I am in the process of fine tuning my 1967 L79 after installing a newly rebuilt carb. One of the critical adjustments is timing-or so I have been told. When loading the motor up pulling away from a stop or out of my garage, it stalls. Also stalls immediately on cold start. Runs perfect on the road and at wide open throttle. I was advised the timing is the likely culprit. I have advanced the timing, setting it by vacuum gauge and ear ie. fastest idle. It seems to have helped, but the weather is bad and I have not been for a ride just yet. Interesting complication though-I can not rotate the distributor any further as the vacuum advance unit is against the intake manifold. I am hoping it needs no further advance, but if so, is there a solution ?
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Re: C2 Timing-Can't rotate the distributor
check to make sure that the dimple in the dist gear is facing the rotor tip because the gear has a odd number of teeth and if installed 180 degrees off it will cause this problem. -
Re: C2 Timing-Can't rotate the distributor
also, it would help to know the readings you are getting. what is the idle advance at now? what rpm? which vacuum can are you using? get rid of the can for a while and just use your distriutor as a mechanical mode unit. after the car warms up, take off the weights and disconnect the vacuum unit [don't forget to plug the vacuum hose]. then start the car, rev to 2,500, and rotate to about +36. you ought to be able to do that . if the can is in the way, somthing is set up very wrong. try this and re-connect the weights and then go back to idle and tell us the advance [without the can connected] at idle. let us know. also, if you have a hand vacuum gun try the vacuum can and see when it begins to open and when it is fuylly open. etc etc. look forward to hearing from you.Comment
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Re: C2 Timing-Can't rotate the distributor
Werner, What do you mean by "take off the weights"? With no weights how would you get mechanical advance?Comment
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Re: C2 Timing-Can't rotate the distributor
If your think the timing is the problem I suggest you get a timing light and find out exactly where you are. If the timing light indicates you need to turn the distributor and the vacuum can hits the intake manifold not allowing you to turn the distributor then I think your distributor needs to be reset. With the engine at top dead center and the rotor aligned with the number one plug wire lift up the distributor turn it to the left one gear. About 1/8 of a revolution. Reset the distributor. Chect to see that the number one wire is still lined up with the rotor. Now you should have room to set the timing.Comment
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Scarry alternative....
if the harmonic balancer is about to give up the ghost and has 'walked' on its rotational axis, the timing mark is no longer calibrated and All (*&^'s about to break loose.... Yep, it's ususally a botched distributor gear install or an off-tooth distributor alignment, but sometimes it can WORSE....Comment
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Re: C2 Timing-Can't rotate the distributor
john, as usual, my muddle age is showing. i meant take off the SPRINGS. then you get instant total mechanical advance. i read one of the posts about rotating the entire distributor one tooth etc. it seems easier to me to move the wires. if you tried my +36 thing, and the can is in the way, then it might work to change the wire position by one wire. this will allow you to move the distributor quite a bit in either direction. it seems that as long as you put the engine into stopped position, with the rotor pointed to the number one wire terminal and the engine at TDC, as someone described, you can tailor the position of your distributor and this might solve your problem. make sure you are at TDC with the rotor pointing to number one wire. loosen the hold down clamp. rotate the distributor in either direction as necessary to free up clearance for the vcuum can. now, rotate until the nearest terminal is opposite the rotor tip. now insert your #1 wire into this terminal and do the others sequentially and correctly [clockwise 8,4,3,6,5,7,2,]. you should be ok. remove the SPRINGS [and disconnect the vacuum line from the can and plug it] and start the engine and rev it to 2,500 rpm. rotate the distributor, with engine running, to give +36. clamp distributor. stop engine. reinstall the springs. you ought to be in the neighborhood for beginning the tuning process. don't forgt to tell us what the advance is at idle if you use this method [that is idle advance WITH THE SPRINGS but WITHOUT THE VACUUM CONNECTED].that ought to give you the total mechanical advance built into your distributor. mine was at +36 and dropped back to +8 at slow idle. this tells me i have 14 distributor [28 crank] degrees of mechanical advance built into my distributor. i'd like to know what yours is. finally, connect the vacuum. now what is the advance at idle [it ought to be higher than with the springs alone], and at what idle speed? let us know. and if you have a hand vacuum pump, you can tell us at what vacuum your can begins to open and at what vacuum it is fully deployed. you can then compare this to the vacuum your engine generates at idle, and begin to tailor things as necessary for your engine.
my BB runs best with mechanical advance of +12 at idle to +40 under maximum load, and a vacuum can that begins to contribute advance at 8 inches and is fully added at 17 inches. my non load [in the garage] maximum advance at 3,000 rpm [mechanical and vacuum combined] is about +52. car runs fine. under maximum load [no vacuum contibution] it drops to about +40. no pinging [these numbers are correct to within 2 degrees]. not a race car but a great city driver. i run the single point delco distributor, ie ancient technology! let us know the readings.Comment
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Re: C2 Timing-Can't rotate the distributor
Well guys, thanks for all of your input. The good news is that with the vacuum pot hitting the intake, timing was too far advanced- off the scale with the light, hard to crank, and bucked a bit driving around town. As I have set it back a bit to approx. 12 degrees, seems a good compromise-cranks properly, no bucking, nice step off the line, but still need to fiddle with the choke ie. cold driveability just a bit. Drive around town with a wrench and screw driver to fine tune it is probably the best. Maybe I end up at 13 degrees.
Werner, thanks for your suggestions, but you are way too good for me. I am not that technically proficient. Jack, thanks for the warning-I think you are wrong, boy I hope so.Comment
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Re: C2 Timing-Can't rotate the distributor
mike
if you think i anm too good for you, i must have ended up making somthing simple sound complicated. sorry, but it is hard to describe in words what is easy to show in real life.
best, wernerComment
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Re: C2 Timing-Can't rotate the distributor
Clem:
If I get what you are saying, if the gear is pinned to the shaft 180 segrees off, then I will have a condition where if the timing is set correctly, I will either have the vacuum can smashed back into the distributor shield or, if the distributor is moved a notch then the can will be against the manifold? I have an engine that is just this way. Distributor has never been apart.
MikeComment
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Re: C2 Timing-Can't rotate the distributor
mike,this should put you in the correct place to set the timing unless your outer ring on you damper has slipped. you could also check the damper for the correct location of the TDC mark by using a piston stop.Comment
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Re: C2 Timing-Can't rotate the distributor
mike
no no no
if your drive gear is rotated 180 degrees the physical position of your distributor will hardly be affected at all [only by 1/2 the distance between two teeth]. consider a clock with 11 hours instead of 12. if you rotate it 180 degrees and end up "between" hours, it is not that big of a deal in terms of position. of course, the more "hours" on the face of the clock, the less difference the rotation makes. i can't remember how many teeth the distributor drive gear has, but it seemed like a lot more that 12, could be 17 or more. do you see what i mean?? this happens because there is an odd number of teeth, and a rotation of a true 180 degrees will end you up in the valley between two teeth. but it is onluy a few degrees to the tooth. that would not be enough to make your vacuum can bang against somthing.Comment
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Re: C2 Timing-Can't rotate the distributor
Okay. Let's start over. I understand the slipped timing marks and the clock. I'l rephrase my question. "What is the net affect on adjusting engine timing if the gear on the distributor shaft is 180 degrees off in relation to the expansion pin and the drill dimple on the gear"?
Always knew the gear went on only one way. Someone told me it would cause timing problems if it was wrong. Never thought much about it until now.
So I go look and there are 13 teeth on the gear. On one side the teeth are split by the pin and on the other, the pin intersects a gear tooth. In other words, 61/2 teeth per side. Agree? So with gear 180 off on the the shaft, I will be off a half tooth on visual distribtor orientation to the manifold. If each tooth (360 divided by 13) is worth 13 degrees then I would be off half that or 6 1/2 degrees.
I saw on another post a few days ago that someone said "this is just another example of a botched gear installation". I think they were talking same subject.
Any comments?
MikeComment
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PS
I have also noticed A lot of people inquiring about the distributor hitting the manifold, or otherwise unable to adjust the timing. I chalked this up to them having the dist. in the wrong notch or the wires wrong on the cap or whatever else you can think of. Could this be related?
MikeComment
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Check Your Math
Mike:
360/13=27 2/3 -----VERY significant!
JoeComment
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