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Carburetors Carb discussion and questions. Upgrading your Third Gen's carburetor, swapping TBI to carburetor, or TPI to carburetor? Need LG4 or H.O. info? Post it here.

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Old 12-08-2011, 02:33 AM   #1
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Loud Popping comming from Carburetor

Ok so this happened tonight when coming home from bowling with some friends. All of a sudden while driving I heard popping while accelling. So i pulled over and had someone sit in the drivers seat and give it gas while i inspect. I found the exact area was the carb. i took off the filter and reved it a little and heard LOUD popping (backfire) coming from the carbs. What could have caused this or what is causing this. How can i go about fixing it? PLEASE PLEASE HELP. THIS IS MY MAIN SOURCE OF TRANSPORTATION AND MY LOVE!
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Old 12-08-2011, 04:10 AM   #2
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Re: Loud Popping comming from Carburetor

I dont know if it relevant but i did swtich over to 91 octane my last fillup and i have 1/4 tank left. i usually put in 87. Could that have anything to do with anything?
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Old 12-08-2011, 05:02 AM   #3
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Re: Loud Popping comming from Carburetor

first coming to my mind would be ignition timing, though it would be rather odd that it would change so fast.
The octane should not affect since its higher so the fuel can take more heat...

What i would do is check the distributors bolts, in case they would have gotten loose and cause the ignition timing to change,

I might be wrong but there is my 2 cents
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Old 12-08-2011, 06:51 AM   #4
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Re: Loud Popping comming from Carburetor

Describe the popping in more detail. Specifically, is it absolutely rhytmic and regular, like once every time some one particular cyl fires; or is it random and unrelated to any particular cyl?

If it's the first kind, pop the valve covers off and look for a broken valve train part. Push rod, rocker, or valve spring.
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Old 12-08-2011, 07:04 AM   #5
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Re: Loud Popping comming from Carburetor

If it's only happening under load (aka acceleration), and you're losing power, I would suspect either a major timing issue or valvetrain issue such as broken spring or wiped cam b/c an exhaust valve isn't opening so the gases have no where to go but back through intake & out carb.
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Old 12-08-2011, 07:20 AM   #6
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Re: Loud Popping comming from Carburetor

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Originally Posted by Ed1LE View Post
If it's only happening under load (aka acceleration), and you're losing power, I would suspect either a major timing issue or valvetrain issue such as broken spring or wiped cam b/c an exhaust valve isn't opening so the gases have no where to go but back through intake & out carb.
sounds like it's also happening at idle as his friend sat in the drivers seat and gave it gas while he inspected it. go back to post #4
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Old 12-08-2011, 07:35 AM   #7
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Re: Loud Popping comming from Carburetor

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sounds like it's also happening at idle as his friend sat in the drivers seat and gave it gas while he inspected it. go back to post #4
That doesn't discount what I typed though...popping when giving it gas isn't the same as it popping while idling (if someone's giving it gas, it isn't idling is it?). Also, it may still pop slightly at idle as well b/c there's still no where for the exhaust gas to go, there just won't be as much so the popping won't be as loud. This is a worse case scenario but the symptoms sound very similar to when I wiped the cam in my Monte Carlo. I'd definitely check timing first & distributor b/c if the timing is way out & engine is firing while intake valve is still open, you can get backfiring through carb as well.
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Old 12-08-2011, 08:19 AM   #8
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Re: Loud Popping comming from Carburetor

Is the car modded in any way? Like the others I am thinking your base timing is retarded. Not sure why the sudden change.

Pull you valve covers and look for damage. What is you engine setup?
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Old 12-08-2011, 11:46 AM   #9
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Re: Loud Popping comming from Carburetor

Could be a valvetrain issue also. After checking timing I would run the car with the valve covers off and make sure every valve is working properly. That could account for a sudden change... losing a lobe on a cam or breaking a rocker arm stud. Will cause it to misfire on one cylinder, depending on whether he lost an intake or exhaust valve. If he lost an exhaust it could ignite and burn and then be forced to escape out the intake valve when it finally opens.
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Old 12-08-2011, 12:15 PM   #10
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Re: Loud Popping comming from Carburetor

i had the 350 in my 79 camaro do this never found out what it was the next day my motor locked up it did the came thing i drove it to udf then it started popping i drove it home and let it sit over night the next day i started it it was hard to keep running and got out my timing light then it died before i could cheak it and did not tturn over again i was gussing the timming chain jumped a tooth it happened very fast and i thought the dizzy has came lose and twisted but it was tight and the rotor button was fine to (had a cadillac do this to me and it was the button)but never looked at it i had a new motor for it anyway
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Old 12-08-2011, 02:08 PM   #11
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Re: Loud Popping comming from Carburetor

WOW THANKS EvERYONE i checked to see if the distributer was loose and nope its tight. Now im going to check spark plugs and wires but i cant find my damn tool lol. So now im off to buy another cause i dont have time to look for it. Next is timing chain, however i do not know how to even check it or where it is for sure.
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Old 12-08-2011, 02:18 PM   #12
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Re: Loud Popping comming from Carburetor

Also align the timing marks so cylinder 1 is at tdc and make sure your rotor is pointing to cylinder 1
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Old 12-08-2011, 02:37 PM   #13
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Re: Loud Popping comming from Carburetor

Well your about to learn beyond the basics... You need to remove the water pump, harmonic Balancer/ with a puller, oil pan... I do not recommend loosening till you can slip the, timing cover, get engine to TDC check timing sprocket marks a tooth on each will line up. you need a puller to remove the crank sprocket, 3 cam sprocket bolts.. you could check the Chain play... But after all this better to replace with a double roller... I know my 82 had nylon teeth... A must replace on day one

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Old 12-08-2011, 02:43 PM   #14
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Re: Loud Popping comming from Carburetor

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WOW THANKS EvERYONE i checked to see if the distributer was loose and nope its tight. Now im going to check spark plugs and wires but i cant find my damn tool lol. So now im off to buy another cause i dont have time to look for it. Next is timing chain, however i do not know how to even check it or where it is for sure.
Pop the valvecovers and check for valvetrain damage.
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Old 12-08-2011, 02:47 PM   #15
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Re: Loud Popping comming from Carburetor

I would suggest checking timing with a timing light and then pulling the valve covers to visually inspect the valve train prior to disassembling the front of the engine. If there isn't anything obvious, may want to let the engine idle w/ the valve covers off (be prepared for some oil to splash out of the engine) b/c then you should be able to see if the valvetrain is all moving like it should. If you have a wiped cam, bent pushrod, broken spring, etc, you'll have much less movement (if at all) of that particular rocker arm. If all seems okay, then I'd check the timing chain and even if that is okay, I'd replace the nylon one, if that's what you have, like 88gta suggested.
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Old 12-08-2011, 02:52 PM   #16
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Re: Loud Popping comming from Carburetor

Quote:
Originally Posted by 88gta3508 View Post
Well your about to learn beyond the basics... You need to remove the water pump, harmonic Balancer/ with a puller, oil pan... I do not recommend loosening till you can slip the, timing cover, get engine to TDC check timing sprocket marks a tooth on each will line up. you need a puller to remove the crank sprocket, 3 cam sprocket bolts.. you could check the Chain play... But after all this better to replace with a double roller... I know my 82 had nylon teeth... A must replace on day one
Whoa. Let's make sure it's not a loose spark plug wire first!

You can turn the motor over with the valve covers off to check the valve action. If the chain were broken it wouldn't be running. If it slipped valve timing it would be running worse than the OP posts.

The OP never answered the question in Post #4 which would help narrow the search somewhat but we may be getting a little far afield here.
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Old 12-08-2011, 05:41 PM   #17
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Re: Loud Popping comming from Carburetor

What about blown power valve in the carb
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Old 12-08-2011, 06:43 PM   #18
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I see "82 Camaro Z28", but I don't see anything specific about the engine or carb. Is it stock? Anything modified?

If stock, q-jets don't have power valves.

Is the 91 octane E10? If so, and the previous gasoline was not, the ethanol may have loosed up crud deposits in the fuel system and clogged the pickup screen, filter, or may have gotten into the carb itself.

Is the SES light coming on?
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Old 12-08-2011, 07:07 PM   #19
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Re: Loud Popping comming from Carburetor

I dont know if engine is stock, im still learning. the guy before me ****ed the car up pretty much. Everything he did was half assed. So today i changed spark plugs, and oil change (just cause it needed one) and nothing has fixed it. ive been told the engine was a 350. It has an edelbrock 4brl carburetor.

What is a power valve? and how do i check it?
Please guys no abbreviations lol, im still not quite there yet on my knowledge of everything.
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Old 12-08-2011, 08:14 PM   #20
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Re: Loud Popping comming from Carburetor

Dude you need to check the valve train - remove the valve covers and check and make sure each valve is moving. It's VERY easy to pull teh valvecovers, adn as long as you'rej ust idling it shouldnt get much oil everywhere if any.
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Old 12-08-2011, 08:23 PM   #21
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Re: Loud Popping comming from Carburetor

would i need to replace the seals?
And if one or more isnt moving correctly, how do i fix it?
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Old 12-08-2011, 09:40 PM   #22
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Re: Loud Popping comming from Carburetor

So my mechanic just stopped by (not a back yard mechanic) and says He's almost sure its my CAM.

If i remember correctly he said he can tell because it gets warm (i dont remember what he said get warm sorry) and he checked the distributer and he said thats not the problem however he thought it could have been the problem prior to inspecting.

Hes gonna stop by tomorrow cause he didnt have enough time to also check my drive train.
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Old 12-09-2011, 05:01 AM   #23
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Re: Loud Popping comming from Carburetor

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would i need to replace the seals?
And if one or more isnt moving correctly, how do i fix it?
Depends on why it isnt moving.

Could be:

1. Broken/bent pushrod
2. Damaged rocker arm
3. damaged valve
4. Damaged lifter
5. Damaged cam lobe(s)

This is the worst case scenario category and is very simple to visually rule out, which is why I keep telling you to pop off the 8 bolts the hold on the valve covers and observe the rockers moving. Every rocker arm should move in rhythm and move the same distance.

http://www.youtube.com/watch?v=HIPno4aFQ_I

Those rocker arms are moving normally.

Did you by any chance over-rev the engine recently? Change the oil?

If you have an old school v8 with a flat tappet cam, the cams can fail if you dont use the correct oil with the correct additives or if it wasn't broken in correctly. The flat tappet lifters ride directly on the cam lobes and if they for whatever reason stop rotating against the cam, they will basically just grind together and destroy each other.

Click the image to open in full size.

And here is a damaged one, notice shiny lobe:
Click the image to open in full size.

Notice how it's not as tall as the other lobes? That valve wont open as far, depend on whether it's an intake or exhaust valve, that can cause popping through the carb.

Will require you to take the engine apart to get to it and replace it and honestly I would pull the engine out of the car to save myself the frustration of tryin to do that job inside the engine bay.

But it could be just a broken rocker arm or something.

http://www.stockcarracing.com/techar...n/viewall.html

Modern camshafts use roller lifters:

Click the image to open in full size.

They have an actual rolling wheel that touches the cam instead of a grinding flat-faced lifter, and they're MUCH more reliable. Camaros got them in 1987. You can convert any sbc to a roller lifter engine, but the costs are fairly high. Will be around $1000 to do the conversion. A flat tappet cam and lifters will cost around $150-$200 (just for parts, not labor) in comparison, which is the main reason they're still used in new engine builds by shadetree mechanics such as myself and if your engine isn't stock, by whoever built it.

They require special attention and oil additives to keep them happy because modern oils dont have the same protective additives in them as they used to because of environmental/pollution/emissions issues.

Last edited by InfernalVortex; 12-09-2011 at 05:15 AM.
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Old 12-09-2011, 05:50 AM   #24
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Re: Loud Popping comming from Carburetor

Quote:
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What is a power valve? and how do i check it?
If you have an edelbrock carb, you don't have a power valve...I would focus on the valvetrain.

InfernalVortex just provided some excellent, indepth explainations on how the valvetrain system works...I'd read that a few times to try and get a better understanding of what you're potentially dealing with.
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Old 12-09-2011, 11:45 AM   #25
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Re: Loud Popping comming from Carburetor

if you have to pull the timing cover there all right it would be dumb not to replace the chain its not very costly
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Old 12-09-2011, 12:26 PM   #26
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Re: Loud Popping comming from Carburetor

Im taking the valve covers off now, should have them off very soon.
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Old 12-09-2011, 12:56 PM   #27
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Re: Loud Popping comming from Carburetor

OK so The valve on the passenger side, first one from the front of the engine is not moving at all. The rest seem to be moving at a rhythm to me.

So what does this mean? How hard? and if i were to pay my mechanic... how much should it cost?
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Old 12-09-2011, 01:09 PM   #28
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Re: Loud Popping comming from Carburetor

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OK so The valve on the passenger side, first one from the front of the engine is not moving at all. The rest seem to be moving at a rhythm to me.

So what does this mean? How hard? and if i were to pay my mechanic... how much should it cost?
Take off the rocker and see if the pushrod is damaged
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Old 12-09-2011, 01:23 PM   #29
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Re: Loud Popping comming from Carburetor

And how do i do this?
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Old 12-09-2011, 01:47 PM   #30
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Re: Loud Popping comming from Carburetor

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And how do i do this?
Remove the nut on top of the rocker it will come right off then pull out the pushrod.
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Old 12-09-2011, 01:54 PM   #31
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Re: Loud Popping comming from Carburetor

I will get right to it!
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Old 12-09-2011, 02:04 PM   #32
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Re: Loud Popping comming from Carburetor

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OK so The valve on the passenger side, first one from the front of the engine is not moving at all. The rest seem to be moving at a rhythm to me.

So what does this mean? How hard? and if i were to pay my mechanic... how much should it cost?
As has been mentioned - it depends on why it's not moving. But now you know it's valvetrain, not ignition or spark plug wires or anything else.

This is a mechanical issue inside the engine that will need to be addressed.

Cost will depend on the reason it's not moving. The nut on top of the rocker arm, just take it off, pull the rocker arm straight off, and then you can pull the pushrod straight out of the engine. If the pushrod is straight, not bent. If it's in one piece. If both ends of it are rounded and undamaged, and the rocker arm is fine, then you have a damaged lifter or cam or both.

Take a picture of the rocker arm and pushrod so we can get a look at it.

The next step is to take a look at the lifter, but you wont be able to get to it unless you take the carb and intake manifold off. And then you'll be able to see it. You pull it out of its lifter bore, and examine the bottom of it. I imagine it will look like this:

Click the image to open in full size.

Click the image to open in full size.

From there you will know you need a new camshaft and lifters. No way around it. You cant replace lifters on a flat tappet camshaft. You have to get a new camshaft entirely This is serious internal engine work, not for the faint hearted. It requires procedural knowledge and familiarity on top of special efforts to make sure it functions properly. The break-in process is critical, as are valvetrain settings and for someone who doesnt do them often, it will probably take a weekend to do.
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Old 12-09-2011, 02:38 PM   #33
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Re: Loud Popping comming from Carburetor

My Mechanic asked me not to remove the rocker arm just yet, as he wants to do it so he can see whats wrong, I will update you guys on what he says and to get second opinions.
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Old 12-09-2011, 03:09 PM   #34
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Re: Loud Popping comming from Carburetor

He checked the lifters and they were good, but before that he noticed that not only was one not moving but the other right next to it was to loose.

So we adjusted both valves by barely turning the key each time and adjusting the bolt on the valve cover.

He says the reason it could have gotten loose could be the fact that the push rods like you guys have stated me be going bad. ORRR the fact that the oil was low and wasnt building enough pressure.

But the popping is gone, going to get new gaskets then going for a test drive.
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Old 12-09-2011, 03:16 PM   #35
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Re: Loud Popping comming from Carburetor

Hydraulic lifters need to be adjusted once. At the factory. And they're good forever.

Either your head studs are pulling out, your rocker nuts are backing off, or your cam is losing a lobe. Keep an eye on it - if it starts again you need to look real close at that lifter or figure out why the "set it and forget it" hydraulic lifters are drifting from the preset valve lash adjustment that Im sure your mechanic set it to.

But if he inspected the lifter and it looked fine I will have to trust his judgment, although I question how he was able to arrive, get out his tools, disassemble the top end of the car and remove the manifold to get to the lifter and inspect it in a matter of 30 minutes. I mean I guess it's possible, as I tend to work at a slow, deliberate pace. He didnt waste any time tearing that thing down. Did he remove the intake manifold? I want to verify he actually DID check the lifters, because otherwise this still sounds like telltale signs of camshaft/lifter failure.

Low oil can and will cause camshaft/lifter failure, but it would be noticable on the lifter's bottom.

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Old 12-09-2011, 03:34 PM   #36
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Re: Loud Popping comming from Carburetor

I may have ment to say the push push rod was i good shape.

But he also said if it starts to happen again then we need to take more stuff off and spend a little more money. But to see how it goes right now being that dont have a whole lot of money and i need transportation.

He said its good to drive. And the popping is gone.
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Old 12-09-2011, 03:37 PM   #37
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Re: Loud Popping comming from Carburetor

what engine is in your car factory?
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Old 12-09-2011, 04:57 PM   #38
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Re: Loud Popping comming from Carburetor

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Originally Posted by Lively13 View Post
I may have ment to say the push push rod was i good shape.

But he also said if it starts to happen again then we need to take more stuff off and spend a little more money. But to see how it goes right now being that dont have a whole lot of money and i need transportation.

He said its good to drive. And the popping is gone.
Okay that makes sense. yeah. If it starts again you're likely looking at needing to replace the cam and lifters. You may get lucky, but whatever caused the valve lash to wander far enough that the exhaust wasn't opening isnt really fixed. Its like having a fuel leak, and you run out of gas- add more gas adn you'll be able to go a little farther, but it's still leaking.

Tell us about your engine. Is it stock?
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Old 12-09-2011, 06:12 PM   #39
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Re: Loud Popping comming from Carburetor

i believe it is stock.

BAD NEWS: it doesnt pop but has no power at all, It did pop maybe once or twice. But i floored it to see why it didnt have any power and it didnt go anywhere and thats when it popped a little. So i turned around. I got maybe 1-2 blocks away.

Called my mechanic and he said that whole cyclinder is out, and the lifters need to be changed out. Hes not available for another week and a half though. And i dont trust myself to do it alone.
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Old 12-09-2011, 06:35 PM   #40
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Re: Loud Popping comming from Carburetor

look for a retro Roller cam & lifter
way to many flat tappet cams.. with wiped out lobes
most say since the zinc additive is no longer in oil
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Old 12-10-2011, 02:14 AM   #41
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Re: Loud Popping comming from Carburetor

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i believe it is stock.

BAD NEWS: it doesnt pop but has no power at all, It did pop maybe once or twice. But i floored it to see why it didnt have any power and it didnt go anywhere and thats when it popped a little. So i turned around. I got maybe 1-2 blocks away.

Called my mechanic and he said that whole cyclinder is out, and the lifters need to be changed out. Hes not available for another week and a half though. And i dont trust myself to do it alone.
Pull that valvecover again and watch that rocker arm and see if it moves as much as the others. Even if you reset lash to take the slack out and have the valve moving, if the lifter/cam lobe is damaged it will not move as much as the others.

A flat tappet cam, once you lose a lobe, is garbage. If a lifter fails - it's garbage. You can try just replacing the damaged lifter, but 99.99 percent of the time it will accomplish nothing because the damage to the lifter is on the camshaft also.

The "whole cylinder is out" is a bit of vague terminology. Him wanting to reset lash and send you off was a good move though, you needed to rule that out before you start tearing the engine down, but now that it's still running badly I think you need to get started with the tear down. That cylinder is, indeed, not functioning properly since the air cannot move out of it after combustion until the intake valve opens again, and that sends hot exhaust shooting up the intake and into the other cylinders. It wreaks havoc on the engine and will make it run like garbage.

You will need a new cam and lifters.

Is your engine stock? This would be a good time for an upgrade... Things like transmission, rear gear ratio, valve springs, exhaust may need to be changed to accomodate certain big cams, or we need to know what they are in order to tell you what will work best. A stock replacement will cost about as much as a performance cam, and you can get a smallish performance cam and not have to replace much and get a little power boost for all your trouble. But in order to pick out a good one we will need to know details about your car and its usage. Just a daily driver car?

If you just want something to drive, and you just want it to run, a stock replacement type cam will be just fine.

Watch this if you're curious to see some of what you're probably in for:

http://www.youtube.com/watch?v=57bn-7Az43M

http://www.youtube.com/watch?v=89o5rLpbCgI

This isnt a difficult job, but it's very time consuming and requires an awareness of procedures and a working knowledge of how the valvetrain and cam works. This is not something that will be a cheap fix unless you do it yourself. If you buy some books and some tools and the cam and lifters (I'd get a new timing chain set too) you can probably be in and out for less than $400 including oil and lubricants, definitely under $500. To be completely honest, there's not really very much in specialized tools you will need that you cant just rent.

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Old 12-10-2011, 09:20 AM   #42
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Re: Loud Popping comming from Carburetor

Cam failure up front is usually from oil starvation. The lifters up there are last in line. Low oil pressure can cause this. I wouldn't put any more money in that motor until the oil pressure checks out OK.

When that lifter/lobe failed, metal was ground off. This metal didn't evaporate. It made the rounds of the oil passages and caused damage as it fought its way through tight clearances. Your bearings, if they were not shot already (causing low oil pressure that likely wiped your cam) are certainly suspect now. This is not something that a simple cam/lifter swap can reliably fix. The motor, certainly the short block, needs to be rebuilt.

Take it for what it is. You can spend $$ now replacing a cam and you may be fine, but you're likely going to be spending $$$ later in addition on this shortblock.
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Old 12-10-2011, 01:15 PM   #43
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Re: Loud Popping comming from Carburetor

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Cam failure up front is usually from oil starvation. The lifters up there are last in line. Low oil pressure can cause this. I wouldn't put any more money in that motor until the oil pressure checks out OK.

When that lifter/lobe failed, metal was ground off. This metal didn't evaporate. It made the rounds of the oil passages and caused damage as it fought its way through tight clearances. Your bearings, if they were not shot already (causing low oil pressure that likely wiped your cam) are certainly suspect now. This is not something that a simple cam/lifter swap can reliably fix. The motor, certainly the short block, needs to be rebuilt.

Take it for what it is. You can spend $$ now replacing a cam and you may be fine, but you're likely going to be spending $$$ later in addition on this shortblock.

I was a bit concerned about this as well...

But how can we say the lifters didnt just begin to fail due to modern motor oils?

However now that I think of it, if his engine is mostly stock ... the stock flat tappet cams are so mild they tend to not have issues. There are millions of 87-95 chevy 350 trucks with flat tappet cams that are running fine, and he DID say that the oil was low...

I think you may be on to something here.
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Old 12-12-2011, 01:52 PM   #44
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Re: Loud Popping comming from Carburetor

I don't have any issues....but this is a darn good learning thread right here.
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Old 12-19-2011, 03:16 PM   #45
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Re: Loud Popping comming from Carburetor

Don't use SM rated oil in a flat tappet engine.
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Old 12-19-2011, 03:30 PM   #46
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Re: Loud Popping comming from Carburetor

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Don't use SM rated oil in a flat tappet engine.


I use rotella T 10w-30 and 15w-40 in all my old flat tappet motors. It is still over 1200ppm way better than regular oils.
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