Crankshaft ID Question

jshcobra · Mar 30, 2004

Anyone viewing this right now know what the casting numbers are for a 28 oz 302 crankshaft vs. the later 50 oz version. I've got my motor apart and need to make sure I have a 28 oz crank before sending it off to be ground.

Dano78 · Mar 30, 2004

Uhhh well it's, to a degree, kinda tuff to tell without have a 28oz next to it to verify.
There should be two different stampings in particular. Both on flyweights. One will either read a 1M or a 2M (not sure if there is a 3M if ther eis, i have yet to see it) a 1M is a 289 crank, a 2M is a 302 crank.
The other stamping is the date code stamping. It'll read just like any other Ford part number reads, 1st letter corresponding to decade 1970, 1980, 1990, etc...) the following number is the year designation within the decade. After that will follow two letter then a dash or space along with an A or AA or AB or B or C, etc... Pay attention to the date code, because I believe all the cranks casted after '80 or '81 (EOAE, E1DE or E1OE, etc.. ) are the 50oz imbalance.
Having a know 28oz imbalance crank right there to compare makes it real easy. it's hard to explain, but visually, the later crank (50oz imbal) is much thinner looking and actually is missing one of the internal counter weights that the earlier 289/302 have. Now the early 289/302 cranks are identical except for the datecodes and 1M/2M markings.

Hope this helps! I definately want to do more reasearch on the '80-up blocks so I can become more familiar with them. I guess I spent too much time im the 28oz world!

jshcobra · Mar 30, 2004

Thanks Dano78. I'm pretty sure I have the right 28oz crank- although the only markings on it are a "2M" on one weight and a "23" and "24" on another. I'll look more closely tomorrow for that date code.

Blue Thunder · Mar 30, 2004

If the crankshaft has a rear-seal flange on the end, it's most likely the old 28-oz imbalance. (The rear-seal flange is there to help the old 2-piece seal from leaking) The crankshafts from the newer engines don't have the flange, because Ford went with the 1-piece rear seal, and the flange isnt required, due to superior sealing.

I learned this when I got a 1985 302 block, which had the 1-piece rear seal, and I had a perfect reconditioned 1970s era crankshaft ready to drop in it.
I ended up having to cut off the flange or else the older crank wouldnt physically fit into the newer block. (The flange hits) I figured removing the flange was easier than finding a recon newer crank, and then trying to get the MII flexplate rebalanced for the newer crank's 50oz imbalance.

I know they switched the imbalance to 50oz sometime in 1981. However, if you get a crank that's near 1981, I'm not certain which rear-seal type it will have. So around those years, I don't know if they possibly made a few 50oz cranks with the flange or not. (or possibly made a few 28oz cranks without the flange) The era of change (1980-1982 in this case) can be tricky.
I like to only deal with 1979 and earlier, or 1982 and later engines. Those 80-81 engines are evil. haha

The part number on the block (and on all Ford parts, in fact) will begin with C for 60s, D for 70s, E for 80s, F for 90s and the second character will indicate the digit for the year. C8 is 1968, D9 is 1979, E2 is 1982, F1 is 1991 and so on)

As was mentioned previously, the 50oz cranks look thinner in the counterweight areas, and hopefully, with all the info from this thread, you'll be able to tell which is which.

Dano78 · Mar 30, 2004

No, I think you're right.. I may have goofed. After posting, I got to thinking... I couldn't actually remember seeing a Date code on any of my 66-79 289/302 cranks. This may have been the other giveaway to IDing a 50oz crank, the crank having a date code. It was on a front flyweight on a flat, notched part. On the earlier cranks it has the same notch cutout, but no casting #'s or even a blank spot.

i have a feeling you'r eright about having a 28oz crank. Another giveaway, is the year to the block it was in. Usually the same date if someone hasn't already switched them.

Blue Thunder · Mar 30, 2004

Dano78 said:
There should be two different stampings in particular. Both on flyweights. One will either read a 1M or a 2M (not sure if there is a 3M if ther eis, i have yet to see it) a 1M is a 289 crank, a 2M is a 302 crank.

Cool, I never knew that.

jshcobra · Mar 30, 2004

Thanks guys. The crank is in a remanufactured short block that I purchased a few years ago from Indy Mustang Performance. I had less than 15K miles on it when the rear main started leaking and oil pressure got bad. I finally gave in and yanked the motor and found that all of the rod and main journals are scored pretty bad and the bearings are toast.

Since they obviously gave me a bum crank, I wanted to make sure it is even the right one for my flywheel before having it ground.

Thanks to you guys, I'll sleep easier tonight.

Blue Thunder · Mar 30, 2004

jshcobra said:
rear main started leaking and oil pressure got bad.

Definately sounds like an old 2-piece rear-seal block!

If someone rebuilt that motor and screwed up the crankshaft, I would seriously think about checking the main journal bores for alignment. If that company line bored the mains incorrectly,(or skipped over without checking them at all) it could explain the scored bearings. (Just a small possibility) Also check piston pins, cylinder walls, (check cylinder bores for irregularities) piston skirts, and oil pump. (They may have re-used a worn original pump or installed some super cheapo aftermarket pump)
Low oil pressure = a very bad thing. And you can't be too careful with critical measurements.

As soon as you find one bad part in a rebuild, assume all parts are bad, until proven otherwise.(checked!)

Dano78 · Mar 30, 2004

Blue Thunder said:
If the crankshaft has a rear-seal flange on the end, it's most likely the old 28-oz imbalance. (The rear-seal flange is there to help the old 2-piece seal from leaking) The crankshafts from the newer engines don't have the flange, because Ford went with the 1-piece rear seal, and the flange isnt required, due to superior sealing.

I agree 100%! Yeah I remember that too now. I've only done 1 or 2 post '79 blocks, so I'm still trying to remember that stuff. I'me like Blue Thunder, I stick to the pre-79 stuff especially the 66-73 blocks.

Blue Thunder said:
I know they switched the imbalance to 50oz sometime in 1981. However, if you get a crank that's near 1981, I'm not certain which rear-seal type it will have. So around those years, I don't know if they possibly made a few 50oz cranks with the flange or not. (or possibly made a few 28oz cranks without the flange) The era of change (1980-1982 in this case) can be tricky.
I like to only deal with 1979 and earlier, or 1982 and later engines. Those 80-81 engines are evil. haha

Laugh... that last post '79 engine I did was for a guy and his MII and lucky me the engine was right on the borderline.... I was praying that it wasn't that lame 255 (a two year wonder engine that was used in the LTD II in 80-82) Luckily it was a 302. The block was casted '82 and the Crank was casted '81 and get this, it still had the 2 piece rear main seal.... Evil is right!!

Blue Thunder · Mar 31, 2004

Dano78 said:
I stick to the pre-79 stuff especially the 66-73 blocks.

From what I've read and seen, and discussed with my machine-shop friend, the newer 5.0 blocks are supposed to be something like 40 pounds lighter than the earlier blocks. (I've never actually weighed one of each era to confirm, but I've carried them both, and there is a noticeable difference in weight)
That 40 pounds of iron was taken mostly away from the main bearing support webbing. (I guess Ford figured the old 302 blocks were overkill, and the weight savings was worth losing the extra strength)

I've heard shops estimate that the old blocks can handle up to about 700 hp without a stud girdle before they split in half from mains to cam and vomit the crank out through the pan.(I run a trusty old '72 block for my stroker, AND a main stud girdle, because I designed the motor to handle a very large shot of nitrous, which could push it past that "safe" limit.)

The newer 5.0 blocks supposedly can handle up to about 450hp without a similar fate.(the main stud girdle will *drastically* strengthen the mains, though)
I've never done any testing specifically to prove this theory, as I don't want to grenade any of my motors! But I have seen a lot of pictures and read a lot of stories indicating there is truth to it.

For this reason, I would never base a serious performance motor(especially a stroker or forced induction) on a newer production 5.0 block.

Crankshaft ID Question

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