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Offset grindin SB crank?

Posted By: HotRodDave

Offset grindin SB crank? - 02/21/09 09:16 PM

How much can a good std journal 273 crank be offset ground? Can it be ground down engough to use the honda rods? There are no holes in the throw so it should be OK right?
Posted By: dizuster

Re: Offset grindin SB crank? - 02/21/09 11:03 PM

I can't answer, but I can't help but wonder why you would want to do it?

Why not just turn the mains down on a 360 crank and be done with it?...
Posted By: HotRodDave

Re: Offset grindin SB crank? - 02/21/09 11:15 PM

I figured 1. I have it, 2. it is forged 360 is cast, 3. with the small journals it would be pretty light and lots of dirt cheap NASCAR rods on e-bay with that journal size in pretty long lengths so I could run a light weight piston also.

According to my calculations it could go to 3.55 stroke, is this remotely close? With a long rod in my 340 block .020 over it would be a rev happy 360 ish Also this crank is for a 4spd and a 360 4spd crank aint easy to find. It is just a though since I already have it.
Posted By: DemonDust

Re: Offset grindin SB crank? - 02/22/09 01:06 AM

Your gonna be taking off about .245. Not sure what That will do to your oiling holes in the rod journals. Good idea, not sure if it will work though. Your oiling holes may end up close to the radius.
Posted By: autoxcuda

Re: Offset grindin SB crank? - 02/22/09 04:09 AM

Quote:

How much can a good std journal 273 crank be offset ground? Can it be ground down engough to use the honda rods? There are no holes in the throw so it should be OK right?




Good question. I wonder if you could adapt Chevy SB honda sized rods. Could would you have any room to ALSO offset grind the journal, if so how much?

The circle track guys use some super lightwieght ones that I think would live in a Sub 400 HP street motor.
Posted By: Anonymous

Re: Offset grindin SB crank? - 02/22/09 05:48 AM

you'll effectively destroy an otherwise good crankshaft if you take it to 1.88 journal size on an offset grind for the aforementioned reasons. the oiling holes will be right at the cheek of the fillet.
Posted By: autoxcuda

Re: Offset grindin SB crank? - 02/22/09 08:44 AM

Quote:

you'll effectively destroy an otherwise good crankshaft if you take it to 1.88 journal size on an offset grind for the aforementioned reasons. the oiling holes will be right at the cheek of the fillet.




So an offset grind with honda journals is a no-go. But just grinding down to a honda journal is ok on the oiling hole placement??
Posted By: Anonymous

Re: Offset grindin SB crank? - 02/22/09 11:39 AM

Quote:

Quote:

you'll effectively destroy an otherwise good crankshaft if you take it to 1.88 journal size on an offset grind for the aforementioned reasons. the oiling holes will be right at the cheek of the fillet.




So an offset grind with honda journals is a no-go. But just grinding down to a honda journal is ok on the oiling hole placement??




no, either way will be a problem.
Posted By: HotRodDave

Re: Offset grindin SB crank? - 02/22/09 06:17 PM

Are 2 inch chevy rods ok?
Posted By: autoxcuda

Re: Offset grindin SB crank? - 02/22/09 10:14 PM

Quote:

Quote:

you'll effectively destroy an otherwise good crankshaft if you take it to 1.88 journal size on an offset grind for the aforementioned reasons. the oiling holes will be right at the cheek of the fillet.




So an offset grind with honda journals is a no-go. But just grinding down to a honda journal is ok on the oiling hole placement??




Thanks.

Now the stock big block cranks don't have a problem going to honda journals? Is that correct?
Posted By: Anonymous

Re: Offset grindin SB crank? - 02/22/09 10:24 PM

Quote:

Quote:

Quote:

you'll effectively destroy an otherwise good crankshaft if you take it to 1.88 journal size on an offset grind for the aforementioned reasons. the oiling holes will be right at the cheek of the fillet.




So an offset grind with honda journals is a no-go. But just grinding down to a honda journal is ok on the oiling hole placement??





Thanks.

Now the stock big block cranks don't have a problem going to honda journals? Is that correct?




no, that's not correct. if the manufacturer plans from the beginning to go to 1.88 rod journals, the drill the oiling holes in the proper place to start with. to do it after the fact by reducing a 2.375 journal down to a 1.88 you'd be removing .495". the oiling hole would be coming out the side of the radius on the crank.

for the crank in question, yes, IMO a 2.00 rod journal is doable.
Posted By: Hot 340

Re: Offset grindin SB crank? - 02/22/09 10:48 PM

Quote:

Quote:

Quote:

Quote:

you'll effectively destroy an otherwise good crankshaft if you take it to 1.88 journal size on an offset grind for the aforementioned reasons. the oiling holes will be right at the cheek of the fillet.




So an offset grind with honda journals is a no-go. But just grinding down to a honda journal is ok on the oiling hole placement??





Thanks.

Now the stock big block cranks don't have a problem going to honda journals? Is that correct?




no, that's not correct. if the manufacturer plans from the beginning to go to 1.88 rod journals, the drill the oiling holes in the proper place to start with. to do it after the fact by reducing a 2.375 journal down to a 1.88 you'd be removing .495". the oiling hole would be coming out the side of the radius on the crank.

for the crank in question, yes, IMO a 2.00 rod journal is doable.


You sure Dan? I was just downstairs looking at my steel sb crank and if you removed .250 off the face of the journal by the oil hole(.495 total dia) it wouldnt bring the hole near the fillet..
Posted By: Anonymous

Re: Offset grindin SB crank? - 02/22/09 11:51 PM

Quote:

Quote:

Quote:

Quote:

Quote:

you'll effectively destroy an otherwise good crankshaft if you take it to 1.88 journal size on an offset grind for the aforementioned reasons. the oiling holes will be right at the cheek of the fillet.




So an offset grind with honda journals is a no-go. But just grinding down to a honda journal is ok on the oiling hole placement??





Thanks.

Now the stock big block cranks don't have a problem going to honda journals? Is that correct?




no, that's not correct. if the manufacturer plans from the beginning to go to 1.88 rod journals, the drill the oiling holes in the proper place to start with. to do it after the fact by reducing a 2.375 journal down to a 1.88 you'd be removing .495". the oiling hole would be coming out the side of the radius on the crank.

for the crank in question, yes, IMO a 2.00 rod journal is doable.


You sure Dan? I was just downstairs looking at my steel sb crank and if you removed .250 off the face of the journal by the oil hole(.495 total dia) it wouldnt bring the hole near the fillet..




your talking about a smallblock crank and someone else mentioned a BB crank. for the sb crank you'd remove .245 total. if you offset grind it then more will come off the bottm half than the top. either way, i wouldn't do it. i'm just relaying what i've personally seen, your results may vary.
Posted By: 69Cuda340S

Re: Offset grindin SB crank? - 02/23/09 12:44 AM

An off the shelf 3.79" stroke crank is available with 318/340 mains. I believe Mopar Performance sells it.
Posted By: RyanJ

Re: Offset grindin SB crank? - 02/23/09 01:41 PM

Quote:

An off the shelf 3.79" stroke crank is available with 318/340 mains. I believe Mopar Performance sells it.




MP does'nt offer it anymore, but Callies & K1 both make a 3.79, but both have a 2.10" GM rod journal.

We do about 10 offset ground stroker cranks a year going to 2.0" Journal, most stuff can not go further unless the forging was intended for it.

We just DE-stroked a Callies 3.58" down to 3.48" a few weeks ago.

Stock 3.31" crank should have no problem going to 2.0"
Posted By: StrokerDart

Re: Offset grindin SB crank? - 02/23/09 03:38 PM

sorry ... off topic .... but, RyanJ your PM box is full ....
Posted By: RyanJ

Re: Offset grindin SB crank? - 02/23/09 04:02 PM

Quote:

sorry ... off topic .... but, RyanJ your PM box is full ....




fixed
Posted By: Moparnut426

Re: Offset grindin SB crank? - 02/23/09 05:11 PM

Also this crank is for a 4spd and a 360 4spd crank aint easy to find. It is just a though since I already have it.




As far as a 360 crank being specific to a 4 speed, its only the flywheel. All you have to do is take a 318 or 340 flywheel inn, and a 360 torque converter in, and any machine shop will balence it for you. My 360 didnt even need the pilot bearing drilled to fit the bushing. Every 360 I have ever owned has had a 4 speed put behind it with no problem. I have had probably half dozen of them without problem.

Kasey
Posted By: Jesse_Lackman

Re: Offset grindin SB crank? - 02/23/09 10:38 PM

Quote:

How much can a good std journal 273 crank be offset ground? Can it be ground down engough to use the honda rods? There are no holes in the throw so it should be OK right?




Yes. If ground to HRJ with max offset the rod oil holes will be in the same place as if you ground the rod journals to a normal undersize. I'll have to check what the stroke increase is.
Posted By: Jesse_Lackman

Re: Offset grindin SB crank? - 02/27/09 05:44 PM

Stroke went from 3.310 to 3.541 using standard Clevite 77CB-1663 H rod bearings. Don't know if those are available undersize, if they are you could get a bit more stroke.
Posted By: polyspheric

Re: Offset grindin SB crank? - 03/01/09 02:21 PM

If the offset is maximum (all surfaces new to start) the diametric difference is the stroke difference.
2.123" - 1.8885" (Manley data) = .2345"
3.31" > 3.5445"

However, usually .005" is left for clean-up.
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