[DML] Re: Manifold Vacuum Question

["content22207" <brobertson@xxxxxxxxxxxx>]

I'm guessing you have a Series 004? (Last 3 digits stamped into the
housing, not cast). Volvo used a lot of those in the late 70's. They
do indeed lack full throttle enrichment, but otherwise operate over
nearly the same parameters as Series 066. Take a little bit longer to
warm up (about 150 degrees F versus 110), but ultimately yield the
same counter pressure. In fact all PRV CPR's ultimately produce 49-53
PSI, so all are interchangeable (Series 021 is a little wierd, but was
only used 1 year in high altitude states like Colorado).

The full throttle enrichment mechanism on a Series 066 is totally
different from all other CPR's. Is much more complicated. Also shuts
off after the engine warms up (via a thermactor valve in the vacuum
line). To plumb one of those properly you need not only the thermactor
valve -- not all Y pipes have a bung for one -- but a delay valve as
well. Full manifold vacuum is routed through the thermactor valve to a
tee that splits vacuum to both sides of the CPR (one of which has a
delay valve inline).

Series 018, 029, and 038 all have much simpler full throttle
enrichment. Full vacuum simply runs from the manifold straight to a
barb on the top.

K Jetronic PRV's do have ported vacuum barbs under the throttle
plates. You wouldn't want to use them for the CPR, but could run a
line straight to the ignition distributor if you wanted to get rid of
the cutoff solenoid (that's how Volvo did it, albeit with some unusual
Rube Goldbergness prior to 1980 -- emissions. After 1980 it's just a
single line straight to the distributor). If you've got both a Series
004 CPR and a vacuum cutoff solenoid on the ignition distributor, your
engine must be 1979 (or at least it's configured that way). Of course
1979 is B27, not B28....

Bill Robertson
#5939

>--- In dmcnews@xxxxxxxxxxxxxxx, "Rick" <rdevaux@xxxx> wrote:
> I'm trying to learn a little about manifold vacuum on the B28 engine.  
> I currently have a warm up regulator that doesn't have a vacuum 
> enrichment on my engine.  If I add a CPR that has vacuum enrichment, 
> where on the intake manifold should I hook the vacuum tubing going to 
> the CPR?  Can I tee into the vacuum line that is taken off of the rear 
> of the passenger's side intake runner (currently goes to distributor 
> retard solenoid)?  What's the difference between ported vacuum and 
> manifold vacuum?  Thanks, Rick D







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