ComicArtist Posted October 30, 2011 Share Posted October 30, 2011 So I replaced the distributor, and timed it to 10 degrees at idle. However, it was still slow and sputtery at low rpms, so I gradually advanced it until it seemed to run right. At 16 degrees idle now, it actually goes through the powerband smoothly. Can that cause any problems? It's not detonating, and runs smoother than it did at 10 degrees. Just wondering if anyone else is running advanced timing, and if so, I'd appreciate the input. Quote Link to comment Share on other sites More sharing options...
neotech84 Posted October 30, 2011 Share Posted October 30, 2011 The only side effect will be a smile on your face. I am pretty sure that it's still considered with in spec. Quote Link to comment Share on other sites More sharing options...
madkaw Posted October 30, 2011 Share Posted October 30, 2011 Advanced timing is a great if your motor can take it . If it runs better and doesn't detonate- go for it. You should listen for detonation during times that your vacuum advance is involved in your overall timing. I run 20 initial. How much mechanical advance are you running? What's your total timing? If you can't answer these questions then it's time to search! Quote Link to comment Share on other sites More sharing options...
ComicArtist Posted October 30, 2011 Author Share Posted October 30, 2011 I'm just running an unmodified stock distributor, using both the vacuum and mechanical advance, so my complete timing should be around 34 degrees. I'm guessing it's kicking in a little early though, since I'm slightly advanced. Where in the rpm-band does the vacuum advance come into play? Quote Link to comment Share on other sites More sharing options...
NewZed Posted October 30, 2011 Share Posted October 30, 2011 (edited) Vacuum. It's controlled by intake manifold vacuum. The specs for the vacuum canister and the mechanical advance mechanism are in the Engine Electrical section of the FSMs. You can use a dial-back timing light or set your timing to zero and measure each, vacuum and centrifugal, independently to be sure. Disconnect the vacuum and measure centrifugal advance, then connect the vacuum to direct intake vacuum to measure vacuum advance. Edited October 30, 2011 by NewZed Quote Link to comment Share on other sites More sharing options...
rejracer Posted October 31, 2011 Share Posted October 31, 2011 Which L28 are you running? If you have open chamber heads, you can run around 38* total timing. If you have a closed chamber head with flat top pistons, 32* is about right. Closed chamber L28's have P79 head from the factory. Everything else is either an open chamber head, or runs dished pistons. Quote Link to comment Share on other sites More sharing options...
ComicArtist Posted October 31, 2011 Author Share Posted October 31, 2011 The L28 is an N47/N47 out of a '78, so that should make it an open chambered head, right? Quote Link to comment Share on other sites More sharing options...
rejracer Posted December 25, 2011 Share Posted December 25, 2011 Yes N47 is an open chambered head. I am running a N42/N42 combo, it's running great at 20* static for a total of 36*. Quote Link to comment Share on other sites More sharing options...
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