78 L48 Timing
Thread Starter
Safety Car
Joined: Jun 2005
Posts: 3,841
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From: Inver Grove Minnesota
78 L48 Timing
I am trying to get this thing to run right. When i went to adjust the timing the sticker under the hood says 6 degrees BTC which mean before top dead center or what? I put it to that and it is really bad. Should it be 6 degrees after TDC? It was at 12 degrees and it would studder sometimes when you would step on it. Could this just be something else like the carb?
Tech Contributor
Joined: Aug 1999
Posts: 14,373
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From: At my Bar drinking and wrenching in Lafayette Colorado
You need to set the car up for total timing: Total timing (with vac disconnected) needs to be 36 degrees. This will, in most cases, give you an initial timing somewhere in the 12-18 degree range. Then, make sure your vacuum advance control unit is functioning and hooked up correctly. It should pull in an additional 16-20 degrees of timing at idle, running your combined total timing at idle with vac hooked up at around 30-34 degrees.
The factory 6-degree spec is for emissions purposes only, and will not produce a performance setup.
The factory 6-degree spec is for emissions purposes only, and will not produce a performance setup.
Racer
Joined: Nov 2004
Posts: 432
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From: Granbury TX
Originally Posted by JustinD
I am trying to get this thing to run right. When i went to adjust the timing the sticker under the hood says 6 degrees BTC which mean before top dead center or what? I put it to that and it is really bad. Should it be 6 degrees after TDC? It was at 12 degrees and it would studder sometimes when you would step on it. Could this just be something else like the carb?
Thread Starter
Safety Car
Joined: Jun 2005
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From: Inver Grove Minnesota
Right, I know this but it is gutless, and doesn't run "like it should". I was at a little abouve 12 degrees when i started. So are you telling me that i shuold look into the carb. I noticed there is a small leak coming from the bottom of the carb only when it is running. It is not even noticeable until you drive it around, then there will be some varnished gas by it in a spot. Should I look into a new carb, if so what one.
Thread Starter
Safety Car
Joined: Jun 2005
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From: Inver Grove Minnesota
Now that you say something, I was reving it up at the carb, and there was no fuel spraying into the back barrels. the ones at the rear of the engine. Only the ones at the front with the choke flap over them. Could this be the problem. BTW the choke was all of the way open i took it out to get it warm before messing with the timing.
Le Mans Master
Joined: Jul 2005
Posts: 5,752
Likes: 4
From: Austin Texas
The carb has vacuum operated secondaries. It is hard to load the engine while the vehicle is stationary. If you hold the throttle full open for a second, you should see the air valve open a little.
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Intermediate
Joined: Apr 2005
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I had a problem timming my 78 when i got it. Always heard of stories of slipped balancers. Actually had that problem. Outer part of the balancer slipped and could get any timming mark. Took about an hour to figure out what it was.
Mike
Mike
Thread Starter
Safety Car
Joined: Jun 2005
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From: Inver Grove Minnesota
No, it wasn't that. I got the timing at about 12 degrees, but it still rins rough. I think that I need a new carb. when I remove the vacum advance hose with it running. Nothing happens. And it is a very new distributor.
Le Mans Master
Joined: Jan 2003
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From: Tuttle OK
Cruise-In VIII Veteran
Originally Posted by JustinD
when I remove the vacum advance hose with it running. Nothing happens. And it is a very new distributor.
Le Mans Master
Joined: Jan 2003
Posts: 6,575
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From: Tuttle OK
Cruise-In VIII Veteran
it very well could be..it could be many things...small or big..
sometimes it's just a process of elimination. If timing is good, vacuume and advance is good, compression is good, then you look at other stuff...
there are many here that can help if you give enough info..
sometimes it's just a process of elimination. If timing is good, vacuume and advance is good, compression is good, then you look at other stuff...
there are many here that can help if you give enough info..
