425 & 455 crankshaft

[edj2001]

Does anyone know if the crank casting # changed between the 425 and the 455? I have two cranks with casting number 384722 and I want to make sure they are both 425 cranks.

Remind me also, the main bearing OD on the both cranks (425 & 455) is 3.000 and the rod bearing crank OD is 2.500, Correct? Stroke increased from 4 inches to 4.25 inches, bore stayed same?

BTW, I have been posting large Toro items on EBay too big to ship so come to Dallas next weekend and pick these up. I have been taking these out of storage, they have been stored since 1985. I will buy you lunch.

Here are some links so far. I will be putting the cranks up as soon as I know which engine.

http://www.ebay.com/itm/161130664979?it ... m=&vxp=mtr

http://www.ebay.com/itm/161130369550?ss ... 1423.l2649

http://www.ebay.com/itm/161130715392?ss ... 1555.l2649

http://www.ebay.com/itm/161130739739?ss ... 1555.l2649

Gene Johnson

[69W34]

384722 would ID a 425* crank which is forged and will have a large parting line, the 455 is cast and will have a 3/4" to 1" tall N on one of the throws ( if memory servers think the front) signifying Nodular and have a small but well defined parting line.

* the same crank was used on the 400 as well.

[Schurkey]

455 cranks can be forged (rumor says first month of 455 production) or cast (everything except the first month of 455 production) There's a forged crank in the 455 currently installed in my Toro.

The cast cranks can have a large "N" (supposedly for "Nodular"), a smaller "cn" (supposedly for "Cast Nodular"), or no letter marking at all. Some folks prefer the "large N" cranks because once upon a time they were believed to be stronger than the others. I'm not sure that strength difference actually exists.

[69W34]

I agree that forged 455 cranks are out there ... BUT... the timing and total volume is suspect hence they are few and far between and no reason to muddy the water with 425 forged cranks.

Now I add the following: it cost money to make the forging dies to make a crank ... but ... it takes longer to cast, cool and season a block, crank or heads before machining. So question is what was the driving force? ......... a late or delayed start of the casting processes for the 455 cranks or a last minute decision to move from forged to cast or was it some other extenuating situation that resulted in the over lap?

[Schurkey]

My understanding is that GM closed the plant that produced the forged crankshafts for Olds (and perhaps others???) in '67 or early '68. The '68 Olds small-blocks also got cast cranks instead of forged.

A cast crankshaft is cheaper than a forged crank. In grocery-getter and mild-to-moderate performance use, a cast crank is "good enough".

[faarigia]

Check with the guys at Cinnabar Engineering in Sandusky Michigan--GMC Motorhome specialists and always very helpful.

I'd bet they can help you get the correct seals.

[Otto Skorzeny]

They could probably help, but the original post is over a year old. Hopefully everyone got their crankshaft issues sorted out already.

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