Re: 356 CI Compression Ratio
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I have found some iron heads from 22nd series and later -- at least three 288 heads, a 327 and a 356, plus one mystery HC head with no displacement indication. I assume HC is high compression, but oddly the combustion chamber is much deeper on this head. It also doesn't have the flat center ridge running front to back. Anybody have info on what this HC head is intended for?
Also, any way to distinguish a 327MT vs. 327AT head?
Posted on: 1/30 13:57
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1942 Clipper Club Sedan
1948 Custom Touring Sedan (22nd Series) 1955 Patrician Sedan 1955 400 Sedan |
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Re: 356 CI Compression Ratio
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They are like hens teeth. I asked about the compression ratio they provided as another data point as to what was run on the 356 in the past. Although the head looks flashy having dissimilar metals with different expansion rates joined together increases the chances of seal/gasket failures as well. Anybody know what the CR was for these heads? I've not yet seen evidence that there were different Edmunds Packard heads for the 288/327/356/359 8 engines, just one. If so, that would give different CR for the different engines which doesn't make much sense. Anybody have information, or know what CR one got with it on the 356?
Posted on: 1/10 15:19
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1942 Clipper Club Sedan
1948 Custom Touring Sedan (22nd Series) 1955 Patrician Sedan 1955 400 Sedan |
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Re: 356 CI Compression Ratio
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Just curious. Anyone know what the Edmunds aluminum head did for the 356 in terms of compression ratio?
Posted on: 1/9 22:40
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1942 Clipper Club Sedan
1948 Custom Touring Sedan (22nd Series) 1955 Patrician Sedan 1955 400 Sedan |
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Re: 356 CI Compression Ratio
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That's generally true, but back in the late 40's automotive gasoline was about 72 octane (AKI). In the 50's it was around 80. It continued to increase until it peaked at 90 in 1974. It's currently running around 87. Consider what Packard had to accommodate in the design. Compression ratios increased industry-wide as octane increased. From the '48 Packard at 6.85, a '54 Packard had 8.70 compression. A '56 Packard V8 had 10.0 compression (which required premium / "ethyl"). BTW, there's a movement to eliminate multigrade gasoline and settle on a single grade of 95-97 so manufacturers can all take advantage of even higher compression ratios, which are now averaging about 10.5 but they want to go even higher for greater efficiency. Today's regular at 87 is a long way from the 76 of 1948, so a 1948 engine can benefit from a CR bump and run more efficiently. Edit: Trivia note -- Union 76 gas stations got their name from the octane rating of their premium "ethyl" gasoline back when they originated in 1935, 76, which had a patriotic sound to it alluding to the year 1776, hence Union 76.
Posted on: 12/31 18:16
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1942 Clipper Club Sedan
1948 Custom Touring Sedan (22nd Series) 1955 Patrician Sedan 1955 400 Sedan |
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Re: 356 CI Compression Ratio
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The '49 Golden Anniversary Std 8 (288) w/OD I used to own gave me up to 20mpg but that was on long trips that were all freeway. Mixed it was around 16-18mpg. I had rebuilt the engine (it had low compression prior to) and custom made a set of leaner metering rods for the carburetor and ignition was set not by spec but by ear (which was more advanced than book but that's why they had the "octane adjuster" Vernier scale on the distributor). Interestingly it actually did better at 70mph than at 55-60mph and that's where I would get the 20mpg. Packard offered different metering rods for the Carter carbs to enrich or lean from stock and I had managed to find the specs on them. One can change the metering jets but that changes the entire range whereas the optional rods had different profiles, not just fatter. In this way one can for example keep acceleration about the same but lean cruise.
My '48 Custom 356 w/OD is more like 13mpg in mixed driving (mostly freeway). I haven't messed with the metering rods in it yet but am contemplating bumping the CR before experimenting with mixture and ignition.
Posted on: 12/31 10:57
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1942 Clipper Club Sedan
1948 Custom Touring Sedan (22nd Series) 1955 Patrician Sedan 1955 400 Sedan |
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Re: 356 CI Compression Ratio
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I've revised the straight 8 compression ratio document to be less confusing. I suggest replacing the existing one with the attached one.
Would still like to know what the distinguishing marks are, if any, on the '48-'52 327 manual transmission head to differentiate it from the others.
Posted on: 12/30 17:52
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1942 Clipper Club Sedan
1948 Custom Touring Sedan (22nd Series) 1955 Patrician Sedan 1955 400 Sedan |
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Re: 356 CI Compression Ratio
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That is confusing, but I see it now. So a '48-'52 327 head will bring the 356 from 6.85 to 7.53. Anything else would be excessive for a flathead running regular. Note that I'm not thinking in terms of HP, per se, but as I said, efficiency. I would expect fuel economy to be improved a little. What are the distinguishing marks on the '48-'52 327 head to differentiate it from the others?
Posted on: 12/30 0:37
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1942 Clipper Club Sedan
1948 Custom Touring Sedan (22nd Series) 1955 Patrician Sedan 1955 400 Sedan |
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Re: 356 CI Compression Ratio
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So the file posted on this site is incorrect?
https://packardinfo.com/xoops/html/downloads/Packard%20Heads%20Compression%20Ratios.pdf
Posted on: 12/29 19:09
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1942 Clipper Club Sedan
1948 Custom Touring Sedan (22nd Series) 1955 Patrician Sedan 1955 400 Sedan |
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356 CI Compression Ratio
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I understand the compression ratio on the '48 356 is only 6.85. It seems this engine would run more efficiently at around 8.00 being that's what the later 9-main 327's ran. It appears swapping heads with any of the smaller displacement engines only lowers the ratio further. I'd like to hear thoughts on this topic.
Posted on: 12/28 23:38
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1942 Clipper Club Sedan
1948 Custom Touring Sedan (22nd Series) 1955 Patrician Sedan 1955 400 Sedan |
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