Why the Spark Plug and Timing Adv. Change from '68 to '69?

[grantclev]

Does anyone know why the 350 c.i. specs show a change in spark plug type from 44TS to R45TS and a timing advance from 2.5 deg BTD to 0 deg TDC from 1968 to 1969 model year?

[TODD]

The R in the spark plug number indicates resistor type which was introduced all across the GM line in 69. The 45 is one step hotter plug than a 44.

Timing was was changed to 0 deg TDC in order to comply with federal emission standards for operation at idle.

[grantclev]

Great info. Thanks! Unfortuneately, I just found out I don't have the original engine. I'm pretty sure its newer than a 68-69.

[bob k. mando]

68-69 engines oil the rockers by weeping through the shafts.

newer Buick 350s use the 'normal Chevy' method of pumping oil up to the rockers through the pushrods.

if you can find the two digit Engine Code, that will tell you the year and spec of the original application.

https://www.teambuick.com/reference/...gine_where.php

[LARRY70GS]

Great info. Thanks! Unfortuneately, I just found out I don't have the original engine. I'm pretty sure its newer than a 68-69.

None of the stock specs apply then, ESPECIALLY ignition timing. Lots of confusion out there about ignition timing. Most Buick distributors are set up so that at WOT, total advance is 30-34*. The 69 distributor had 30-34* of mechanical advance. That is why it is initially timed at 0* (TDC). Being that you are dealing with an engine and car that is 40 + years old, it is likely the distributor has been changed at some point. That means you should set the total advance.

[TODD]

Looks like our Tuneup Specs need correction. Those 68 350 numbers are carried over from a 67 430. Shop manual gives a 45TS plug and 0 deg TDC timing for the 68 350. Also in there is a description of the Controlled Combustion System. A blurb describes how emissions are reduced by retarding the idle advance to TDC.

If you could post the part number of the distributor we could tell more about what we're working with.