1966 Chevelle Engine ID Suffix Codes

The engine identification code consists of the engine assembly plant, the engine assembly date, and 3 letter suffix indicating the cubic inch displacement, the horsepower rating, and generally, what type of transmission was to be installed with the engine. Manual transmissions required a bushing in the rear of the bellhousing where an automatic transmission did not. Many engine "accessories" such as the carburetor, alternators, and power steering units were not installed at the engine assembly plant but rather at the final assembly plant.

Engine			Transmission	Notes
Code	Size	HP-RPO
AA	194-1	120	Manual	Overdrive
AC	194-1	120	Manual	Heavy Duty Clutch
AG	194-1	120	Manual	A.C.
AH	194-1	120	Manual	Heavy Duty Clutch/A.C.
AL	194-1	120	Powerglide
AS	194-1	120	Manual	Overdrive/A.I.R.
AT	194-1	120	Manual	A.C./A.I.R.
230 ↓
BL	230-1	140-L26	Powerglide	A.I.R. (Domestic only)
BM	230-1	140-L26	Powerglide	A.C./A.I.R. (Domestic Only)
BN	230-1	140-L26	Manual	Overdrive/A.I.R. (Domestic Only)
BO	230-1	140-L26	Manual	A.C./A.I.R.
BP	230-1	140-L26	Powerglide	Export only
BR	230-1	140-L90	Powerglide	A.C.
CA	230-1	140-L26	Manual	Overdrive
CB	230-1	140-L26	Manual	A.C.
CC	230-1	140-L26	Powerglide
CD	230-1	140-L26	Powerglide	A.C.
283-2 ↓
DA	283-2	195	Manual
DB	283-2	195	Manual
DC	283-2	195-L92
DE	283-2	195	Powerglide
DF*	283-2	195-L92	Powerglide
DI	283-2	195	Manual	Overdrive/A.I.R.
DJ	283-2	195	Powerglide	A.I.R.
DK	283-2	195	Manual	A.I.R.
DN	283-2	192	M01
283-4 ↓
DG	283-4	220-L77	Manual
DH	283-4	220-L77	Powerglide
DL	283-4	220-L77	Manual	A.I.R.
DM	283-4	220-L77	Powerglide	A.I.R.
DO	283-4	220-L77	M01
327 ↓
EA/EAH	327-4	275-L30	Manual	Rochester/Carter or Holley Carb
EB	327-4	275-L30	Manual	A.I.R.
EC	327-4	275-L30	Powerglide	A.I.R.
EE	327-4	275-L30	Powerglide
EO	327-4	275-L30	M01
327-L79 ↓⁽³⁾
EP#	327-4	350-L79	Manual
ER#	327-4	350-L79	Manual	A.I.R.
ES#	327-4	350-L79	M01
396-L35 ↓
EDR	396-4	325-L35	Manual	Rochester Carb ⁽¹⁾
ED/EDH	396-4	325-L35	Manual	Holley Carb
EH	396-4	325-L35	Manual	Rochester Carb/A.I.R.
EKR	396-4	325-L35	Powerglide	Rochester Carb ⁽²⁾
EK/EKH	396-4	325-L35	Powerglide	Holley Carb
EM	396-4	325-L35	Powerglide	Rochester Carb/A.I.R.
396-L34 ↓
EF	396-4	360-L34	Manual
EJ	396-4	360-L34	Manual	A.I.R.
EL	396-4	360-L34	Powerglide
EN	396-4	360-L34	Powerglide	A.I.R.
396-L78 ↓
EG**	396-4	375-L78	Manual	Holley Carb/Solid Cam

⁽¹⁾ It is doubtful that any manual transmission L35 engines were built with a Rochester carburetor w/o A.I.R.
⁽²⁾ It is doubtful that any Powerglide transmission L35 engines were built with a Rochester carburetor w/o A.I.R.
⁽³⁾ Although an engine code was assigned to the L79 engines, none were ever installed in a 1966 Chevelle.

According to accepted production numbers and GM Heritage Center, the 396 engines break down as follows:
2-door sedan pickup L35 325hp base engine - 1,865 (engine standard in both SS 396 models)
2-door sedan pickup L34 360hp high performance engine - 1,025
2-door sedan pickup L78 3675p special high performance engine - 83
2-door coupe/convertible L34 360hp high performance engine - 23,786
2-door coupe/convertible L78 375hp special high performance engine - 3,016
An estimated 2,973 2-door sedan pickup El Caminos were ordered with one of the 396 engines

Roughly 32.6% of the 325hp 396 was ordered with a Powerglide transmission.
Roughly 67.4% of the 325hp 396 was ordered with a manual transmission.

Roughly 5.8% of the 360hp 396 was ordered with a Powerglide transmission.
Roughly 94.2% of the 360hp 396 was ordered with a manual transmission.

DF code is RPO L92.

* April 11, 2023 - Thanks for Jeff Helms for updated 1966 396 engine breakdown.

New entries in ORANGE are from GM docs dated 6-17-66

# Chevrolet records show this engine in production as early as February 7, 1966. The release date was due sometime in late February or early March. No L79-optioned Chevelles were reported sold in 1966.

** The L78 engine option was canceled early in 1965 and reinstated October 7, 1965. Many early Chevrolet publication materials, such as this page from an early training program booklet also listed this engine at 425hp and, oddly, the L34 (360hp) engine does not show a horsepower rating at all.
© ChevelleWorld

GM of Canada documentation indicates that 499 (total) L34 13617 and 13667 Malibus were produced for sale in Canada.

1966 Chevelle 396-cid Engine Production

The base engine for the SS 396 series for 1966 was the L35 396-cid 325hp engine. This engine (along with the L34 and L78) was also an optional engine in the El Camino and 1,865 L35 engines were sold. There were 72,272 SS 396 sport coupes (66,380) and convertibles (5,393) sold.

L35 engines could be equipped with either a Rochester (or Carter equivalent) Quadrajet carburetor or Holley carburetor; all L34 and L78 engines were equipped with a Holley carburetor.

RPO	hp	Transmission	Suffix	Production	Notes
L35	325	Manual	ED/EDH ⁽⁴⁾	28,430	Holley
L35/K19	325	Manual	EH	3,775	Rochester & A.I.R.
L35/M35	325	Powerglide	EKR	21	Rochester/Holley
L35/M35	325	Powerglide	EK/EKH	12,592	Holley
L35/K19/M35	325	Powerglide	EM	2,963	Rochester & A.I.R.
				47,781	Total L35 Engines
				47,335	Total L35 Cars ⁽³⁾
				466	Service Engines

L34	360	Manual	EF	20,283
L34/K19	360	Manual	EJ	4,037	A.I.R.
L34/M35	360	Powerglide	EL	1,179
L34/K19/M35	360	Powerglide	EN	323	A.I.R.
				25,822	Total L34 Engines
				24,811	Total L34 Chevelles
96.1% of total L34 engine production went into Chevelles.				1,011	Service Engines

L78	375	Manual	EG	3,167
				3,167	Total L78 Engines
				3,099	Total L78 Chevelles
				68	Service Engines
97.9% of total L78 engine production went into Chevelles.

(3) L35 Chevelle engine breakdown
Total SS 396 Chevelles	72,272
LESS L34 engines	23,786	1,025 in El Caminos
LESS L78 engines	3,016	83 in El Caminos
Total L35 engines	45,470
PLUS L35 El Caminos	1,865
Total L35 Chevelles	47,335

(4) Original data published years ago by NCOA only lists ED (no EDH), and it is specifically labeled as "Holley", with no separate quantity for any ED Rochester engines. That fact (when he did list the oddball EKR code separately) suggests to me that there was never a 66 ED engine built for a Rochester carb. Perhaps there was a plan to build both varieties (which resulted in the additional H suffix), but for whatever reason it did not happen, and the Tonawanda records (or maybe just Fran) therefore only listed ED since no need to differentiate. - Courtesy Jeff Helms

Chart clearly shows that any 396 engine available in 1966 could be ordered in both the 13480 and 13680 series El Camino.

© ChevelleWorld
The 375hp L78 engine required an additional bracket on the passenger side of the engine; GM's solution to keep the alternator belt from flying off.