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Back And Forth Shaking Started While Accelerating In 1St Gear


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I had 4 days that i did not used my car since last sunday. Car was cold! pull the choke to start it and left it on for 5 minutes. I have the idle set up at 900 RPM with headlights on. Once i backed off the choke cable, the car presented the following problems:

 

1. Shaking back and forth when accelerating in 1st gear.

 

2. Backfire / Popping in 1st and 2nd gear.

 

Turn back home: the first 3 plugs from the front carb were okay. the last 3 ones were black. I am using NGK BP6ES spark plugs and Castrol 10w 30 engine oil as damper oil for both carbs. Am i missing something here? I did a vacuum test spraying carb cleaner to each an every hose near the carbs and at the brake booster and did not noticed any change in idle.  

 

The idle mixture knob / Screw is turned counterclockwise 3.5 turns which in my opinión is a lot. Should i keep turning until 4 to richen the mixture or is there something else i shall check?

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While I don't have SU carbs on my car, your post suggests several things.

 

First black plugs indicate rich running, so increasing the idle mixture would enrich an over rich mixture even more.

 

You idled the engine with the choke on for 5 minutes. SU carbs actually don't have a choke per se, they have an enrichment function. Again idling with enrichment for an excessive period would tend to lead to carbon fouling. It is not unusual to see some carbon fouling while running rich that burns itself off after a few minutes of normal operating conditions.

 

The fact that you found a difference between the front and back cylinders indicates different operating conditions between the carbs. Either that or you fouled the back plugs so bad that they were miss firing once enrichment was turned off and you were essentially running on three cylinder. Check enrichment functions work identically on both carbs.

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2.5 turns, like the DVD shows.  Turn them towards the passenger's side, all the way up, then turn them out towards the drivers side 2.5 turns.  I live near the Gulf of Mexico and have mine at 2 turns out.  I've never been to Panama but it seems like I've read that's a tropical climate and choke isn't needed.  My car stays in 60 degree garage and my chokes are only pulled for 1 minute at the most.  Sounds to me like you are using the choke as an idle adjusting mechanism.  Are you using an air synchrometer to balance them individually with the screws by the dome tops?  That's the way to set the idle.  Your rear carb is out of adjustment or the float level is too high which could occur during shipping, it's covered in the DVD.

 

Maybe watch the DVD again, it's extremely helpful.

 

 

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Got an old school mechanic who came to my house today and inspect the car. After lifting the valve cover, He found out that the engine valves were too tight and will need to adjust them all. He did not brought his feeler gauge and will need to take care of that on monday. He is quoting me US$100 for the following:

 

1. Valve adjustments which according to my Schneider 274F cam should be set to  0.8 and 0.10. Am i correct?

 

2. Timing Chain and distributor adjustment.

 

He also noted the car is leaving black residues out of the muffler due to the bad valve adjustment. Is there any additional recommendation i can give him before he starts to adjust the valves? The shop that installed the cam has followed all the steps mentioned in the Hayes Manual and adjusted the timing to 10 degrees. Maybe here is my problem and after all this adjustements are concluded, there will be no more hesitation in 1st gear and backfiring,enabling me to adjust the carbs to 2.5 turns.

 

Any opinions?

Edited by jalexquijano
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If you drove it much with the valve lash too tight you might have damaged some valves.  "Burned", or warped.  Without feeler gauges though, it's hard to see how your "old-school" guy could tell that the lash was too tight.  I don't know if I'd use that guy.  Why not take it back to the shop that installed the cam?

 

You didn't address John Coffey's post at all.  Could the choke be stuck?  Seems like a carburetor problem.  Three black plugs is too rich, not bad valve lash.  I wouldn't let the old-school touch the car.

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To add to previous post, after pulling the choke, starting it, and pushing the choke lever back, if you can push one of the nozzles up with a finger, then it's sticking. Try Lithium spray grease on nozzle and choke linkage. Good to do that anyway.

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