No start on rebuilt 360LA

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B3RE said:
From what the pics show, here are my observations.

1. The cap appears to be wired for #1 to coincide with the rotor position in the distributor as pictured.

2. The timing mark is about 9-10 degrees after TDC. Is it #6 or #1 ATDC?

3. The intake valve is open at that point. Should it be?
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DAMN!!! You got way more out of that than I did!!! I completely spaced looking at the valves!!! I agree with this assessment.
 
Did you ever get this started?
 
Professor Fate said:
Umm... if that pic is your current setup, you're 180* off.
Your rotor is pointed at #6.
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Follow the plug wires. The wire on that terminal appears to be headed in the direction of cyl #1. All plug wires one terminal off will result in a no fire or banging out the exhaust or intake.
 
Dale Davies said:
Polarity on distributor leads reversed? What kind of double speak is that? If you reverse the primary wires on the coil the secondary current will be reversed and not work as well.
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He is talking about the electronic distributor pickup coil leads. This DOES change timing and it DOES change what has become known as "rotor phasing." Look it up. This is a big deal with us who swap different ignitions, such as HEI onto a Mopar dist. The wire colors are "not always" correct

IN this case he is running an MSD instead of Mopar dist and MSD ignition, so the chances of this are unlikely. However in the case of weird timing settings, you should consider testing "rotor phasing."

The OP hasn't been "back" so who knows?
 
Back to basics when you are lost.
Fuel? Yep popping out of carb
Spark? Yep popping out carb.
Really only two things could be wrong. Spark at the wrong time or valve open at the wrong time. Set the engine at TDC on the compression stroke on number 1, ensure valves are both closed fully. Pull rotor off distributor and line up reluctor point in middle of sensor. Reinstall rotor and whatever tower it points to make that number 1. Install the other wires in correct order clockwise from there. If you do all that it should run. However, Is the original msd plug on the distributor? and are you using the corresponding msd twisted pickup cable? If you made the connections yourself you may have the polarity reversed on the distributor! For whatever reason, I’m sure an electrical engineer can tell you why, if you reverse the polarity it either adds or subtracts like 25-30 degs of timing I can’t remember which. Oops, took so long typing this someone else asked it!
 
I told you why.........directly above. "rotor phasing." Reversing the magnetic pickup wires changes the spark timing IN RELATIONSHIP TO THE ROTOR This causes the spark to jump further and may crossfire to the wrong cap contact. Google it. "rotor phasing."
 
one more thing to check if you have an MSD, you need 12v to the switched power wire to the MSD with the ignition in the start position AND the run position. There are a few ways to accomplish this. You should just check yr voltage to the MSD in both start and run to be sure..
 
Rotor phasing is change by one thing only from where the stacked tolerances put it during manufacturing and that is the vacuum advance mechanism. The vacuum advance actually moves the pick up location as a way to advance the timing. Using the advance plate was how I corrected my horrible phasing. Put the plate were it needed to be and pinned the plate there. Never planned on running the vac advance anyway.
 
jtn2655 said:
Recently rebuilt the motor from the junkyard. Had cylinders bored .030 over. KB107 pistons, stock crank/rods. Comp Cams XE .525/.525 cam. Rpm Performer heads, comp cams roller rockerS, RPM Air Gap intake, Holley 750 DP carb. Outside motor: MSD Magnetic pickup/mechanical advance distributor, -6AL MSD Ignition box, Holley electric fuel pump (regulated to 7psi) battery (relocated to trunk via summit racing kit) summit ignition switch panel.

Turns over smooth, getting fuel, all tolerances/torques checked. Timed +- 10 degrees. We are getting backfires but no start.
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Just a thought....is this a hydraulic cam? Did you pre lube engine to get lifters pumped?
 
furrystump said:
Rotor phasing is change by one thing only from where the stacked tolerances put it during manufacturing and that is the vacuum advance mechanism. The vacuum advance actually moves the pick up location as a way to advance the timing. Using the advance plate was how I corrected my horrible phasing. Put the plate were it needed to be and pinned the plate there. Never planned on running the vac advance anyway.
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I'm sorry but you are incorrect. With a magnetic trigger such as the Mopar factory breakerless ignitions, if you reverse the pickup wires IT WILL CHANGE the trigger point in relation to the rotor.
The magnetic pickup generates a positive going and a negative going spike sort of like a modified sine wave. "Let's say" the factory has the pos spike first and "let's say" the positive spike is what triggers the "box." When you reverse the pickup wires you reverse the position of the spikes........the positive spike is now after the neg and happens at a slightly different time--that is degrees of rotation in relation to the rotor position.

This is no different, than for example screwing with breaker points. If you change the points gap, you change the timng, and although it will change by a minor amount compared to the magnetic trigger, it WILL change rotor phasing by some amount. Another example is is you had dual points. "Let's say" you were out somewhere and the "firing" set of points failed/ burned so they were no longer making contact. Now the "closing" set would be acting as the only set of points.......and they would be opening at a different time than the normal firing set, and would also change rotor phasing. I have not tried this, but that problem might be enough change to cause problems.

I suspect that the term "rotor phasing" got "big" in the last few years with the various home/ DIY/ self installed electronic timing control and EFI systems where guys are still using a distributor, either for trigger as well, or as "only" spark distribution
 
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Thanks, the reason why it changes with the polarity wasn’t clear to my what was happening inside the sensor. Logical with the change in which edge is the trigger the leading or trailing edge changes the trigger point.
 
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