ConcoursMustang Forums
Restoring - General discussions that span across many different groups of years and models => Drivetrain => Topic started by: Matt1968 on June 29, 2015, 10:47:34 PM
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I have my 390 running now BUT, I am getting backfires out of my exhaust. At idle it's popping and backfiring. I know if it backfires at the carb its a specific issue and if you backfire at the exhaust its a different issue.
Can someone educate me please. Are there any FE specific items I need to look at?
Matt
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ALWAYS, with such a problem, begin with the basics. Not really an "FE ONLY" sort of a thing.
1.) Check and double check Firing Order. This is it 90% of the time.
2.) Make sure the dwell angle of your points is correct and NOT moving around. You need a dwell meter to accomplish this while it is running. (assuming you have points ignition).
3.) lastly, if all above is OK you have valve(s) leaking some. A compression test would then be in order to determine the cause.
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More basics:
- Check the plug wires to make sure they are securely attached on both ends.
- Check the condition of the plug wires.
- Check the routing of the plug wires (crossfire).
- Check the inside of the distributor cap for moisture or other foreign material.
Beyond basics:
- Check the timing chain for excessive play (have to remove the fuel pump from the timing cover).
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I had a problem similar to this on my FE and it about drove me crazy. I checked ALL of the basics as listed above and many more only to find out it was the mufflers causing the problem that disguised itself as a backfire and was not an engine problem at all. The noise had the identical sound. While the engine is idling in part take a rubber mallet and bang on the mufflers and see if that changes anything. The mufflers looked like new on the outside but the guts where all rusted out causing the problem. I disconnected the mufflers and problem solved.
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What Chris just posted made me think of another scenario:
WITH a THERMACTOR SYSTEM, the Smog Pump could be injecting AIR into the exhaust if things are not connected or working correctly. The AIR should only be entering the exhaust ONLY DURING ACCELERATION, if at other times (Idle or deccelerating) it will produce a backfire effect in the exhaust system, MOST PRONOUNCED BACKFIRING WHEN DECELERATING, to the point where it can blow up the exhaust system (usually the mufflers).
The AIR should be diverted away from the downstream (exhaust) when connected and operating correctly. The backfiring in this scenario would be caused from the addition of AIR which helps (any) unburned fuel to detonate. BOOM-BOOM BOOM
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Guessing this is a 68 390?
Also would check the vacuum hose routing since the diaphragm could get the wrong signal/vacuum at the wrong time
Basics and one thing at a time
I'm guessing your using the original point style of ignition. Before I rebuilt my Boss I had a bad backfiring issue once the car warmed up to the point of it just shutting down. Cool down and it would fire right up. Issue was the Pertronics
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What Chris just posted made me think of another scenario:
WITH a THERMACTOR SYSTEM, the Smog Pump could be injecting AIR into the exhaust if things are not connected or working correctly. The AIR should only be entering the exhaust ONLY DURING ACCELERATION, if at other times (Idle or deccelerating) it will produce a backfire effect in the exhaust system, MOST PRONOUNCED BACKFIRING WHEN DECELERATING, to the point where it can blow up the exhaust system (usually the mufflers).
The AIR should be diverted away from the downstream (exhaust) when connected and operating correctly. The backfiring in this scenario would be caused from the addition of AIR which helps (any) unburned fuel to detonate. BOOM-BOOM BOOM
No thermactor on my engine..
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Guessing this is a 68 390?
Also would check the vacuum hose routing since the diaphragm could get the wrong signal/vacuum at the wrong time
Basics and one thing at a time
I'm guessing your using the original point style of ignition. Before I rebuilt my Boss I had a bad backfiring issue once the car warmed up to the point of it just shutting down. Cool down and it would fire right up. Issue was the Pertronics
Yes 68.....yes single points
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Did you have the distributor out?
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http://www.concoursmustang.com/forum/index.php?topic=11315.0
Yes dist was out recently. Please see original post.
3 years ago I parked it. At that time it ran incredibly well. Took the dist out to oil prime the engine.
Now backfiring every 5 seconds.
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http://www.concoursmustang.com/forum/index.php?topic=11315.0
Yes dist was out recently. Please see original post.
3 years ago I parked it. At that time it ran incredibly well. Took the dist out to oil prime the engine.
Now backfiring every 5 seconds.
Did you cover the tailpipes? Do you have any cats on patrol where the car was stored? ;)
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Anyone in the Toledo OH want to check this thing out?
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http://www.concoursmustang.com/forum/index.php?topic=11315.0
Yes dist was out recently. Please see original post.
3 years ago I parked it. At that time it ran incredibly well. Took the dist out to oil prime the engine.
Now backfiring every 5 seconds.
Logically if it ran well and then after removing and reinstalling the distributor it started backfireing , the distributor is the source of the problem and in this scenario the most likely thing is that the distributor has been re installed incorrectly.
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Anyone in the Toledo OH want to check this thing out?
I'm 2 hours away in NE Ohio, do you have a trailer?
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HI Matt
Give me a call 517 861 7630 (North of Ann Arbor) It sounds like you know car pretty well -do you think you need a second set of eyes, work together and just confirm correct?
Can you take the time to work on car in one day if planned (or plan a visit and a return if you want to work on it)
Would you need timing light, fresh plugs - have floor jack and stands (clutch) ?
Let me know if you can only work weekends OR if you are avail weekdays (stays light until 9:30).
Mark Haas
P.S. I'm not a certified tech, but never met an engine I couldn't start !No cost no obligation - other than a follow up post to inform all. (good or bad) LOL
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I'm 2 hours away in NE Ohio, do you have a trailer?
Hey 67 ...no trailer :{
Where are you , near Cleveland?
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HI Matt
Give me a call 517 861 7630 (North of Ann Arbor) It sounds like you know car pretty well -do you think you need a second set of eyes, work together and just confirm correct?
Can you take the time to work on car in one day if planned (or plan a visit and a return if you want to work on it)
Would you need timing light, fresh plugs - have floor jack and stands (clutch) ?
Let me know if you can only work weekends OR if you are avail weekdays (stays light until 9:30).
Mark Haas
P.S. I'm not a certified tech, but never met an engine I couldn't start !No cost no obligation - other than a follow up post to inform all. (good or bad) LOL
Hey Mark , I'll give you a call. I actually took a new job in Taylor and have been commuting. Looking for a house in Mich right now AND I'm degreed through Ohio State....gettin' crazy.
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Time table of "saga"
See original post for background
1000 miles on newly rebuilt engine, running fine, clutch breaks, Mustang sits 3 years without starting.
Pulled dist to oil prime
Won't start. Looked at plug wires. Somehow plug wires are mis-wired (from engine rebuilder) as compared to ford specs. Don't understand how it ran like that.
Wired routed correctly now.
Backfired few timed from carb.
Engine running ok but seems rough
Timing shows way off, harmonic had to have slipped
Guessing at timing
After starting and running several times, a backfire out of the exhaust develops (back firing through the exhaust only began after several sessions of 5 minute start and runs). Advancing and retarding, no change in backfiring.
Today realizing that exhaust backfires are much worse after initial startup then lessen after warmed up, but still continue.
VIDEO of the backfiring coming soon.
STUCK VALVE? Dist? Points? Carb?
I can't believe I went from a sweeting running rebuilt engine to this mess.
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Forgot to mention could this be a muffler issue like one gentleman stated? I just can't see that being the issue.
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Forgot to mention could this be a muffler issue like one gentleman stated? I just can't see that being the issue[
I would never believed it either and never considered it, fortunately my father is a retired Ford mechanic (old school) and he was checking it out one day for me and found the problem. The exhaust looked liked new as I stated however it was almost 20 years old with little miles and the moisture over the years rusted out the inside baffles causing the flutter that sounds just like a backfire. Your exhaust may have the same issue from sitting that long. It won't take but a second to confirm or deny.
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Hey 67 ...no trailer :{
Where are you , near Cleveland?
East of CLE about 50 miles
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http://sendvid.com/uas90eit
Link to backfiring vid for what its worth. I seems like the backfires are coming from the drivers side bank. Also its obvious something is going on in at least on cylinder, she is not running smooth when revving it....I can feel it.
Next step pulling the plugs (terrible task with this car), then the valve covers.
Matt
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Forgot to mention could this be a muffler issue like one gentleman stated? I just can't see that being the issue[
I would never believed it either and never considered it, fortunately my father is a retired Ford mechanic (old school) and he was checking it out one day for me and found the problem. The exhaust looked liked new as I stated however it was almost 20 years old with little miles and the moisture over the years rusted out the inside baffles causing the flutter that sounds just like a backfire. Your exhaust may have the same issue from sitting that long. It won't take but a second to confirm or deny.
Chris let me know if the vid sounds like your muffler situation.
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Plug wires are all run correctly? Distributor is installed in the proper position? Timing is set to specs? Harmonic balancer has not shifted from dried out elastomer? Plug wires are not ancient and cross firing? You've checked for vacuum leaks? All these things have been covered, right? If not, they should have been.
If the valve covers are easier to take off than it is to remove the plugs, do that first. Make sure the valves are opening/closing. A valve could be sticking in the guide and hanging open. Could even be carbon deposits on the valves. If you do remove the plugs, get a bore scope and take a peek inside the cylinder at the valves as long as you're in there.
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ALSO ASSUMING YOU RULED OUT ALL OF THE EASY ITEMS MENTIONED BEFORE~I listened to the video,
This is not an easy of fun thing to do, but try figuring out whch cylinder it if first, on a pre-warmed engine, remove a spark plug wire, one at a time on the left bank. (you could get a jolt here, be careful, they make insulated pliers specifically designed for this...I suggest using them and electricians gloves) If the popping stops, you've narrowed it down. If it gets BETTER, but still popping, you might yet have a crossed wire :o Once you narrow it down to which cylinder(s) and you ruled out any possibilty of a crossed wire, THEN, I agree w/ Smokey, pull the V.C. first...look also for a broken valve spring and/or a flat cam lobe.
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What brand of plugs are you using? What heat range?
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If I where you before I remove them miserable spark plugs I would remove each plug wire at the distributer and set it back on but don't click it in. I would run the car for awhile and take a spark plug wire pliers and pull up one wire at a time from the distributer. You should notice a difference in the sound of the engine each time a wire is pulled and if you don't than you have a dead cylinder that could be caused by several things. I would also study the engine vibration when it backfires and see if it misses at the same time. I would not rule out the mufflers either at this point. Do the easy stuff first before you get into the hard stuff. As someone else mentioned I would put a vac. gage on the engine and see how steady the reading is. If you don't have one this is a very good tool to have for little investment. Most vac. gages come with a troubleshooting guide based on the readings.
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Okay, nobody likes a cliff hanger. My money has been on a sticking valve, or other valve train issue.
Hope you didn't roll it back in the garage and give up???? :o ???
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Okay, nobody likes a cliff hanger. My money has been on a sticking valve, or other valve train issue.
Hope you didn't roll it back in the garage and give up???? :o ???
+1...We're on the edge of our seats! ;D
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What brand of plugs are you using? What heat range?
Don't remember. Why would brand and heat have anything to do with it?
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Okay, nobody likes a cliff hanger. My money has been on a sticking valve, or other valve train issue.
Hope you didn't roll it back in the garage and give up???? :o ???
I rolled in into the garage and gave up :{
Actually I never give up. Just taking a break before I dig into the plugs and covers.
What would cause a sticking valve? These are Edelbrock assembled heads.
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Don't remember. Why would brand and heat have anything to do with it?
I did call svo2scj and he volunteered to tale a look at it, but I need to pull the plugs and covers first.
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Don't remember. Why would brand and heat have anything to do with it?
Heat range, if they're too hot could possibly cause preignition. probably a low percentage of that. Brand - without getting too subjective or causing a ruckus, let's just say I've had more than a little trouble with Champion plugs... :(
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Heat range, if they're too hot could possibly cause preignition. probably a low percentage of that. Brand - without getting too subjective or causing a ruckus, let's just say I've had more than a little trouble with Champion plugs... :(
Gotcha. The thing is it ran like a swiss watch (sorta) with the same plugs prior to storage, if you didn't read the full thread.
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Gotcha. The thing is it ran like a swiss watch (sorta) with the same plugs prior to storage, if you didn't read the full thread.
I've been following it ;) That's not inconsistent with the spark plug problems I've encountered. Had issues with a certain brand in multiple cars (including a '68 Mustang 289), one truck, a boat, a lawnmower, a snowmobile, and I think a weed wacker too. In all cases I switched to Motorcraft or NGK (for the small engines) and the problems were gone. I don't recall backfiring being the issue, though; usually it was rough running or fouling.
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One thing that I do recall is that the Edelbrock heads need a very specific plug......not sure what brand I currently have. I will report as I start to pull them. Surprising that Champions are problematic for you , maybe they are being made in China now?
Matt
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One thing that I do recall is that the Edelbrock heads need a very specific plug......not sure what brand I currently have. I will report as I start to pull them. Surprising that Champions are problematic for you , maybe they are being made in China now?
Matt
I don't know what the deal is, that's why I didn't want to bad-mouth them. All I know is that they've been a curse for me :o
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There is nothing worse trying to diagnose a problem and replacing a part assuming it's a known good since it's new. I never had issues with spark plugs until the last couple years where I have purchased at least 2 bad ones. One was an off beat brand for a lawn mower and the other was an NGK on my dirt bike. It's hard to have faith in any brands these days as everything is made so cheap thanks to the DISCOUNT store mentality comparing apples to oranges telling you it's the same thing. Sorry getting off topic a little.
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... It's hard to have faith in any brands these days as everything is made so cheap thanks to the DISCOUNT store mentality comparing apples to oranges telling you it's the same thing. Sorry getting off topic a little.
NOT REALLY off topic at all. I work 40-60 hours a week on all types of cars, some call it making a living at it. (I beg to differ about the "living" part of that statement)
I REFUSE TO TUNE UP A CAR WITH A CUSTOMER'S OWN PARTS for this very reason. It isn't because "I earn less on the job" that I refuse, it is because I refuse to go with "anything unkown" about what somebody else calls out as "I already tuned it up". People stick cheap parts in to save a few bucks while costing themselves on the other end. THEN, people drop spark plugs, crack them, smash down the electrode and so on. When a tune-up arrives that somebody else has already been working on, it usually is a larger nightmare than one that was left alone. "To many cooks" sort of a thing and they don't want to here they screwed up.
This situation on this particular car is really along the same line. This car has aftermarket heads on it designed to make it "run better". Well, at this point in time as in most aftermarket "upgrades", the O.P. has an epic fail. It might also have aftermarket ignition system, who knows. I "assumed" earlier since this is a Concours forum, it was all stock. This is obviously not true. The ONLY logical first step approach is to start with the basics and the OP claims all of that is good. The only logical next step is to pull the plugs and run a compression test and/or pull valve covers and check for proper valve function. Having listened to the sound bites in the video link provided earlier, I am over 95% sure it isn't simply "a spark plug issue" (again, "assuming" stock components & running on regular pump gas)
"ASSUME"=ass-u-me Quit "assuming" since it ran good when it was parked, that ANY of these aftermarket components are "known good" since these aftermarket, "made to make parts stores money" items are the #1 cause of grief to the professionals and the Do-it-Yourselfers alike.
As far as "Spark Plugs" are concerned, the only "correct" plug for any car (or lawn mower for that matter) is WHATEVER THE FACTORY INSTALLED. Now, remove factory components and replace them with aftermarkets junk and you open up a can of worms. You better have it Dyno'd when you are done "re-inventing the wheel"...just like the engineers all do whenever they have a new creation. You cannot simply "bolt on new parts" and expect it to work right. These things were engineered to run on Pump Gas of the 60's, we need to have minor adjustments to make them run right on pump gas of today, but this is a science...You cannot just simply "guess" or listen to the Parts Store Geek.
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As for Champion plugs, they are trash. I don't care what anyone says about them. When I worked for Chrysler Corp awaiting my slot at the academy, I saw thousands of them come back from new vehicles for warranty return.
I have two sets of BF32's for my Shelby, but the only current Autolite replacement is a BF45 which is a different heat range than even the BF42.
As for the one who asked for help: People usually ask questions for a reason, and snippy replies don't make people want to jump through hoops for you.
I thought a couple here were very generous with their time, and being you don't have a thermactor system to contend with, the 30 minutes required to answer a simple query. If it ran before you pulled the distributor, likely the issue is the distributor/firing order.
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As for Champion plugs, they are trash. I don't care what anyone says about them. When I worked for Chrysler Corp awaiting my slot at the academy, I saw thousands of them come back from new vehicles for warranty return.
I have two sets of BF32's for my Shelby, but the only current Autolite replacement is a BF45 which is a different heat range than even the BF42.
FYI your 67 GT500 is supposed to run BF 42 not BF 32 from the factory according to the owners manual and the Ford service specification manual . Other owner engine modifacations may cause the needs to vary.
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Time table of "saga"
See original post for background
1000 miles on newly rebuilt engine, running fine, clutch breaks, Mustang sits 3 years without starting.
Pulled dist to oil prime
Won't start. Looked at plug wires. Somehow plug wires are mis-wired (from engine rebuilder) as compared to ford specs. Don't understand how it ran like that.
Wired routed correctly now.
Backfired few timed from carb.
It ran fine, then you moved the wires around and now it runs rough. I would move the wires back where the engine builder had them. He may have a different cam that requires a different firing order.
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Bob, question.
There was a blue performance book that is about the size of the owner's manual. It calls for BF32 as a performance plug for the 428 and 427.
Was this book part of the factory supplied manuals? I noted it covers most of the high performance engine combinations.
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Bob, question.
There was a blue performance book that is about the size of the owner's manual. It calls for BF32 as a performance plug for the 428 and 427.
Was this book part of the factory supplied manuals? I noted it covers most of the high performance engine combinations.
I have never seen an FE with a cam that required a firing order change. I have only seen that when 289/302 cams are used in 351W.
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Bob, question.
There was a blue performance book that is about the size of the owner's manual. It calls for BF32 as a performance plug for the 428 and 427.
Was this book part of the factory supplied manuals? I noted it covers most of the high performance engine combinations.
There was a 65 ,66,and 67 high performance supplement .The 65.66 ones are reproduced .The 67 one is not reproduced . They were among other things supplements to the 65,66,67 Shelby's owners manuals and came in the glove box. The High Performance supplement typically covered information NOT covered in the owners manual. Since they were designed to be supplements to a wide spectrum of vehicles some of the information did not apply to other vehicles and the Shelby specific owners manual information SUPERCEDED anything that was also covered in the performance supplement in a different way. Case in point the supplement mentions a BF32 for the 428 but the owners manual supersedes that information with specifying the BF42 plug. FYI the 67 service specification manual also specifies the BF42 for the 428. That is if we are talking factory specifications. Owner engine modifications and usage may require different needs. BF 42's work better then BF 32 especially on a duel four 428 where there is typically so much extra fuel on a street driven occasional spirited driving type of useage . The BF32 plug will foul out much more quickly then a BF42. It was typical for us to switch out the BF32 plugs on single four CJ engines so that they didn't foul out quickly on a street car when they were every day transportation let alone the short use you got out of BF32's before fouling on duel four 67's. . If only drag strip service the needs are different.
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Remember that the composition of gas has changed a lot since the late 60's/early 70's.
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I found 16 NOS BF32 plugs. I did used them and noted they fouled quickly because the vehicle was only being moved inside and out of the garage and shut down. I used to take it around the block to try and allow it to come up to temperature before putting it away. A couple whiny neighbors bitched because the front end wasn't on the vehicle. Now that it's back from paint I am reassembling the vehicle. I went through the engine and re-cammed it being the duration was too short and it was coming on too fast. The rich idle mixture kept the rings from seating the first time. I am trying to find someone in the Dallas area that has a stand at home to break it in on before putting the new engine in the vehicle.
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Unless I missed it, have you replaced the old fuel after sitting for three years. My 390GT had the same problem, fouling plugs, back firing, etc. I drained the fuel, flushed the line, refreshed the carb and now it runs great. I checked all the things you mentioned and finally went to the old fuel, which was the culprit. Mike
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Good point. When I start a vehicle that has been sitting a long time, I unhook and plug the fuel line from the tank. I then run a fuel line into a 5 gallon can of fresh fuel.
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Any Update? What did you find out about the fuel? Just curious. Mike
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Information that would have been helpful from the get-go. Anyone knows that fuel after three years degrades and is essentially varnish at that point. The only fuel I have even seen that may survive that long is race gas.