Please note that the information for this guide was obtained through 3rd party sources so use at your own risk. There are also size overlaps with certain pulley sizes. This Guide should be used as just that -- a guide.

If you are using the new Billetflow Idler Bracket you will have to add 1/2" to the belt sizes shown below for your application due to its larger size, except where the configuration already notes a Billetflow bracket.

Note that wherever a 75" belt is recommended that the stock 75.1 belt can be used as well.

FYI -- Stock idlers are 90mm.

Also note that some of the belts below may no longer be available. I have been informed, for example, that the Gates K080735 is discontinued, and that the K080733 can be used in place of the K080735.

No Idlers

Pulley Size	Belt Size	Gates Micro-V Part #	Gatorback Poly-V Part #
3.65 (stock)	75.1"	K080751	4080750
3.40	75"	K080750	4080750
3.20	74.5"	K080745	4080745
3.10	74.5"	K080745	4080745
3.00	74.5"	K080745	4080745
2.95	74”	K080740	4080740
2.93	74”	K080740	4080740
2.90	74”	K080740	4080740
2.80	73.75”	K080735 (discontinued)	4080735
2.76	73.75”	K080735 (discontinued)	4080735
2.75	73.75”	K080735 (discontinued)	4080735

With 1-Piece Idler (100mm)

Pulley Size	Belt Size	Gates Micro-V Part #	Gatorback Poly-V Part #
3.65 (stock)	75.1”	K080751	4080750
3.40	75"	K080750	4080750
3.20	74.5" or 75"	K080745 or K080750	4080745 or 4080750
3.10	74" or 74.5"	K080740 or K080745	4080740 or 4080745
3.00	74" or 74.5"	K080740 or K080745	4080740 or 4080745
2.95	74” or 74.5"	K080740 or K080745	4080740 or 4080745
2.93	74” or 74.5"	K080740 or K080745	4080740 or 4080745
2.90	74" or 74.5"	K080740 or K080745	4080740 or 4080745
2.80	74"	K080740	4080740
2.76	74"	K080740	4080740
2.75	74"	K080740	4080740

With 3-Piece Idler Set (1-92mm and 2-100mm)

Pulley Size	Belt Size	Gates Micro-V Part #	Gatorback Poly-V Part #
3.65 (stock)	75.1”	K080751	4080750
3.40	75”	K080750	4080750
3.20	75”	K080750	4080750
3.10	75”	K080750	4080750
3.00	75”	K080750	4080750
2.93	74.5” or 75"	K080745 or K080750	4080745 or 4080750
2.90	74.5” or 75"	K080745 or K080750	4080745 or 4080750
2.80	74.5"	K080745	4080745
2.76	74” or 74.5"	K080740 or K080745	4080740 or 4080745
2.75	74” or 74.5"	K080740 or K080745	4080740 or 4080745

With 4-Piece Idler Set (1-92mm and 3-100mm)

Pulley Size	Belt Size	Gates Micro-V Part #	Gatorback Poly-V Part #
3.65 (stock)	76.5"	K080765	4080765
3.40	76”	K080760	4080760
3.20	75.5”	K080755	4080755
3.10	75” or 75.5"	K080750 or K080755	4080750 or 4080755
3.00	75”	K080750	4080750
2.93	75"	K080750	4080750
2.90	75"	K080750	4080750
2.80	74.5" or 75"	K080745 or K080750	4080745 or 4080750
2.76	74.5” or 75"	K080745 or K080750	4080745 or 4080750
2.75	74.5” or 75"	K080745 or 4080750	4080745 or 4080750

Miscellaneous Combos with Larger and Stock Lower Pulley

Upper Pulley	Lower Pulley	Idlers	Alternator Pulley	Misc. Parts	Gates Part #	Gatorback Part #
3.65 (stock)	8 lb.	Stock	3.2"	Lower idler in upper position (recommended position)		4080839
3.65 (stock)	6 lb.	1-100mm 1-90mm	Metco 3.5"	90mm idler (3 hole bracket) in hole closest to crank No snub idler bracket	K080806
3.65 (stock)	6 lb.	3-92mm	3.2"	Lower idler in upper position (recommended position)	K080816
3.65 (stock)	6 lb.	3-92mm	3.2"	Lower idler in lower position (see above recommendation)
3.65 (stock)	6 lb.	Stock	3.5"		K080820	4080820
3.65 (stock)	6 lb.	3-92mm	Metco 3.2"		K080806
3.65 (stock)	4 lb.	3-92mm 1-100mm	3.2"	Idler mounted in lower position	K080797
3.50 Kenne Bell	6 lb.	3 idlers	Stock		K080810	4080810
3.50 Whipple	Stock	Metco stock sized idlers	Stock	Whipple tensioner	K080764 or K080760
3.50 Whipple	Stock	Metco stock sized idlers	Stock	Stock tensioner with tab broken off	K080774
3.50 Kenne Bell	Stock	4 Metco stock sized idlers	Stock		K080755	4080755
3.50 Whipple	Stock	1-100mm	Stock		K080774
3.50 Kenne Bell	6 lb.	1-100mm	3.5"		K080830	4080830
3.25 Whipple	Stock	Metco stock sized idlers	Stock	Stock tensioner with tab broken off	K080765
3.5 Whipple	4 lb.	3-100mm 1- 90mm	3.2"	LFP snub idler bracket	K080816
3.25 Whipple	4 lb.	3-100mm 1-90mm	Stock	Lower idler in upper position (Tensioner notched as recommended by Stiegemeier)	K080825	4080825
3.25 Kenne Bell	4 lb.	3-100mm 1-90mm	3.5"	Old style snub bracket	K080825	4080825
3.25 Kenne Bell	8 lb.	3-100mm 1-90mm	3.5"	Hermann's S/C spacer	K080830	4080830
3.10	4 lb.	1-100mm	Stock		K080800	4080800
3.10	4 lb.	2-92mm 2-100mm	3.2"	Updated version of Billetflow idler bracket	K080820	4080820
3.10	6 lb.	1-100mm Snub Idler	3.2"		K080816
3.00 Whipple	Stock	Metco stock sized idlers	Stock	Stock tensioner with tab broken off	K080760
3.00	4 lb.	1-100mm 3-90mm	3.2"	Idler on upper position	K080810	4080810
2.93	Stock	3-100mm	Stock		K080740	4080740
2.93	4 lb.	2-90mm 2-100mm	Stock	Idler on Metco bracket in upper position	K080797
2.93	4 lb.	3-100mm 2-92mm	Stock	Updated version of Billetflow idler bracket Lower idler in upper position	K080797
2.93	6 lb.	3-100mm 1-90mm	Stock		K080797
2.93	6 lb.	1- 100mm	3.5"		K080816
2.93	6 lb.	Stock	3.5"		K080825	4080825
2.93	4 lb.	3-100mm 1-90mm	Stock	New Billetflow bracket Lower idler in upper position	K080797
2.93	4 lb.	3-100mm 1-90mm	3.2"	Lower idler in upper position	K080810 or K080816	4080810 or 4080820
2.93	4 lb.	3-100mm 1-92mm	3.2"		K080810	4080810
2.93	4 lb.	Stock	3.5"		K080797	4080772
2.93	4 lb.	1- 100mm	3.2"	Lower idler in lower position (Tensioner notched as recommended by Stiegemeier)	K080780	4080780
2.93	4 lb.	1- 90mm	3.2"	Lower idler in lower position (Tensioner notched as recommended by Stiegemeier)	Dayco Poly Cog Gold Label 5080785
2.93	4 lb.	Stock	3.2"	(Tensioner notched as recommended by Stiegemeier)	K080797 (some have used K080810)
2.93	6 lb.	2-90mm 2-100mm	3.5"	Tensioner notched	K080810	4080810
2.93	2 lb.	1-90mm	Stock			4080760
2.93	2 lb.	3-100mm 1-90mm	Stock	New Billetflow bracket Lower idler in lower position	K080774 or K080780
2.80	Stock	3-100mm 1-90mm	3.5"		K080755 or K080760
2.80	2 lb.	Stock	Stock	Lower idler in lower position	K080760	4080760
2.80	2 lb.	1-90mm	Stock	Lower idler in lower position	K080765	4080765
2.80	4 lb.	One?	Stock		K080774
2.80	4 lb.	1-100mm	3.2"	Lower idler in lower position	K080780	4080780
2.80	4 lb.	2-100mm	Stock	Lower idler in upper position	K080790
2.80	4 lb.	2-100mm	3.2"	Lower idler in upper position	K080806
2.80	4 lb.	3-100mm 1-90mm	Stock	Lower idler in lower position	K080774
2.80	4 lb.	3-100mm 1-90mm	3.5"		K080760 or K080755
2.80	6 lb.	3-100mm 1-90mm	Stock		NAPA 25-080806
2.80	4 lb.	3-90mm 1-100mm	3.2"	Lower idler in upper position	K080810
3.10	6 lb.	3-100mm 1-92mm	3.5"		K080825	4080825
2.76	6 lb.	3-100mm 1-92mm	3.5"		K080816HD	4080820
2.76	2 lb.	3-100mm 1-90mm	Stock	Old-style Billetflow bracket	K080780	4080780
2.76	2 lb.	3-100mm 1-90mm	Stock	New-style Billetflow bracket	K080785	4080785
2.76	4 lb.	3-100mm 1-90mm	Stock	Lower idler is lower position	K080780	4080780
2.76	4 lb.	3-100mm 1-90mm	3.2"	Tensioner not notched	K080806
2.76	4 lb.	3-100mm 1-90mm	3.5"	Old-style Billetflow bracket	K080780	4080780
2.76	4 lb.	3-100mm 1-90mm	Stock	Old-style Billetflow bracket	K080790
2.76	4 lb.	Stock	3.2"		K080797	4080772
2.76	Stock	3-100mm 1-92mm	3.2"	Lower idler in upper position Old Billetflow bracket	K080765	4080765
2.75	2 lb.	1-100mm	Stock		K080780	4080780

Gatorback Functional Part Number Gives You The Size Of The Belt

Example - Part No. 4 08 074 5
     1st digit (4) represents a K section Poly V-belt.
     2nd and 3rd digit gives the number of ribs.
     4th, 5th, and 6th digit are the length in inches.
     7th digit is tenth of an inch.
Part number 4080745 would be a K section Poly-V belt, eight ribs wide, with a length of 74 and 5/10 inches.

Goodyear Gatorback 2001 Catalog Reference

Effective Inches	Gatorback Poly-V Part #
72.5	4080725
73.5	4080735
74	4080740
74.5	4080745
75	4080750
76	4080760
77.25	4080772
78	4080780
79.75	4080797
81	4080810
82.5	4080825
83	4080830
83.75	4080839
85.5	4080855