The Stovebolt Site Forums The Shop Area Engine Shop Why I won’t journey far from home!

First off we’re working with a 1950, absolutely stock 216 with the original Rochester and single stage AC glass bowl fuel pump with an AC sediment bowl filter in between the two. About everything involved here has been completely and meticulously dismantled and brought back to factory specs within the past couple of thousand miles. That is, the carburetion, ignition and mechanical such as the head completely redone.

Well earlier this summer I posted a thread about a sudden backfire through the carb that occurred during a normal drive. It happened only once then all was fine on the ride home. Since then I have had it happen on a couple of more outings over the summer, just one loud bang which causes the hood and cowl vent to take a little jump then all is fine. At first I passed it off as possibly a tiny piece of carbon causing a hot spot in the cylinder since I couldn’t find anything out of spec.

All of my driving is just to keep the old gal limbered up, just pleasure drives. Most of my drives are not more than twenty or thirty miles one way and usually only once or twice a week. A few weeks ago I was coming home from a drive and all of a sudden the engine lost power, like it was running out of fuel and started backfiring through the carburetor when I fed it throttle. The first thought was plugged fuel line/filter or pump going bad. But, if I kept the pedal all the way down to the floor then I could at least keep it running without backfiring and although it was very sluggish and lacked power I could nurse it up to 50 or 55mph. If I backed off on the throttle then I could feel the power completely drop off and if I slowly tried applying power it would go on it’s nose and backfire more. So since it would run up to highway speed I think I eliminated fuel starvation. Still when I got it home I pulled the Rochester apart and checked everything inside and all was clean, clear and in adjustment. I reinstalled the carb and drove it for a couple of more weeks without incident.
Yesterday I took a ten-mile drive to see a buddy and she ran real nice and smooth out to his house. We BS’ed for a 35 or 40 minutes and I started home. A block away from his house she started to backfire whenever I added partial power and would just die out, given full throttle I could again at least keep the R’s up enough to get it home at highway speed.

Once home in the garage I checked the fuel flow through the glass and fuel was flowing free and clear. I pulled the plugs and they looked fine and all were firing every time with the plug tester. Pulled the cap and rotor, they looked fine, points looked fine and gap was proper and plug wires are new a few thousand miles ago. Pulled the valve cover and checked the clearances, all that was fine. I started her up and checked the valve movement, all were fine and all the push rods were taking a nice little quarter turn every click. Checked the timing and she’s riding right on the ball at idle and advances as you bring up the R’s. Checked the vacuum at the manifold and that was correct and steady.
Sitting parked in the garage when I revved it up it takes the fuel fine, no backfiring no hesitation.
So this one has me absolutely baffled. You hope that when you nurse it home and start to look that you will find a broken rotor, or trace in the cap or vacuum leak or that the timing slipped or bad advance or plugged fuel circuit, or stuck valve, but notta thing seems to be out of place.
I’ve got a beautifully prepared Carter W-1 sitting on the bench that I was going to try this week but I don’t want to take a chance on adding another problem until I figure out what is causing this erratic loss of power and backfire.
Once again, I’m open to all opinions, don’t mean I’ll take all of your advice but I sure will give it some consideration.
Denny Graham
Sandwich, IL

I had a 235 in my 52 with the mallory electronic ignition.. the thing went on a blink and almost drove me crazy because it would not do it all at once but got worse...........it would just die, spit and sputter and then pick back up.........

on the hiway at 65 it would stop running and sometime pick back up after a back fire... I replaced the electronic module in it and never had anymore problem.........I doubt that you have one but a lot of back fire can be caused by electrical rather then fuel..

crack dist for one can cause it.............
also a bad lobe on a cam can do a similar thing..
had this to happen on a dodge with a 383.. thing would be on the hiway, start to sputter and back fire..

I never could find it, my dad in law said Fred, it is in the cam....I would think that would be unusual but..

another deal is that you might have hair line crack in a spark plug that you cant see..not likely but I have seen this too.....

crazy stuff can happen, I installed a tach on a 55, never could finger out why when I took off that it would skip and jump, had a stick..dad-in-law came over and found that when I installed the tack, I had some of the extra wire wrapped around the clutch pedal cause it to short out when I went to change gears.

at anyrate, I know you will be glad when you find it..

I would like to hear what it is in the end that causes all that trouble. I think , putting the new carb on will fix it. Good luck with that---dave

Are you getting any smoke when its running rough? Next trip out, carry a jumper wire and go straight from battery to + side of coil, maybe even second wire to ground side. You will bypass the whole ignition wire harness this way. You might also add a temporary fuel gauge to monitor pressure at the carb.

Nothing mechanical will come and go, its either broke/worn or its not.

A lean condition will cause backfires and no smoke, so fuel pressure or delivery is a real possibility. Joe

No smoke Joe, "nothing mechanical" stuck valve would cause the backfire but wouldn't account for the drop off in power and would still be there when I was at full throttle. I ordered a new fuel pump and a kit for this one yesterday when I got home. But I just don't see how it could be that since it will run at highway speed with the trottle wide open. Ya got a point though with the fuel gauge. I have to make new fuel lines anyway to switch over to the Carter so I could rig a new line with a tee while my Rochester is still on it. Think I'll run down to the flaps and see if I can pick one up.

Denny G

i would loose that rochester carb in my opinion they are worthless
philip

Worthless Phil, naw, plagued with problems yep, that's the whole idea behind my switching to the Carter W-1. Gonna try it for a while. Don't think the 'B' is what's causing this problem though.
Workin' on the pressure gauge as we speek Joe! Got everything I need on the shelf cept for the fuel line and a hole to get it in the cab so I can watch it while I'm on the road. Think I'll just drive it round the block for 10 or 20 miles during the test so the towing bill won't be so big if it quits on me and I can't make it back to the garage!
Denny G

Denny:I'm sure you check these but you do have the insuator block under the carb and you check the heat riser to make sure it's open As you discribe it only happen when the engine is hot. When you went to visit your friend for 30 min. the temp under the hood went up possible the gas in the carb bowl is perolating causing the float to rise shuting off the fuel.Also I don't know if the condenser in the disturbter can open up when hot causing a problem Just a thought

Paul

I had the same problem with my '66. It would do the exact same thing as Denny's.

I think they have it already figured out..
takes about 10 min to pull the carb,, should be easy to figure that deal out.. change carbs.. and see

most might disagree with me, not the first time,,,, a carb is usually the last thing that goes out....

I never had any trouble with the carb on my 235, and drove it almost 9 yrs .. ever where..

i got 2 b rochesters in a box i have put kits in them tweaked them
and just when you think you got one right and running perfect
take off over a rough road or driveway and shake it up good it
either sputters and dies or pours gas down the motor a good way to get a fire i hate them. im putting a new holly webber on mine
a carb can be rebuilt a thousand times but its only new once.
hope the w1 does the trick phil

best little carb in the world

click here

If carb is not the problem I would change the coil and condenser and maybe the ballast resister, I have seen them brake down after they get warm and cause these same problems.They are hard to diagnose because they work fine when they are cold,and show good when tested and yet they begin to fail after they run for a while.

that was my case...tested good according to the guide line from mallory but..............thing almost drove me crazy,
I was told to check ever thing from fuel to ignition switch..

Much as I would like to blame the Rochester B for everything from global warming to the national debt ☺ ☺, I really don't think the B is at fault here.

A backfire through the carb occurs when you have fire in a cylinder and an intake valve open.

Even though the wires were replaced a few thousand miles ago, I would look very hard at both wires and distributor cap. We once had a situation where the carbon in a set of modern spark resistant wires developed an airgap in one wire. The airgap acted as a capacitor, thus slightly delaying the spark to that plug. Would often run fine at cruise, but would backfire violently through the carb at light load (trying to maintain speed on an incline). A carbon track or light crack in the distributor cap could have the same result.

Let us know what you find.

Jon.

The world was able to live (in safety) without cell phones until the electronic ignition was invented. Soon after this invention, it was necessary to invent the cell phone to call the tow truck ☺

Jon.

I think metal shaper got it. Since the carb checks out, and every thing in the fuel line does too, and just about everything else was checked and nothing had failed. That only leaves the coil and the rest of the electrical ignition system(as far as I know, there could be more serious problems???? I'm a novice mechanic) so it could range from a loose wire or one being shorted out on the firewall from cut insulation to the coil getting hot and shorting out. I am not sure how keeping the pedal to the floor would keep the engine running, but everything else checks out, right?

I had almost identical symptoms with a failed ignition condenser on my daughter's Triumph Spitfire. The engine would run like a molested monkey at full throttle, but any drop off wide open resulted in an immediate cutoff. I drove it home about 5 miles with the tach pegged, and used the 4-speed transmission to get whatever road speed was appropriate. Most of my neighbors thought my kid was acting up, so I had to field several concerned phone calls that night!
Jerry

Remember guys the thing will run at highway speed 50-60 with the pedal to the floorboards acts kind of retarded and low on power but it's the only way it will run without balking or backfiring. That kind of eliminates an electrical problem.

I just picked up some rubber fuel line a few minutes ago and I'm putting together the fuel pressure gauge. Have to make up a new metal fuel line from the AC filter to the carb with a tee in it for the gauge. I’m gonna do a temporary mount of the gauge in the cab where I can monitor it the next time I get the nerve up to take her out on a jaunt. If the pressure falls off or is erratic next time she acts up then I'll look into that further, if not I can eliminate that from the equation.

Cross firing was one of the options that was on the list yesterday when I got her back to the garage Jon. But it seems to clear up once I was back home and wasn’t acting up while I was testing checking things out. And again, how could full throttle affect a problem with the ignition wires?

I have been thinking of buying a spare coil just to have around but I haven't had a chance to look for one, are 6v coils available anywhere anymore???

Shaper thanks but, one more time, it's completely stock; it's a 6v system, no ballast resistor.

Hey Jerry, thanks for stoppin' by. How would you account for that behavior? Doesn’t seem logical the a full throttle condition would effect a bad condenser either.

Denny Graham
Sandwich, IL

distributor problem - vacuum advance bad maybe

Bill

Denny - distributor cross-firing still needs to be checked. Advance at WOT would be different than at part-throttle. Thus an intake valve partially open at part-throttle misfire might not be open at a WOT mis-fire.

When we had the carbon gap problem, the engine would NOT misfire under WOT conditions.

Jon.

She crankin the advance around just fine Bill, and for course I'm watching it advance on the mark with the timing light in it.
Denny Graham
Sandwich, IL

watching when yer drivin and the intermitant problem happens?

as someone who depends on an old truck for daily transport, I have lots of spares on hand, and with your symptoms I'd pop in a different distributor and carry on, unlikely to experience the same problem again ... theories are fine, but it don't get me to the store

Bill

Interesting Jon, like I replied to Jerry, what would account for that??? I'm gonna start eliminating one thing at a time till I hit the right spot.
Bill I do have two more distributors that I have restored. If I get to that point I can swap one of them out but it's pretty simple so I would think that if there is a problem with the distributor it would be obvous.
I think it was Jerry that brought up the distributor machine, sure wish I had one of those Sun testers that they junked at all the high schools a few years ago when they eliminated the auto shop classes.
Denny Graham
Sandwich, IL

It just sounds like an electrical problem to me. If its fuel its in the fuel pump.....but I have no idea which. I will bet when Denny figures it out we'll all say

Thanks Chip, I might just end up using that distributor you sent me last year to solve this. gotta take it a little slow, I'm still getting over food poisoning from last weekend.
Denny Graham
Sandwich,IL

The only time I had a bad backfire problem was a bad cam. Put that on the "maybe it's the" list.

Hey Big, intermittent, rules out the cam, gears etc.
Denny Graham
Sandwich, IL

I would start with the condenser, then move to the coil, then distributor. My boat used to run similar (low on power, then backfire like someone kicked it in chin), turned out to be a combination of condenser and coil (changing one only reduced the symptoms).

Good Luck

Denny,
Just another vote here for ignition. I had an old Mercury that acted a lot like you're describing. I could rev the snot out of her in the driveway, but take her out on the highway under a partial load and she'd buck and spit unless it was wide open.
The previous owner had just had a garage do a complete tune-up so I didn't think ignition. Went through the carb, filter, pump, etc, all to no avail. Finally after a lot of suggestions, I dug into the distributor. To make a long story short, even though it was brand new and I couldn't see any cracks or carbon traces, the cap was at fault. A new cap and she ran like a champ.

Bob

Well the survey seems to be in favor of the ignition, that seems illogical to me but I've got a couple of caps and new condensers here. I still haven't had a chance to look for a coil.
I need some time to do the testing, one thing at a time you know or else I'll never be able to put my finger on what the problem really was!
Thanks for the input guys,
Denny Graham
Sandwich, IL

Have you considered something in the gas tank, such as rust or particles floating around? Or even water in the gas tank? My initial thought would be to check something like this since the problem is so intermittent. I've never had this problem myself, but I have heard of fuel lines getting clogged or partially blocked with things moving around in the tank, causing the vehicle to run fine otherwise. If you turn off the engine, let the truck sit, and start it up again does the problem go away?

If you're not driving the truck too much how often do you fill up the gas tank? It could be possible that you have bad gas in the tank as well.

Just my $0.02... and I'll be curious to know what the problem is too!

~Neil

Denny, you are just going to have to start changing parts and doing a lot of test driving. You have to be brave!!!!

I worked for a year and half trying to get a bad miss out of my 250. It would only act up pulling a long hill, worked great everywhere else, hot or cold. After changing intakes, carbs, ignition, cam, lifters, drive shaft, one axle shaft (bent slightly) I finally changed the head. It turned out the porting I had done messed with the air flow intake to exhaust ratio, the exhaust could flow the same amount of air as the intake side, and on a long hill with plenty of throttle, the exhaust was sucking the intake charged air out when the cam lobes were over lapping. Dad has a Superflow air bench so after rechecking the numbers and talking it over with some head porting guys, they confirmed what we suspected.
Now with a stock head, it runs like a top. I never would have suspected the head, but I was out of ideas. It ran great at full throttle and around town, but try to pull a hill and you would drop from 65 to 35 before getting to the top! It shock so hard, that the Lokar shifter bracket broke.....

Joe

Haven’t got much time today, guitar practice this morning and lesson this afternoon. But I snuck in an hour to check the plug wires and cap again. Used a 10x loupe on the cap, absolutely clean, no cracks, no traces, no burned terminals inside.
The wires are new copper core and even though they were lighting up the plug tester, I checked then for continuity with a DMM. Found one that was open and when I pulled it from the cap the brass had sooty green corrosion on it. This was the type that has the barb in the center that you poke into the center of the wire to make contact and squeeze the two barbs on the side in to hold it in place. I cleaned it in Tarn-X which is my favorite way of cleaning brass, then cut back an eighth of an inch to assure clean core and soldered the center lead just to make sure. All the rest of the wires checked out fine. Even though it seemed totally illogical that this could be the culprit, I at least, actually found something that was out of kilter. And it did go along with a lot of the opinions that it’s ignition, which I still can’t quite buy.
She started first turn over with a 1/4 choke, one pump on the pedal then off and idled nice and smooth and strong about 700-800 rpms. A couple of minute warm up and I took it for a ride around the block and it was running just beautiful. The temp was coming up to about normal so I turned out on to the highway. I got about a hundred yards down the road and I thought I’d run out of gas. Down shifted, pulled the choke out and started pumping the gas, found a wide spot and swung a U turn and full throttled it back to the house in second gear with the choke out. When I pulled into the garage it was idling about normal a little high but the choke was pulled out more than half way. I pushed in the choke and she idled down and died.
I popped the bonnet and the AC filter/sediment bowl in front of the carb was full. I noticed that the carb base was sweating quite profusely, humidity today is only 63%, dp is 61 and temp is 74. The carb base was as cold as ice when I touched it. I noticed a couple of weeks ago when I pulled the ‘B’ apart to check the innards that the cast iron base had a lot of surface rust forming in the venturi, this struck me as odd because I had cleaned it meticulously with wire brushes when I had last rebuilt it a year or so ago. Not the outside, just the inside of the throat. From my flying days before the Bendix fuel injection I had a few experiences with carburetor icing. I’m now beginning to wonder if I could be having a problem with icing, a lot of things point to that.
Okey dokey, we can scratch that one off the list!!! She’s been sitting for the half hour or forty-five minutes that I’ve used up composing this trash. The carb base is now warm, as is everything else, just warm, where you can lay your hand on anything on the engine and its just warm to the touch. Started her up as I usually do when she’s warm, that is, with out touching the throttle, she started then immediately died. I half choke and pump it a couple of times, she starts, runs smooth, push in the choke and she dies, pump the pedal a couple of pumps and she catches right up but then dies off, with choke out and idling I slowly feed throttle and she dies. Low speed circuit???? All of that was clean and open last week when I checked it.
So I’m back to the first line, “This one really has me baffled.”

Gotta go work my frustration out by beating on the guitar, get back to this in the late afternoon.
Denny Graham
Sandwich, IL

Denny: Have you checked the rubber hose from the tank to the fuel line the inside maybe coming apart and blocking the flow it may look good from the outside and while your at it you can check for dirt or water in the tank Just a thought.

Paul

I remember when I started this I just don't remember why.

Denny, I have no idea why that spitfire acted that way, but it did it twice in the relatively short time my daughter drove it. It would be terribly hard to start, and when it did finally catch, full throttle was the only way it would continue to run. In both instances, changing the condenser was all that was necessary to cure the problem, even used the same set of points!

Yours sounds more like a fuel supply problem or a piece of trash floating around in the carburetor. Have you tried running a temporary supply line to the fuel pump out of an auxiliary tank? I'd suggest a test drive with a 2-gallon gas can in the passenger's side floorboard and a piece of rubber fuel line to the pump inlet.
Jerry

Denny:The reason you have moisture on the carb is the same as clouds high and low presure I don't know how much air 216 cu. in.can take in at high RPMs with the thottle wide open but when you draw it though an 1 1/2 opening it's going to cause a low presure area making condensation that could make ice in below zero weather but not on 80 degree day

Paul

My 65' had a similar problem. It would backfire after driving 20-30 minutes...Finally found that the ignition switch would heat up and arc across the poles behind the dash. I replaced the switch and it solved the problem. It had the original bakelite switch. I found the problem using a timing light. The light would randomly miss a beat indicating an electrical problem.

I had a similar problem with my '47 F**D. I thought it was the ignition switch also, so I installed a new one. Things worked good for a few months then the gremlin showed up again. It ended up being a bad wire connector that connected to the back of the ignition switch. The crip looked good but I think that things would wiggle and then the wire would go open causing the car to buck, stumble ect. The car has the original steel wire, not copper. I ended up putting all new ends on each wire and have been driving it without trouble for 2 months now. Just something I learned after about pulling out every hair on top of my head.

Oh I replaced the Rochester with the Carter W-1 and guess what Jon, you were correct in saying, “Much as I would like to blame the Rochester B for everything from global warming to the national debt ☺ ☺, I really don't think the B is at fault here.” Yep the problem was still there.
OK Jerry, this one is for you and that distributor machine of yours. The Vacuum Advance, advances. Just how far, I can’t tell exactly, but it looks like all the way, drops off at full throttle. On the bench it stars at around 6 or 8 inches will max out at around 16 or 18 which looks to be about 10deg but it will only stay up there if I keep pumping fast, she bleeds off in about 3 or 4 seconds when I quit pumping. That taint right, is it? Shouldn’t it hold 18 inches pf vacuum till I let it up? I do believe I looking at a bad Vacuum diaphragm. I have another one on another distributor but it leaks so bad I can't even get it to hold past 5 inches and it won't even move the plunger.

When you think about it, it’s the only thing that is related to the throttle position especially at low power settings and becomes less of a factor as you load the engine or use higher throttle settings.

This would account for the fact that I could run it home at high throttle settings yet had troubles below1600 or 1800 rpm.
Well I got a new advance coming but won’t get it till next week. Looks like it’s gonna be a slow weekend, that’s alright, it’s supposed to rain all weekend any way.
So what do ya think Jarry???
Denny Graham
Sandwich, IL