<PAGE>
                                                                    EXHIBIT 10.1

        SEPTEMBER 26, 2001 AMENDMENT TO MUTUAL AGREEMENT BETWEEN MAGNETI
                  MARELLI USA, INC. AND EDELBROCK CORPORATION

     This September 26, 2001 Amendment is entered by and between MAGNETI
MARELLI POWERTRAIN USA, INC. ("Magneti"), formerly known as Magneti Marelli
USA, Inc., and EDELBROCK CORPORATION ("Edelbrock") to amend in part, as set
forth below, the Mutual Agreement between Magneti Marelli USA, Inc., and
Edelbrock Corporation dated January 1, 2000 (the "Agreement"), as modified by
letter dated September 20, 1999, November 1, 1999, and November 5, 1999.

1.   Paragraph No. 1 of the Agreement is amended, to add to the definition of
     Product, Part Number 1412 and Part Number 1413.

2.   Paragraph No. 5 of the Agreement is amended to replace the first sentence
     with the following:

     Edelbrock agrees to purchase from Magneti, and Magneti agrees to sell to
     Edelbrock, a minimum quantity of Product equal to 225,000 units in
     calendar year 2000, 200,000 units per year in calendar years 2001 through
     2003, and 150,000 units per year in calendar years 2004 through 2009,
     provided, however, that Edelbrock shall be deemed to have complied with
     such purchase requirements in each year that its purchases are not less
     than ninety percent (90%) of such targeted minimum amounts.

3.   Paragraph No. 8 is amended to read in its entirety as follows: The term of
     this Agreement shall commence on January 1, 2000, and shall end on
     December 31, 2009.

4.   New Paragraph No. 15 shall be added as follows:

     Cancellation Election and Purchase Option:

     If, at any time during the course of this Agreement, (a) any unrelated
     person directly or indirectly acquires an ownership interest in either
     party exceeding fifty percent (50%), or (b) market conditions restrict
     competitiveness prohibiting the parties from meeting their mutual
     objectives, then all provisions of this Agreement, other than commitments
     outlined in Paragraph 5, if the triggering event is a change of control,
     may be cancelled by either party with twelve (12) months prior written
     notice. Upon written notification that Magneti elects to cancel this
     Agreement in accordance with this paragraph 15 and during the twelve (12)
     month period following, Edelbrock shall have the Right of First Refusal to
     match any third party offer for, or acquire from Magneti at a fair market
     value, all equipment, machinery, molds, tooling and all other assets
     including manufacturing rights (free and clear of all liens and
     liabilities) used by Magneti to manufacture the Product (Shall include
     Edelbrock throttle bodies and electronic fuel injection-related
     components). Upon written notification that Edelbrock elects to cancel
     this Agreement in accordance with this paragraph 15 and during the twelve
     (12) month period following, Magneti shall have the Right of First Refusal
     to continue distribution of the product and will receive such assistance
     from Edelbrock as is available to provide the product through the same
     distribution network as was used by Edelbrock and access to market
     information accumulated by Edelbrock relative to the product, its
     competition and market characteristics. Should Magneti distribute the
     product, it will do so under a different brand label and not carry the
     Edelbrock name.


MAGNETI MARELLI POWERTRAIN USA INC.        EDELBROCK CORPORATION


By:        /s/ FRED GOPAL                  By:      O. VICTOR EDELBROCK
    -------------------------------            -------------------------------
               Fed Gopal                            O. Victor Edelbrock
           President and CEO                         President and CEO