Lebowski

What causes a carb to backfire?

Recommended Posts

If you think you need the help of a hobbyist, you should join the local AACA Region. The Kyana Region certainly has some good people who can help you learn how to work on your Edsel.  

 

Kyana Region
President - Fred Trusty
2012 Bear Camp Rd
Louisville, KY 40272

Share this post


Link to post
Share on other sites

If you think you need the help of a hobbyist, you should join the local AACA Region. The Kyana Region certainly has some good people who can help you learn how to work on your Edsel.  

 

Kyana Region

President - Fred Trusty

2012 Bear Camp Rd

Louisville, KY 40272

I've checked with them several times in recent years and they are "not accepting new members at this time." 

 

I'm going to get a cheap compression tester today and see what happens. I stick the thing in the spark plug hole and crank over the engine after I remove the coil wire-right? Since I'll be doing it by myself will it stay in the hole when I crank it? What reading is considered good and what isn't? Thanks again to all who responded....

Share this post


Link to post
Share on other sites

Get a compression tester that screws into the spark plug hole.  The ones that push in are not accurate and usually need two people to do a check.  Disconnect and ground the coil wire.  Open the throttle and crank the engine over for at least six times on each cylinder to get the best reading.  Then squirt some oil in the cylinders, roll the engine over briefly to spread the oil and do another check.  If the readings go up on each cylinder, that is an indication of worn rings.  If they stay much the same on one or two cylinders, that can indicate sticking, burnt or improperly adjusted valves.  A difference of ten pounds between cylinders is acceptable.

 

Terry

Share this post


Link to post
Share on other sites

I misunderstood your first post. When you mentioned the 100 miles on it, I assumed engine, and you meant carburetor.

 

Suggestion: buy some test equipment.

 

I would suggest any enthusiast working on older vehicles needs a minimum of 3 items of test equipment. These are:

 

(1) Timing light

(2) Compression testing gauge

(3) Dwell/tach combination meter

 

Since your engine has 100k plus miles, I would suggest (especially on a Ford 6 of this period - been there, done that!), that your backfire is much more likely to be a burned/stuck intake valve. We burned a couple by 60k miles on a 1960 Ford 223 6-cylinder that Dad bought new. A compression test would verify/deny this long distance diagnosis. The compression test is quite easy to accomplish.

 

I would also suggest the acquisation of a factory shop manual for your car. In the meantime, Motors/Chiltons aftermarket manuals have lots of useful information, and are relatively inexpensive.

 

As a general rule, engine running issues should be approached as:

 

(1) compression

(2) ignition

(3) fuel

 

And when purchasing test equipment, I personally (OPINION, others may/will differ) believe good, used made in the USA equipment from the 1960's and 1970's is vastly superior to the offshore stuff currently available new.

 

Jon.

I agree with all Jon's suggestions. Wayne

Share this post


Link to post
Share on other sites

"Not accepting new members" ? Say what ? Never heard of a chapter like that. Now they may require you to join National first but that just does not sound right. Any Kyana members here ?

Share this post


Link to post
Share on other sites

Get a compression tester that screws into the spark plug hole.  The ones that push in are not accurate and usually need two people to do a check.  Disconnect and ground the coil wire.  Open the throttle and crank the engine over for at least six times on each cylinder to get the best reading.  Then squirt some oil in the cylinders, roll the engine over briefly to spread the oil and do another check.  If the readings go up on each cylinder, that is an indication of worn rings.  If they stay much the same on one or two cylinders, that can indicate sticking, burnt or improperly adjusted valves.  A difference of ten pounds between cylinders is acceptable.

 

Terry

I bought a Chinese compression tester for $31 and change that screws into the hole. I disconnected the coil wire but am not sure if it was grounded or not. I'm not sure what "open the throttle" means so I probably didn't do that. I checked each cylinder once and when I was done I put in about an ounce of oil. Then I went from front to back again and took a second reading. Here are the results of both tests starting from the front of the engine. Most of the plugs were black and pretty oily. Let me know if this tells you anything and thanks again for the help....

 

1 - 85 - 90

2 - 90 - 95

3 - 90 - 95

4 - 90 - 95

5 - 100 - 105

6 - 105 - 105

Share this post


Link to post
Share on other sites

If you could hear - or see - sparks jumping while turning the engine over, the coil wire wasn't grounded.  By "open the throttle" I meant shove the gas pedal down to the floor while cranking the engine.  The engine can breath better which could have an effect on your compression readings.  Black plugs could be a result of having to run with the choke out at times and the oiliness is an indication of the mileage on the engine - you have said it smokes.  At the least you need to replace the valve stem seals.  The compression on cylinders 1 to 4 is a little low but it is consistent.  However, there is a 20 lb difference between 1 and 6 on the dry test and 15 on the wet test, which is outside the usual 10 lb acceptable level.  Since number 6 didn't change, that might indicate a sticking/burnt valve which could be the source of the pop back in your carb.

 

Terry 

Share this post


Link to post
Share on other sites

I made a 5 minute video today (very poor quality as usual) of me driving around in the Edsel and you can hear some of the backfiring from the carb. At about the 4 minute mark I pull up to the auto parts store and put the phone next to the tailpipe and you can hear it missing or whatever. Then I open the hood and you can hear it run and see more smoke. Let me know what you think....

 

https://www.youtube.com/watch?v=F4Olz-FS9eE

Share this post


Link to post
Share on other sites

 since you are new to old cars

 

When did I say that? This is the sixth Edsel I have owned. In the last 30 years I have also owned a 1930 Ford Model A, 1937 Packard, 1949 Buick, 1950 Pontiac, 1950 Studebaker, 1951 Chevy, 1952 Ford, 1956 Buick, 1957 Chevy, 1958 Mercury, 1959 Cadillac, 1961 Rambler, 1961 Mercury convertible, and several more....

sorry for my post. from the way i read your post i thought you were new to the car. i didn't mean any harm.

Share this post


Link to post
Share on other sites

If you could hear - or see - sparks jumping while turning the engine over, the coil wire wasn't grounded.  By "open the throttle" I meant shove the gas pedal down to the floor while cranking the engine.  The engine can breath better which could have an effect on your compression readings.  Black plugs could be a result of having to run with the choke out at times and the oiliness is an indication of the mileage on the engine - you have said it smokes.  At the least you need to replace the valve stem seals.  The compression on cylinders 1 to 4 is a little low but it is consistent.  However, there is a 20 lb difference between 1 and 6 on the dry test and 15 on the wet test, which is outside the usual 10 lb acceptable level.  Since number 6 didn't change, that might indicate a sticking/burnt valve which could be the source of the pop back in your carb.

 

Terry 

Do you think a valve job will solve the problem as opposed to a complete engine rebuild? I haven't even owned the car for two weeks yet and my wife isn't too thrilled about the possibility of me spending a lot of money on it right away. Do any of you guys do valve jobs? Also, I found another engine that has had a valve job but it's over 1000 miles away in Austin, Texas so I guess that's another option. Should I just find someone to do a valve job and hope that solves the problem? Since I don't know anyone around here who does them is there anyone within a couple hundred miles of Louisville who could do one? I could go back to U-Haul and get another tow dolly and go that route again. Let me know. Thanks....

 

http://austin.craigslist.org/pts/5288725355.html

post-101899-0-77632800-1448400591_thumb.

Share this post


Link to post
Share on other sites

If you are experienced with vacuum wiper motors, you probably know that letting up on throttle increases the wiper speed, because the butterfly on the carb is restricting the airflow, hence more vacuum.  Choking the carb also has that effect.  In either case, the vacuum advance is not advancing the spark as much as it should.  This could result in your backfire which is lighting the fire  with an intake valve open.  As another poster mentioned, I would check for manifold vacuum leaks and also see if the timinig is set right.

Share this post


Link to post
Share on other sites

While there is a lot of "audio information" in your video, I, personally, wasn't able to discern as much as I would hope to have. It's just that there is so much distortion in the sound when recording on a tiny microphone. When you held the camera by the tailpipe, I thought that maybe the timing sounded somewhat retarded. A retarded spark will make an engine sound like it has a little "lope" to it at an idle. A sound similar to a high performance cam. That didn't seem to be the case when I heard the sound of the engine from under the hood. I'm afraid that you are just going to have to learn how to use a timing light accurately and confidently. When you are confident that the timing is correct, then a search for a vacuum leak or carb problem can be undertaken. In advance of that I'll offer that I'm thinking that it's less likely that there is a burnt valve if you feel that all of the plugs looked pretty much the same. Weak valve seals will cause an engine to puff out smoke after accelerating from an idle. I don't think that I have ever known them to cause the amount of oil consumption that you are indicating, though. I spent a good deal of time under the hoods of cars of this era and even Ford sixes that were running wonderfully still seemed to have a whole lot of blow-by coming out of the breather cap. While it's true that engine timing rarely wanders off by itself, worn or improperly set points change timing quite a bit. I would suggest that you start with new points and plugs, also look at the cap and rotor. Then set the timing (even if you have to invest some time in learning how). After that, return here and one of us will gladly take the time to talk about using a Burnz-A-Matic to locate vacuum leaks.

Edited by Hudsy Wudsy (see edit history)

Share this post


Link to post
Share on other sites

 talk about using a Burnz-A-Matic to locate vacuum leaks.

 

 This sounds interesting ?

Share this post


Link to post
Share on other sites

The way it is smoking tells me the rings are bad. What else it needs, hard to say without taking the engine apart.

 

You need a good old fashioned mechanic, one who understands the old motors.

Edited by Rusty_OToole (see edit history)

Share this post


Link to post
Share on other sites

The way it is smoking tells me the rings are bad. What else it needs, hard to say without taking the engine apart.

 

You need a good old fashioned mechanic, one who understands the old motors.

That still doesn't address the back firing. It seems a lot of folks would like to see this fellow start over with a new engine and everything else, but I think we should apply our talents first to solving the miss fire. The oil burning may diminish some after he puts some miles on the car. I wasn't going to get into this yet, but a can of "Restore" can go a long way towards diminishing oil consumption in engines that have sat a while. I know that I'm leaving myself wide open here to abundant criticism on that point because not many car guys believe in miracle-in-a can-solutions. I learned from another forum that the product really has value. I've used it myself and have been quite surprised at how well it works .I'm not chemist, so don't ask me how or why.

Share this post


Link to post
Share on other sites

Just noticed that the code V 6 cyl for '60 is 8.4:1 compression so stock is 123 psi. All are low just some more than others.

 

Does sound a lot like lean surge and too much advance at idle. Puffing out the breather is usually rings pressurizing the crankcase.

 

I always liked the one that had the pushbutton tranny in the steering wheel hub.

 

Cast-iron, Overhead valve design
223 cubic inch displacement
Compression ratio: 8.4:1
145 brake horsepower @ 4000 rpm
Bore: 3.62 Stroke: 3.60 inches
Holly single barrel carburetor
4 Main bearings

Share this post


Link to post
Share on other sites

 a can of "Restore" can go a long way towards diminishing oil consumption in engines 

 

Is this what you're referring to? I think I'll pick up a couple cans of this stuff tomorrow. If one is good then two is better-right? Thanks for the tip. I'll let you know what happens....

post-101899-0-47058600-1448420838_thumb.

Edited by Lebowski (see edit history)

Share this post


Link to post
Share on other sites

If you were a little closer I could help you out,you are about 3 hours from me and I used to hit that swapmeet at the state fairgrounds but have not been there in about 10 years.

Share this post


Link to post
Share on other sites

If you were a little closer I could help you out,you are about 3 hours from me and I used to hit that swapmeet at the state fairgrounds but have not been there in about 10 years.

 

I'm an hour from the I-71/75 bridge into Ohio and about 2 hours from Dayton.

 

 

The guy who sold me the radio for the Edsel lives near you in Cedarville. Also, last summer I met a guy from Dayton who was down in Elizabethtown, Ky for a big 1000+ car show in the downtown area. I hung around with him for 2-3 hours since we were both there by ourselves and he had a canopy with a generator-powered cooling unit that blew cool air on us. He brought a restored '55 Corvette and he owns a Dairy Queen in Dayton. I can't think of his name right now but he was a big guy in his 60s. (If I owned a DQ I would be pretty damn big too. LOL) Do you know him?

Edited by Lebowski (see edit history)
  • Like 1

Share this post


Link to post
Share on other sites

Have to say the video is showing a very tired engine, plus (if 123psi is correct) there is an unacceptable drop with your compression  figures across all the cylinders. 

 

Whilst it may be satisfying to correct the the backfire problem, I really think you are just avoiding the inevitable with an engine in that condition. 

Share this post


Link to post
Share on other sites

I, myself, would add the product in the quantity that the manufacturer recommends. Also, I would only add it if I felt that the oil was recently changed. After that, I would drive the car quite a bit on the highway. I would accelerate relatively quickly to higher speed and then releases the gas pedal fully and let the speed drop quite a bit. I would do that several times with each outing. Don't, however, be a traffic hazard. It's not going to change things immediately, it will take time. I think that the present concern about the back firing is the one that you should address first. I mentioned new points and plugs, but I was implying that you install a new condenser, and perhaps a cap and rotor, as well. Also, sometime when you can, run the engine in the dark and watch for spark plug wires shorting out to grounds under the hood or even down the sides of the plugs. This type of shorting out sometimes won't show itself real well, unfortunately. It is the type of short that will act up most when the engine is under a load (accelerating). Frankly, I think that you may eventually find that the carb has a problem, maybe float height or a crack in the base, etc, but ignition problems can imitate so very many other symptoms (especially fuel problems) that I recommend going through the engine's electrical first in order to confirm that all is well there. When you have the distributor cap and rotor off, you should look closely at the small wire that sends current to the points. If that wire has missing insulation or is pinched under the points, it can intermittently short out causing miss fires. This can be the cause of particularly aggravating miss fires that occur only when turning corners. When you install new points and condenser you will need to use a "feeler" gauge to set the point gap correctly. It's also a very good idea to have and use a "dwell" meter to confirm that you have set the points properly. Most dwell meters also come with a tachometer to set the idle speed. Pawn shops, estate sales, Craigslist and ebay are some of the places that you may find these items at reasonable prices. An old "Motor's Manual" of that era is one place to find decent instructions on how to use these tools. You may have some luck with You Tube, but in my experience I've come across a lot of individuals who only have limited knowledge of things to begin with, compelled to pass off their opinions as truths while stumbling over the English language as if it were new to them entirely. I say read it in a book and you'll remember it. Go through the electrical and we'll talk about vacuum leaks later.

Edited by Hudsy Wudsy (see edit history)

Share this post


Link to post
Share on other sites

Here are a couple additional considerations to add to those already posted:

 

1)" Wiggle" and re-position any spark plug wires that touch other wires. A weak spot in the insulation can allow the high voltage to jump to another wire, causing a spark in a cylinder that may have an open intake valve.

 

2) Be sure there are no carbon or metallic-particle tracks between terminals on the inside of the distributor cap. These conductive pathways can also lead to a crossfire.

 

3) Another sign of retarded or non-advancing ignition timing is overheating. Watch your temperature gauge. 

  • Like 1

Share this post


Link to post
Share on other sites

Here are a couple additional considerations to add to those already posted:

 

1)" Wiggle" and re-position any spark plug wires that touch other wires. A weak spot in the insulation can allow the high voltage to jump to another wire, causing a spark in a cylinder that may have an open intake valve.

 

2) Be sure there are no carbon or metallic-particle tracks between terminals on the inside of the distributor cap. These conductive pathways can also lead to a crossfire.

 

3) Another sign of retarded or non-advancing ignition timing is overheating. Watch your temperature gauge.

All true. Thank you for your thoughts.

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now