midnightmoonlight Posted October 16, 2006 Share Posted October 16, 2006 Hi, This is my first post. I tried searching and it just led to more unanswered questions. Here goes. I have a stock 260 with lots of miles 160k. My cam is on the number three setting. Thats where it was when I bought it. The chain and gear is pretty worn so I asume thats why its in the #3 position. It also has electronic dizzy from a zx maybe. Im not real sure. I need to figure that out I set it to 7.5BTDC @ 750 rpms and it ran like well not to good. I read in a few threads here that people are running 12-15BTDC and disconnect the vaccum advance. Ive also seen everywhere that your total advance should be 32 @ 2500rpms. Getting to my question here. What does total advance mean? If I start at 7BTDC does that mean it should advance to 39BTDC @ 2500rpms? And say if I start at 15BTDC it should hit 47BTDC @ 2500rpms? Or does this mean I cant go over 32BTDC @ 2500rpms? This always happens I figure things out when I Type it. I remember now reading to set it at 32BTDC @ 3000rpms and dont wory about what it is at idle. I guess I answered my own question. Confirmation would be great. Now because I dont have the fancy timing light I was going to mark out where 32BTDC would be on the crank pully which would be 12 degrees back from the main mark on the crank. So when that mark hits the 20BTDC on the scale I will have gone 12 degrees more past 20. I was going to set the crank pully so the mark is on 20 then use the scale to count back 12. This will work right? Also if I set it 32BTDC @ 3000rpms I need to disconnect the vacum advance correct? I set the timing to 15BTCD and the car went nice but I put it back to 10 until I get this all figured out. Thanks for your time Quote Link to comment Share on other sites More sharing options...
naviathan Posted October 16, 2006 Share Posted October 16, 2006 I would back it up the number two position and try it there. Three seems a little much for taking up slack to me. Quote Link to comment Share on other sites More sharing options...
JMortensen Posted October 16, 2006 Share Posted October 16, 2006 1st thing to do is figure out what distributor you have. You've got 2 forms of advance on any Z or ZX distributor (except the 280ZX turbo). Mechanical or centrifugal advance has weights inside the distributor that swing out as the distributor shaft spins faster and faster. When they hit their stops, this is referred to as the advance being "all in". So this is 17 or 19 degrees on the ZX distributors, more on the 240 thru 280Z distributors. If you start with about 15 degrees advance at idle on the ZX distributor, that gets you into the mid 30s all in, which is good. The vacuum advance is more for mileage and throttle response at low rpms. If you don't need it, you can disconnect it. It provides more advance at high vacuum situations like idle or part throttle. When you stomp on the gas, there is not enough vacuum to actuate the vacuum advance mechanism, so it relies on the mechanical + the static advance (where you set the distributor with the timing light at idle) for total advance. The ZX vacuum advance mechanism sucks and it is almost always broken. When it breaks it can allow the pieces inside the distributor to hit each other. You can fix the vacuum advance if you want to use it for the extra mpg or two. Harbor Freight occassionally has the timing lights with the advance function built in. I bought one a while back for $25 I think. If you have the advance function then you can just set the dial to 32 or whatever and set the timing on the 0 mark. Quote Link to comment Share on other sites More sharing options...
naviathan Posted October 16, 2006 Share Posted October 16, 2006 Your vacuum advance should not be pulling at idle. It's connected to the ports on the bottom of the throttle body that only draw when the throttle plate is opened. Quote Link to comment Share on other sites More sharing options...
midnightmoonlight Posted October 16, 2006 Author Share Posted October 16, 2006 Well Im not sure how to tell which dizzy I have but it is advancing 22 degrees. That is if Im figuring this right I set the timing to 32degrees @ 3000rpms. I did this by making a mark 12 degrees back on the crank pully from the original mark. The new mark is closer to the distributer. When I drop the rpms down to 650 my timming is at 10. This was with the vac adv still attached. Having my cam sprocket set on #3 does this mean I have to advance my timming more to make up for the difference compared to if I set it at #2? I dont really understand the cam setting part I need to read more about it. I have the system down pat for changing it though. Ive been practicing on a spare motor. I advanced the timing to 20 and reved it to 3000rpms and didnt get any pinging. It actually ran very well. Thanks for all the help Quote Link to comment Share on other sites More sharing options...
JMortensen Posted October 16, 2006 Share Posted October 16, 2006 Your vacuum advance should not be pulling at idle. It's connected to the ports on the bottom of the throttle body that only draw when the throttle plate is opened. Correct. My mistake. Ported vacuum... As far as cam timing vs ignition timing, they're TOTALLY different. The more the cam timing is advanced the better low end power you'll have, and top end suffers. Retarding the cam timing gives more top end power. I don't know why your cam timing would be on the #3 mark, but if it's due to a slackened chain that's a pretty good indication that the chain needs replacing. If you haven't been into the L series timing chain before do a search. If you start screwing around in there you're liable to lose the tensioner (it will fall out if you give the chain too much slack), and then you have to pull the front cover to put it back together. On the igntion you need advanced timing to run at higher rpms. Generally you get the best hp somewhere in the mid 30's degrees advanced. Go farther than that and you're likely to LOSE power. Quote Link to comment Share on other sites More sharing options...
midnightmoonlight Posted October 16, 2006 Author Share Posted October 16, 2006 I have had the cam out and swapped it with a 240 cam so Ive been through the procedure without any problems. I have a new chain sprocket and tensioners. What should I do? I was going to change out everything when the snow comes. The cam sprocket looks very worn so Im asuming the crank sprocket looks the same way. I advanced the timing to 15, ran it around the block, and it ran better. What happens if I go to advanced beside loosing power doesnt run to hot and I could burn up valves? So if I get 22 degrees advance out of my dizzy can I asume its from a 280 then? I have another question. Im getting lots of gray smoke all the time. I was going to try to retorque the head but I think Im in for something deeper. I thought this smoke issue went away. I got leaned out It was black smoke but I noticed today after driving 25 miles or so its smoking bad. Any ideas of what I should start reading about would be nice. Ive started searching. Quote Link to comment Share on other sites More sharing options...
JMortensen Posted October 16, 2006 Share Posted October 16, 2006 It could be a 260 or a 280 distributor. I think the 260s came with electronic ignition as well. If you advance the timing too far and you're not pinging, you're basically just giving up hp. Retarding timing will burn valves, but I don't think advancing a little farther than optimal is going to hurt anything as long as it isn't pinging. Gray/black smoke? Compression test would help, maybe bad rings. Hard to say. Do that searching like you said and you might come up with something. Quote Link to comment Share on other sites More sharing options...
midnightmoonlight Posted October 16, 2006 Author Share Posted October 16, 2006 Ill do a compression test and a leak down test see what I can figure out and search. Keep your eye out for a new thread. I still dont understand the cam numbers and what they do. From the way I see it if its at TDC and set to #3 then I change it to #2 shouldnt I then have to change the ignition timming to compensate for the different position of the cam...Im haveing a brain fart on this one. They are different but they are very much dependent on one another right. Okay Ill start reading and stop talking now Thanks for the help its greatly appreciated. Quote Link to comment Share on other sites More sharing options...
naviathan Posted October 17, 2006 Share Posted October 17, 2006 You'll have to re-set the timing obviously, but no the setting wouldn't be any different because we believe it was an attempt to compensate for chain wear. Number three is just way to far advance for chain wear though. If it's that bad off then you need to put a new chain kit in quick. Quote Link to comment Share on other sites More sharing options...
midnightmoonlight Posted October 17, 2006 Author Share Posted October 17, 2006 The chain is tight but the sprocket looks worn. If I move it back to #2 or #1 and the chain is still tight should I run it like that? Of course you read my other post and I need rings so Im not sure if Im going to fix this motor, or my 240 motor. If the PO set it on #3 to try to get more hp and advanced the the hell out of the dizzy could that wreck the rings? Quote Link to comment Share on other sites More sharing options...
naviathan Posted October 17, 2006 Share Posted October 17, 2006 If he caused it to ping/detonate, yes he could have damamged the rings. Quote Link to comment Share on other sites More sharing options...
JMortensen Posted October 17, 2006 Share Posted October 17, 2006 Just MHO, but on a stockish motor it takes a lot of advance to cause detonation and a LOT of detonation to damage pistons. The PO would have to be a special type of moron to keep driving until damage was done. Not to say it doesn't happen, just that it is unlikely and takes some "What's that noise? F it, turn up the radio!" kind of mentality to do it. Quote Link to comment Share on other sites More sharing options...
midnightmoonlight Posted October 17, 2006 Author Share Posted October 17, 2006 If I move the cam back to #1 or #2 how do I know that its a good setting? Will the chain be loose if its not right? Quote Link to comment Share on other sites More sharing options...
JMortensen Posted October 17, 2006 Share Posted October 17, 2006 Get a Haynes manual. It shows the cam timing marks, where they should align, and how to advance the cam timing so that the marks are in the right spot. Quote Link to comment Share on other sites More sharing options...
midnightmoonlight Posted October 17, 2006 Author Share Posted October 17, 2006 I get it know. I have 3 books and the fsm for my 260. I hope you will still answer my dumb questions Quote Link to comment Share on other sites More sharing options...
naviathan Posted October 17, 2006 Share Posted October 17, 2006 We'll answer your questions don't worry. If the chain starts to slack on #2 replace it. You'll know it's slack because you'll be able to hear it when the engine is running. Quote Link to comment Share on other sites More sharing options...
midnightmoonlight Posted October 17, 2006 Author Share Posted October 17, 2006 Thats good to hear. Thanks again for the help. The internet has become one of my favorite research tools. Before this good luck finding special parts you need. For the most part the internet can do just about anything you ask of it. Quote Link to comment Share on other sites More sharing options...
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