Author Topic: Distributor cap/ rotor air gap Question  (Read 7502 times)

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Offline MN_samurai

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i have a question concerning the proper air gap between the distributor cap terminals and the rotor button terminal.

how much air gap is needed? how much tolerance is there?

also... how does one measure this air gap in a real world setting as the cap and rotor need to be installed on the disty to get proper centering or is there another way?  please explain as i am not getting it.

reason i am asking is i am trying to install a side terminal Honda disty cap, samurai or Honda rotor button on a 91 swift vacuum advance disty.  please do not try and tell me the gtx turbo cap will fit because it is WAY too big around for the 8v disty.. i know because i ordered it in along with other caps that have been suggested and all were way too large of diameter.  the parts i am trying to make work were sourced by going through every single cap and rotor on hand at my local parts house and trying them for fit and selected the "closest" to fitting.

i am just getting frustrated with this and need some guidance or help.
WTB: Good running Swift GTi in Minnesota

http://www.infowars.com/

Offline lxer96

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I think you need about a 1/16" gap.  I measured from the (inside of the cap) the from the posts to the ouside edge of the cap then measured the distance from the top edge of the distributor to the tip of the rotor, subtracted the two and got 1/16".  This was with all stock parts.  My Mazda cap and swift rotor have the same gap as stock.  Hope this helps.   

Offline MN_samurai

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thanks.  that sounds good.  i don't have a caliper at home for measuring but according to the highly accurate tape measure (lol) i have similar measurement.  i *may* have found a solution to my rotor issue.  i was scrounging around in my garage and noticed that samurai rotors have slightly different sized (width) contact tips depending on the brand.  i was able to match up a rotor contact tip from a honda 1.5 carbed engine (same length tip as the rotor from the 83 prelude i got the cap from) to fit an old samurai rotor button.  this *should* get me to where i need to be.

lets see the mess of parts i am using for the ignition on my carbed swift gti engine: 91 swift sohc vac advanced distributor (was really hard to find), 83 honda prelude disty cap from a hitachi non-tec car, plastic 87 samurai rotor button (appears as if the borg warner has the correct width contact), 86 honda civic 1.5 carb fed emmisions rotor contact tip (unknown rotor brand at the moment).
WTB: Good running Swift GTi in Minnesota

http://www.infowars.com/

Offline lxer96

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Sounds good Dr. Frankenstein!  lol  Just to check does the rotor or the center brush have a spring?

Offline MN_samurai

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no spring.
WTB: Good running Swift GTi in Minnesota

http://www.infowars.com/

Offline ZUKIDUKE

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A trick we used to use when mocking up engines was to put a lump of modeling clay on whatever your trying to measure and give it a spin. Take it apart and measure your clay thickness. I might work give it a try  [idea]

Offline lxer96

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I could be wrong but my school of thought always was one or the other has to have a spring because you want the rotor to touch the center brush and as it wears the spring expands to maintain contact.  In other words you don't want it arcing twice because it loses voltage and may melt something without it.   

Offline MN_samurai

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i am sorry, i misunderstood about the spring.  the honda cap i am using has a spring-like contact located in center of the cap that the rotor terminal contacts.
WTB: Good running Swift GTi in Minnesota

http://www.infowars.com/