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Old 02-16-2020, 12:16 PM   #1
Bob Bidonde
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Default The Diamond Mark Challenge

Where did this myth about the "Diamond" marked engines and parts being superior to factory items come from. I think the diamond is a pattern maker's and or foundry trademark having nothing to do with the attributes of items bearing the "Diamond."
By the way, I have 2 Model "B" engines and some Model "A" parts with the infamous "Diamond" mark. I do not see any quality, functional or ruggedness differences in comparison to their original factory parts.
I challenge anyone to show me facts / physical evidence / era literature that substantiates the "Diamond" mark has any worthwhile significance.
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Old 02-16-2020, 03:21 PM   #2
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Default Re: The Diamond Mark Challenge

I'm all ears too.
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Old 02-16-2020, 03:43 PM   #3
Kurt in NJ
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Default Re: The Diamond Mark Challenge

what i see is a original A block has a X reinforcement under the stud in the center, diamond blocks have none ---most diamond blocks have exhaust seat inserts
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Old 02-16-2020, 04:19 PM   #4
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Default Re: The Diamond Mark Challenge

I have yet to come across a diamond "A" block but have been through a number of diamond "B" blocks that were beyond restoration because of casting flaws, mainly core shifts that resulted in thin walls in the upper deck, valve pockets, and the roof of the valve chamber. Cracks running everywhere. Try to pin a crack and new ones form at the periphery. The original Ford produced "B" blocks have their issues as well. Since most all of my "B" engines spent their lives in an industrial application it is possible that they were not always well maintained. All told, I found one repairable diamond "B" block out of 7 that were hot-tanked and magnefluxed - not a good record.

As far as the diamond "B" blocks are concerned, my take is that their claimed superiority is a myth.
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Old 02-16-2020, 04:36 PM   #5
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Default Re: The Diamond Mark Challenge

I have had three diamond A blocks, two came out of tugs that I had bought, that were used on the water front. none of the three had exhaust seat inserts.
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Old 02-16-2020, 04:55 PM   #6
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Default Re: The Diamond Mark Challenge

I believe the diamond is just a casting artifact seen on mid 30’s produced parts. It shows up on v8 parts as well. No special significance
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Old 02-17-2020, 07:21 AM   #7
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Default Re: The Diamond Mark Challenge

Vince Falter has quite a bit of information on diamond blocks on his Ford Garage site. Check it out. I have a diamond block in my '29, certainly a replacement as the casting date is either '35 or '37. ( away from home now and can't check ) Runs just fine and has for years. Bill
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Old 02-17-2020, 12:02 PM   #8
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Default Re: The Diamond Mark Challenge

The diamond is a foundry mark, most, if not all were made after regular production, up to the war years. All were not the same, I have one diamond B block that was extremely thin in #3 exhaust port, another was ported to 1 3/4" and was still serviceable. The mark was A & B blocks, heads bell housings and on rear bearing (transmission) retainers and probably more??? They came with no serial number from the factory, most were used commercially. Were they better? They were newer, and most had exhaust seat inserts.
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Old 02-17-2020, 03:15 PM   #9
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Default Re: The Diamond Mark Challenge

My 1930 Town Sedan has a diamond block, but have no idea if it was original. It also has standard valve seats.....
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Old 02-17-2020, 05:24 PM   #10
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Default Re: The Diamond Mark Challenge

I have a Model A Diamond Block and head.casting date is very hard to read but looks like 37
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Old 02-18-2020, 11:58 AM   #11
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Default Re: The Diamond Mark Challenge

I think for a while everyone thought that a diamond mark somehow affirmed "better quality?"

Now perhaps not so? I have seen diamond blocks sell for premium over a regular block. Well, I have seen diamond blocks ASK a premium.

I'm not sure I would bother. IMHO, the most "bulletproof" blocks seem to be motherhood & apple pie "A" blocks from the original production. My B "Gordon Smith" compressor (no counterweights) suffers from deck cracks on cylinders 2 and 3 - and this seems common for B - although the block may have been chosen for the GS Head BECAUSE it developed cracks.

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Old 02-18-2020, 02:30 PM   #12
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Default Re: The Diamond Mark Challenge

Ford farmed out almost all replacement casting stuff after normal production of parts ended. Model A & B blocks were used in industrial & agricultural related applications long after the automobiles that used them had stopped production. I've only seen foundry marks on replacement transmission cases but not on engine block castings other then the diamond. Those that I have seen had the distinctive marking of Fairmount Tool and Forging Division of Houdaille Industries of Cleveland, OH but there were likely others too. Ford Motor Company seldom ever counted on any one supplier.
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Old 02-18-2020, 03:08 PM   #13
Dan Partain
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Default Re: The Diamond Mark Challenge

I have a diamond block with the exhaust seats. I don't know if all diamond blocks had them. It may be difficult to see them unless you have the block decked.
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Old 02-18-2020, 07:01 PM   #14
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Default Re: The Diamond Mark Challenge

Not all had them.
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Old 02-18-2020, 08:39 PM   #15
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Default Re: The Diamond Mark Challenge

I think the diamond was put on all motors, A and B that where Industrial motors not to be put in autos but work horses. I could be wrong but I think I read that somewhere
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Old 02-18-2020, 09:14 PM   #16
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Default Re: The Diamond Mark Challenge

I wasn't aware that there was any difference.
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Old 02-19-2020, 09:37 AM   #17
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Default Re: The Diamond Mark Challenge

There were two foundries in Cleveland Ohio that used a diamond casting mark. I always wondered if either of them were involved with these blocks. There is blind theory and then there is consensus among experienced folks in the restoration hobby. After 1933, Ford was busy casting V8 blocks so it's doubtful that they wanted to cast more 4-cylinder blocks if they didn't have to. Ford Motor Company certainly built up 4-cylinder engines through the 30s & early 40s for replacements and industrial/agricultural customers but that doesn't mean that they fabricated all the parts in house. Low production fabrication was farmed out a lot.
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Old 02-23-2020, 10:11 AM   #18
Bob Bidonde
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Default Re: The Diamond Mark Challenge

So far, I see no factory documentation or aftermarket testing that substantiates that "Diamond" blocks and parts are more rugged and or function better than OEM parts.
Thus in the market place, the "Diamond" should not add any $$ value to blocks and or parts with the "Diamond."
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Old 02-23-2020, 12:18 PM   #19
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Default Re: The Diamond Mark Challenge

Bob,

You are probably correct about the value perceived of the Diamond castings.

But, someone could perceive that the Diamond block is more valuable just due to the age of the casting from the 40's, vs the 20's.
IMHO, a good block isn't just based on the date of manufacture, rather it is the condition and not having some questionable machining performed on it.

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