Re: [T3] 72 FI timing question

["Dave Hall" <dave@hallvw.clara.co.uk>]

Factory settings are on the club website:  T3 Ignition timing.  It shows the
timing marks, the distributor hoses (off) etc.  There's no note about any
variation on some of the later engines.

Dave.
UK VW Type 3 & 4 Club
http://www.hallvw.clara.co.uk/
------
----- Original Message -----
From: "Jim Adney" <jadney@vwtype3.org>
To: <type3@vwtype3.org>
Sent: Monday, July 16, 2001 4:33 PM
Subject: [T3] 72 FI timing question


> As Mike and I were finishing up our marathon engine swap, I got to
> the point of checking the timing. The 72 FI requires a different
> timing process because of the vacuum retard which its distributor
> has, but my question is:
>
> What is the timing supposed to be set to? (with vacuum hoses off,
> idle speed adjusted properly)
>
> The sticker ON THE ENGINE (original, from VW) says 5 degrees
> A.T.D.C. There used to be a separate sticker with a picture of the
> pulley, but this has disappeared.
>
> Bentley, and Without Guesswork say 5 deg B.T.D.C. and have
> pictures that are consistent with this.
>
> If I study the distributor advance curves carefully I find that it
> appears that all the advance graphs are given in distributor shaft
> degrees and RPM, while the chart for the 72 cars appears to be in
> crankshaft degrees and RPM. If I compare the 72 and 73 data
> presented there, it looks like all this is consistent with timing both
> to 5 deg BTDC.
>
> I have not checked my Haynes. I also need to look in the owner's
> manual to see if it has anything about this.
>
> Everything about this appears to indicate that the factory sticker is
> just wrong. The only thing I can think of is that either VW meant
> something different by the A in ATDC (like Ahead, or Advanced) or
> that it was just a bonehead mistake. This engine came out of a
> VERY early 72 production car, so I wonder if it is possible that VW
> corrected this mistake later.
>
> I'd love to move the timing from 5 deg BTDC to 5 deg ATDC as this
> would make for much better power and fuel economy, but this is
> such a big change that I'm reluctant to make it unless I'm sure that
> it won't damage something. The only way it could hurt something
> would be if I'm wrong about the 72 distributor charts in the Bentley
> manual being in crankshaft degrees and RPM. If I have to double all
> of these numbers, then this would result in too much advance.
>
> Russ, do you remember what you timed them to? The 72-3 pulleys
> have marks  |   |   | |, which are at -5,0,5,7.5. Is the correct mark
> the left mark or the 3rd from the left?
>
> Does anyone else out there have a 72 FI engine with the original
> sticker still on it? If so, I'd love to hear whether yours says ATBC or
> BTDC.
>
> Mike is happily back on the road, but he's going to call me in a
> couple of days to see what your verdict is. He has the tools to
> change all this on the road if it looks like a good thing to do.
>
> BTW, I've torn down his old engine part way and found a couple of
> things:
>
> The upper control rod for the air flaps had fallen out and wasn't
> doing anything.
>
> The metal air covers over the spark plug wires were both missing,
> so most of his cooling air was spilling out there.
>
> The metal cooling tin that guides the air on the underside of the left
> fan outlet was bent and fallen out of place, so the left bank was
> running even hotter. You may remember that his left spark plugs
> were running hotter than the rights. There were quite a few of the
> small cooling tin screws missing, so that they were poorly sealed.
>
> Keep in mind that this was not Mike's doing, he was just dealing
> with a typical engine rebuild/carb conversion coming from someone
> that didn't know type 3 engines well enough.
>
> thanks, and please let me know about the timing question....
>
> -
> Jim Adney
> jadney@vwtype3.org
> Madison, WI 53711-3054
> USA
>
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