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Offset grinding RB crank for a Lowdeck stroker #1446983
06/03/13 05:27 PM
06/03/13 05:27 PM
Joined: Jul 2010
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Delray beach, Florida
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I do quite a bit of this. The crank I started with was brand new and a relatively inexpensive Import. This is just the roughing in process of the rod and main journals. I already ground the counterweights down to 7.240 diameter. I'll try to get some pictures of the finished journals tomorrow.
By the way, the stroke on the crank as delivered varied by more than .004"
When it's finished the stroke will be within .001" and the index will be corrected.

Last edited by Performance Only; 06/03/13 05:28 PM.

machine shop owner and engine builder
Re: Offset griding RB crank for a Lowdeck stroker [Re: Performance Only] #1446984
06/03/13 05:28 PM
06/03/13 05:28 PM
Joined: Jul 2010
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Delray beach, Florida
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2nd look

7729755-2ndlook.JPG (516 downloads)

machine shop owner and engine builder
Re: Offset griding RB crank for a Lowdeck stroker [Re: Performance Only] #1446985
06/03/13 05:29 PM
06/03/13 05:29 PM
Joined: Jan 2003
Posts: 75,329
A gulag near you.
JohnRR Offline
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What company makes a stepped bearing to fit that journal ?

Re: Offset grinding RB crank for a Lowdeck stroker [Re: Performance Only] #1446986
06/03/13 05:30 PM
06/03/13 05:30 PM
Joined: Jul 2010
Posts: 2,091
Delray beach, Florida
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3rd look

7729758-3rdlook.JPG (439 downloads)

machine shop owner and engine builder
Re: Offset grinding RB crank for a Lowdeck stroker [Re: Performance Only] #1446987
06/03/13 06:05 PM
06/03/13 06:05 PM
Joined: Jun 2003
Posts: 52,972
Romeo MI
MR_P_BODY Offline
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Thats a lot of material to take off... didnt want to
off grind it for more stroke

Re: Offset grinding RB crank for a Lowdeck stroker [Re: MR_P_BODY] #1446988
06/03/13 07:32 PM
06/03/13 07:32 PM
Joined: Jul 2010
Posts: 2,091
Delray beach, Florida
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Quote:

Thats a lot of material to take off... didnt want to
off grind it for more stroke





If you look a little bit closer at the 2nd picture you'll see that most of the material is coming off of the bottom side of the journal. In other words, yes, the stroke is also being changed. here's another view.

7729875-100_1452.JPG (378 downloads)
Last edited by Performance Only; 06/03/13 07:33 PM.

machine shop owner and engine builder
Re: Offset grinding RB crank for a Lowdeck stroker [Re: Performance Only] #1446989
06/03/13 07:37 PM
06/03/13 07:37 PM
Joined: Jan 2003
Posts: 15,976
Chilliwack B.C. Canada
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RUNCHARGER Offline
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How many hours does this take?

Sheldon

Re: Offset grinding RB crank for a Lowdeck stroker [Re: Performance Only] #1446990
06/03/13 08:11 PM
06/03/13 08:11 PM
Joined: Jun 2003
Posts: 52,972
Romeo MI
MR_P_BODY Offline
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Quote:

Quote:

Thats a lot of material to take off... didnt want to
off grind it for more stroke





If you look a little bit closer at the 2nd picture you'll see that most of the material is coming off of the bottom side of the journal. In other words, yes, the stroke is also being changed. here's another view.




Got ya.. I didnt see that

Re: Offset grinding RB crank for a Lowdeck stroker [Re: Performance Only] #1446991
06/03/13 08:11 PM
06/03/13 08:11 PM
Joined: Oct 2006
Posts: 596
Mass.
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80fbody Offline
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Thinking about offset grinding a fresh 413 crank for a 400 block.

Is it a similar process?

What's a rough cost to get the counterweights cut & the journals offset?

Re: Offset grinding RB crank for a Lowdeck stroker [Re: Performance Only] #1446992
06/03/13 08:14 PM
06/03/13 08:14 PM
Joined: Jan 2003
Posts: 9,672
Lima, Peru
domingo Offline
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Lima, Peru
Ive always wanted to do that with an OEM 440 forged crank I have to fit it in my 400 block....

Does it take any special equipment to do that? Or can it be done in the same machine used to machine cranks to undersize journals, which is standard operation in any machine shop?

Re: Offset grinding RB crank for a Lowdeck stroker [Re: 80fbody] #1446993
06/03/13 08:29 PM
06/03/13 08:29 PM
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Posts: 19,318
State of confusion
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Quote:

Thinking about offset grinding a fresh 413 crank for a 400 block.

Is it a similar process?

What's a rough cost to get the counterweights cut & the journals offset?


Pettis found my 3.900 stroke 413 crank here locally and it was only about $250-$300 iirc not sure on labor though to have it done..........


72 Dart 470 n/a BB stroker street car `THUMPER`...Check me out on FB Dominic Thumper for videos and lots of carb pics......760-900-3895.....
Re: Offset grinding RB crank for a Lowdeck stroker [Re: MR_P_BODY] #1446994
06/03/13 08:51 PM
06/03/13 08:51 PM

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Anonymous
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Quote:

Quote:

Quote:

Thats a lot of material to take off... didnt want to
off grind it for more stroke





If you look a little bit closer at the 2nd picture you'll see that most of the material is coming off of the bottom side of the journal. In other words, yes, the stroke is also being changed. here's another view.




Got ya.. I didnt see that





You got a little red paint on your glasses Mike???

Re: Offset grinding RB crank for a Lowdeck stroker [Re: domingo] #1446995
06/03/13 08:56 PM
06/03/13 08:56 PM
Joined: Jul 2010
Posts: 2,091
Delray beach, Florida
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Quote:

Ive always wanted to do that with an OEM 440 forged crank I have to fit it in my 400 block....

Does it take any special equipment to do that? Or can it be done in the same machine used to machine cranks to undersize journals, which is standard operation in any machine shop?




Special equipment? I guess that depends on how you look at it. Considering what crankshaft grinders cost I consider mine kind of special.

Some people like to turn down the counterweights in a lathe. Either way you do it it's a time consuming process to do the whole job.
I highly recommend if your going to do this with a factory crank, make sure to have it magnafluxed first.


machine shop owner and engine builder
Re: Offset grinding RB crank for a Lowdeck stroker [Re: Performance Only] #1446996
06/03/13 08:59 PM
06/03/13 08:59 PM

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Anonymous
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Can't wait to see mine done.

Re: Offset grinding RB crank for a Lowdeck stroker [Re: ] #1446997
06/03/13 09:01 PM
06/03/13 09:01 PM
Joined: Jul 2010
Posts: 2,091
Delray beach, Florida
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Quote:

Can't wait to see mine done.




You want me to grind it like this one?


machine shop owner and engine builder
Re: Offset grinding RB crank for a Lowdeck stroker [Re: Performance Only] #1446998
06/03/13 09:06 PM
06/03/13 09:06 PM

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Quote:

Quote:

Can't wait to see mine done.




You want me to grind it like this one?




4.625 man...........4.625.......

Re: Offset grinding RB crank for a Lowdeck stroker [Re: ] #1446999
06/03/13 11:38 PM
06/03/13 11:38 PM
Joined: Jan 2011
Posts: 511
florida dade
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cesar perez Offline
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florida dade
thats my billet crank from moldex

Re: Offset grinding RB crank for a Lowdeck stroker [Re: Performance Only] #1447000
06/03/13 11:58 PM
06/03/13 11:58 PM
Joined: Jan 2003
Posts: 9,672
Lima, Peru
domingo Offline
EL Master
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Lima, Peru
Quote:

Quote:

Ive always wanted to do that with an OEM 440 forged crank I have to fit it in my 400 block....

Does it take any special equipment to do that? Or can it be done in the same machine used to machine cranks to undersize journals, which is standard operation in any machine shop?




Special equipment? I guess that depends on how you look at it. Considering what crankshaft grinders cost I consider mine kind of special.

Some people like to turn down the counterweights in a lathe. Either way you do it it's a time consuming process to do the whole job.
I highly recommend if your going to do this with a factory crank, make sure to have it magnafluxed first.




for sure,

When you do this on an OEM crank, how do you end up finishing the fillets? Do they end up having radiused fillets??

Re: Offset grinding RB crank for a Lowdeck stroker [Re: domingo] #1447001
06/04/13 12:27 AM
06/04/13 12:27 AM
Joined: Jul 2010
Posts: 2,091
Delray beach, Florida
P
Performance Only Offline OP
top fuel
Performance Only  Offline OP
top fuel
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Joined: Jul 2010
Posts: 2,091
Delray beach, Florida
Quote:

Quote:

Quote:

Ive always wanted to do that with an OEM 440 forged crank I have to fit it in my 400 block....

Does it take any special equipment to do that? Or can it be done in the same machine used to machine cranks to undersize journals, which is standard operation in any machine shop?




Special equipment? I guess that depends on how you look at it. Considering what crankshaft grinders cost I consider mine kind of special.

Some people like to turn down the counterweights in a lathe. Either way you do it it's a time consuming process to do the whole job.
I highly recommend if your going to do this with a factory crank, make sure to have it magnafluxed first.




for sure,

When you do this on an OEM crank, how do you end up finishing the fillets? Do they end up having radiused fillets??




Since OEM cranks have an undercut radius there isn't usually much of a radius when they're done. I've done a couple of them where I welded the radius first to narrow the rod throws and then did the grind to reduce the side clearance for GM width rods. I can't say if it helped with strength or longevity but they're still out there running.


machine shop owner and engine builder
Re: Offset grinding RB crank for a Lowdeck stroker [Re: Performance Only] #1447002
06/04/13 08:00 AM
06/04/13 08:00 AM
Joined: Apr 2006
Posts: 3,675
Akron, Ohio U.S.A.
roadhazard Offline
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Nice work Dan A crank sure grinder is a special piece of equipment..... the operator is also "special"

In all seriousness though geometry, sizes, surface finish, balance and I'm sure many other things have to be taken into account before the first stone touches the crank.

When I had my stocker crank index ground here locally. The crank was so far off on index it removed all of the rolled radius in one area of a rod throw

It's been surviving though

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