Rough idle
Thread Starter
Intermediate
Joined: Jan 2010
Posts: 26
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From: Balto Md
Rough idle
Ok rebuilt quadrajet carb and seems to works fine. Got 20 on vacuum gauge. Choke works great and idle screw is all the way off. Put new MSD street fire distributor in. Set timing at 12 degrees with vacuum advance plugged. Run motor up to about 3000 an mechanical advance was coming in at around 1200 witch is to late in my opinion for a stock 350 so I took off one of the heavy springs and put on a stock spring. Now it comes in at idle. Got that fixed I think. Now back to the vacuum advance. Plugged vacuum back up and its running around 23 degrees. I also put the vacuum advance stop plate on an used the B catch for 11 thru 14 degrees because it looked like I had two much total timing. Car runs great, four barrel and passing gear operate as they should. O and car idles great with out vacuum advance. Car has only 105000 miles on it. Any idea on this. Thanks.
Tech Contributor
Joined: Aug 1999
Posts: 14,370
Likes: 6,364
From: At my Bar drinking and wrenching in Lafayette Colorado
You've got your timing all screwed up, but what's the question..? Timing won't cause a rough idle.
You can e-mail me for the timing papers so you can set it up right.
Lars
V8FastCars@msn.com
You can e-mail me for the timing papers so you can set it up right.
Lars
V8FastCars@msn.com
Thread Starter
Intermediate
Joined: Jan 2010
Posts: 26
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From: Balto Md
Ok so I am going to put the MSD timing tape on balancer. Then I want my centrifugal advance all in at 36 degrees at 2500 to 3000 rpms. Then run my vacuum advance from manifold and hopefully it will be an 8 degree unit for a stock 1976 350 with dual exhaust an no egr. Will that get me close because centrifugal I somewhat got. Vacuum advance I don't got. 
What about the stop plate for the MSD or buy the adjustable one? I'm guessing with the 8 degree can you know exactly what your getting. Thanks for your help.
What about the stop plate for the MSD or buy the adjustable one? I'm guessing with the 8 degree can you know exactly what your getting. Thanks for your help.
Last edited by DM76; Oct 27, 2013 at 08:46 AM.
Tech Contributor
Joined: Aug 1999
Posts: 14,370
Likes: 6,364
From: At my Bar drinking and wrenching in Lafayette Colorado
You want your centrifugal curve to be short enough (about 20 degrees long) so you can achieve 36 degrees total timing and still end up with about 16 initial. You want this 36-degree total to come all-in and be pegged out somewhere in the 2500 - 3000 rpm range. Your vacuum advance control unit should add about 12 - 14 crankshaft degrees of timing as outlined in the vacuum advance tech paper - you can change it as outlined in the paper. By running it off manifold vacuum, this 12-14 vacuum added to your 16 initial will get you actual timing at idle of about 30 degrees. This will get you a good performance setup that will idle nicely and produce excellent power.
Lars
Lars
Thread Starter
Intermediate
Joined: Jan 2010
Posts: 26
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From: Balto Md
Ok I went to two auto stores and called two. I felt smarter sense I was the only one there that seemed to know what a centrifugal advance spring kit was. O and they tried to sale me a harmonic balancer in place of the timing tape. I will order all of it from Amazon. I have a 6.75" balancer. I am going out now to clean and paint if needed the balancer so tape will stick properly. Its a shame car runs great otherwise. It can really throw your head back for what it is. Stock. I'll keep you updated on progress. I'm going to have wife run rpms up to 2500 and 3000 an mark the throttle linkage. That way I can run it up myself when checking timing. thanks.
I will order all of it from Amazon. I have a 6.75" balancer. I am going out now to clean and paint if needed the balancer so tape will stick properly. Its a shame car runs great otherwise. It can really throw your head back for what it is. Stock. I'll keep you updated on progress. I'm going to have wife run rpms up to 2500 and 3000 an mark the throttle linkage. That way I can run it up myself when checking timing. thanks.
Last edited by DM76; Oct 27, 2013 at 12:16 PM.
Le Mans Master
Joined: Apr 2011
Posts: 6,284
Likes: 1,170
From: Hermosa
Get one of these. it has rpm and you can dial in timing without timing tape that will come off.
http://www.sears.com/craftsman-profe...a=00914066000P
http://www.sears.com/craftsman-profe...a=00914066000P
Thread Starter
Intermediate
Joined: Jan 2010
Posts: 26
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From: Balto Md
Update, just cleaned balancer and painted. Once paint dried a little I than took a small strip of duck tape (90 mph stuff) 
and measured timing marks on it. I have a 6.75 in balancer so 3/4 of an in is 12 degrees. Plus I measured my timing tab and it is exactly 3/4 in from 0 to 12. I put one long line for 0 and a short line for 12 another for 24 and a long line for 36. Put tape on balancer starting on timing groove. And transferred lines to balancer with marker. I hope that will get things started. When wife comes home I will get my throttle linkage marked for 2500 an 3000 rpms. Then go from there.
and measured timing marks on it. I have a 6.75 in balancer so 3/4 of an in is 12 degrees. Plus I measured my timing tab and it is exactly 3/4 in from 0 to 12. I put one long line for 0 and a short line for 12 another for 24 and a long line for 36. Put tape on balancer starting on timing groove. And transferred lines to balancer with marker. I hope that will get things started. When wife comes home I will get my throttle linkage marked for 2500 an 3000 rpms. Then go from there.
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Thread Starter
Intermediate
Joined: Jan 2010
Posts: 26
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From: Balto Md
I'll have to put that light on Christmas list. 
Well I had to put the heavier spring back on the weight that came on the street fire. One heavy and one light didn't get me to 36 degrees at 2600. I now have around 35 at 2600 rpms. Now my initial timing is now 14 btdc. Plugged the vacuum advance back in and now have the stop plate at C setting witch is 8 to 11 degrees. Idles now at 800 witch is to high for torque converter . Needs to idle at 650 to ease into gear. Should I turn air/fuel mixture screws in to lean engine slightly? Engine also now has a slight hesitation up to around 1600 rpms. I'm thinking need one medium spring. I do have about 20 degrees total centrifugal range. So I have 14 initial and 20 centr and 11 max degrees vac for 45 total degrees. Dam thing.
I'm going to buy a spring kit again hopefully I won't lose them this time.
Well I had to put the heavier spring back on the weight that came on the street fire. One heavy and one light didn't get me to 36 degrees at 2600. I now have around 35 at 2600 rpms. Now my initial timing is now 14 btdc. Plugged the vacuum advance back in and now have the stop plate at C setting witch is 8 to 11 degrees. Idles now at 800 witch is to high for torque converter . Needs to idle at 650 to ease into gear. Should I turn air/fuel mixture screws in to lean engine slightly? Engine also now has a slight hesitation up to around 1600 rpms. I'm thinking need one medium spring. I do have about 20 degrees total centrifugal range. So I have 14 initial and 20 centr and 11 max degrees vac for 45 total degrees. Dam thing. I'm going to buy a spring kit again hopefully I won't lose them this time.
Thread Starter
Intermediate
Joined: Jan 2010
Posts: 26
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From: Balto Md
Screw not touching stop and checked for vac leaks with wd 40. Tried to E mail back don't know if I did. Still trying to get use to this new computer. Thanks. So far I have rebuilt the carb, new MSD wires and distributor and AC plugs gapped at 45. Engine never runs over 195 temp and has good oil pressure. Compression test on pass side was good.
Last edited by DM76; Oct 27, 2013 at 06:29 PM.
Drifting
Joined: Feb 2005
Posts: 1,879
Likes: 38
From: Los Gatos CA
With the screw all the way out, the throttle blades should be closed. Something's binding or your fast idle cam ain't shutting down.
And the wrong base gasket will cause problems. Don't ask me how I know...
And the wrong base gasket will cause problems. Don't ask me how I know...
Tech Contributor
Joined: Aug 1999
Posts: 14,370
Likes: 6,364
From: At my Bar drinking and wrenching in Lafayette Colorado
If you cannot get the idle rpm lower than 800 with the idle speed screw backed out, you either have a vacuum leak or you have something holding the throttle open. You don't adjust idle rpm with the mixture screws. The idle speed screw should kill the engine when fully backed out. If not, you have other problems.
Lars
Lars
Thread Starter
Intermediate
Joined: Jan 2010
Posts: 26
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From: Balto Md
I found out tonight after buying a spring kit that the MSD street fire has two medium springs on it. It ran good when I put the one light spring on and I thought the other spring was a heavy one. I then run the two mediums springs (that I thought was heavy) and from idle to 1500 rpms did not feel right. So I put the light spring back on tonight an its fine. I did lock down the vacuum advance from 11 to 14 degrees to 8 to 11 and to get idle down a little I took initial timing from 14 to 12 degrees. No vacuum leak found yet and no smoke so I think valve seals are alright of now. Does seem to idle a little better. Might pull plugs to see how they look then TEST RUN..... 
Racer
Joined: Jan 2013
Posts: 287
Likes: 16
From: Florida New York
Screw not touching stop and checked for vac leaks with wd 40. Tried to E mail back don't know if I did. Still trying to get use to this new computer. Thanks. So far I have rebuilt the carb, new MSD wires and distributor and AC plugs gapped at 45. Engine never runs over 195 temp and has good oil pressure. Compression test on pass side was good.