On Tue, 20 Aug 1996, Will Zehring wrote:
> Fellow fiends:
>
> Please settle these issues: I'm having a 'discussion' with a member of my
> local car guy support group on timing the venerable B-series engine. Please
> tell me if the following statements are true or false:
>
> Statement #1: "Don't bother dynamically tuning the B-series engine. Just
> static tune it at 10 BTDC and you'll be fine. Leave me alone!"
Um, usually there will be a dynamic timing spec, which will give you
better timing in the event that the distributor's advance curve is not
what it was/should be. It is my humble opinion, to boot, that tiny
variations from engine to engine (cam timing, actual compression
ratio, etc.) will result in each engine's ideal timing being a little
different; I always noodle it around to where it runs best.
>
> Statement #2: "The vacuum advance on the B-series doesn't really matter.
> You can drive the car with perfectly good performance with out the vacuum
> advance working at all. Now push off!"
This is true, however, the vacuum advance is a boon to idle smoothness
and in-town gas mileage. It wasn't put there for decoration.
> Statement #2.5: "Don't worry about the centrifugal advance springs in your
> distributor. You're just imagining you're losing power at high rpms. Its a
> B, for chrissake (!), you don't have power at any rpms anyway! Enjoy the
> car and stop bothering me." (editor's note: my friend is a bit of a snot
> when it comes to MGs).
In my experience, a worn distributor is the last thing people check when
performance is inexplicably down, and often it is the cause. If the B
engine ran in a speed range only 2-3000 rpm wide, maybe the mechanical
advance wouldn't be important, but it runs in a 6000 rpm wide range; the
distributor needs to be able to adjust. And yes, a healthy, properly
tuned B Series engine will make usable power up to at least 5500 RPM.
> Statement #3: "Your car is too far advanced if its at 15+ BTDC at 1200 RPM.
> Like I say, just static tune it and stop bothering me."
Set the timing where the car runs best. Don't worry too much about
numbers, unless you end up 20 degrees off or something.
> Statement #4: "Don't even think of enhancing performance in the B-series
> with a bunch of tricks like a hot cam or gas porting. The thing's a lump,
> always has been, always will be. Be happy with what you have and don't get
> fancy. Now beat it!"
If you are of the opinion that the B engine is a lump (and I, personally,
would consider that an exaggeration, albeit grounded in a kernel of
truth), the reason it is a lump is because 1) the head does not flow well;
and 2) the cam is, ahem, modest, among other things. Fix those two things
alone, and the engine should improve nicely. Balance and cc it, up the
compression, and it should be perfectly jolly. An International
Harvester Diesel is a lump. A GM Iron Duke is a lump. A B-Series is a
sports car engine waiting to be born.
Michael Chaffee
mchaffee@staff.uiuc.edu
I speak only for Diesel Fried Chicken Motorsports. CCSO frequently disagrees.
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