Packard Forum Index » General

My 327 9 main came with a "Thunderbolt" head, but it only says "327" on it, not "MT" or "AT".

Attach file:

---

  (41.31 KB)

My car, a 1951 convertible, has the original engine in it (number J 405166) and has "Thunderbolt" written on it.

Tom

Attach file:

---

  (25.65 KB)

TW, is the casting date on your head also 1951? I may easily have been incorrect thinking that 1953 or so was then the trademark began to be used. But as others have pointed out, many cars still have original engines but have had cylinder head replacements over the years that I don't think that's a reliable indicator. But it seems we can either find out thru the Patents and Trademark Office when Packard registered "Thunderbolt", or just start collecting casting dates on heads that have "Thunderbolt" cast into them. Sounds like a fun little project for someone to collect data on.

My 1948 Custom 8 had a replacement 356 head with a 1951 casting date (factory replacement with 14mm spark plugs) and doesn't have the Thunderbolt on it so I'm inclined to think the Thunderbolt trademark was later than the end of the 23rd series.

I will try to find the casting date tonight.

Tom

Looks like I stirred up some interesting conversation. My 51 300 has the engine number J406807 and is original to the car. I am the second owner but the original owner had passed on before I got the car. Got the car from the owners grandson. Was told the engine was rebuilt in the early 60's. Don't know why the head would have been changed. It's interesting that there were so many different heads. What was the compressionratio for a 327 with the head that just says 327 on it?

Our 52 Mayfair said "Thunderbolt" on the head. As a kid I was really impressed.

Bob1951;
I believe the compression for your 51 would be the same as the 48-50, which was 7:1. With a 288 head it would have increased to 7.5:1.

The head that was on my 1948 Custom is for a 327, it says "Packard Thunderbolt" and was cast on 3-4-54. The head on my other 1948 Custom engine says "Packard" and was cast on 1-28-48. So, it would seem that somewhere between 1948 and 1954 Packard adopted the name Thunderbolt. If we keep checking casting dates we should be able narrow this down even more.

As far as I know are 3 "standard" compression heads used in the 51-54 production run for the 327/288 Motors:

288 AT
288 STD/327 AT
327 STD

I wonder if the switch to the new body style in '51 also brought forth the "Thunderbolt" usage. I am beginning to belive that the 288 Thunderbolt, 327 Thunderbolt marked heads are the ones that came with the cars when the left the factory. Then non-thunderbolt heads with just the 288AT, 288 STD/327 AT, 327 STD markings, were the service replacements versions.

I guess we would need everyone to take a picture of their head, and note down any markings (casting numbers, dates, P/N's, etc), and lets see if we can figure this all out. Eventually a pattern will shake out.

Std = standard trans

AT= automatic trans

HA= high altitude, have seen postwar Packard head marked this way, higher compression meant for Denver, Mexico City or Pike's Peak.

Wonder if there were any other compression ratios? How about the aluminum heads?

I don't know what year it was, but I saw a head marked HC. I assume it stands for high compression. Does any one know for sure what it means and what year(s) it was for?