Bad luck, Tex...
...but you're lucky it did not toast your entire car!
Olaf.
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| Two Barrel Trouble https://slantsix.org/forum/viewtopic.php?t=46270 |
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| Author: | ceej [ Sun Oct 02, 2011 5:02 am ] |
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Get an idle vacuum reading, then take a look at vacuum under load. It's handy to have a friend with a clip board for this. A tach is nice too, along with an A/F ratio meter. This could very well be related to timing, Both igntion and cam. 22° initial is a lot. I've seen slants take that much before. If it's not due to a slipped harmonic balancer, and your actually running that much advance, be ready for over heat issues out on the road. If the damper has slipped, actual timing may be considerably different. Hopefully somebody will chime in with a great suggestion. Your working on a "Hands On" problem that may be difficult to diagnose remotely. Make sure to get the PCV hooked back up soon. You will need the calibrated leak to get your tune right, and the sweep air will keep your oil clean. Did you degree the cam? CJ |
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| Author: | Tex [ Sun Oct 02, 2011 8:50 am ] |
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The timing is 22 degrees spot on, it has signs of being too far advanced, but the engine runs better, it actually ran its best at 30+ but the poor starter probably got its life cut in half. The pcv is hooked back up, that was just a test to see if it was sticking open causing a vacuum leak. The cam hasn't been degreed, but the compression test was normal (assuming Chilton's 125 psi as normal), all the cylinders were right around 120 psi, all within a maximum of 3 psi from each other. The next step I guess I'll try is amplifying the vacuum signal. |
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| Author: | ceej [ Sun Oct 02, 2011 11:02 am ] |
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Amplifying the vacuum signal to where? You're setting base timing with the vacuum advance disconected. At idle there should be no vacuum signal to the vacuum advance. Correct? CJ |
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| Author: | Tex [ Sun Oct 02, 2011 11:30 am ] |
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Yes, I always disconnect the vacuum line when setting the timing. I would like to see if amplifying the vacuum signal to the distributor would make any difference. |
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| Author: | Reed [ Sun Oct 02, 2011 11:36 am ] |
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Did you check for vibration dampener slip like CeeJ suggested? |
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| Author: | Tex [ Sun Oct 02, 2011 11:43 am ] |
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Yes, the timing is unfortunately accurate. |
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| Author: | ceej [ Sun Oct 02, 2011 12:43 pm ] |
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Take a vacuum pump and connect to the distributor. At idle, you should be able to advance the timing by pulling a deeper vacuum on the can. What is the condition of your distributor? Have you mapped your timing curve to see what engine speeds result in what timing advance? The OEM timing curve for a 1bbl isn't right for a 2bbl or otherwise modified induction system. If the timing is jumping around at idle, check the mechanical advance springs. Verify ported vacuum to the vacuum advance. All I can think of right now. CJ |
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| Author: | olafla [ Sun Oct 02, 2011 3:10 pm ] |
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My Aspen definitely run better with an overhauled but very, very worn original BBD, than any 318 BBD or Holley setup, and I have several of each to choose from! Use the carburetor links in the FAQ to rebuild your BBD to stock specifications for a slantsix. Even with some moderate leaks in the throttle shaft, which may give a rougher idle, you engine will most likely run better with a stock SL6 setup. To see what the factory said about the differences, take a look at page 26 -> on in Carter BBD operation and repair manual (pdf). You can make a SL6 run good with a 318 BBD, especially at top end, but never perfect over the entire power band - the parts are too different, even visibly when you hold them side by side. To achieve that, you need a well adjusted SL6 BBD, it is set up to interact with the vacuum signal and air flow that is specific for the SL6, over the entire rpm range. Or you could try fixing the leaky Motorcraft, but good as it is, even that one need some fine-tuning to work properly. Ford used more than 130 versions of it... Olaf. BTW, with a stock distributor, that initial timing will give you about 44° advance with full initial+mechanical advance, and some 66° advance with full vacuum: Way too much! My engine runs best with near stock setup; 12-14° initial (with slack timing chain), plus 18° mechanical, plus 18° vacuum, in a recurved distributor. |
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| Author: | Tex [ Sun Oct 02, 2011 3:16 pm ] |
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Well I got her running better now just through trial and error. I hooked up the original OSAC valve off of the Super Six air cleaner and it improved the performance, so for laughs I hooked it up backwards and it almost got rid of the hesitation. It is now drivable and the hesitation is only when you take off very slowly and hold the throttle constant, it stumbles for a second when it hits the flat spot then recovers. I bumped the timing back down to around 12 and it runs ok now. The distributor is in good shape but I'm not sure if it is original to the engine. I'll check the timing curve and see. Thank you for your help and patience. |
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| Author: | SlantSixDan [ Sun Oct 02, 2011 4:27 pm ] |
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Quote: You can make a SL6 run good with a 318 BBD, especially at top end, but never perfect over the entire power band
False. It's been done. I've done it.
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| Author: | Tex [ Mon Oct 03, 2011 7:39 am ] |
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Well for some reason the car decided to cook its own wiring harness from the ignition resistor back. It melted a hole in my mechanical oil pressure sending unit line which pumped oil all over the exposed mess... Well needless to say I got a real nice mess to clean up after I get it towed back. |
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| Author: | olafla [ Mon Oct 03, 2011 4:14 pm ] |
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Bad luck, Tex... ...but you're lucky it did not toast your entire car! Olaf. |
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| Author: | Tex [ Mon Oct 03, 2011 5:15 pm ] |
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It happens, as frustrating as it may be it's nothing that can't be fixed. I'm just glad I was wearing a jacket (would have been an awkward walk home without my Levi's) and was able to get it put out before it became absolutely catastrophic. |
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| Author: | Tex [ Fri Oct 07, 2011 8:02 am ] |
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I came across the box for the replacement vacuum advance that I put on the engine, but I noticed this go around that it has, "For engines with a manual transmission," written on it. I used the vin off of the distributor to purchase it and never thought twice about it. I wouldn't think this would make a difference, but could this be the source of my problem? Good news though, I'm almost done with reconstructing the wiring harness. |
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| Author: | Tex [ Tue Nov 01, 2011 12:50 pm ] |
| Post subject: | Finally FIXED |
After all this time, the problem wasn't air/fuel related. At some point during this engine's life someone had tried to do a distributor recurve on it and failed horribly... Extremely light spring on one side and shortened the other heavy spring. The curve was so far off it wasn't even funny. This explains the running at over 20 degrees advance, because the mechanical advance wasn't even operating. Stuck on a different distributor out of a junkyard, and it runs like a charm. I'm sticking with the 1.21 Motorcraft, due to it's impressive power increase over the 1.08, the Holley, and the Carter(s). Thank ya'll for the help. |
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