Slant Six Forum :: Smoooth running - can it get smoother?

Sounds like you have set the timing to 3 degrees after TDC. The 5 and 10 marks are BTDC. Turning the distributor counter clockwise should advance the timing and make the engine run smoother and faster.

I might be getting confused. What side of tge motor is you timing tab on? I was thinking your timing tab was on the passenger side of the motor.

You said your timing was at three degrees above the 0/tdc mark.

For now, set the base timing so the timing mark lines up to the 5. Leave the timing there and find out why your motor is running rough. I would start with valve lash and checking for vacuum leaks.

OK- your timing mark is in between the 0 and the 5? Good- that means you are running at 3 BTDC. Leave it for now.

If the motor gets rougher as the timing is increased, I think you have a problems somewhere. Leave the timing at 3 and then do the valve lash and triple check for even a tiny vacuum leak.

If your engine runs smoother by retarding the timing, then the timing is likely over advanced. However, 3 degrees BTDC is not over advanced at all. I suggest you re-verify your timing mark.

Author:	Eatkinson [ Sun Nov 10, 2013 7:44 pm ]
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Quote: Sounds like you have set the timing to 3 degrees after TDC. The 5 and 10 marks are BTDC. Turning the distributor counter clockwise should advance the timing and make the engine run smoother and faster. The opposite is happening. It's running faster but there's far more vibration. Explain what you mean please about 3Â° ATDC vs. BTDC. If the scale to the right (rear of the damper) reads 0Â°-10Â°, 0Â° being at the bottom where TDC should lie, 10Â° at the top, with the 5Â° mark in the middle, and my TDC mark on the damper hovers around the 3Â° mark, you're telling me I'm timed 3Â° ATDC, when reading the same scale, adjusting the dizzy so the mark lands at the 5Â° and 10Â° mark should time me BTDC? That doesn't make sense. And something else: The distributor's original position was smack in the middle of the adjustment hold-down strap. The engine was running faster there, but rougher with far more vibration. I don't know where the timing mark was ending up as the stroboscope wasn't working then, so I couldn't tell if it was closer to the 0Â°, or closer to the 5Â°. I had to turn it clockwise nearly as far as possible to get it to run with less vibration. The engine slowed down, but the idle smoothed out. Can you explain further? You're telling me to rotate the dizzy back in the direction that was causing a faster idle, with rough vibration. That seems like it will achieve the opposite of what I want.

Author:	Reed [ Sun Nov 10, 2013 8:42 pm ]
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I might be getting confused. What side of tge motor is you timing tab on? I was thinking your timing tab was on the passenger side of the motor. You said your timing was at three degrees above the 0/tdc mark. On engines with the timing tab on the passenger side of the motor, a timing mark that is three degrees above 0 means that the engine is firing 3 degrees after TDC. As a rule of thumb, the more you advance the base idle timing (to a point, around 20 degrees btdc), the faster and smoother the engine will idle. The opposite is also true- the more you retard the timing the slower and rougher the engine will run. On a stock motor the motor should not run noticeably rougher or smoother until you approach the extreme ends of the base timing setting: about 20 btdc to 5 atdc (roughly). With that range (assuming a stock motor) the main effect of changing the base timing at idle will be to change the idle rpm of the motor. Of course, off idle you will experience very noticeable changes in driving characteristics. But at idle the most noticeable change should only be engine rpm. For now, set the base timing so the timing mark lines up to the 5. Leave the timing there and find out why your motor is running rough. I would start with valve lash and checking for vacuum leaks.

Author:	Eatkinson [ Sun Nov 10, 2013 8:50 pm ]
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Quote: I might be getting confused. What side of tge motor is you timing tab on? I was thinking your timing tab was on the passenger side of the motor. Incorrect. My timing tab is on the drivers side of the motor. Quote: You said your timing was at three degrees above the 0/tdc mark. Correct. So given my timing tab is on the drivers side, does that mean I'm running 3Â° BTDC? Quote: For now, set the base timing so the timing mark lines up to the 5. Leave the timing there and find out why your motor is running rough. I would start with valve lash and checking for vacuum leaks. So your recommendation is still the same? "Rough" is subjective at this point. It's almost as smooth as I want it. But I may play with the valve lash a little. There are no vacuum leads I can detect, but I've not used a stethoscope anywhere yet. And, I have yet to convert to HEI. That's next.

Author:	Reed [ Sun Nov 10, 2013 10:21 pm ]
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OK- your timing mark is in between the 0 and the 5? Good- that means you are running at 3 BTDC. Leave it for now. If the motor gets rougher as the timing is increased, I think you have a problems somewhere. Leave the timing at 3 and then do the valve lash and triple check for even a tiny vacuum leak.

Author:	Eatkinson [ Sun Nov 10, 2013 11:37 pm ]
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Quote: OK- your timing mark is in between the 0 and the 5? Good- that means you are running at 3 BTDC. Leave it for now. Thanks. I will. Quote: If the motor gets rougher as the timing is increased, I think you have a problems somewhere. Leave the timing at 3 and then do the valve lash and triple check for even a tiny vacuum leak. Given what you've just told me, that means that as I rotate the dizzy right (clockwise) I am advancing the timing (smoothing it out), which means the timing mark would move closer to 5Â° and if I could rotate it more, it would move closer to 10Â°. And further to this, that means if I were to rotate the dizzy left (counter clockwise), that means the timing mark would move to 0Â° and beneath 0Â°. Correct? If this is true and I understand what I was doing, then the motor was running smoother the more I rotated the dizzy right. BUT the engine was running hot: too hot for a routine test drive around a few blocks. After seeing that, I retarded the timing by a degree or two and that seemed to restore normal operating temperature. And of course I lost some of the silky idle when I did that. I'd like to rotate it right again but I can't have the engine running hotter than normal.

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Author:	Reed [ Mon Nov 11, 2013 1:04 am ]
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Rotating the distributor clockwise retards the timing (moves it closer to firing after TDC). Rotating the distributor counter clockwise advances the timing (fires it increasingly before TDC, moves the timing mark "up" towards 10). If your engine runs smoother by retarding the timing, then the timing is likely over advanced. However, 3 degrees BTDC is not over advanced at all. I suggest you re-verify your timing mark.

Author:	Eatkinson [ Mon Nov 11, 2013 9:01 am ]
Post subject:
Quote: If your engine runs smoother by retarding the timing, then the timing is likely over advanced. However, 3 degrees BTDC is not over advanced at all. I suggest you re-verify your timing mark. Re-verify TDC and the location of the mark on the damper? Or re-verify where the timing light is reading the TDC mark? Yes, I discovered my cam is advanced 2-3Â° when we degreed-in the cam.

Author:	Reed [ Mon Nov 11, 2013 9:15 am ]
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Sorry- reverify that the timing mark on the damper is actually at TDC. In other words, break out the piston stop tool again and verify the accuracy of the timing mark. Have you tried richening your idle fuel mixture?

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