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Username Post: 235 bucking,        (Topic#353635)
Alegm 
Poster
Posts: 25
Alegm
Reg: 01-05-13
10-27-18 09:08 PM - Post#2749742    

My car is beginning to be a real pain to drive. I cannot get a good idle from it and when I'm coasting, the car starts jerking back-and-forth. At low speeds, this jerking can get pretty violent if I don't release the clutch. it got a YF carter automatic choke on my '58 235 6cyl. Is it possible to have a vacuum leak here but I sprayed starting fluid in likely leak areas and the only area that caused an increase in rpm was on the choke stove in the exhust manifold.
When I atach a vaccum gauge the needdle doesn't stay steady as they say it should be. Here a link to the video
https://www.youtube.com/watch?v=p2MlsLpnbBs
Any idea what may be causing this??
maybe a valves problem?



 




DonSSDD 
Silver Supporting Member
Posts: 6908
DonSSDD
Loc: Nova Scotia, Canada
Reg: 08-21-01
10-28-18 12:50 AM - Post#2749750    
    In response to Alegm

Try some Sea Foam in the gas and use some premium fuel. Avoid ethanol if possible. Take it for a drive on the highway at about 70 MPH for an hour to get it nice and hot.

That should clean out any crap in your valves and carb system. If nothing changes, let us know.

I'm not extremely experienced in vacuum, but that needle bounce doesn't look that bad to me. If you have been doing mostly city driving at speeds below say 40 MPH, a good hot highway drive may clean things out.

63 Pontiac Parisienne Sport Coupe(CDN Chev mechanically (409, 4 speed),62 Bel Air SC (sold), 59 El Camino (sold), 62 Bel Air SC(sold), 63 SWC Vette (sold),
Member #2194


 
58Yeoman 
Poster
Posts: 31

Loc: Burlington, Ontario
Reg: 12-22-15
10-28-18 05:19 AM - Post#2749754    
    In response to Alegm

How long has you engine had this problem? Did you do anything (ignition parts changed?) before this issue started? I have a '58 with a 235 and had a similar problem. Figured out that the rotor installed by the PO was for an earlier 235 that has a smaller distributor cap. The rotor electrode was too short to properly activate the electrodes in the distributor. The car would run but stumbled when under load and when idling.

1958 Chevrolet wagon (Yeoman)
1958 Belair (parts car)
1961 Impala convertible


 
Dave in VA 
Contributor
Posts: 138
Dave in VA
Age: 68
Loc: SW Virginia, USA
Reg: 03-11-18
10-28-18 05:38 AM - Post#2749756    
    In response to Alegm



"Knowledge is Good" -- Emil Faber

U S Navy MM2 1970-75 USS Canisteo AO-99, USS Miller DE-1091 (The Champagne of Ships)

1950 Styleline Deluxe 2dr, mostly stock, driver quality...new to me 3/18
2016 Equinox LTZ
2017 Silverado LTZ 6.2


Edited by Dave in VA on 10-28-18 06:50 AM. Reason for edit: No reason given.

 
Alegm 
Poster
Posts: 25
Alegm
Reg: 01-05-13
10-28-18 04:47 PM - Post#2749802    
    In response to DonSSDD

I dont think is a problem of not driven the car at high speeds since I make a 90 miles run at 75 mph at least once a week.
i've tried combinations of all kind of gaping the points and the plugs.... and I've found that what it likes the most is gaping the plugs close to .40(gaping them less than .34 make them dirty)....the only way i've notice that stops these problem is retarding the time at the point that the egine hesitates when you suddenly push the gas pedal wich is basically not a solution



 
Alegm 
Poster
Posts: 25
Alegm
Reg: 01-05-13
10-28-18 08:02 PM - Post#2749824    
    In response to 58Yeoman

how did you find out the problem in the distributor cap??



 
cahartley 
Contributor
Posts: 354

Loc: Central Wisconsin
Reg: 01-16-14
10-28-18 10:18 PM - Post#2749828    
    In response to Alegm

If you mean it bucks when in gear and rolling to a stop my '59 does that too but only before the automatic choke is off.
Ditto on opening the plug gap to .040".
It also helps to advance the timing but I can't tell you how much.
I can tell you I advanced the timing on mine until the ball was nearly hidden at the right side of the timing window.
I don't know far one can go without getting into starting difficulties but it's happy where it's at right now.

www.youtube.com/cahartley7


 
58Yeoman 
Poster
Posts: 31

Loc: Burlington, Ontario
Reg: 12-22-15
10-29-18 04:18 AM - Post#2749841    
    In response to Alegm

I discovered that the engine ran better when I temporarily by-passed the firewall resistor, which indicated an electrical issue. I bought new points, condenser and rotor and noticed rotor was different. When I installed new rotor, problem was solved.

1958 Chevrolet wagon (Yeoman)
1958 Belair (parts car)
1961 Impala convertible


 
Alegm 
Poster
Posts: 25
Alegm
Reg: 01-05-13
10-29-18 06:39 PM - Post#2749948    
    In response to 58Yeoman

today someone came with the idea that the jerking may be caused by "excess clearance in the rear gears"
is that possible??



 
ragtp66 
Contributor
Posts: 710
ragtp66
Reg: 12-09-07
10-29-18 07:08 PM - Post#2749953    
    In response to Alegm

Check the distributor shaft for excessive play you should have a little bit up and down but NONE side to side. I would also check and make sure both the vacuum advance is working properly and that the weights are free and where they pivot are not loose and worn out. Try taking a spray bottle with the engine running and lightly mist the plug wires and see if you either see or hear any arcing. If your not using a AC Delco cap and rotor I would replace them as well. Simple as it sounds also check that your wires to coil are hooked up correctly. The wire from the distributor goes to the -(negative) on the coil the + goes to your ballast. They will run if hooked up backwards although not very well.


Toys:
1958 Impala 2dr Hardtop Under Construction
1966 Chevelle Malibu Convert M20/350 Aztec Bronze
1987 Sea Ray Pachanga 22
2002 Cadillac Escalade EXT Parts chaser
2007 Trailblazer SS -gone and missed


 
Alegm 
Poster
Posts: 25
Alegm
Reg: 01-05-13
11-04-18 03:38 PM - Post#2750458    
    In response to ragtp66

thanks guys... i've bought a Langdons mini HEi set and the engine runs like crazy



 




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