Lebowski

What causes a carb to backfire?

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Could also just drive for a while and see if the compression comes up (you did have the acellerator floored when taking the readings ?). Sometimes miracles do happen..Readings are not bad for a '58 engine (6.6:1 compression) but not a 60 (8.4:1). Are you certain it is the original engine ?

 

Puffing out the breather is a sign of ring problems.

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Could also just drive for a while and see if the compression comes up (you did have the acellerator floored when taking the readings ?). Sometimes miracles do happen..Readings are not bad for a '58 engine (6.6:1 compression) but not a 60 (8.4:1). Are you certain it is the original engine ?

 

Puffing out the breather is a sign of ring problems.

 

I wasn't told to floor the gas pedal until after I was finished. The car has had several owners so I have no idea if it's the original engine. I'm going to get a bottle of that "Restore" stuff and change the oil and filter and put that in and see what happens....

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When I drained the oil pan and removed the oil filter there was only about one quart of oil in the drain pan. That's very surprising to me because the dipstick showed it as being about a quart low. Since I bought the car (tomorrow will be two weeks) I've put in 3 pints of STP so where did it all go-up in smoke ( as Cheech and Chong would say) or what? There is no puddle of it under the car in the garage either. Anyway, I put in 5 quarts of Quaker State 5W30 plus the bottle of Restore and a new Fram filter and then took it for a drive and floored it several times up to 70 as someone suggested but it still smoked about the same amount. Now what? Does anyone have any experience with Jasper rebuilt engines? Do they even rebuild old ones like mine? What do they charge for a rebuilt straight 6? Thanks again for helping me through this ordeal....

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i put a jasper motor in my 89 mercury11 yrs ago, there motor, mine was the core. also at the same time a jasper transmission. still have the car and no problems.

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"When I drained the oil pan and removed the oil filter there was only about one quart of oil in the drain pan. That's very surprising to me because the dipstick showed it as being about a quart low."

 

Somewhere along the way it might have aquired the wrong dipstick - fairly common occurrence.

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Pull the valve cover and see if the oil return holes are not plugged and mighr be able to come down and check it out some weekend if you can not get anyone closer to look at it..

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Don't expect it to stop smoking right away, because it won't.  Products like this need time to do their work,  If anything is going to happen, the more driving you do, the faster it will happen.

 

Terry

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I will again recommend contacting your local AACA Region. It seems strange to me that they have a waiting list for membership but even if they do, I suspect that if you contact them and express an interest, there is certainly a local Region member who would be interested in helping you with your car. An experienced hobbyist in your area can do a lot more to help you in an hour or two visit than all of the people who are attempting to help you over the internet. If nothing else, they could probably recommend an experienced trustworthy mechanic in your area.

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During the video at the engine compartment part I noticed blowby from the valve cover breather. I notice the tappets a little noisy. I notice the engine to be fairly smooth and appeared to be hitting all cylinders. We know the engine is tired, but I think it has some life left in it sans the blowby. The compression is low ( it's a well worn engine ) but more importantly the compression is more or less EVEN. The compression test tells us the valves are seating. For the most part on the road test we see ( but didn't see a WOT test ) decent normal acceleration which tells us the ignition and timing are doing it's thing reasonably well and part of the carburetor's circuit( there are seven circuits ) function is ok.

What I would like to see the owner do is take that air cleaner off, make sure it's clean, but with the engine off to take a flashlight and look down the throat of the carburetor and with the other hand manipulate the carburetor to full throttle. The accelerator pump should squirt a nice shot of fuel down on the venture or on the throttle plate. If it dribbles or does not shoot a steady stream this will cause a backfire in some cases, in others it will cause the engine to as we call in the trade fall over or fall on it's face.

With the engine running go to the distributor. We need to check the vacuum advance so pull the vacuum advance hose. Does the idle speed drop? It should unless this is a newer carburetor that has been put on by mistake and has a ported vacuum signal. OK the engine speed dropped like it should? OK reinstall the vacuum hose. The timing light needs to be installed to check initial timing ( initial timing is checked at idle with vacuum advance disconnected ) after that is accomplished bring the engine up to about 2500 rpm while your watching the timing marks, do this with the vacuum advance disconnected again because we need to see if the mechanical advance is working now connect vacuum advance for total timing. Notice I'm not asking for specific's....We just want to determine if the distributor is doing it's job. Lack of advance ( mechanical ) on acceleration can also produce a backfire or a flat spot. Remember there is no vacuum signal or vacuum advance when the engine is under hard acceleration, just mechanical.

For those of you who think a compression test is the only way to find a bad valve there is what we call a simple power balance test using a tachometer or with a good ear we can determine by pulling a spark plug wire one at a time with the engine idling if a cylinder is doing it's job or fare share of the work. A good cylinder who's ignition source has be disconnected will show a rpm loss. No rpm loss most likely is a burnt valve, very less likely would be broken rings. Or worn out cylinder.

Also another quick way to see if you have a bad or leaky valve is to quickly put a vacuum gauge on the engine intake manifold while it's idling. The vacuum gauge should read at idle depending on the engines camshaft somewhere between 15 and 21 inches of vacuum, and more importantly it should be a steady reading. wild swings on the gauge indicate a burnt valve. With that vacuum gauge you can also ( because it will show not only a negative or vacuum but it also shows pressure) disconnect the fuel line to the fuel pump and with the engine running with the fuel that's left in the carburetor fuel bowel and connect the fuel pump discharge line ( that supplies fuel to the engine) to the vacuum gauge to show how much fuel pressure the pump is putting out.

Try these simple things first.

Edited by helfen (see edit history)

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Lebowski, my suggestion would be to print helfen's post, take it out to your shop,  and do exactly as he suggests, in the order that he indicates.  

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Just make sure if you pull plug wires on a running engine to wear rubber gloves or use a pair of insulated pliers. Preferably both. 40k-60k volts can have quite a bite.

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 One thing I would like to say to all collector enthusiast. Cars that sit longer than a few days need a couple of precautions before starting. When getting in a car and starting the engine a simple way to protect the carburetor and your engine bearings and all friction parts is to turn the key and crank the engine, but do NOT touch the accelerator! The reason for this is twofold. One if you pump a dry carburetor the first thing that is going to wear prematurely is the accelerator pump. The accelerator pump cup when pumped without fuel wears out super fast. Cranking the engine primes the engine oiling system and the carburetor..

 

On my cars that have been sitting I crank the engine foot off the gas pedal, I watch the oil pressure start to climb ( with the idiot light I  watch to make sure the light goes out) Just about time the oil pressure gauge has swung past 40+ PSI the engine starts to sputter. The sputtering tells me fuel is being sucked into the idle circuit of the carburetor or that the carburetor is receiving fuel. Now with the engine oiling system primed, and the carburetor is primed, I can manipulate the carburetor and it's choke and start the engine. 

 

How many times on a TV show where the expert goes out to a barn or garage to a car that's been sitting for who knows how long gets a battery hooked up and gets in and starts mashing the accelerator pedal while cranking? What madness. Ever notice on some makes of engine that have no anti oil filter drain back devise ( and some that do ) that even overnight when you start up one of these engines with the choke fast idle cam on that the engine rattles for just a second on the start up? That noise is a few things, connecting rod bearings and piston slap and engines that have a oil pressure fed chain tensioner.... all due to lack of oil for an instant on start up. I always oil prime first. Please, after you start up don't just drive off. Engines and their tolerances need to expand to OPERATING tolerance before you apply work to them, even more susceptible to this are air cooled engines like VW and Porsche because it take longer for them to warm up that a water cooled engine. Remember,  just like a human, you don't run a 50 yard dash without warming up first.

90% of the wear in a engine is in the first ten minutes.

Edited by helfen (see edit history)

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Second that & why I always fill an oil filter with oil before cranking. It always bothers me on some of these "reality" shows how they just stomp the accelerator.

If the Judge has been sitting for over a month I pull the coil wire and just crank 'til I see the oil pressure gauge move.

Computer cars are different so I just crank immediately when turning the key on so fuel pump does not have time to pressurize the fuel system. Daily drivers I turn on, wait a second or two, then crank.

Storage is the only good use for motor honey (STP, et al.) I know since it will coat bearings and such. Change the oil when taking out though.

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During the video at the engine compartment part I noticed blowby from the valve cover breather. I notice the tappets a little noisy. I notice the engine to be fairly smooth and appeared to be hitting all cylinders. We know the engine is tired, but I think it has some life left in it sans the blowby. The compression is low ( it's a well worn engine ) but more importantly the compression is more or less EVEN. The compression test tells us the valves are seating. For the most part on the road test we see ( but didn't see a WOT test ) decent normal acceleration which tells us the ignition and timing are doing it's thing reasonably well and part of the carburetor's circuit( there are seven circuits ) function is ok.

What I would like to see the owner do is take that air cleaner off, make sure it's clean, but with the engine off to take a flashlight and look down the throat of the carburetor and with the other hand manipulate the carburetor to full throttle. The accelerator pump should squirt a nice shot of fuel down on the venture or on the throttle plate. If it dribbles or does not shoot a steady stream this will cause a backfire in some cases, in others it will cause the engine to as we call in the trade fall over or fall on it's face.

With the engine running go to the distributor. We need to check the vacuum advance so pull the vacuum advance hose. Does the idle speed drop? It should unless this is a newer carburetor that has been put on by mistake and has a ported vacuum signal. OK the engine speed dropped like it should? OK reinstall the vacuum hose. The timing light needs to be installed to check initial timing ( initial timing is checked at idle with vacuum advance disconnected ) after that is accomplished bring the engine up to about 2500 rpm while your watching the timing marks, do this with the vacuum advance disconnected again because we need to see if the mechanical advance is working now connect vacuum advance for total timing. Notice I'm not asking for specific's....We just want to determine if the distributor is doing it's job. Lack of advance ( mechanical ) on acceleration can also produce a backfire or a flat spot. Remember there is no vacuum signal or vacuum advance when the engine is under hard acceleration, just mechanical.

For those of you who think a compression test is the only way to find a bad valve there is what we call a simple power balance test using a tachometer or with a good ear we can determine by pulling a spark plug wire one at a time with the engine idling if a cylinder is doing it's job or fare share of the work. A good cylinder who's ignition source has be disconnected will show a rpm loss. No rpm loss most likely is a burnt valve, very less likely would be broken rings. Or worn out cylinder.

Also another quick way to see if you have a bad or leaky valve is to quickly put a vacuum gauge on the engine intake manifold while it's idling. The vacuum gauge should read at idle depending on the engines camshaft somewhere between 15 and 21 inches of vacuum, and more importantly it should be a steady reading. wild swings on the gauge indicate a burnt valve. With that vacuum gauge you can also ( because it will show not only a negative or vacuum but it also shows pressure) disconnect the fuel line to the fuel pump and with the engine running with the fuel that's left in the carburetor fuel bowel and connect the fuel pump discharge line ( that supplies fuel to the engine) to the vacuum gauge to show how much fuel pressure the pump is putting out.

Try these simple things first.

 

Thank you for all the advice. I did 3 of the things you asked. I removed the air cleaner and pulled on the throttle linkage and a nice blast of gas squirted into the carb. I removed the vacuum advance line and the idle speed definitely dropped. I pulled the plug wires with the engine running (and only got shocked once) and it was definitely noticeable on all cylinders except #2. There was a lot of smoke coming from the exhaust manifold near the firewall so I checked the bolts and the last one wasn't even finger tight. Some of the others were fairly loose too so I tightened all of them up. I also made a video of me driving it with the usual cloud of smoke behind me and with the same backfiring from the carb. When I pulled the choke out it stopped backfiring and pushed it back in 3 seconds later there was no more backfiring. What's up with that? Thanks again to all who are trying to help me and Happy Thanksgiving!

 

2 minute video of me driving it with lots of smoke and backfiring....

 

https://www.youtube.com/watch?v=OkyZo2w6z-s

 

 

One more thing-it accelerates fine in first and second gears now (it's a 3 speed manual) and only backfires in third gear. It used to backfire in all 3 gears until I adjusted the idle mixture screw on the carb. Why would that be?

Edited by Lebowski (see edit history)

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The blue smoke on acceleration after a deceleration is caused by worn valve guides or worn valve guide seals. The high vacuum on the decel. pulls oil past the valve guide and the valve seal ( some cars don't have a seal ) and into the combustion chamber and is burned ( your smoke on acceleration). The spark plugs need to come out to make sure this oil burning has not fouled them. A plug that is fouling can fire under a no or lite load condition an appear fine, however under high demand or load can misfire. so check and clean/replace them. Also the carburetor is suspect also because in you video the engine was backfiring long past when a accelerator pump would have been the cause. The accelerator circuit is only one circuit of the carburetors seven, you said it squirts a steady stream so that can be eliminated, the choke circuit can be eliminated and the idle circuit can be eliminated because it runs fine at idle. If there is dirt in the other circuits we might be able to dislodge the pieces by taking the air cleaner off and starting the engine, now with one hand manipulate the throttle with one hand and with the other your going to close off air going to the carburetor. Raise the rpm to about 3,000 rpm and with the other hand put your hand over the hair horn of the carburetor blocking all air entering the carb, then manipulate the carb from wide open throttle to idle back and forth, but before the engine stops remove your hand from the air horn and with your other hand manipulating the carb hold the throttle wide open until the engine recovers. Repeat this procedure several times. What happens is when the engine is running at 3000 rpm and you stick your other hand over the air opening of the carburetor and now manipulate the carb back and forth through all it's circuits the high amount of vacuum sucks any debris that's dislodged out and through the engine. You see with the air blocked off only fuel can be sucked through the circuits. Anyroad look at the plugs first, if they are N/G replace them or clean them and try again. If they are good then try our old mechanic's carburetor trick. Note some crud will never come out this way and will require the carb to be disassembled and cleaned with carburetor cleaner, but this trick has had surprisingly good results, so if the plugs are ok give it a try.

Happy Thanksgiving to you and all our guy's here!

Edited by helfen (see edit history)

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Let's face it the engine is worn out with that much blowby. It may be possible for a good mechanic to make it run better but it will never be right until the engine is rebuilt.

 

On the good side, it is a very simple engine, chances are there is no serious damage inside, so it should be a simple job to rebuild it and not too expensive.

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Let's face it the engine is worn out with that much blowby. It may be possible for a good mechanic to make it run better but it will never be right until the engine is rebuilt.

 

On the good side, it is a very simple engine, chances are there is no serious damage inside, so it should be a simple job to rebuild it and not too expensive.

 

I removed the plugs a couple of days ago when I did the compression test and none of them were fouled. Why does it only backfire in third gear when it used to backfire in all 3 gears before I adjusted the fuel mixture screw on the carb? 

Edited by Lebowski (see edit history)

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Let's face it the engine is worn out with that much blowby. It may be possible for a good mechanic to make it run better but it will never be right until the engine is rebuilt.

 

On the good side, it is a very simple engine, chances are there is no serious damage inside, so it should be a simple job to rebuild it and not too expensive.

 

How much is "not too expensive" and do you know someone who can do it? I just bought the car 2 weeks ago today for $16k and my wife is furious because it's turning out to be a real POS....

Edited by Lebowski (see edit history)

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Lebowski, almost every vintage car I've ever bought--no matter how good its appearance--has needed some degree of mechanical "sorting," and I have learned to allow for that in what I am willing to pay.

I've followed your thread attentively, and believe you probably can in fact get it running acceptably well without doing an engine rebuild. So what if it uses some oil, even 200-400 miles per quart; you can buy a lot of oil for the cost of major surgery on the engine. As someone said, compression is acceptable and relatively even, and it may well improve with some driving. I'd also check valve lash adjustment. It's a very nice, quite unusual car. Hopefully your wife will be able to enjoy the car with you and that your dissatisfaction will not linger once you have it running decently.

Do you have a mechanic with an oscilloscope, as on a Sun machine? A couple of mechanic's diagnostic hours (someone experienced in pre-electronic-ignition and with old school equipment) would be money well spent rather than guessing at problem areas and replacing components willy-nilly.

Valve stem seals (if that engine uses them) can usually be replaced without removing the head **IF** your mechanic has the proper tool to maintain pressure in each cylinder from shop air.

Best wishes! We all feel your pain and are trying to help.

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Let's face it the engine is worn out with that much blowby. It may be possible for a good mechanic to make it run better but it will never be right until the engine is rebuilt.

 

On the good side, it is a very simple engine, chances are there is no serious damage inside, so it should be a simple job to rebuild it and not too expensive.

That is not what is causing the backfire through the carb.

Lebbowski, take it slow and methodical, you'll get this sorted out. Take the day off and try not to think about it until later on this long week-end.

I remember about a hundred years ago when I first started in this business I had a car with a electrical problem that really had me. One of my colleagues knew I was having problems so he said to me, look in this great universe and it's totality your problem is only between these two bumpers-take a load off and regroup. It helped bring it into perspective.

We will help you if we possibly can.

Edited by helfen (see edit history)

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Lebowski, almost every vintage car I've ever bought--no matter how good its appearance--has needed some degree of mechanical "sorting," and I have learned to allow for that in what I am willing to pay.

I've followed your thread attentively, and believe you probably can in fact get it running acceptably well without doing an engine rebuild. So what if it uses some oil, even 200-400 miles per quart; you can buy a lot of oil for the cost of major surgery on the engine. As someone said, compression is acceptable and relatively even, and it may well improve with some driving. I'd also check valve lash adjustment. It's a very nice, quite unusual car. Hopefully your wife will be able to enjoy the car with you and that your dissatisfaction will not linger once you have it running decently.

Do you have a mechanic with an oscilloscope, as on a Sun machine? A couple of mechanic's diagnostic hours (someone experienced in pre-electronic-ignition and with old school equipment) would be money well spent rather than guessing at problem areas and replacing components willy-nilly.

Valve stem seals (if that engine uses them) can usually be replaced without removing the head **IF** your mechanic has the proper tool to maintain pressure in each cylinder from shop air.

Best wishes! We all feel your pain and are trying to help.

 

It's extremely embarrassing to be stopped at a traffic light and have a big cloud of smoke around me. I feel like that "Pigpen" character in the Charlie Brown cartoons who always had a cloud of dirt swirling around him. Instead of getting a thumbs up I'm seeing a different finger. Also, I'm not originally from the Louisville area and don't have a mechanic or know of a decent shop around here that will work on old cars. 

I would be willing to rent a tow dolly again and pull the car a couple of hundred miles if someone would check the timing, adjust the valves or do some of the other things that have been suggested. Thank you for taking the time to respond....

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I agree with Helfens post 65 100%. I do that all the time.

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Since you are only a hour from the Cincy area I could stop by some sunday in a couple weeks,all I ask in return is to feed me and have some cold ones if  you drink beer and if not soft drinks are fine.

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Someone else has already said it, but you have 2 issues going on here

 

1 The smoke, I think it needs re ringing at at least a hone, the valve guides could be a problem, but valve smoke is usually very brief as there is very little oil on a valve stem, where the cylinder bores have at least splash oil on them constanly

 

Basically, the engine is tired.

 

2 The carby backfire has to be the engine running to lean. Someone has already instructed you on how to check for a vacuum leak, so assuming you had no luck there, I would take your car to someone and have the carby re done (I know you said it has been rebuilt) as I think the main jets are partially blocked

 

As a final advice from an auto electrical tradesman, you dont sound very proficient in mechanical repairs, and this is fine, no one says you must be mechanically proficient to own an old car (Although, it helps :) ), so the best advice I can give you is to take it to someone who is, let them diagnose it and take their advice on its repair

 

Keyboard diagnosis is fraught with danger and can become exceptionally expencive

 

If your wanting this car to be a learning experience for you to learn mechanics, that is also a good thing, but study the manuals until you understand what you are doing completely, they were written by the people that built them (generally), so (in most cases) they know what they are talking about, but the manuals do rely on some mechanical aptitude

 

Always good to have a go, but always good to know if your drowning also

 

Miick

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Since you are only a hour from the Cincy area I could stop by some sunday in a couple weeks,all I ask in return is to feed me and have some cold ones if  you drink beer and if not soft drinks are fine.

 

That sounds great. We have a fridge full of Diet Coke, Diet Mountain Dew, Diet Sunkist Orange and Diet A&W Root Beer. My wife will make a big crock pot full of beef or chicken stew or her excellent shrimp and mushroom alfredo and whatever you don't eat here you can take home with you. I'm not a drinker but if you want beer just tell me what kind, or if you don't like diet sodas let me know what you want. I really appreciate the offer. I'll send you a PM with my address and phone number. I'm only half a mile from the exit 17 offramp of I-71 so I'm not way out in the middle of nowhere. Thank you for your very generous offer....

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