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Discussion Starter #1
last week I drove my 74 spider to work since my pickup was down with clutch problems, it ran great all week except friday on the way home it got hotter than usual and th idle dropped. Saturday I went to pick up my pickup and it would hardly run, backfireing through the carbs and nto wanting to idle. after checking, the only thing I found was the timing was way too fast. I still have the origional marelli distributer and this is the first tiime for any problems. I retarded the spark to the limit on the distributer and now it runs ok again. Any one else have this problem before? Any ideas?
1974 alfa spider with dellorto's and no other changes.
cliff
 

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Cliff, be safe. back to basics. Was the distributor loose when you went to adjust it? If not I would start at the beginning. Crank pully on TDC, Pull the cam cover and see if your cams are timed up correctly and where your rotor falls. Between the crank pully and the cam timing you will know immediately. Ck the chain tensioner. Have you heard the chain banging around?
 

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As Joe said, I'd ensure that the distributor pinch bolt is tight (this is not the nut you loosen to adjust the timing). I'm assuming here that the timing nut was always roughly in the center of the slot? If the pinch bolt is okay, I'd suspect, as Dan suggested, the advance is sticking. The reason I'd suspect this is because you had to retard the timing to get the engine to run right. Burned points or a broken/worn rubbing block will retard the timing, not advance it, so I'd rule out the points.
The easiest way to check the advance is with a timing light. Hook it up and see what the timing is at both idle (F mark) and 5000 rpm (M mark). If the timing does not advance when the engine is revved, or does not advance to the M mark, somethings wrong with the advance mechanism.
If you don't have a timing light, you can check the advance by first removing the distributor cap. Then, try to turn the rotor. It should turn clockwise a few degrees and then spring back when released. If the advance is stuck, you'll be able to turn the rotor counter-clockwise.
 

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Discussion Starter #5
I pulled the distributor cap yesterday evening and checked the3 advance, it does rotate and spring back with no interference. I will check the cam timing this evening and put on the timing light. thank you.
cliff
 

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Discussion Starter #6
turns out that the timing had retarded (kinds like me) not advanced, a little advance and no problem now. I dont know why the timing causes backfireing when retarded, I always thought too advanced would causej this.
cliff
 

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Trained (ex)Professional, , 1953-2018 RIP,
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Ah, Hah! So the timing was retarded. I'd have a look at what I said couldn't be a problem if the timing were advanced. Seems that the points are suspect now. Glad you got it running!!

papajam said:
Burned points or a broken/worn rubbing block will retard the timing, not advance it, so I'd rule out the points.
 

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Discussion Starter #8
I just put in new points, condenser, rotor and cap a few months ago, I guess it could have shaved off the block tho. just never had backfireing with retarded ignition before.
thank you
cliff
 
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