Ignition timing issues [message #262955] |
Sun, 28 September 2014 21:31 ![Go to next message Go to next message](/GMCforum/theme/default/images/down.png) |
kwharland
![United States United States](/GMCforum/images/flags/us.png) Messages: 246 Registered: November 2005 Location: Central Florida
Karma: 0
|
Senior Member |
|
|
I'm going to start a new thread about my problems getting my engine running correctly since the focus has changed. I realize there's also a recent thread on this same subject but don't want to hijack it.
To bring everyone up to speed, I was having a problem with the engine bogging down badly when the throttle was partially opened and after having gone through the carb multiple times, was suspicious of a possible clogged exhaust. That was disproven as a problem and the last suggestion was to try fresh fuel. That proved of no benefit either although I did find the old fuel was foul.
I had previously disassembled the distributor and both cleaned and lubed all components, insuring that both the vacuum and centrifugal advances worked freely. I had set the initial advance at 12* with the vacuum advance disconnected.
I have a dial-back timing light that I've never trusted too much and I find I'm not alone with many professional engine builders preferring timing tape. This timing light was showing far less advance from both vacuum and centrifugal than I was expecting so I decided to go the timing tape route.
Prior to this, my research indicate that the correct vacuum advance unit was supposed to be a VC1847 that provided 12* of advance and that the centrifugal should add 20*. As it turns out, the vacuum advance is only 8* and centrifugal is 12*. So it's no surprise I have no power at 1500 to 3000 RPM. I have no idea where the PO had the initial timing set but I now suspect it must have been much more than 12* considering it ran fine previously.
I've removed the vac can and find that it's not correct, in fact it's actually stamped with the numeral '8' in addition to a '609'. I'm sure I can find a correct can but I'm not sure what's restricting the mechanical advance. I need to find another distributor and compare parts. I do see that the distributors built by Dick Paterson have 18* so I just have to figure how to correct mine.
1978 Eleganza II
|
|
|
Re: Ignition timing issues [message #262958 is a reply to message #262955] |
Mon, 29 September 2014 00:48 ![Go to previous message Go to previous message](/GMCforum/theme/default/images/up.png) ![Go to next message Go to next message](/GMCforum/theme/default/images/down.png) |
roy1
![United States United States](/GMCforum/images/flags/us.png) Messages: 2126 Registered: July 2004 Location: Minden nevada
Karma: 6
|
Senior Member |
|
|
I have mine set at 10 deg initial and another 22-24 deg centrifugal all in at around 2500 rpm crank degrees the vacuum pot is a 10 degree pot. It doesn't detonate with the 8 to one compression. The shape of the weights will limit the total advance. The springs will determine at what rpm you will obtain full advance. The number 8 stamped on your pot signifies it is an 8 degree pot you could open the slot a little for more vacuum advance if it isn't adjustable but 8 is ok if you can gain more centrifugal. You need to buy a rev kit to get lighter springs at summit or autozone etc. the rev kit weights may not give you enough advance . I used some weights from a Cadillac I don't remember what year. At the time I just looked at distributor weights in the junk yard cars and took some skinny ones as they allow more advance when they open out before they touch the cap limiting max advance. The timing light with the knob makes it easier to set it up just check the calibration against your timing tape.
Roy Keen
Minden,NV
76 X Glenbrook
|
|
|
Re: Ignition timing issues [message #262972 is a reply to message #262958] |
Mon, 29 September 2014 09:16 ![Go to previous message Go to previous message](/GMCforum/theme/default/images/up.png) ![Go to next message Go to next message](/GMCforum/theme/default/images/down.png) |
kwharland
![United States United States](/GMCforum/images/flags/us.png) Messages: 246 Registered: November 2005 Location: Central Florida
Karma: 0
|
Senior Member |
|
|
roy1 wrote on Mon, 29 September 2014 01:48I have mine set at 10 deg initial and another 22-24 deg centrifugal all in at around 2500 rpm crank degrees the vacuum pot is a 10 degree pot. It doesn't detonate with the 8 to one compression. The shape of the weights will limit the total advance. The springs will determine at what rpm you will obtain full advance. The number 8 stamped on your pot signifies it is an 8 degree pot you could open the slot a little for more vacuum advance if it isn't adjustable but 8 is ok if you can gain more centrifugal. You need to buy a rev kit to get lighter springs at summit or autozone etc. the rev kit weights may not give you enough advance . I used some weights from a Cadillac I don't remember what year. At the time I just looked at distributor weights in the junk yard cars and took some skinny ones as they allow more advance when they open out before they touch the cap limiting max advance. The timing light with the knob makes it easier to set it up just check the calibration against your timing tape. I have several sets of springs around but as you say, they won't affect total advance. I've found I need a #375 center plate and #41 weights. I'm about to pull this distributor and check numbers of it's components, then go searching for the correct ones. I'll stop by my favorite FLAPS for a new, correct vac can.
1978 Eleganza II
[Updated on: Mon, 29 September 2014 09:30] Report message to a moderator
|
|
|
Re: Ignition timing issues [message #262973 is a reply to message #262972] |
Mon, 29 September 2014 09:37 ![Go to previous message Go to previous message](/GMCforum/theme/default/images/up.png) ![Go to next message Go to next message](/GMCforum/theme/default/images/down.png) |
roy1
![United States United States](/GMCforum/images/flags/us.png) Messages: 2126 Registered: July 2004 Location: Minden nevada
Karma: 6
|
Senior Member |
|
|
Typo I ment to say the rotor interference limits the total advance rather then the cap. You are on the right track. I used to set up my olds powered boat motors this way total 36deg @ 2500 rpm no vacuum it made a big difference in power.
Roy Keen
Minden,NV
76 X Glenbrook
|
|
|
Re: Ignition timing issues [message #262998 is a reply to message #262973] |
Mon, 29 September 2014 15:43 ![Go to previous message Go to previous message](/GMCforum/theme/default/images/up.png) |
kwharland
![United States United States](/GMCforum/images/flags/us.png) Messages: 246 Registered: November 2005 Location: Central Florida
Karma: 0
|
Senior Member |
|
|
I've found that the center piece is a #360 and the weights are #053. I don't know what Dick P uses but I guess I'm going to have to resort to some junkyard prowling. I can't get a correct vac can locally so I just opened up the slot on this one until I got 12*. Seems to run better but have't driven it yet.
1978 Eleganza II
|
|
|