Re: "Forbidden" Brass Screws

["content22207" <brobertson@xxxx>]

Just received 2" of vintage B27/B28 Volvo factory manuals. Is going to
take a while to wade through it all, but did flip directly to the
"forbidden screws":

Are NOT primary idle speed system. Either was bad info from
www.brickboard.com (you'd think they would know) or I misunderstood
(will search bulletin board tonight to figure out which). According to
Swedes themselves screws are used to "balance" the engine (odd firing
sequence?). Are properly set with an exhaust gas analyzer, but most of
us will have to do setting with tach:

Volvo idles 600 RPM without bypass circuit, 900 with. 900 is correct
final idle BTW (only close inlet screw temporarily to verify correct
throttle plate setting in lieu of idle speed motor). Throughout
factory procedure idle maintained at 900.

You're supposed to set balancing screws by observing impact on CO2
from each side of engine. Brickboard guys accomplish more or less same
thing by observing impact on engine RPM's -- they count number of
turns each side to take from 600 to 1200.

I'm currently idling off throttle plates alone. Same effect as idle
speed motor (it routes same amount of air to each side of engine
simultaneously). No problems stalling etc, but engine does rock &
roll, especially given higher compression and probably more aggressive
cams. Will re-balance tonight and post results.

Bill Robertson
#5939

>--- In dmcnews@xxxxxxxxxxxxxxx, "Richard" <dmc_driver@xxxx> wrote:
>
> I know that someone out there is going to tell me and probably you
> too, that we shouldn't have messed with those screws because we're
> just masking an underlying problem with the idle system, but it works
> great for now, and I will parking my DMC soon for the winter anyway
> and doing lots of work on it the next few months, so I figured what
> the heck. :-)
> 
> 
> Richard Rowe
> 5853