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Distributor Indexing

It might be Renix-specific. It was issued as a TSB (Technical Service Bulletin) in either 1989 or 1990 -- the Renix era. I know it applies to Renix, but I don't know if it applies to the HO.

BTW -- it's 0.020 AFTER contact. Various sources have reported it as before, and I've been guilty of spreading that SPOBI myself, but it doesn't work. The correct setting is a gap of 0.020 with the rotor having gone beyond the #1 terminal in the cap -- crankshaft positioned with #1 piston at TDC on compression stroke.
 
Yeah - any thought that went into those posts would'a been a head-slapper when the "hey, BTDC means BEFORE Top Dead Center" :smack:

Anyway - an easier method (IMHO - aka "works for me") of getting to the same results is to turn the engine to 17*BTDC (+/-2*) and center the rotor's contact on the cap's contact (you'll still wanna window an old dist cap)

Figure that the rig runs to 35* total advance - split that with 0* and shazam! (seemed silly to me to measure a linear cord of 0.020 between some contacts that you're not sure of tollerances on (I've seen wide and skinny rotor contacts and there's some variance in cap-tower contact diameters and finish -- all that varience would easily exceed the 0.020" value anyway.) I add a 5* BTDCs for the high-altitude CPS

I've played with a few HOs and don't see much change in cap-losses, but the Renix years did have a deck-height spec issue (the referenced TSB from above) and several cam manufacturers are making odd assumptions about same...
(IMHO I believe that this is more related to the pre-production changes made in the distributor to block gasket not being communicated to vendor until after they'd started production...)

Remember that this moves the injector timing as well -- something to "play with", but leaving the fuel in the intake longer than necessary can really drop mileage/efficiency
 
Thanks for the insights! This 87xj was manufactured in the fall of 86 and every third or forth start was real rough. Turns out the distributor was installed one tooth off. Anyway, I corrected that about 70,000mi ago and now at 148,000mi, every now and then I get a bit of a rough start remanicent of the old days. I have an 84-87 manufacturer shop manual that has old bullitans bound in the back. There is one about early cars assembled with the distributor off by one tooth(mine) but the bullitan does not say anything about the .020 gap setting procedure.
 
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