Main
Forged Alum Flat Top Pistons
Forged 5.7 Rods
Lunati Hydraulic Cam 246 Duration / 520 Lift
Camel Hump Heads
Comp Cams Valve Locks, retainers, springs, etc.
Stainless steel valves
Victor Jr. Intake Manifold w/ Air Gap
Holley 750 Double Pumper Carburator w/ 2" Spacer
Double Roller Timing Chain
Mallory fuel filter canister type w/ replaceable filter
Jegs Pro Starter 4.41:1 gear reduction 1.9HP w/ Push Button Start
MSD Pro Billet Distributor
MSD 6AL Ignition
MSD Blaster 3 Coil
MSD Adjustable Timing Control
MSD 8.5mm Super Conductor Plug Wires
Hedman Headers 1 3/4" Primaries to 2 1/2" Pipes w/ Flowmaster Mufflers
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Old 02-03-2006, 06:28 PM   #2
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It sounds like your timing is off. Is your distributor hold down loose?
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Old 02-03-2006, 08:07 PM   #3
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Quote:
Originally Posted by Strokinit383
It sounds like your timing is off. Is your distributor hold down loose?
everything on the dist. is on tight plus it's never been messed with. however i do have a msd adjustable timing control **** inside the cab that's always been set on 7 and goes to 10. it's been played with a little but it always goes back to 7 when i'm done. although i never heard a difference in the motor before while turning the ****.
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Old 02-04-2006, 10:18 AM   #4
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Sounds to me like its firing too late. Try advancing the timing a little.
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Old 02-04-2006, 05:56 PM   #5
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Quote:
Originally Posted by Strokinit383
Sounds to me like its firing too late. Try advancing the timing a little.
would that be an adjustment from the adjustable timing **** or do i need to advance the distributor? what am i suppose to hear while the motor is running when i adjust the timing control ****? because when i tinkered with it before i never heard a difference.
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Old 02-04-2006, 07:26 PM   #6
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Im not quite sure how those timing ***** work. I would try it there 1st since it so easy to do. Maybe write a small mark on your distributor base and intake manifold as a reference to where you started. That way when you try advancing it if it doesnt work youll know where to go back to.
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Old 02-05-2006, 07:54 AM   #7
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bad plug or wire?
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Old 02-05-2006, 11:09 AM   #8
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bad plug or wire?
i just changed the plugs to some champion race plugs a couple months ago. but the car has never been driven. it has just been sitting in my driveway and i crank it up every now and then. i do remember when i first put the plugs in it cranked up really easy and it has progressively gotten harder to start since then. and then now it started doing the backfires and barely idleing. i just don't understand because nothing has been messed with i mean the car just sits there.
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Old 02-05-2006, 02:41 PM   #9
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I'd check to make sure your wires are arcing for any reason. I'd pull the distributor and get your timing in the general vicinity by finding top dead center, then installing your distributor per directions I'm sure you can find somewhere on the net. You could always check your timing with a light, but that can go bust if you have a different style balancer then was marked for your engine.

I'd for sure pull the adjustable timing **** though, sounds like more trouble then it's worth.

Definitely a timing problem though, cause mine did the same thing when I installed a new distributor. Turns out it's got a new balancer on it, with the wrong timing marks.
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Old 02-05-2006, 11:04 PM   #10
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Originally Posted by CarelessAndImprudent
I'd check to make sure your wires are arcing for any reason. I'd pull the distributor and get your timing in the general vicinity by finding top dead center, then installing your distributor per directions I'm sure you can find somewhere on the net. You could always check your timing with a light, but that can go bust if you have a different style balancer then was marked for your engine.

I'd for sure pull the adjustable timing **** though, sounds like more trouble then it's worth.

Definitely a timing problem though, cause mine did the same thing when I installed a new distributor. Turns out it's got a new balancer on it, with the wrong timing marks.
not saying the timing thing is wrong but why would it all of a sudden just start acting up like that when it only gets started once or twice a week and never driven? it doesn't make sense. it ran so perfect when i first got it... real responsive fast revving up and down. it would rev down just as fast as it would rev up. perfect idle. so it wouldn't be a carb problem? for sure a timing problem? once i do figure out what the problem is i'll be sure to post it on here.
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Old 02-06-2006, 05:59 PM   #11
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Quote:
Originally Posted by Strokinit383
Sounds to me like its firing too late. Try advancing the timing a little.
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Originally Posted by CarelessAndImprudent
Definitely a timing problem though, cause mine did the same thing when I installed a new distributor. Turns out it's got a new balancer on it, with the wrong timing marks.
points for you guys. it was definately a timing problem. i advanced the dist. a few degrees and tweaked the air/fuel adjustments and she lined right out. now it runs the way it did before. one of my buddy's (who has a 10 sec monte carlo) suggested i reduce the jet size on the carb though. it still has a little smoke out of the exhaust and has always done that. i know that 750 double pumper is dumping some juice so i might jet it down and see what it does then.
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Old 02-07-2006, 10:20 AM   #12
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Glad to hear its back running correctly.
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Old 02-26-2006, 11:34 PM   #13
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Quote:
Originally Posted by Strokinit383
Glad to hear its back running correctly.
Yea for a week or so. I've had to recharge the battery a couple times from it turning over so much and not starting. When it does start it runs fine. Well I did have that issue where it was backfireing incredibly loud so I advance the dist. some and cured that. But it gets to the point to where I have to change the plugs every couple months or so because they get fouled. I don't drive the car it just sits in my driveway and I crank it up every week or so. I had it running fine last weekend and then today I go to crank it and it starts doing it all over again just turning over and over and barely hiccuping like it wants to start. Also today it started making a new noise while trying to start. While it's turning over occasionally I get these loud metal on metal grinding noise from the motor and gas spurts up out the carb and the starter stops for a second then starts again all while never letting up off the push button starter. It sounds like the motor internally is where it's coming from but it's hard to tell. Any clue where to start looking for the problem? Starter maybe? It's the Jegs Pro Starter 4.41:1 gear reduction 1.9HP. Carb issue maybe? I was once told it needs to be jetted down some but I haven't fooled with that yet. But that wouldn't be why it's making that louding pop/grind noise while turning over. It used to run so great and start fairly easy and now it's not and it never gets driven. I don't understand.
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Old 02-28-2006, 05:57 AM   #14
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If its shooting gas and air up out of the carb, it now has a little too much advance. Try retarding it by spinning the distributor about 1/4" or less counter clockwise. See if that fixes it.
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Old 02-28-2006, 02:59 PM   #15
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Sounds like you may want to go ahead and redo the timing completely to see if that fixes all your problems. Put it at top dead center and set your distributor per its directions and then start it and put a light on it.

The 750 dp does sound a bit big, but it shouldn't be causing your problems
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Old 03-01-2006, 02:13 PM   #16
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Take it to yer local dyno and do a run with a sniffer in. Get the timing right, get the A/F right and find out what it's putting down all in one trip.
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Old 03-01-2006, 09:00 PM   #17
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Quote:
Originally Posted by Strokinit383
If its shooting gas and air up out of the carb, it now has a little too much advance. Try retarding it by spinning the distributor about 1/4" or less counter clockwise. See if that fixes it.
I might have to try that.


Quote:
Originally Posted by CarelessAndImprudent
The 750 dp does sound a bit big, but it shouldn't be causing your problems
yea but can it just be jetted down some and keep the carb.. that's my main wonder with the carb.

Quote:
Originally Posted by CharlieCobra03
Take it to yer local dyno and do a run with a sniffer in. Get the timing right, get the A/F right and find out what it's putting down all in one trip.
I'll let you take a look at the car and you'll see why I can't do that.

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Old 03-02-2006, 11:19 AM   #18
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What? It'll still work on a Dyno. Might be tough if the polizie see ya driving there though. Nothing a bigger hammer wouldn't fix.
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Old 03-02-2006, 11:00 PM   #19
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Looks like you should build the first convertible nova!
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Old 03-03-2006, 05:51 PM   #20
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Quote:
Originally Posted by Strokinit383
If its shooting gas and air up out of the carb, it now has a little too much advance. Try retarding it by spinning the distributor about 1/4" or less counter clockwise. See if that fixes it.
i did and then went to turn on my ignition, full pump etc.. and i had nothing. no juice. my dome light and small things come on but nothing else. no fuel pump, ignition, dash lights, electric fan... nothing. it's funny how i dont touch the car for a week and things keep breaking. if it ain't one thing it's another.
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Old 03-03-2006, 05:51 PM
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