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I replaced my wiper motor with a new motor from the wiperman. Works great but now my engine has developed a sputtering backfire. Cranks and idles fine, adding throttle constant it backfires. Any clues? Washer port plugged.

The 2 new things I did was replace the wiper motor(thinking a vacuum leak
and I put 5 gallons of high priced gas in. It was about to run out.
I checked and replace the fuel filter. The fuel pump filled it quickly and
is operating fine.
Vacuum leak , bad gas or something in the carb that got sucked in from a low tank. Are my thoughts.

If backfires when let off on the foot feed, exhaust manifold leak.

Ed

Thanks Ed.

If it backfires when you step on the gas, often it indicates a timing problem...usually this is backfiring through the carburetor and it can also be caused sometimes by an air/fuel mixture that is too lean. A vacuum leak can cause this. You're allowing too much air into the engine and that dilutes the air/fuel mixture.

ah,, it`ll sputter backfire with constant gas. Not during idle. I tried adjusting the air /fuel mix but no change.
I need to check the timing. Seems an odd coincidence with the wiper motor recent.

The vacuum wiper motor makes me wonder if a vacuum loss as a result of the change in the motor (vacuum wiper motor) is the root cause. Maybe a break in the rubber hose or something? This can also affect your timing as there may not be enough vacuum present to make the vacuum advance on the distributor work as it should.

I think I`ll bypass the motor and see if that fixes it.

If a rubber hose connects the manifold vacuum and the wiper motor, check it too. I've had these crack where they fit on to the nipples at either the manifold or the motor.

High octane gas may be part of the problem. Use the octane selector to advance the timing to see if the problem goes away. If it doesn't' go away, all you need to do to restore the original timing is readjust the octane selector to the original position.
Do you currently have the timing set with the needle on the ball (5 degrees before top dead center)?

Thanks. Its the same gas I`ve been putting in. Just no ethanol. The hoses are all brand new.
I`ll check for cracks. What I`d like to try is a different tube for the manifold hose. Its copper and not steel.
There may be a crack there. Are those nuts sold with a steel tube and bend?

Guit,

Remember when Ol' Roy had the backfire problem back in December? It turned out to be a load of bad gasoline from Sam's Club. There were stories around the same time of modern cars' engine being ruined by bad gas from Costco.

Anyway, drain the tank and refill it or, hook up a rubber hose to the fuel pump and stick it in a gasoline can filled with fresh new gas of the kind you normally use (from a different station, of course).

See if that helps.

Otto. Yes, its not the wiper motor or a vacuum leak. I switched all that back to the way it was just now. Still back firing.
I will drain the fuel out tomorrow. Put some fresh from a different station. thanks all. I`ll let ya know.

If its not the gas and it is not a vacuum leak from the wiper motor, then it is time to break out the timing light and see if the needle is on the ball (5 degrees BTC). The wrong timing will cause a backfire.

Yep, if its not the fuel ,then it must be the timing. I go on the more likely than not category.
I don`t know how it would change timing just sitting in the quazi hut. But stranger things have happened.

Drained the tank and new in. The backfire subsided a great deal to almost gone.
Question the knob on the firewall side of the DIST is for what? Octane or vacuum advance adjustment?
thanks all!

That's great. I was in the same boat as you thinking something had gone wrong with the points or condenser etc etc and it turned out to be that crap gasoline that was brown. Unfortunately the picture didn't post because there's something wrong with the site but the gasoline that came out of my truck looked like iced tea.

The knob on the distributor is called the octane selector. But what it does is advances or retards the timing in case of such an occurrence as you experienced. You got some really low octane fuel you retired the timing if you have good or high octane fuel you can advance the timing without having to move the distributor itself around. But if it was running fine before make a note of where it is so you can move it back after you clear out all of the crummy gasoline.

I put a little bit of marvel mystery oil or a bottle of Heet in the tank just in case there's any water in there from the crap gasoline you got. That's usually the problem with bad gas is water.

My fuel was clean looking. I`m thinking it had water or not 91 octane fuel.
Adjusting the octane selector in ward adjusts the octane up or down?

I am happy you found the issue, but why are you using 91 octane and not 87 octane ?

Jon

The knob in the pic is the grease cup.
The slotted hole with the hash marks is the octane selector. It screws to the dist pad. You can fine tune from 0 deg to 10 deg advanced or retarded and return to the original setting anytime.
Hope this picture comes through!

Duh, I'm an idiot. He asked about the knob but in my mind I was thinking about the octane selector pointer.

91 has no ethanol?

Jethro, Thats a great pic. I won`t be able to see that on my engine I don`t think. I`ll look. A grease cup?
Hmmmm. should I unscrew it for any reason? Thats the knob I was speaking of. So that has little bearing?
But if this helps anyone.

The fuel was purchased from a very small town and I don`t think many get 91 oct at this place.
It must have been a low tank at the gas station. It took it about 2 minutes to stop back firing. The new gas was purchased
at a bigger town. (and there ain`t many close to me)
It cranked before with just showing the key to the engine. But after the bad gas, it would crank but not
as easy. Now, with new gas its back to starting really quick. You just have to barely bump the key and wham.

I`m not so sure now about the gas being bad. Its still backfiring some. I`ll have Dan ride by and check the timing for me.
Should I be using 87 oct?
I `ve been so into body work, I`ve not looked at the motor much.
But I noticed a milky (water/oil) on the dipstick and vent cap. Very little mind you.
But there. The top of the valve cover has some as well. I don`t drive the truck at all.
So it sits and idles mostly. I hope its not a head gasket. The oil on the stick look clean and clear. The milky substance
is collecting at the top of all I mentioned. Dipstick, vent cap and valve cover. About half a fingers worth total.

If you don't drive enough to boil the water out of the oil, it will show up in the valve cover, top of the dip stick, etc. I don't use 91 octane in anything I own, all running on 87 octane.

Guitplayer... screw that cup off and fill it with whatever grease you use and screw it back on. Each time you screw it in some it lubes the distributor shaft. I give it a little turn about every 500 miles or so. Some do it at each oil change. Lots of folks never did it back in the day because they didn't know.

Thanks guys! I am losing ZERO coolant so fingers crossed no head gasket issue. I just drive this Panel truck around the
yard. So it does not get "driven".
I`ll try using 87 octane in my 235. Wondering now for my 327s what's best.
Ill put some grease in the cup today!

In any engine, use the lowest octane rated gasoline that your engine will operate on without knocking, pinging, dieseling, or running-on. There is absolutely ZERO benefit to using premium fuel in an engine that doesn't require it (despite what the advertising would have you believe).

And higher octane fuel will often cause the fuel level in the bowl to be too high, causing the engine to run rich.

A hundred years ago, Stromberg specified float adjustment settings if using higher octane than for which the engine was designed. Generally, Stromberg would specify an "initial" setting based on the octane, and a final fuel level setting. Generally the initial setting would be close, but the level setting was the one desired.

Those old low compression engines were much more forgiving on settings than modern ones. If the settings were worth changing on 6.0 compression engines, certainly worth checking on more modern engines.

A good "rule of thumb" is the needed octane number should be about 10 times the compression ratio. If I remember right (and if I didn't, someone will point it out ), higher compression 235's were 8.0 to 1, whereas the lower compression 7.5 to 1.

Thus 75~80 octane should be about right.

EDIT: the post by Otto above is correct, if real gasoline:

87 octane has 117,600 BTU/gallon
91 octane has 117,600 BTU/gallon
93 octane has 117,600 BTU/gallon
and (if you can still find it)
Sunoco 260 has 117,600 BTU/gallon

Jon

Guitplayer, do you know the compression ratio of your 327? if it's a low output with 9.5:1 or lower, you can run 87 octane.

I do not know that of both of them. The one I have papers on ,the engine and it would say.
That would save me a great deal money at least to me to be able to get 87 octane .

Just fill it up with 87 at the halfway point and you'll end up with 89 octane or so. If it doesn't knock or ping, you're great. Keep doing that and you'll eventually end up with 87 octane in the tank. If it isn't knocking under load, you'll be saving 50 cents a gallon or more. $10 per tank or so.

Just idling around never gets the engine hot which causes condensation to form in the engine and exhaust system. You really need to run the engine at a fast idle for about 1/2 hour so it can burn all the moisture out. Short trips do more harm than good...if your just trying to keep the battery charged, get a battery tender/maintainer.

Mike B

I will definitely do that. Thanks!

Thats great news! I just crank the engine up now and again. I like to hear it run.
Its not road worthy..yet.

I hate dealing with ethanol and the only e-free gas in my area is 91 octane. I have heard mixing a bit of diesel will lower octane. How much per 10 gallons would be about right?

Same here. Contains Ethanol, Some ethanol and No ethanol(91) Confused I guess.
Should I run any Ethanol?

How much of a smoke screen you want?

Zero diesel added to 10 gallons of gas will be perfect in that example.

You can remove ethanol by adding water to ethanol gas. As I recall the ratio is 15 parts gas to one part water. Add a little cheap food color to the gas to make it more visible. Mix the two and shake the container (preferably a clear plastic jug). Let it sit overnight. In the morning you'll have 2 distinct layers. One will be gasoline (on the top) without ethanol and one will be water and ethanol mixed together. Siphon the gasoline off and take the other to a haz mat disposal place in your community. Hydrogen bonding has just happened here.

Now, what will you have? Gasoline with a lower octane rating. 87 octane turns into roughly 81 or 82 octane without the ethanol so you might want to start with 91 or 92 octane before you do this. Ethanol adds octane to unleaded gas and it is added just before the fuel is delivered to the gas station (so it won't absorb water).

Guit,

Ethanol was mandated in the Metro Atlanta area in about 2007. Every single vehicle I own is an antique and has a carburetor. I use ethanol fuel in all of them simply because finding ethanol free is somewhat difficult, and if you do find it it's over a dollar a gallon more.

All of my vehicles including the 1939 Packard and my 1950 Chevy truck all burn 87 octane without any problems at all. The Cadillac and the Toronado get premium. They both knock if I use lower octane. The Cadillac knocks because I advanced the timing beyond factory specs and the Tornado of course, is a high compression engine that requires high octane fuel.

Other than that as long as you don't let the ethanol gas sit around in there and go bad, you won't have any problems but that means you have to drive your vehicles.

If they're just going to sit around doing nothing, like that one with the water in the oil that just sits around and gets started once in a blue moon, by all means use ethanol free fuel.

I should also mention that the ethanol has not hurt the accelerator pump in my YF carburetor. Some people seem to think it ruins the black rubber ones. It's been over three years and 8000+ miles since I rebuilt the carb and it still works like a charm. I think the key is keeping your carburetor filled with fuel so the rubber doesn't dry out. You have to drive it to do that or at least run the engine frequently.