Re: TBI pressure regulator mod

["Walter Sherwin" <wsherwin@home.com>]

A few thought starters regarding 2bbl Rochester "220 style" TBI's  & fuel
pressure issues touched upon in your post..........................



1) Increased fuel pressure is one of the best ways to increase the TBI fuel
delivery rate/capacity of your system.  In fact, it is often the ONLY way in
extreme applications, when the duty cycle of the injectors has been maxed
out.

2) The fuel regulator mods shown on the page you noted do work, but will
only adjust the fuel pressure about +/- 2psig from the midpoint.  The
procedure shown is fine, if you really want to spend that much time
adjusting things.  There is a quicker/easier way.  Grasp the meter cover
assembly in your left hand, and firmly clinch the metal boss at the base of
the regulator can with a medium sized pair of Channel-Lok adjustable pliers.
Slowly & gently persuade the boss counter-clockwise and the small tack welds
will break free.  Voila, adjustability in just a few seconds in the field,
without disassembling the regulator.  For what it's worth, this will get you
+/- about 6-7% more fuel.

3)  If you have a 2bbl "220" TBI, you can pretty much pick & choose &
interchange the available regulators from various years and applications.
Most of the stock regulators will give you 9-13psig.  All of them will bolt
into place, if they were designed for a "220".

4)  There are two other (that I know of) significant OE TBI regulators that
you should also be aware of for the "220" TBI family.  P/N 17113186, which
will provide about 18psig fuel pressure, and  P/N 17113079  which will
provide roughly 30 psig.  These are bolt-on GM regulators which can provide
a finished "factory" look for your project.  Of course software mods will be
required, to compensate for the new-found fuel flow rates.

5)  Most of the low pressure TBI "220" (aka MAXI) TBI injectors that I have
bumped into can be reliably operated 7&24 at 2bar fuel pressure.  Many, but
not all, can also be reliably operated at upwards of 4+bar of fuel pressure.
Of course all the above is with an individual 4/1 amp driver per injector.

6)  Pressures other than above will require the use of an external PFI style
regulator, in the return line, in series with the TBI regulator.  Optimally,
you should blank-off the TBI regulator and turn it into a simple passageway
rather than a regulator.  This requires a small machined aluminum bit.

7)  The 2bbl (2") Holley TBI comes equipped with their version of an old
Bosch design that they later turned into an 80 pound per hour TBI injector
(nominally rated at 15psig).  These injectors should never be operated at
more than 18-20psig fuel pressure, for fear of hydraulic lock issues (again
with a 4/1 amp driver).  Hydraulic lock means ZERO fuel flow when you least
expect/want it, and the grey pressure zone leading up to the "lock" zone
translates to very irregular pulse width responses.

8)  No matter what intake manifold you use for your project, make sure that
the plenum holes at least match the diameter of your TBI bores.  I'd stick
with dual plane TBI intended manifolds, unless your engine is rather
peculiar.  A lot of people junk the TBI manifolds & stuff, without a clue as
to their potential,  had the parts been suitably tweaked.




TBI fuel does not have to be boring and/or constrained.   I'm in the midst
of machining a 2bbl TBI assembly, which will fit the footprint of a "220",
but which will have about 820cfm @1.5"HG of airflow and about 500#/Hr of
fuel  (for an artificially aspirated blow-thru application).  Bit of a
different approach, but should have a huge fun factor :)



Walt.









>That's just pretty pictures of what was a thread here years ago.
>BTW, be careful with the drill, the weld is harder then the steel around
it.
>Spares never hurt.
>You really need to use a Pressure guage to set it.
>Gm has more part nos for any one item then anyone I've seen.
>Probably a slight difference in pressure setting.
>Might look for an ol cross fire, generally the regs aren't welded on them
>Grumpy
>
>> > Does anyone have any thoughts on changing fuel pressure for TBI
>> > applications by doing the following instead of purchasing a regulator?
>> > http://www.dynosources.com/dyno_sources_GM_Pressure_Regulator_Hat.htm
>> >
>> > I'm trying to be economical (OK, cheap!) rather than buy a $70-80
>> > regulator.
>> >
>> > Also, does anyone know if there is a difference (& what it is) between
>> > the a late 80s car TBI and the 87-91-ish TBI regulators? I have a car
>> > TBI that looks like the one on my '93 Suburban (not the project -
yet!),
>> > which is different than the one on my '88 Blazer & I wanted to hack one
>> > with a spare in case I screw up (me? Never! Well, maybe...).
>> >
>> > Is one TBI unit preferred over the other? I don't see them as readily
>> > interchangeable.
>> >
>> > Last question - if I go to a 2" TBI (Holley offers one inexpensively
for
>> > my year truck as an option to a BBC TBI, plus it comes with bigger
>> > injectors - 53# I think), should I punch out the intake holes in my
>> > intake to 2" as well or buy an aftermarket TBI (or dual plane?) intake
?
>> > I have a spare intake in case I screw my original one up.
>> >
>> > TIA!
>> >
>> > Eric D
>> > 88 K30 Blazer
>>
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