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I was wondering why the head on my 51 327 dosn't say Thunderbolt. Just looked at an engine that was supposed to be from a 51 327 that did say Thunderbolt. Also say a 53 Clipper with Thunderbolt on the head. What gives?

I believe the reason is simply that Packard hadn't adopted the trademark "Thunderbolt" until 1953. But the engines, within the same displacement, only differed in marginal details over the years other than changes in carburetion on some (4 bbl).

Someone stole your "Thunder", Bob.

The '48 Packard 288 and the '51 Packard 288 that I used to have both had "Thunderbolt" on the heads. Can't say if they were the original heads, though.

My 1948 Custom had a Thunderbolt head when I purchased it. However, I don't believe it was the original. As you probably know, it was and is common practice to change heads to increase compression.
I also believe that the Thunderbolt trade name didn't get placed into production until around 1953.

Greetings Friends my 52 Mayfair which has Auto Trans has the 327 ci and the 150 hp engine with Thunderbolt on the head and is the original factory motor. However if it came from Detroit with a Stick Shift it had a 135 hp motor and not the HI compression 150 hp head. I believe the 150 was an optional motor for Stick Shift.

Again looks like Packard did all sorts of things. My engine is a 1951 327ci with an ultramatic behind it. The head which I'm sure is original says 288ST 327AT. I thought that this head was used on both displacement engines and that was why it was marked 288 standard and 327 automatic referring to the transmission. Also everything I have read says that the 327 with a standard transmission had a lower compression head ( 7 to 1 ) and developed 150 hp and when an automatic trans was installed the above higher compression head was used (the one marked 288ST 327AT) which raised the compression ratio to 7.8 to 1 and the horse power to 155.
Looks like the The Thunderbolt name wasn't added until 1953. Too bad, I'd like to have my Thunder. Think the engine looks great with the Thunderbolt on top in red

Don't know when the 'Thunderbolt' designation was physically added to the head ... but Packard referenced 'Thunderbolt' engines in a 1951 Sales Brochure

I'm going to write Packard and complain. At least I can call it a Thunderbolt engine.

Bob, I have a spare head from a '53 288 that says "Thunderbolt" on it if you want it. If I remember right, it's marked "288ST 327AT".

Bob,

I have a '54 327, with a "288 AT" head on it. The "288 AT" Head gave the highest compression when compared to the "288 STD/327 AT", or the "327 STD" heads, and was often swapped onto the 327 motors. BTW my 288 AT does not have the "Thunderbolt" on it either. So I wonder if the ones without the "Thunderbolt" were service replacement heads.

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