<PAGE>

EXHIBIT 9.2

                             STOCKHOLDERS AGREEMENT


         This Stockholders Agreement (this "AGREEMENT") dated as of April 2,
2004 is made by and among Energy Spectrum Partners, LP ("ENERGY SPECTRUM"), the
Investors Group (as defined in Section 1.1 below), the Directors Group (as
defined in Section 1.1 below), and Allis-Chalmers Corporation, a Delaware
corporation (the "COMPANY"). Energy Spectrum, the Investors Group, and the
Directors Group shall, as long as each such Person or group of Persons owns
Stock, be collectively referred to herein as the "STOCKHOLDERS".

                                    RECITALS

         WHEREAS, the Company is currently required, pursuant to the terms of
the Certificate of Designation, Preferences and Rights, as amended (the
"CERTIFICATE OF DESIGNATION"), of the Series A 10% Cumulative Convertible
Preferred Stock ($0.01 par value) of the Company (the "PREFERRED STOCK, SERIES
A"), to redeem all except one share of the shares of Preferred Stock, Series A
held by Energy Spectrum;

         WHEREAS, the Company and its directors recognize and acknowledge that
it is in the best interest of the Company for Energy Spectrum to waive its right
to mandatory redemption, and to instead convert its shares of Preferred Stock,
Series A into shares of Common Stock pursuant to the conversion terms of the
Certificate of Designation;

         WHEREAS, in light of the foregoing Recital, Energy Spectrum has agreed
to waive its right to mandatory redemption, and to convert all of its shares of
Preferred Stock, Series A into shares of Common Stock (as defined in Section 1.1
below), on the conversion terms set forth in the Certificate of Designation and
in the Preferred Stock Conversion Agreement (the "Conversion Agreement"), by and
between Energy Spectrum and the Company, dated the date hereof;

         WHEREAS, Energy Spectrum is willing to enter into the Conversion
Agreement in reliance upon the Company, the Directors Group and the Investors
Group fulfilling their respective obligations under this Agreement;

         WHEREAS, it is a condition of the consummation of the transactions
contemplated hereby that A-C will, prior to or concurrently with the execution
of this Agreement: (1) obtain a one year extension on the maturity date of
certain loan obligations, and (2) enter into a Stock and Warrant Purchase
Agreement (the "SWP Agreement") pursuant to which it will issue and sell to the
Investor Group 3,100,000 shares of its Common Stock and warrants (the
"Warrants") to purchase as additional 4,000,000 shares of Common Stock;

         WHEREAS, the Company and its directors recognize and acknowledge that,
in waiving its right to mandatory redemption, Energy Spectrum is waiving a
valuable right, both in economic terms and in non-economic terms, and that
Energy Spectrum would not agree to waive its mandatory redemption right without
assurances that the Company would honor its obligations under this Agreement;

                                       1
<PAGE>

         WHEREAS, the Company and its directors recognize and acknowledge that
the directors of the Company have certain fiduciary duties to the common
stockholders of the Company; including the duties of loyalty, care and good
faith;

         WHEREAS, the Company and its directors recognize and acknowledge that
under certain circumstances, the fiduciary duties of the directors of the
Company to its stockholders may require the directors to sell or consider the
sale of the Company;

         WHEREAS, the parties to this Agreement recognize that Energy Spectrum
would not agree to convert its shares of Preferred Stock, Series A pursuant to
Article 3 of this Agreement without assurances that, if no Qualified Public
Offering occurs on or before September 30, 2005, Energy Spectrum will have the
rights, and the Company will perform its obligations under, Article 4 of this
Agreement;

         NOW, THEREFORE, in consideration of the premises and the mutual
covenants set forth herein and other valuable consideration, the receipt and
sufficiency of which is hereby acknowledged, the parties hereto, intending to be
legally bound, agree as follows:

   DEFINITIONS; USAGE

   DEFINITIONS. For the purposes of this Agreement, unless the context otherwise
requires, capitalized terms used and not otherwise defined in this Agreement
shall have the following meanings:

         "AFFILIATE"--as defined in the rules promulgated under the Securities
Act.

         "AGREEMENT"--as defined in the first paragraph of this Agreement.

         "ALTERNATIVE INVESTMENT BANK NOTICE"--as defined in Section 4.3(a).

         "AS CONVERTED BASIS" -means after giving effect to the exercise and or
conversion of all securities exercisable for or convertible into Common Stock.

         "BOARD"--the board of directors of the Company.

         "CERTIFICATE OF DESIGNATION"--as defined in the Recitals above.

         "COMMON STOCK"--the common stock of the Company, par value $0.15 per
share, any stock into which such stock shall have been converted or changed, or
any stock resulting from any reclassification of such stock and all other stock
of any class or classes (however designated) of the Company, the holders of
which have the right, without limitation as to amount, either to all or to a
share of the balance of current dividends and liquidating dividends after the
payment of dividends and distributions on any shares entitled to preference.

         "COMPANY"--as defined in the first paragraph of this Agreement.

         "COMPANY RESPONSE"--as defined in Section 4.2(a).

                                       2
<PAGE>

         "CONSENT"--any approval, consent ratification, waiver, or other
authorization.

         "CORPORATE TRANSACTION"--either of the following transactions to which
the Company is a party:

   a merger, reorganization, consolidation or share exchange in which securities
possessing more than 50% of the total combined voting power of the Company's
securities outstanding immediately prior thereto are transferred to, or in the
event of a share exchange more than 50% of the total combined voting power of
the Company's outstanding securities immediately thereafter come to be held by,
a Person or Persons different from the Person or Persons holding such voting
power immediately prior to such transaction; or

   the sale, transfer or other disposition of all or substantially all of the
Company's assets.

         "DIRECTORS GROUP"--each of Munawar H. Hidayatallah, Jens Mortensen and
Saeed Sheikh.

         "DIRECTORS GROUP DESIGNEE"--the director the Directors Group has the
right to designate for election to the Board pursuant to Section 2.2(c).

         "ENERGY SPECTRUM"--as defined in the first paragraph of this Agreement.

         "ENERGY SPECTRUM DESIGNEES"--the directors Energy Spectrum has the
right to designate for election to the Board pursuant to Section 2.2(a).

         "ENERGY SPECTRUM RESPONSE"--as defined in Section 4.2(b).

         "INVESTMENT BANK"--the investment banking firm retained pursuant to
Section 3 hereof.

         "INVESTMENT BANK NOTICE"--as defined in Section 4.1.

         "INVESTORS GROUP"--each of the persons so designated on Exhibit "A."

         "INVESTORS GROUP DESIGNEES"--the directors the Investors Group has the
right to designate for election to the Board pursuant to Section 2.2(b).

         "PERSON"--any individual, corporation (including any non-profit
corporation), general or limited partnership, limited liability company, joint
venture, estate, trust, association, organization, labor union, or other entity
or Governmental Body.

         "PREFERRED STOCK, SERIES A"--as defined in the Recitals above.

         "QUALIFIED PUBLIC OFFERING"--the closing of an underwritten public
offering of Common Stock by means of a registration statement filed by the
Company under the Securities Act, which offering: (i) does not exclusively
relate to securities under an employee stock option, bonus or other compensation
plan; (ii) is at a price of not less than $0.50 per share of Common Stock (such
amount to be ratably adjusted to reflect any stock splits, subdivisions,
combinations or any other action that would cause an adjustment pursuant to any

                                       3
<PAGE>

antidilution provisions); and (iii) yields net proceeds to the Company of not
less than $10,000,000 (net of underwriting discounts and other expenses and
including proceeds received by the Company upon exercise of any over-allotment
option by underwriters).

         "SECURITIES ACT"--the Securities Act of 1933, as amended.

         "STOCK"--means all capital stock of the Company held by a Stockholder.

         "STOCKHOLDER"--Energy Specturm, each Person in the Investors Group,
each Person in the Directors Group, and each additional stockholder of the
Company who becomes a party to this Agreement by executing a counterpart to this
Agreement and delivering it to the Company.

   USAGE. In this Agreement, unless a clear contrary intention appears:

   the singular number includes the plural number and vice versa;

   reference to any Person includes such Person's successors and assigns but, if
applicable, only if such successors and assigns are not prohibited by this
Agreement, and reference to a Person in a particular capacity excludes such
Person in any other capacity or individually;

   reference to any gender includes each other gender or, in the case of an
entity, the neuter;

   reference to any agreement, document or instrument means such agreement,
document or instrument as amended or modified and in effect from time to time in
accordance with the terms thereof;

   reference to any law means such law as amended, modified, codified, replaced
or reenacted, in whole or in part, and in effect from time to time, including
rules and regulations promulgated thereunder and reference to any section or
other provision of any law means that provision of such law from time to time in
effect and constituting the substantive amendment, modification, codification,
replacement or reenactment of such section or other provision;

     "hereunder", "hereof", "hereto" and words of similar import shall be deemed
references to this Agreement as a whole and not to any particular Article,
Section or other provision thereof;

     "including" (and with correlative meaning "include") means including
without limiting the generality of any description preceding such term;

     "or" is used in the inclusive sense of "and/or";

   with respect to the determination of any period of time, "from" means "from
and including" and "to" means "to but excluding"; and

   references to documents, instruments or agreements shall be deemed to refer
as well to all addenda, exhibits, schedules or amendments thereto.

                                       4
<PAGE>

   BOARD OF DIRECTORS; VOTING

   BOARD SIZE. At all meetings (and written consents in lieu of meetings) of
stockholders of the Company, each Stockholder shall vote all of such
Stockholder's Stock and other securities entitled to vote in respect of the
election of the directors of the Company and take all other actions as may be
necessary to cause the number of directors on the Board to be not less than nine
(9) directors.

   ELECTION OF DIRECTORS. At all meetings (and written actions in lieu of
meetings) of stockholders of the Company at which directors are to be elected,
each Stockholder shall vote all of such Stockholder's Stock and other securities
entitled to vote in respect of the election of the directors of the Company to
elect as directors of the Company the Energy Spectrum Designees, Investors Group
Designees and Directors Group Designees:

   ENERGY SPECTRUM DESIGNEES. At each of the Company's annual or special
meetings of stockholders at which directors are to be elected, Energy Spectrum
shall have the right to designate in writing:

   three (3) nominees for election to the Board, so long as Energy Spectrum
and/or its Affiliates collectively hold a number of shares of Stock (on an As
Converted Basis) greater than 66% of the number of shares of Stock held by them
(on an As Converted Basis) at the date hereof, after making ratable adjustments
in the event of any stock splits, stock dividends or stock combinations;

   two (2) nominees for election to the Board, so long as Energy Spectrum and/or
its Affiliates collectively hold a number of shares of Stock (on an As Converted
Basis) greater than 33%, but less than or equal to 66%, of the number of shares
of Stock held by them (on an As Converted Basis) at the date hereof, after
making ratable adjustments in the event of any stock splits, stock dividends or
stock combinations; and

   one (1) nominee for election to the Board, so long as Energy Spectrum and/or
its Affiliates collectively hold a number of shares of Stock (on an As Converted
Basis) greater than five percent (5%) of the outstanding Common Stock on an As
Converted Basis, but less than or equal to 33%, of the number of shares of Stock
held by them (on an As Converted Basis) at the date hereof, after making ratable
adjustments in the event of any stock splits, stock dividends or stock
combinations.

                   This Agreement does not grant Energy Spectrum the right to
          have more than: three (3) directors on the Board at any time if
          designating directors pursuant to Section 2.2(a)(i), two (2) directors
          on the Board at any time if designating directors pursuant to Section
          2.2(a)(ii), or one (1) director on the Board at any time if
          designating directors pursuant to Section 2.2(a)(iii).

   INVESTORS GROUP DESIGNEES. At each of the Company's annual or special
meetings of stockholders at which directors are to be elected, the Investors
Group shall have the right to designate in writing the following:

                                       5
<PAGE>

     two (2) nominees for election to the Board, so long as the Investors Group
and/or Affiliates of any member of the Investors Group collectively hold a
number of shares of Stock (on an As Converted Basis) greater than 50%, of the
number of shares of Stock held by them (on an As Converted Basis) at the date
hereof, after making ratable adjustments in the event of any stock splits, stock
dividends or stock combinations; and

     one (1) nominee for election to the Board, so long as the Investors Group
and/or Affiliates of any member of the Investors Group collectively hold a
number of shares of Stock (on an As Converted Basis) greater than five percent
(5%) of the outstanding Common Stock on an As Converted Basis, but less than or
equal to 50%, of the number of shares of Stock held by them (on an As Converted
Basis) at the date hereof, after making ratable adjustments in the event of any
stock splits, stock dividends or stock combinations.

                   This Agreement does not grant the Investors Group the right
          to have more than: two (2) directors on the Board at any time if
          designating directors pursuant to Section 2.2(b)(i) or one (1)
          director on the Board at any time if designating directors pursuant to
          Section 2.2(b)(ii).

     DIRECTORS GROUP DESIGNEE. At each of the Company's annual or special
meetings of stockholders at which directors are to be elected, the Directors
Group shall have the right to designate in writing one (1) nominee for election
to the Board, so long as the Directors Group and/or Affiliates of any member of
the Directors Group collectively hold a number of shares of Stock (on an As
Converted Basis) greater than five percent (5%) of the outstanding Common Stock
on an As Converted Basis.

     REMOVAL. Each Stockholder agrees to vote such Stockholder's Stock
(calculated on an As Converted Basis), at all meetings (and written actions in
lieu of meetings) of stockholders of the company, for removal of a certain
director as directed by the Person or Persons having the right to designate such
director pursuant to Section 2.2(a), (b) or (c) above.

     VACANCIES. Each Stockholder agrees to vote such Stockholder's Stock
(calculated on an As Converted Basis), at all meetings (and written actions in
lieu of meetings) of stockholders of the Company, to fill any vacancy on the
Board caused by the resignation, death or removal of any director designated
under 2.2(a), (b) or (c) with a nominee selected as provided therein.

     corporate transaction

     NO QUALIFIED PUBLIC OFFERING. If a Qualified Public Offering does not occur
on or before September 30, 2005, then at any time on or after October 1, 2005,
Energy Spectrum may send notice to the Company that the Energy Spectrum
recommends that the Company retain an Investment Bank (the "INVESTMENT BANK
NOTICE") to seek and report on candidates interested in entering into a
Corporate Transaction, with a view toward maximizing stockholder value.

     INVESTMENT BANK PROCESS.

                  Within 45 days of receipt of the Investment Bank Notice, the
Board of Directors shall appoint an investment banking firm to seek and report
on candidates interested in entering into a Corporate Transaction, with a view
toward maximizing stockholder value. If the Company does not give Energy

                                       6
<PAGE>

Spectrum the Company's response of its selection (the "Company Response") within
the 45-day period described in this Section 3.2, Energy Spectrum may elect, in
its sole discretion, to give the Company the Alternative Investment Bank Notice
as set forth in Section 3.3(a). If Energy Spectrum elects to give the Company
the Alternative Investment Bank Notice, the Company shall relinquish its rights
under this Section 3.2, and the parties' rights under this Article 3 shall be
governed by Section 3.3.

     ALTERNATIVE PROCESS.

          If the Company does not give Energy Spectrum the Company Response
     within the 45-day period set forth in Section 3.2 above, Energy Spectrum
     may elect, in its sole discretion and at any time after the expiration of
     such 45-day period, to give a list of three (3) investment banking firms to
     the Company (the "ALTERNATIVE INVESTMENT BANK NOTICE"), each of which
     investment banking firms shall, by virtue of being recommended by Energy
     Spectrum, be considered an Investment Bank for purposes of this Agreement
     if eventually retained by the Company pursuant to and for the purposes set
     forth in this Article 3.

          Within thirty 30 days of its receipt of the Alternative Investment
     Bank Notice, the Company shall retain one (1) Investment Bank listed in the
     Alternative Investment Bank Notice.

     3.4 RETENTION. The Investment Bank selected pursuant to this Section 3
shall be engaged to seek and report on candidates interested in entering into a
Corporate Transaction, with a view toward maximizing stockholder value.

     GENERAL PROVISIONS
     ------------------

     NOTICES. All notices, Consents, waivers, and other communications required
or permitted by this Agreement must be in writing and will be deemed to have
been given to a party when:

     Delivered to the appropriate address by hand or by nationally recognized
overnight courier service, costs prepaid (with written confirmation of receipt);

     Sent by facsimile or email with confirmation of transmission by the
transmitting equipment; or

     Received or rejected by the addressee, if sent by certified mail, return
receipt requested, in each case to the following addresses, facsimile numbers or
email addresses and marked to the attention of the designated Person (by name or
title), or to such other address, facsimile number, email address or Person as a
party may designate by notice to the other parties:

        The Company:                       Allis Chalmers Corporation
                                           7660 Woodway, Suite 200
                                           Houston, Texas  77063

                                       7
<PAGE>

        with a copy to:                    Joseph P. Bartlett
                                           Spolin Silverman Cohen & Bartlett LLP
                                           1620 26th Street, Suite 2000 North
                                           Santa Monica, California 90404

        Stockholders:                      The contact information of
                                           each Stockholder is provided
                                           on Exhibit A hereto, which
                                           shall be updated by the
                                           Company whenever a transferee
                                           delivers a counterpart to this
                                           Agreement to the Company.

     RESTRICTIVE LEGEND ON STOCK CERTIFICATES. The Company and each Stockholder
agree that all certificates representing all shares of Common Stock of the
Company which at any time are subject to the provisions of this Agreement shall
have endorsed upon them in boldface type the following legend:

         THE SECURITIES REPRESENTED BY THIS CERTIFICATE IS SUBJECT TO
         RESTRICTIONS ON TRANSFER AND OTHER OBLIGATIONS CONTAINED IN A
         STOCKHOLDERS AGREEMENT BETWEEN THE CORPORATION AND CERTAIN OF ITS
         STOCKHOLDERS, A COPY OF WHICH IS ON FILE WITH THE CORPORATION AND WILL
         BE FURNISHED WITHOUT COST TO THE HOLDER HEREOF UPON WRITTEN REQUEST TO
         THE SECRETARY OF THE CORPORATION.

     TRANSFEREES. Under no circumstances shall any sale or other transfer of any
Stock subject hereto be valid until the proposed transferee thereof shall have
executed a counterpart and become a party to this Agreement, and thereby shall
have become subject to all of the provisions hereof, unless the requirement is
waived by written consent of the parties hereto; provided that this Agreement
shall terminate with respect to any shares sold in an offering registered under
the Securities Act or in a broker's transaction pursuant to Rule 144 under the
Securities Act.

     FURTHER ASSURANCES. Each party hereto agrees to perform any further acts
and to execute and deliver any further documents which may be reasonably
necessary to carry out the provisions of this Agreement.

     REMEDIES. If a breach of any party to this Agreement occurs, any party may
pursue any available remedy by proceeding at law or in equity to enforce the
performance of any provision of this Agreement. Except as otherwise provided by
law or as otherwise provided in this agreement, a delay or omission by any such
party in exercising any right or remedy accruing upon any such breach shall not
impair the right or remedy or constitute a waiver of or acquiescence in any such
breach. No remedy is exclusive of any other remedy. All available remedies are
cumulative.

     SEVERABILITY. In the event that any of the provisions, or portions thereof,
of this Agreement are held to be unenforceable or invalid by any court of
competent jurisdiction, the validity and enforceability of the remaining
provisions, or portions thereof, shall not be affected thereby.

                                       8
<PAGE>

     GOVERNING LAW. This Agreement has been executed in and shall be governed by
the laws of the State of Delaware.

     INUREMENT; ASSIGNMENTS. Subject to the restrictions against transfer or
assignment as herein contained, the provisions of this Agreement shall inure to
the benefit of and shall be binding on the heirs, assigns, successors in
interest, personal representatives, estates, heirs, and legatees of each of the
parties hereto.

     AMENDMENT. This Agreement may only be amended by the written consent of all
then current parties to this Agreement.

     ENTIRE AGREEMENT. This Agreement contains the entire understanding between
the parties hereto concerning the subject matter contained herein.

     COUNTERPARTS. This Agreement may be executed simultaneously in multiple
counterparts, each of which when so executed shall be deemed to be an original
and such counterparts shall together constitute one and the same instrument.

     REPRESENTATION BY COUNSEL. All of the Stockholders represent that they have
consulted, or have had an opportunity to consult, separate counsel in
negotiating and executing this Agreement.

             [THE REMAINDER OF THIS PAGE INTENTIONALLY LEFT BLANK.]

                                       9
<PAGE>

         IN WITNESS WHEREOF, the parties hereto have executed this Agreement to
be effective on and after April 2, 2004.


                                            THE COMPANY:
                                            -----------


                                            /S/ MUNAWAR HIDAYATALLAH
                                            ------------------------------------
                                            Munawar Hidyatallah,
                                            Chief Executive Officer



                                            DIRECTORS GROUP
                                            ---------------


                                            /S/ MUNAWAR HIDAYATALLAH
                                            ------------------------------------
                                            Munawar H. Hidayatallah


                                            /S/ JENS H. MORTENSEN
                                            ------------------------------------
                                            Jens H. Mortensen


                                            /S/ SAEED M. SHEIKH
                                            ------------------------------------
                                            Saeed M. Sheikh



                                            INVESTORS GROUP:
                                            ----------------


                                            /S/ LEONARD TOBOROFF
                                            ------------------------------------
                                            Leonard Toboroff

                                            Engel Investors Defined Benefit Plan

                                            /S/ DONALD ENGEL
                                            ------------------------------------
                                            By: ________________________________
                                            Title: _____________________________


                                       10
<PAGE>

                                            RER Corp.
                                            ---------


                                            /S/ ROBERT NEDERLANDER
                                            ------------------------------------
                                            By: ________________________________
                                            Title: _____________________________


                                            /S/ DONALD ENGEL
                                            ------------------------------------
                                            Donald Engel


                                            /S/ CHRISTOPHER ENGEL
                                            ------------------------------------
                                            Christopher Engel



                                            ENERGY SPECTRUM PARTNERS LP
                                            ---------------------------
                                            By: Energy Spectrum Capital LP,
                                                General Partner


                                            By: Energy Spectrum LLC, General
                                                Partner


                                            By:   /S/ THOMAS WHITENER
                                                  ------------------------------
                                            Name: THOMAS WHITENER
                                            Title: _____________________________

                                       11
<PAGE>

                                    EXHIBIT A

                   LIST OF STOCKHOLDERS AND ADDRESS FOR NOTICE


-------------------------------------- -----------------------------------------
             STOCKHOLDER                         ADDRESS FOR NOTICE
-------------------------------------- -----------------------------------------
Energy Spectrum                        5956 Sherry Lane, Suite 900
                                       Dallas, TX  75225
                                       Attention: Thomas Whitener

-------------------------------------- -----------------------------------------
Directors Group

Munawar H. Hidayatallah                7660 Woodway, Suite 200
                                       Houston, Texas 77063


Jens H. Mortensen                      7660 Woodway, Suite 200
                                       Houston, Texas 77063


Saeed M. Sheikh                        1050 17th Street, N.W.
                                       Suite 450
                                       Washington DC 20036
-------------------------------------- -----------------------------------------
Investors Group

RER Corp                               1450 Broadway
                                       20th Floor
                                       New York, NY  10022

Engel Investors Defined Benefit Plan   570 Park Avenue
                                       New York, NY  10021

Donald Engel                           570 Park Avenue
                                       New York, NY  10021

Christopher Engel                      1075 Park Avenue
                                       New York, NY 10128

Leonard Toboroff                       39 N. Moore Street
                                       New York, NY 10013

-------------------------------------- -----------------------------------------

                                       12