"318-3" cast on block... what does it mean?

[Ray Bell]

I'm told that various 318 blocks are cast with numbers '318-1' and 318-2' and '318-3' on the side of the block...

Some are musing that these relate to end use. For instance, that the 318-3 is for trucks, and that it has thicker cylinder walls.

Is this information correct, or just surmise?

[TK]

It basically is a block thickness/core shift mesurment. The -3 blocks were a "Premium" block, built for extreme duty, and can be bored further without running out of cylinder walls.
-3 and -12 are the best blocks to build, if you are going the 318 route.
Most -3's had steel cranks, stronger rods, and a bigger camshaft to boot. The -12 was a good block, mostly with a cast crank, but had the strong rods.
The -2 is a good block, but wasnt nothing special, and a -1 is your normal car 318.
(-3's have less room for coolant in the block)

[mopartodd]

That's cool. Are all smallblocks suffix'd that way??

[jelsr]

The -3's were HD truck units and used a water heated intake vs ex heat so the heads and intake are different also! The BB -3's used a different ex manifold bolt pattern, not sure about that on SB.

[DartGT66]

This is absolutely not true. Mopar did not have any special blocks for different purposes on their "regular" engines, they all came from the same line. The digit after the displacement only tells teh amount of repairs done to the mold the block has been cast in. If I remeber correctly -1 is not used, the numbers start from -2? And the biggest numbers are over 10 before the mold was replaced with a new one.

[John Kunkel]

The dash number after the displacement is called the Core Casting Index Number, it is the number of core plugs that were replaced in the casting core that was used to make the sand mold.

DartGT66 is correct, there is no correlation between the dash number and the final configuration of the engine.

There is a theory that a low number should result in a block with less core shift and consistent thickness cylinder walls but that has never been proven.

[TK]

Well, for once, you guys are both wrong? A 318-3 is a heavy duty truck motor, hell, they even made a 675 casting head, with ford spark plugs, for marine and Heavy duty trucks. Yup. (and called it a 318-3, jeslr, you are right on)
I find it funny, that, if this weren't true, all the -3's I have, or have seen, have steel cranks, my 1/2 ton trucks, and one 3/4 ton truck built from 67-71 have -2's, and the other 3/4 ton trucks, have -12's. I happen to have, a 1969 block, that has the -12 (out of a 3/4 ton camper custom) and a 74 318 block, in my dually, also has a -12. Might be more than a coincidence.
If anyone has some actually written proof, I would love to see it! (The only proof I have is what I have seen, from trucks themselves) (and, there is less room in the plug to cylinder wall on a -3, than the others.
ps?
I happen to have, right here, a 318 block, numbers are..........2535030-318-1
It came out of a 75 1/2 ton truck.

[Ray Bell]

What I'd like to know is this...

If it relates to 'core shift', then how do they cast the number in?

You see, core shift wouldn't be known until after the casting is done...

I'm still not convinced either way.

[B1owner]

Yep, what DartGT66 said....thats my understanding as well.

[TK]

Originally Posted by Ray Bell

What I'd like to know is this...

If it relates to 'core shift', then how do they cast the number in?

You see, core shift wouldn't be known until after the casting is done...

I'm still not convinced either way.

Would it be possible, that different molds are used for different engine applications?

[Ray Bell]

Entirely possible... or that it relates to either whoever assembled the cores or what line they were on or what shift they were working or... well, I'm sure you follow my thinking there.

Thinking about the prospect of it being the number of 'repairs' made... well, that sort of leaves me dumbfounded as the number casting on the side of the block would be a part of the very first piece assembled... would it not?

[cageman]

My truck 318 3's have an added motor mount boss on the side of the block too, both of them are 68's

[turbododge]

As was said, it could not in any way be related to core shift, because it is in the mold and you do not know shift until after the casting is done. It could mean different wall thickness, different shift, different material (because of shrink) or a multitude of other things, including the number of repairs or simple mold number.

Could someone take a good look at the number and check for a line around it? If there is no line, the number hasn't been changed, which would eliminate several of the possible scenarios.

[Ray Bell]

While we're there, there is a similar thing on Poly engines... at the front of the block, not on the side... here's a couple of examples:



From top to bottom (all Australian assembled vehicles):

The original from the '64 sedan
Block from a truck
Another from a sedan
Unknown origin (truck or car)

The numbers, incidentally, on the block we've got from a Case combine harvester are:

3
2488230

This last one we haven't pulled down yet to measure core shift, but all have it to some degree or another... especially the one from the truck.

And here's another truck one, we've never measured the walls of this one because it's got pistons corroded so badly into the cylinders it's nigh on impossible... also a useless exercise because most of the main bearing webs have been torn out by a busted crank:



There is another number on the side of the block, in this case it's a '1'...

So in all of this, no consistence, no '3' on a truck engine.

[Ray Bell]

Sorry... 'consistency'... not 'consistence'!

[TK]

Seems like everything i have seen has just been proven wrong.
So, basically, there is no difference in blocks, all are the same.
Cage? I think I remember the motor mount holes, also, look at the back of the block, at the last bell housing bolt hole on your trucks, is there a web that isn't on others?
The is a web on the -3's and -12's I have.
Also, no one has figured out why, I have different blocks, from different years, with the same dash. And, they seem to run in the same class of vehicles.
There has to be another explanation.

[TK]

Originally Posted by Ray Bell

While we're there, there is a similar thing on Poly engines... at the front of the block, not on the side... here's a couple of examples:



From top to bottom (all Australian assembled vehicles):

The original from the '64 sedan
Block from a truck
Another from a sedan
Unknown origin (truck or car)

The numbers, incidentally, on the block we've got from a Case combine harvester are:

3
2488230

This last one we haven't pulled down yet to measure core shift, but all have it to some degree or another... especially the one from the truck.

And here's another truck one, we've never measured the walls of this one because it's got pistons corroded so badly into the cylinders it's nigh on impossible... also a useless exercise because most of the main bearing webs have been torn out by a busted crank:



There is another number on the side of the block, in this case it's a '1'...

So in all of this, no consistence, no '3' on a truck engine.

From what I just saw, L engines are designated different too.

[DartGT66]

"While we are on the subject of casting numbers, often there will be what is known as a "tooling revision number" or a "dash number" after the casting number. A 1968 440 block, for instance, might read 2536430-12, or sometimes there will just be a space, such as 2536430 12, or sometimes 253643012. While 2536430 would be the casting number, the 12 would be the tooling revision number, which indicates how many times the tooling (core molds) have been reconditioned back to the proper specifications or modified to include improvements. After so many "pours" the tooling gets worn and needs to be reshaped or reconditioned. So theoretically, higher numbers will be later dates and have any casting improvements incorporated into them. The only problem with this theory is that engines were produced in such volume that many many different sets of tooling were used concurrently to meet the necessary output. So while some may have lasted for quite a while, (in which case you will find later dates with earlier revisions) some got worn quickly and needed to be revised after a short time. So while in some cases, parts with later numbers may include some improvements the earlier parts may not have, on a practical level, it means nothing as far as the quality of the piece. In other words, don't waste your time looking for an early or late tooling revision number. Blocks, heads, water pump housings and many other cast parts have revision numbers as well."

[Ray Bell]

And where is that quote from?

Maybe there's more interesting stuff from the same source...

[DartGT66]

Yes there is, big block stuff, http://www.440source.com
I heard about these things several years ago and just looked if I could find anything about it in the net, and that's the first one I found.

[Ray Bell]

That's great stuff, thanks for that!

I've posted a link on the other forum for the guys to read...

[jelsr]

The -3 BB's have a large WP that bolts to the head as well as the block and makes it difficult to mix parts. The SB -3's do not look different externally and parts can be bolted up just fine. If you bolt up a reg cyl head on a -3 engine you will get a surprise, the coolant will run out the exhaust pipe when you start filling the radiator. Been there, done that. The -3's do not run exhaust thru the intake heat riser passage, they use water. There is a small line (3/8") from the manifold (next to the carb) to the t-stat hsg that is the only clue. I don't remember on the SB but the 361-3 and the 413-3 use a different bolt pattern for the exhaust manifolds (the end cyl studs are staggered) and the flange is a square 4 bolt pattern instead of the normal 2. As was posted the -3's have steel cranks and on some BB's I have seen (irrigation motors) the crank has an 8 bolt flange. (like the Hemi)

[John Kunkel]

Originally Posted by Ray Bell

What I'd like to know is this...

If it relates to 'core shift', then how do they cast the number in?

You see, core shift wouldn't be known until after the casting is done...

I'm still not convinced either way.

The block is made by pouring molten iron into a sand mold, the mold is made by packing moist sand around a "casting core"; the core gives the mold its shape.

The cylinder casting core is made up of a series of core plugs mounted on a frame, the plugs are made of a material that wears out from continuous interaction with the abrasive sand. When each individual core plug wears out it is replaced and the placement of the new core plug in the frame might be slightly out of tolerance causing that core plug to be "shifted" out of position which leads to "core shift". Remember, this is mass production performed by workers that might be tired, drunk, unhappy or all of the above.

The dash number is not a measure of core shift, it merely denotes how many core plugs were changed in that particular casting core; the higher the number of core plugs changed, the higher the possibility of core shift. On some blocks the parting lines (sprues) left by the mating edge of the various casting cores can be seen to be shifted out of position and in some cases the lifter bores are visually off center in the cast bosses.

The actual raised casting numbers on the side of the block are made by a female impression in the sand of the mold, as each core plug is replaced the dash number is changed in the die that makes the impression.

Other raised casting symbols on the sides of the block are similarly made, a pointer points to either D or N to signify on which shift (Day or Night) the block was poured and a circle comprised of a number of dots with a central pointer denotes on which of several pours during a shift the block was cast.

[TK]

I am feeling very light headed right now.......................

So, basically, you might want to build a -2 before a -3, and a -3 before a -4 and so on, because there is less chance of core shift? HUH.

So, does anyone have a theory on my engines, out of trucks, wich are mostly -3'a and -12's?
I cant find any 8's, 6's, 15's..............just 1's, 2's, 3's, and 12's.

(9 different motors, in a span of 10 years)

The -3 318's, with the funny heads, are just a 675 casting head, with the big ford plugs. I saw one, it was a 67 318, adn the bolts went strait down, like a magnum in the intake.

[turbododge]

It was stated that the -3 castings had the water run differently, which is contrary to the core replacement idea. If the -3 is not a different part number designating the water routing difference, and is only a core maintenance reference, you would have two different castings with the same casting number because you would ignor the dash for identification. I can't see how that would work in the production environment.

Is there a way to confirm which blocks had the water run differently? Anyone ever see one with other than a -3 with water heated manifold?

[Ray Bell]

I think, actually, we should leave big blocks out of this...

While the questions raised are relevant, the real core of the issue is the small blocks.

Thus far, as I see it, there are three or four theories (and really, until one is proven correct, that's what they are!) about what it's all about.

Proof, then, is what we're seeking...

[TK]

-3 318's, that I have seen, in the Arctic/marine, with the heated manifolds, there is no difference in the block, in fact, there is no difference in the heads, just the intake manifold.
Just like a BB, you can slap the normal stuff on top and go.
The -3 318's I have here, have less room between the freeze plug opening, and the cylinder wall.
So, is sounds like they had different castings for different pourposes?

[Ray Bell]

Might be different to the Polys, then?

We've proved that the numbers make no difference in them.

[pishta]

I dont think the 318-3 is a 3rd casting core revision of a 318. I believe the 318-3 in question, or what everyone thinks it is, is a 318 HD/truck or industrial motor that came with a steel crank. Im positive that the 6 behind my old 340-6 was the core revision and not a "6" pack motor. The casting core revisions were discussed on the 440source website and are also echoed in the "rebuilding the LA motor" by Dave Emmanuel. he states that the cores do erode over time and sometimes are modified in mid production to reflect subtle design changes. I would probably build a 12 over a 2 or 3 as it is the most refined core change, might be the strongest but maybe not the thickest. As being rare, I dont know, the only 318 I bought, out of the local paper, had a steel crank and I paid 100 bucks for it. There was a cast and a forged crank that both had the same "casting" number according the the same book!

[TK]

Really hard to say...........................
There might be differences in the block, the only way to tell, I guess, would be to get a whole bunch, and have them sonic tested.
I found a 87 318 today, out of a 1/2 ton truck, it has a -2, but, the casting in the valley look HORRIBLE.