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TOPIC: Timing, Inches .vs degrees

Timing, Inches .vs degrees 11 years 2 weeks ago #85977

Am I correct that:
.222 inched BTDC = 32.5 degrees BTDC.

What would .015 inches BDTC be in degrees.

I've picked back up my long dormant Pertronix points conversion project

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Re:Timing, Inches .vs degrees 11 years 1 week ago #86078

Damm near zero. Not sure if you typed the numbers correctly but 15 thou before tdc is almost zero degrees. If you meant .150 btdc it would work out to (.222/32.5) X .150 or about 10.25 degrees Btdc.

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Remember, my opinion in no way diminishes your opinion, nor yours mine. Collectively, there is a middle ground that is \\\"correct\\\" for the reader balancing all the input.

Re:Timing, Inches .vs degrees 11 years 1 week ago #86112

I did mistype - and thank you!!

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Re:Timing, Inches .vs degrees 10 years 11 months ago #87466

  • 63g3
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Ummmm need to know the stroke to determine conversion.

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Re:Timing, Inches .vs degrees 10 years 11 months ago #87468

  • 63g3
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On the topic of conversion I have done a lot of thinking, tinkering and designing ( HAVE ACCESS TO MACHINE SHOP)
What makes points really stink is contact pitting wear from the current draw they switch. Granted there is rubbing block wear but it is insignificant for a lot of hours of operation. An electronic pick up obviously eliminates this.
I have designed a few distributor base plates to hold the pick up to replace the dual point plates seen on the Merc 6's. Then did a dist shaft stub to take the rotor but also hold a 6 cyl reluctor.
Most stuff available is said to perform OK to 10,000 rpm on a 4 stroke 8 cyl. That's about the equivalent of a Merc 6 2 cycle running at 5500 to 6000 so far so good.
Butr it really it gets expensive for the needed machine parts and then there needs to be more done to set up timing marks etc. as you cannot static time like you can a points system.
While working/ thinking hard I acquired a 66 Merc 950. This is first year thunderbolt so it has the switchbox and super duper coil but the trigger is NOT electronic it is a dual set of points. The current draw is nil so the point faces last forever. The only bugaboo is the before mentioned Rubbing block wear.
Also coincident to this is I was looking up wire harnesses and saw CDI makes a combo coil and switchbox for this style Thunderbolt.
I think a good solution is to simplyadjust a good set of clean points to the thunderbolt specs using the timing plate and then use one of the CDI combo mounted where the (not now needed) merc coils reside. CDI said the current the points would switch is milli amps rather than several amps of a standard ignition so point faces stay fresh.
This gives the big spark performance and simplifies the triggering and also you can still set up timing using static method where points are still there. I do not believe rubbing block wear is of a concern for YEARS so this might be a good easy compromise in time money and ease of conversion. I'm gonna do this on my 62 700.
As a side note I did convert the 66 950 distributor to a later 67 and later with the electronic pick up. This would also be a possibility as these early year Thunderbolt distributors would fit the earlier 6's. But the Merc switchbox and coil does not package into the early motors as easy as the CDI would.
My two cents...Randy

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