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Discussion Starter · #1 ·
I have a problem with my rebuilt* 289 for my 68 Mustang. To achieve anything close to a smooth idle I have to set the initial timing (vacuum advance plugged) to 40 degrees BTDC, this is also were I achieve maximum vacuum. I can only achieve a maximum vacuum of 17 psi, which to me seems low. At this setting there is some slight pinging under hard acceleration, from 3rd gear; which to me implies the timing is very close to optimum. At city and highway speeds the engine performs very well, the only problems I have is I can't get a good, smooth idle, there is some hesitation when accelerating from a full stop, and sometimes it tries to die when shifted in gear. The poor idle/low speed performance suggests a vacuum leak but I haven’t been able to locate one using carb cleaner. I even checked for a possible vacuum leak to the lifter gallery by pulling all the plugs and looking for one that shows evidence of burning oil; but, all eight plugs appeared almost identical.
The distributor was rebuilt and tested on a distributor machine so the advance curve and performance should be correct. I thought the TDC mark on the replacement harmonic balance may be off so I built a piston stop to locate TDC, I did find it to be slightly off, TDC actually occurs at the 6 degrees BTDC mark.
I am beginning to suspect the crankshaft and cam are not aligned and the crankshaft gear is off my one tooth.
I am about ready to pull the timing chain cover and take a look, but before I do this is there anything I have overlooked or could try before pulling the cover? Any suggestions would be greatly appreciated.
*Block bored 0.04” over, new internals, valves, new stock cam, Autolite 2100 carb (rebuilt by pony carbs), Pertronix ignitor II, coil, wires

Jim
 

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Before you take anything apart. Remove the vibration Dampner and examine it. If the rubber has rotted, the outside ring may have moved, and changed where the timing marks are. Makes it appear your timming is wrong, when it is not.
 

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#1 cylinder on a 289 is on the passenger side, not the driver's side like on GM cars...I've made the mistake since I own Fords and GMs...it's an easy mistake to make!
 

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Discussion Starter · #5 ·
Thanks for your repllies. I am positive that the correct cylinder was being used for the timing light. I forgot to mention the the harmonic balancer is brand new, even so I have check the outer ring and it has not moved. All of this is what makes be believe my engine rebuilder got the crankshaft gear one tooth off!
 
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