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346 ci Compression Test

Started by jackworstell, April 12, 2016, 09:02:19 AM

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jackworstell

....For a 1941-1948   346ci engine in good shape.....what kind of readings should I expect from a compression test    ( test with all spark plugs removed and choke and throttle wide open   and a warm engine )

Jack Worstell   CLC  # 7558

Bill Ingler #7799

Jack:  Here is what Cadillac said in a their engine book .  Bill


jackworstell

Thanks Bill

    Two questions:

     First, where exactly did this write-up come from ?   I have a bunch of old Cadillac manuals but some some reason I don't remember seeing this ??   (   how in the world did I miss this basic stuff ???)

     Second and more importantly....the date of the article....ie,  is it speaking to 1941 and up 346ci engines (  7.25 compression  ratio )  or 346ci engines prior to 1941 ( say  6.25  compression ratio ) ?

Thanks   Jack Worstell  CLC  #7558

Bill Ingler #7799

Hi Jack: Years ago at Hershey I found a Cadillac manual which was falling apart from age and the fact that it had just been soaked from a Hershey rain. I think it was called Cadillac Engine Diagnosis Manual. I could not save the cover but did save most of the rest. A couple of years ago I scanned what remained into my computer. Sorry but nothing from what I had left of the manual gives me a date as to if the numbers for compression are before or after 1941.   Bill



jackworstell


Alan Harris CLC#1513

I have a reprint of the same book. The first page says that it covers Cadillac 1937 through 1948 and LaSalle 1937 through 1940.

Since compression rose over the years, I always assumed that the earlier cars would show slightly less.

Also from experience, they can run quite well with somewhat larger differences between cylinders. My 1940 LaSalle shows between 105 and 90. I am pleased with its performance.