Author Topic: 79 T/A with a L78 motor?  (Read 984 times)

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Offline 1coolZ71

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79 T/A with a L78 motor?
« on: July 11, 2011, 08:03:16 PM »
I have a 79 T/A with a 400- 4 speed.
According to the info on this sight, the 400 engine code was W72 with the PWH stamp for the 1979 4 speed cars.
My car has a L78 motor with YA on it.
Funny thing is the original window sticker actually says L78  6.6 Litre (400) 4-bbl
I also have the 6X-4 heads on it.
The vin doesn't match so I think it's not the correct motor but the original owner swears the motor was never changed.
Was it possible for the factory to put a different motor in when they ran out in 1979?
The shipping date was 10/30/1978

Offline ta78w72

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Re: 79 T/A with a L78 motor?
« Reply #1 on: July 11, 2011, 10:00:01 PM »
They saved some W72 engines for 1979 and didn't even offer the base 400.  So, to answer your question, no they didn't just throw in another engine because they ran out.  Your car, if it has a Z in the VIN, came with the W72 engine.  If the VIN on the engine is different it has been replaced.  I think factory replacements (under warranty) had a specific VIN series.

Offline John Witzke

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Re: 79 T/A with a L78 motor?
« Reply #2 on: July 11, 2011, 10:01:16 PM »
All of the original Pontiac build bulletins and memos identify the T/A 6.6 engine as W72 or T/A 400 in 1977-78 and L78 or T/A 400 in 1979. The T/A 6.6 engine carried UPC code W72 on the 1977-78 Firebird dealer order forms and was available only on Firebird Trans Am and Formula models, except for the 1977 Can Am.  All Pontiac bulletins and memos for the 1979 model year list the T/A 6.6 engine (W72) in the dealer order guide under UPC code L78.  

All 1977-79 Firebirds produced with the T/A 6.6 engine option list UPC code W72 PERF PACKAGE (NORWOOD, OH) or W72 PERFORM PKG (VAN NUYS, CA) on the factory build sheet.

A YA code block would not be the original block for a W72 car.  The correct block code for a 1979 car would have been PWH and have a casting number of XX 481988.  

Your car shipped in Oct 1978 would have been too early to have run out of blocks.  The final 1979 W72 cars were produced at Norwood assembly in May 1979.
« Last Edit: July 11, 2011, 10:03:29 PM by John Witzke »
John Witzke

Offline 1coolZ71

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Re: 79 T/A with a L78 motor?
« Reply #3 on: July 12, 2011, 08:07:03 AM »
Thanks guys.
It would appear that my car has a replacement 78 motor by using the vin stamped on the front of the block and the info you told me.
The casting number by the bell housing is 500557
Does that tell us anything more about the motor?

Follow up:  I found out the 500557 motor is not as beefy as the W72 motors.
I'll now start my search for a casting XX 481988 PWH block
« Last Edit: July 13, 2011, 10:55:46 AM by 1coolZ71 »