AMENDMENT OF THE
                          INTERIM OPERATING AGREEMENT


DATED:          As  of  March  21,  1997

The parties agree that they will amend the Interim Operating Agreement between
Wilson  Technologies  Incorporated  and  Wilson  Acquisition Corporation dated
March  7,  1997  in  the  following  manner:

1.          Wilson Acquisition Corporation ("WAC") will purchase inventory and
other  assets  (excluding  accounts  receivable)  of  Wilson  Technologies
Incorporated  ("WTI")  at  an agreed price of $394,000.00 to be paid to WTI in
cash  in  7  equal  $42,000.00 payments to be made per the following schedule:

     Two  payments  at  closing of the unamended agreement, and one payment on
each  of  the  following  dates:

                                March 20, 1997
                                 April 5, 1997
                                April 20, 1997
                               May 5, 1997, and
                                 May 20, 1997

     The  balance of $100,000.00 will be payable in the form of a note payable
20%  per year with interest at the prime rate, with the first payment due June
5,  1998.

2.      The Cessation Notice shall be effective without any further notice and
allow  assumption  of  all  S,G&A  expenses  by WAC on June 1, 1997 (including
selection  of  which  WTI  employees  will  be  retained  by  WAC).

     WAC  will  allow  a  single  individual  (SAFECO  job  manager, currently
anticipated  to  be  Rick  Remington) to be selected by WTI to be used for the
purpose  of  completing all field related activity of SAFECO bonded jobs (WORK
to  be  directed  by  WTI).    Salary  and expenses of this individual will be
reimbursed  to  WAC by WTI.  It is anticipated this SAFECO job manager will be
required  on  a  full-time basis for 30 to 60 days after the Cessation Notice,
with a reduced activity period extending beyond this full-time period.  Notice
will  be  given to WAC by WTI when the SAFECO job manager's full-time activity
is completed, and a sharing of his related expenses on a go forward basis will
be  agreed  to  by  the  parties  at  this  time.

     Note  there are no changes anticipated in the original agreement relating
to  the 40 man hours per week to be made available to WTI on a cost free basis
(to be directed by the SAFECO job manager) except that it will continue for as
long as the SAFECO job manager is on his full-time basis.  In addition, at the
conclusion  of  the  SAFECO  job  manager's full-time basis, it is agreed this
ratio of time by the SAFECO job manager to free man-hours will continue during
the  SAFECO  job  manager's  reduced  activity period, i.e., if the SAFECO job
manager  is  working  20  hours  paid  by  WTI,  WAC  will furnish 20 hours of
additional  man-hours  before  charging  cost  plus  10%.

     WAC will have the right to hire any WTI employees effective June 1, 1997.
The  parties  are  aware that WAC will assume 1 years vacation liability as of
May  31,  1997.    The  remaining amounts as of May 31, 1997, when paid to the
employees  will  be  reimbursed  by  WTI  or  offset  against  the note or any
inventory  or  other assets purchased by WAC.  In addition, Mr. Rick Remington
will  be  the  expense  of  WTI  as the SAFECO job manager as set forth above.

     WTI  will  be  responsible for reimbursing WAC for any allocable employee
and  material expenses (not including the free employee hours set forth above)
at a rate of cost plus 10% to finish warranty, SAFECO or other tasks which are
not  related  to  Penn  Wilson-CNG.

3.        WAC will have the right to use the name Penn Wilson-CNG, or any name
which  may  include  Wilson,  or  any  derivation  thereof.

4.          WAC  shall  have  the  right  to  carry  on  its  CNG  business.

5.       WAC will have the right to assume, and have assigned, if desired, the
Service  Contracts.

6.     WTI will be entitled to receive royalties for a cumulative amount of $2
million,  less  any  mutually  agreed upon offsets.  Thus far, the parties are
aware  of  several items, such as payments for the benefit of WTI to Rob Adams
and  other  "old  Wilson"  payments  which have been agreed upon to date.  The
royalty  will  be calculated at 5% of Net Revenue as defined in and payable on
the  terms  set  forth  on  Exhibit  A  to  the  Purchase  Agreement.

7.        All signatories (WTI, ZHI, WAC and POC) will exchange mutual general
releases  as  soon  as  practicable  following  the  date  hereof.

8.          Except  to  the extent set forth herein and in Paragraph 15 of the
Purchase Agreement, the Interim Operating Agreement and the Purchase Agreement
referred  to  herein  are  hereby  terminated.

Agreed  to  as  of  the  date  set  forth  above  by:

BUYER                                         COMPANY

Wilson  Acquisition Corporation               Wilson Technologies Incorporated


By:  By: /s/ IAN T. BOTHWELL                         /S/ LARRY DODSON
    ----------------------------------------      ----------------------------
       IAN T. BOTHWELL                                   LARRY DODSON
Title: SECRETARY AND TREASURER              Title: SENIOR VICE PRESIDENT AND
                                                   CHIEF FINANCIAL OFFICER

Penn  Octane  Corporation                     Zimmerman Holdings, Inc.

By: /s/ IAN T. BOTHWELL                       By: /S/ LARRY DODSON
    ----------------------------------------     ----------------------------
        IAN T. BOTHWELL                               LARRY DODSON
Title: VICE PRESIDENT AND CHIEF FINANCIAL     Title: SENIOR VICE PRESIDENT AND
       OFFICER                                       CHIEF FINANCIAL OFFICER