TAC Tech > Number Crunching
1978 L78 T/A 6.6 Original Block?
stros:
I had the L78 before replacing it with an LS3. It was the 500557 block. While I understand your desire to return it to original, the L78 is a dog of an engine. It has very little power and at least mine had a multitude of problems. I couldn't save it.
If I were you I'd find an engine that you'll enjoy driving the car with. The L78 will not be it, just to be frank.
langss:
--- Quote from: 5th T/A on September 13, 2023, 07:28:55 AM ---
Why someone would go through all the work to install a Ponitac 301 is beyond me. While engine mounts are the same and the trans will bolt up. The Power steering and alternator brackets are different. Most the AC compressor brackets are different. The 301 engine has a lower deck height and intake manifold requiring a much taller shaker baseplate. All these items will have to be changed back if you wish to install a Pontiac 400. The reason I know all thois is I swaped the stock 301 out of my 1980 TA and replaced it with a Pontiac 400.
--- End quote ---
I think I can provide a little insight into what may have happened...I didn't know it at the time... But the 78 TA that is my project, was bought as a parts car... It was hit hard on the rt front side. The guy that bought it from the Insurance Company, Thought he was buying a car that was compatible with the 78 he already had...Just because you own a Wrecking Yard...Doesn't mean you know MODEL SPECIFIC... So his Out Of California Model which he thought had the lesser engine(400) was in know way compatible with the California Model with the (403)...He was only going on the assumption that a 78 is a 78 and when he found out that nothing was usable from one car to the next...He decided to sell it. The guy that removed that Questionable Blown Up 400 and replaced it with the 301...probably thought he was cutting a fat hog... Whether the engine is any good or not...It was a 400...as compared to a 301, that may or may not have been on its last legs... In my case, the only thing the guy managed to swap from car to car, was the Speedometer and the original installed radio and speakers...And I only found that out after contacting the original owner. People do shady stuff when they think they wont get caught....
Wallington:
Why? Because it was their quick and easy way out of adding another engine, one easily obtained and cheap and they likely had it already. Not every car is a 100 point restoration candidate, some are simply cars.
roadking77:
Whether or not an L78, or a 557 block which most will put down, the 400 can be built with plenty of power to move the car up and down the road. Yes, new (1977/79sh) these cars are anemic compared to new (20--) cars today. However in the day just about the only car that had more power and performance was the corvette. I would think if you are looking for a Pontiac motor you will most likely have it rebuilt. The 557 block (I have one in my 77) is quite capable of more than stock h/p. This motor is fine and will run great. Would I stroke and run it on the drag strip, NO! But to cruise around its more than fine. Same can be said of an L78 motor. Stock configuration means ZIP if your doing a rebuild. Would an LS swap be cheaper maybe, as its not cheap to have a Pontiac motor built.
5th T/A:
--- Quote from: langss on September 13, 2023, 06:50:45 PM ---
--- Quote from: 5th T/A on September 13, 2023, 07:28:55 AM ---
Why someone would go through all the work to install a Ponitac 301 is beyond me. While engine mounts are the same and the trans will bolt up. The Power steering and alternator brackets are different. Most the AC compressor brackets are different. The 301 engine has a lower deck height and intake manifold requiring a much taller shaker baseplate. All these items will have to be changed back if you wish to install a Pontiac 400. The reason I know all this is I swapped the stock 301 out of my 1980 TA and replaced it with a Pontiac 400.
--- End quote ---
I think I can provide a little insight into what may have happened...I didn't know it at the time... But the 78 TA that is my project, was bought as a parts car... It was hit hard on the rt front side. The guy that bought it from the Insurance Company, Thought he was buying a car that was compatible with the 78 he already had...Just because you own a Wrecking Yard...Doesn't mean you know MODEL SPECIFIC... So his Out Of California Model which he thought had the lesser engine(400) was in know way compatible with the California Model with the (403)...He was only going on the assumption that a 78 is a 78 and when he found out that nothing was usable from one car to the next...He decided to sell it. The guy that removed that Questionable Blown Up 400 and replaced it with the 301...probably thought he was cutting a fat hog... Whether the engine is any good or not...It was a 400...as compared to a 301, that may or may not have been on its last legs... In my case, the only thing the guy managed to swap from car to car, was the Speedometer and the original installed radio and speakers...And I only found that out after contacting the original owner. People do shady stuff when they think they wont get caught....
--- End quote ---
I understand your point. Back in the day that the original engine was probably destroyed on this car, I hung around with a group of guys who tore up their TA's. I could get a running junk yard Pontiac 400 for $200.00. It was a quick easy way to get their cars back on the road again (they were used as daily drivers). I never did an Olds 403, but if one needed replacing, I would have used an Olds 350 that would go right in and the 403 air cleaner and shaker would have worked. I never did one with a small block Chevy either, but if it needed doing I would have put in another small block Chevy. These were usually one day engine swaps because everything was the same, nothing had to be modified. Occasionally I had to pull a two barrel intake from the junk yard engine in replace it with the blown engine's four-barrel manifold.
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