[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] [New Search]
>From: "David Vargas" <mordala@ValuServe.Com>
Dave,
You asked a lot of good questions here, so I thought I would send them to
the whole group since many of them will probably be of general interest.
> I also have two type III's ('69 and '70 and both are SqrBcks.)
>and was wondering what could be done if any about Compression Ratio's?
>That is, unfortunatly your rebuttal does not mention anything about it
>and my '69 was running 7.2:1 (Estimated using Berg's decking tool with
>my digital vernier and his CC kit for the heads.) I was using regular
>(89 octane) and it literally was overheating for some time and blew a
>hole next to the spark plug tap in #3 cyl. head. Also, the distributor,
>as you know is unique for the FI. I could not locate the springs for it
>and had to modify existing springs and wound up retarding the TDC
>setting to keep it from advancing past what I thought was safe (30
>degress?)for total advance. I arrived at this from the standard settings
>for type I's. However, I now know that is not correct. The Bentley
>settings as best as I can see show a measley 15 to 21 degrees and less
>for the Automatics (which incidently mine are, the '70 I recently
>acquired and does not run: no distributor)so If I may have your input I
>would really appreciate it.
I only ever saw one distributor that needed a replacement spring, and that
was due to an owner screwup. I do worry about what I would do if one of
them rusted up, so I soak them in LPS-3 any time I'm in there.
You need to read the Bentley manual VERY carefully in this section to notice
that all the numbers shown are in DISTRIBUTOR degrees. If you are doing
this on the car, then you're seeing crankshaft degrees (which happens to be
what the Bill Fisher book uses.) To get the crankshaft number from the
Bentley book just multiply by 2. The Bentley numbers are what one uses if
you have access to a distributor machine, which just runs the distributor by
itself. Once the Bentley numbers are doubled you can see that these
distributors actually have very nice advance curves. In fact one of the
better curves in the Fisher book IS one of our FI distributors.
Both of your cars should use an "M" distributor, which actually has MORE
advance than any of the others. I have used the "L" and "M" distributors in
many of my cars (MT and AT, respectively) with good results. I usually set
the timing to factory spec for the distributor.
I think your compression ratios sound pretty reasonable, but you don't
mention whether your engines knock or ping. These are things everyone talks
about, but most people don't really know what they sound like. My '68 used
to do it badly, but I didn't know what it was at the time.
Knocking is a phenomena that occurs at low RPM and full throttle. It goes
away as the car speeds up past some point. It really sounds like something
is rattling around back there, kind of like a loose piece of cooling tin
around the engine. A friend once described it as sounding like dropping a
handfull of ball bearings slowly into a steel wastebasket.
If your engine pings, your CR is too high or your gas octane is too low. If
it doesn't ping, but it still overheats, then you have some other problem.
Perhaps it's running too lean, or maybe some of the cooling tin was left off
by someone who "just knew that it wasn't important," or maybe the air intake
bellows at the rear of the engine is torn, or gone, so your engine only gets
warm air to cool itself.
>I have Berg's technical books and I have found most of what he
>espouses to be true but as you imply he really does not address the type
>III in any detail. I recently purchased P/C set from him (stock) and
>would like to address the CR issue. Berg, as you know, advocates 6.6:1
>for regular and 6.9:1 for hi-test. I would think the type III with its
>FI might support more (since better fuel contol with the D-Jetronic than
>carbureators?)and benefit from the semi-head more (flame travel).
>Finally, according to the Bentley manual the "U" engines had 7.7:1 and
>the "X" engines had 7.3:1 both according to Berg are not supportable
>with today's gas. What are you running?
I believe Berg's logic and advice regarding CR and octane is good. It is
only prudent to lower your CR if you would like to run your car on today's
pump gasoline.
As I rebuild my 1600 engines, I have been using the late heads with the step
in them if I could. These heads came on the engines that started out with
7.3:1. I also use the dished pistons if they seem still good enough. Then
I lightly face the cylinder sealing surface and semi-hemi cut the cumbustion
chambers on a mill at work with one of Berg's cutters on an arbor I made.
I'm careful to work all 4 chambers in a single engine consistently, but I'm
a little embarrased to admit that I have never bothered to calculate the CR
that I ended up with. I port the heads per Berg's instructions.
One of my cars has non-step semi-hemi heads in it with flat top pistons (69
AT FI w/"M" distributor timed to TDC.) It runs perfectly and does not ping.
I know that Berg advises against the semi-hemi on the FI type 3s, however I
had already done one when I first saw that, and when I found that that car
ran fine, I just went ahead and continued doing it. I now have 4 such
engines on the road; three are mine and the forth belongs to a friend.
They've been on the road between 2 and 6 years, and all run just fine. I
expect them to last 10-15 years each.
Hope some of this helps.
Jim
---------------------------------------------------------------------
Melissa Kepner Jim Adney
jadney@vwtype3.org jadney@vwtype3.org
Laura Kepner-Adney
Madison, Wisconsin
---------------------------------------------------------------------