Editing Pontiac V8 engine (section)

===400 W72 "T/A 6.6"===
At the end of 1976, Pontiac was no longer able to continue production of the 455 (7.5 L) V8 motor due to the tightening emissions requirements. As Pontiac still wanted to offer a performance motor to compete in the performance market, they looked back to the 400 Pontiac and how it could be improved to offer greater performance while meeting CAFE standards.

In 1977 the {{Convert|400|CID|L|1|adj=on}} T/A 6.6, ([[Regular Production Option|RPO]] code W72) was created to fulfil the performance engine gap in the Pontiac line-up. The W72 offered many improvements over the standard L78 400 Pontiac. One of the key upgrades were the 6x4 heads. The standard head seen on an L78 400 Pontiac was the low compression 6x8 head, while the 6x4 head seen on the W72 had hardened valve seats for a higher RPM operating range, improved air flow, and higher compression. These heads can be distinguished from 6x8 heads through a small stamped "4" on the top of the front boss. The head design was incorporated from the earlier 1970s 350 Pontiac heads, and could satisfy emissions in all states except for high-altitude emissions states and California. The W72 also featured a camshaft with a higher duration, finer tuned 800cfm Rochester Quadrajet, insulated fuel line, larger 60PSI oil pump, chrome valve covers, a larger harmonic balancer, and the "T/A 6.6" Shaker decal.<ref>{{Cite web|url=https://www.angelfire.com/wa/angryclown/CanAmW72.html|title = The T/A 6.6 (W72) Pontiac 400 Engine}}</ref> All of these improvements provided the W72 with a power rating of {{cvt|200|hp|PS kW|0}} at 3600&nbsp;rpm and {{cvt|325|lbft|0}} of [[Torque#Machine torque|torque]] at 2400&nbsp;rpm, while the standard L78 400 only produced {{cvt|180|hp|PS kW|0}} at 3600&nbsp;rpm and {{cvt|325|lbft|0}} of [[Torque#Machine torque|torque]] at 1600&nbsp;rpm.<ref>{{Cite web|url=https://tran-zam.com/fhistory/1977Engines.aspx|title=Tran-Zam.com|website=tran-zam.com}}</ref>

The W72 engine was standard in all 1977 [[Pontiac Can Am]]s (bar the 1977 Can Ams sold in California/High Altitude states which received the [[Oldsmobile V8 engine#403|L80 Oldsmobile 403]]) and was optional in all 1977-79 [[Pontiac Firebird]] Formula and Trans Am models. The W72 package was a standalone option, and although was discounted when ordered in conjunction with the Y82/Y84/Y88 Special Appearance package, did not come included with Special Edition Trans Ams, it remained an extra cost option. With some WS6 "Trans Am Special Performance Package" bundles in 1978, the W72 engine was incorporated with the WS6 option group and not listed on the dealer order invoice. However, it can easily be determined by examining the cost price of the option, where the package excluding the W72 engine cost $251, and with the engine, cost extra at $324.<ref>{{cite web | url=https://www.hitmantransam.com/Pages/ws6ws7.htm | title=Hitman's Pontiac Trans Am Site - WS6 and WS7 }}</ref>

All 1977-1978 Trans Ams ordered with the 4-speed Borg Warner Super T-10 manual transmission received the W72 T/A 6.6 engine. There are no manual transmission equipped Trans Ams that came factory with the standard L78 400 motor in 1977–79. The W72 Performance Package also included an upgrade to the rear differential ratio, setting the rear gear ratio to 3.23 for all 1977 and 1979 W72 Firebirds, with the exception being 3.42 for 4-speed equipped W72 Firebirds in 1978 only.

All W72 equipped Trans Ams featured the "T/A 6.6" shaker decal. A common misconception made by enthusiasts was the notion that all Pontiac engine equipped Trans Ams featured the "T/A 6.6" decal on the shaker, however, it was exclusive to the W72 engine that was featured on less than half of all Trans Ams made during this period. All L78 Pontiac 400 equipped cars received the same shaker decal as the [[Oldsmobile V8 engine#403|L80 Oldsmobile 403]], being "6.6 LITRE". This may have been propagated by the only authorized company that is licensed to reproduce these decals not including the "6.6 LITRE" in the Trans Am decal kits, and only including "T/A 6.6" with no extra cost.

For the 1978 model year, Pontiac re-incorporated the earlier thicker cast cast engine block denoted by the cast number 418988 and a "XX" cast into the side of the block. The earlier 1975-78 blocks had metal shaved from the journals and bottom end as well as a decrease in the nickel content of the block in an attempt to decrease the overall weight of the vehicle to help alleviate emissions and cost. The camshaft was also revised to have a slightly higher duration, the carburetor jets tuned and a dual exhaust was implemented allowing the power to increase to {{cvt|220|hp|PS kW|0}} at 4000&nbsp;rpm and {{cvt|320|lbft|0}} of [[Torque#Machine torque|torque]] at 2800&nbsp;rpm.<ref>{{Cite web|url=https://tran-zam.com/fhistory/1978Engines.aspx|title=Tran-Zam.com|website=tran-zam.com}}</ref> By mid-1978, the W72 could no longer be ordered in conjunction with the MX1 [[Turbo-Hydramatic#THM350|3-speed Turbo-Hydramatic 350]] automatic transmission, and could only be ordered with the 4-speed manual transmission.

By 1979, Pontiac was no longer allowed to produce the 400 engine as emissions further tightened. Pontiac had prepared for the forthcoming cancellation of the venerable 400 by producing large volumes of the stronger cast "XX" 400 blocks in 1977 that were assembled in 1978, and stockpiled at a warehouse by the assembly plant for later use. The 1979 Firebird model line was the last year for the Pontiac 400, and by this point not only was it required with the 4-speed manual transmission, it also required the WS6 Special Handling Package as mandatory equipment. The W72 was only available for a very short time, with the majority of 1979 model year W72 Firebirds ordered in late 1978. By early 1979, orders for the W72 package were being rejected by dealers as they supply had run dry. Instead, they were substituted with the [[Oldsmobile V8 engine#403|L80 Oldsmobile 403]], or the [[#301|L37 Pontiac 301]] if they still requested a 4-speed transmission. On the invoicing for the 1979 model year Firebirds, they had the option listed as L78, however, every 1979 400 equipped car received a W72 engine.

According to the June 2019 issue of ''Muscle car Review'' magazine, during dyno testing performed during that era, the National Hot Rod Association (NHRA) rated this Pontiac W72 400 T/A 6.6 engine at 260 to 280 net horsepower instead of the 220-hp rating published by Pontiac. The 1979 W72/WS6 equipped Trans Am was considered to be one of the overall best performing cars of the decade due to having a powerplant that produced more power than any other competitor on the market at the time with handling equipment to supplement the performance.<ref>{{Cite web|url=https://www.hemmings.com/stories/article/1979-pontiac-trans-am-2|title = 1979 Pontiac Trans Am}}</ref>