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hello all I'm a new oldsmobile owner just got a 71 cutlass supreme convertible 350 2bbl 37,000 original miles. engine is original except for carb which was replaced with remanufactured factory carb about 8yrs ago per date sticker on carb. the issue I'm having is it seems to take forever to start once it does it idles fine. I am getting an occasional backfire thru carb on acceleration and it hesitates on acceleration some times but not all the time. does this sound like a carb issue or could it also be something else?
hello all I'm a new oldsmobile owner just got a 71 cutlass supreme convertible 350 2bbl 37,000 original miles. engine is original except for carb which was replaced with remanufactured factory carb about 8yrs ago per date sticker on carb. the issue I'm having is it seems to take forever to start once it does it idles fine. I am getting an occasional backfire thru carb on acceleration and it hesitates on acceleration some times but not all the time. does this sound like a carb issue or could it also be something else?
It could be many things or a combination of things. For the hard starting, before starting, look down into the carburetor and open the throttle. You should see some fuel squirt. If it's not there either the fuel is getting out of the carburetor somehow or the accelerator pump is malfunctioning. If you still have an automatic choke, it should be closed when the engine is cold and open when the engine is hot. If it isn't, fix it. These will likely fix the starting problem. The backfire could be many things. If the 37K miles is accurate the engine probably has little wear, but is still 45 years old. You could check the spark plugs, wires, and the distributor. If anything looks irregular fix it. Whenever you get a vehicle that you don't know the history of it's good to check most things on it. After that you will know what you have and it will probably operate better.
1).... it seems to take forever to start once it does it idles fine.
2).I am getting an occasional backfire thru carb on acceleration and
3).it hesitates on acceleration some times but not all the time.
does this sound like a carb issue or could it also be something else?
As Ozzie said: Could be anything.
My opinion as to what is likely wrong:
1). choke not working or you are not setting it by depressing the gas pedal to the floor once before cranking.
2). Running lean - check spark plugs after a run at the degree of throttle that causes it.
Timing out of adjustment.
Bad accelerator pump.
3). Bad accelerator pump.
Running lean.
Timing out of adjustment.
Need more information to get any closer than that, and that would include clear photos of your engine compartment and carburetor, because sometimes the problem is easy to see.
here's a pic of the carb. I looked down in carb and depressed the throttle I'm getting a steady stream of fuel but not with every depression of throttle sometimes the streams of fuel are kinda like sputtering
That gizmo is the Transmission Controlled Spark solenoid.
TCS artificially retards your timing unless you are in top gear - it's an early, ineffective, and performance- and mileage-robbing emission control that you can leave disconnected.
Just connect the distributor vacuum advance directly to either the ported vacuum nipple on the carburetor or directly to manifold vacuum (whichever runs better).
... And with the irregular accelerator pump flow, I think it's time to rebuild your carburetor.
Okay, looking closely, it looks to me as though your TCS is already disconnected, and your distributor is connected to ported vacuum on the front passenger side of the carburetor.
Also, the air feed for your hot air choke, high on the back of the carburetor, seems like it isn't connected to anything - is the place where the hot air choke draws air in actually able to suck in air?
thanks I could not figure out what it was not use to seeing emission stuff I've mostly owned pre 70's cars. this is my first olds. never knew this 350 was different than a chevy 350. learning knew things everyday love the car though. it's been sitting for a long time the old man who had it hasn't driven it in a year so it just sat. I'm gonna order a new carb and give it a tune up. I'll disconnect that solenoid
yeah your right I may just give it a try I know there's tons of videos on you tube. maybe I'll just get a manual and do it.thanks for your input it's much appreciated
I maintain that with an 8.5:1 350 with a factory cam, especially with a single exhaust, you will notice no real improvement.
There are those who say they have done this and gotten noticeably more power.
When I did it once, when I was a kid, with dual exhausts, I was disappointed that I did not feel any more power.
If you do the math, with a normal 85% pump efficiency, your stock 350, with a factory cam designed for low-RPM torque, at its power peak of about 4,500 RPM, pulls in about 387 CFM of air. Do you really need a 600 CFM Edelbrock or a 750 CFM QuadraJet?
It's cheap and a lot less work to spend the $30 on a rebuild kit and a float and see whether you like the results first.
I'm gonna check all the vacuum lines first all the lines look to be original and dry rotted. this only has 37,000 miles on it but it sat a lot original owner rarely drove it. he had all the maintenance records and it looks like one tune up and several oil changes and a replacement carb that's it.
From personal experience I have felt a huge power difference when the secondary lockout on my QJet prevented the rear air door from opening (I did this deliberately to see the difference, so the primary choke was fully opened and not restricting air flow). If this is similar to the difference between a 4bbl and a 2bbl, it is quite dramatic.
Last edited by Fun71; April 26th, 2016 at 09:55 AM.
From personal experience I have felt a huge power difference when the secondary lockout on my QJet prevented the rear air door from opening (I did this deliberately to see the difference, so the primary choke was fully opened and not restricting air flow). If this is similar to the difference between a 4bbl and a 2bbl, it is quite dramatic.
There is no comparison between a QuadraJet operating on its small primaries (which are designed to work with much larger secondaries) alone and a 2-Jet with it's much larger venturies, designed for full range use.
I'll have to get home to check some information before I say anything about your other point, which is a fair one.
well I changed the plugs they definitely needed replaced 2 front driver side cylinders were black with build up the rest were not bad had a small bit of white residue. changed the plugs and it fired right up still have a back fire on acceleration once in awhile but not as bad and seems to go away after driving it awhile. I replaced all the vacuum lines. it does smell like it's running rich so maybe I'll try some carb adjustments
Have you checked your dwell(if applicable) and timing? The condition of the points? I'd pop a new fuel filter in there also. Look at the plug wires in the dark and see if there are sparks jumping around, they may be cracked and leaking.
yes the points and rotor and cap look good im gonna change out the wires they look pretty old. also when I get time I'll check the timing gotta get out my timing light haven't used it in years hopefully I remember how to use the damn thing lol. does anyone know what my timing should be set at?
The factory timing spec. for your car is 10°BTDC @ 1,100 RPM, which is probably more retarded than it should be for ideal mileage and performance, so I would use that as a starting point and advance from there.
I should add that the conventional recommendation is to set the timing (vacuum advance disconnected) to about 35°BTDC at about 2,500 or 3,000 RPM (and, ideally, to adjust the centrifugal advance, using replacement springs to max out the advance at 3,000 RPM).
ok hope this doesn't sound stupid I know ford's are different and I've mostly have had mustangs I just gave up on them thought I'd try something other than a mustanf. looking at the olds 350 standing in front of it which is number one cylinder? I'm only asking cause I'm watching a video on timing.
ok great I'm not with the car right now guess I could of went down in the garage and looked. I'm gonna try and set the timing when I'm off later this week I'll let you know if it makes a difference. thanks very much. appreciate your time
Backfiring... Not trying to muddy the waters
I wrenched on Buicks in my formative years. They used plastic coated cam timing gears, less noise supposedly. Olds did the same??? I bought a bunch of cheap buicks that had timing issues...replace the timing gear set, clean the gunk out of the oil pan (where the plastic chunks fell when it disintegrated) put it all back together... new life. The slop in the timing chain caused spits/sputters/backfires/...
Easy to check, pull the distributor cap, turn the crankshaft back and forth, notice where the rotor button is and how long it takes to move. If the gear set is tight, should move as soon as crank is turned... Timing light on the mark will also show some "wander" in the timing mark...
just a thought
Backfiring... Not trying to muddy the waters
I wrenched on Buicks in my formative years. They used plastic coated cam timing gears, less noise supposedly. Olds did the same??? I bought a bunch of cheap buicks that had timing issues...replace the timing gear set, clean the gunk out of the oil pan (where the plastic chunks fell when it disintegrated) put it all back together... new life. The slop in the timing chain caused spits/sputters/backfires/...
Easy to check, pull the distributor cap, turn the crankshaft back and forth, notice where the rotor button is and how long it takes to move. If the gear set is tight, should move as soon as crank is turned... Timing light on the mark will also show some "wander" in the timing mark...
just a thought
Unfortunately Olds did the same. It usually requires a bit more than 37K miles for it to get serious, but it is a consideration which should be fixed before it fractures. Whenever time allows replace the cam gear and chain at a minimum.
I'll check the timing this weekend I'm hoping it's just a carb issue. I just got the car so I'm hoping to not get to far into it yet so I can enjoy it for the summer. I'm trying like hell to resist the urge to tear it down and have the heads freshened up and do cam intake carb headers rear gears. but I told myself I'd leave it stock and enjoy it I also told my wife I wasn't going to do anything to it and just drive it and enjoy it lol. I thank all of you for your input it's nice to have a hobby so many others passionate about and knowledgeable about. I will let you know how the timing goes this weekend.
April 25th, 2016, 12:48 PM
