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So I’m disassembling my 1985 300 6 out of a F150. I get the head off and see that there are 2 pistons that are different. I haven’t gone any further due to lack of time. My question is which pistons are the ones that came in the motor. Also if some one could point me in the right direction to find out the exact year of the motor. Like where is the date stamp or some type of identifying number on it. After seeing the pistons I’m assuming the motor has been out of the truck before and I would like to know if this is a different motor than original. Thanks
The D-shaped dished pistons are for the later EFI engines and the smaller dished are for the older Carbed engines if I am not mistaken. My guess is the engine has been gone through before and two pistons where replaced with the newer style.
The other ones are a 70's style. And if I remember correctly they are also a shorter piston/compression height ( lower compression ) .
And to find the date of the engine look on the lower passenger side of the block. The casting/engineering # will be just above the oil pan rail in the starter area.
Here's a picture from one of my engines.
The red circle is the casting #. It will give a general idea of the oldest year your engine block could have been cast.
The first letter should be either a "C" = 60's, "D" = 70's, "E" = 80's, or "F" =90's.
The second digit will be a # and that will be the first year of the above decade that this engineering version of the engine was produced.
So let's say your first digit is a "E" and the second is a "5". That means the oldest your engine could be is 1985. But could also be a few other years newer.
The blue circle is the actual date code. It will give you the exact year, month and day your block was cast.
You may need to do some scraping/cleaning to find them. Here's a picture of one of my other engines. You can see the grease build up covering the area.
If you post both the casting # and date code we can tell you exactly what you've got for a block.
Ithink that is 'CF 24', meaning 'Cleveland Foundry core box #24'
Are you sure on this one? I've always been told the fake looking tag was the date codes. If it's a date code and it's "0F24" that would be a 6/24/1980 casting date.
That area on all my blocks are either a 3 or 4 digit code. All being a number, then a letter, then another number or two.
Ouch, someone didn't know what they were doing. The "D" shaped pistons are 25cc pistons and the "O" shaped pistons are 19cc. So, you had 2 pistons with around 8.5:1 CR and 4 with around 8:1.
From what I recall while researching pistons for my build, the "O" shaped ones were used in the 70s, and the "D" shaped ones were used in the early 80s on when they wanted to lower compression for emissions.
The '78 block I rebuild had the O shape, and my original '81 had the D shape.
Nope - not sure, that's why I said "I think...". Maybe NumberDummy can confirm my thought.
What is the part number on the head, under the 'stat outlet hole?
He's said something in the past that those casting #'s have nothing to do with the actual Ford part #. But I don't know if he's ever chimed in on the date code. So maybe he can let us know.
Originally Posted by AbandonedBronco
Ouch, someone didn't know what they were doing. The "D" shaped pistons are 25cc pistons and the "O" shaped pistons are 19cc. So, you had 2 pistons with around 8.5:1 CR and 4 with around 8:1.
From what I recall while researching pistons for my build, the "O" shaped ones were used in the 70s, and the "D" shaped ones were used in the early 80s on when they wanted to lower compression for emissions.
The '78 block I rebuild had the O shape, and my original '81 had the D shape.
And to confuse things even more the "O" shaped ones weren't the only pistons used in the 70's either. I've personally come across 3 or 4 different types of pistons on engines that were supposedly never rebuilt. Including a true flat top piston in a HD engine. They were a flat top but were much shorter to give a very low compression. And at least some of the 240's also used 302 pistons (the ones with 4 valve reliefs ) .
I've personally come across 3 or 4 different types of pistons on engines that were supposedly never rebuilt. Including a true flat top piston in a HD engine. They were a flat top but were much shorter to give a very low compression.
I remember seeing some of those available when I was researching. I thought it was cool there were flat top pistons available for the 300 until I saw that the top of the piston came up somewhere around 1/4 inch lower than a stock one and gave it something like an abysmal 7:1 compression (can't remember exactly).
10-23-2017, 08:03 PM
And at least some of the 240's also used 302 pistons (the ones with 4 valve reliefs ) .
