[Amc-list] Stroker crank grinding input needed

[Nick ALFANO <71amx@xxxxxxxxxxxxx>]

Greg,

I am confused with options 1&2.  Why would you keep the same stroke but reduce the journal size down to a SBC 2.100 journal?  I am missing something there?  It sounds like you are trying to make everything else fit a set of pistons verses making the pistons fit what you are building. Either way, I can't see saving money that way.  If anything, you will find out after it is too late, it is costing you more.  I have yet to see a Chevy rod drop right in an AMC engine without needing some additional work.  
 
With the crank .001 under, you should be fine but if after checking crank to rod bearing clearance you find that you have .003 + (spec is .001-.002 but you can go a little looser) rod to bearing clearance,  I would just grind it .010 under and be done with it.  Use stock rods (5.858) and you are done.  You are correct, they don't offer bearings in the + .001 and .002 std anymore but that was to make up slack.  Lets say you had a crank that had .0025 clearance, you could put in one half a .001 and the other have std and get .002 clearance.  If your clearance is only .001, you are right on the mark.  You don't want it any tighter than that.    

Also, $200 for off-set grinding sounds too cheep.  Are they doing anything to re-harden the crank?  It doesn't appear that way to me at $200.  Cross drilling the crank weakens it.  Now grinding it down to 2.100 while increasing the stroke will mean you are taking much more off of one side on the journal which will require it to be re-hardened.  Just going down to 2.100 without increasing the stroke you should do this.
 
Just my .$.02
 
Nick

Alfano Performance
4849-76 st.
Kenosha, WI. 53142
262-308-1302
262-942-8271 after 6pm central and weekends


Message: 12
Date: Sat, 29 Mar 2008 19:33:16 -0700 (PDT)
From: Greg Taylor <amundaza@xxxxxxxxx>
Subject: [Amc-list] Stroker crank grinding input needed
To: AMC-LIST <mail@xxxxxxxxxxxx>
Message-ID: <128244.495.qm@xxxxxxxxxxxxxxxxxxxxxxxxxxx>
Content-Type: text/plain; charset="iso-8859-1"

Hey guys,
  Got my NOS 390 crank back from the shop for cleaning up some surface rust from all these years.  The mains are STD, but the rods are 0.001" under and that undersize is no longer available.
  
  So, since the crank has to be turned 0.010" under, I am considering going in a couple of  slightly different directions with rods/pistons ... Can I get some feedback from you guys that have stroked cranks before.  
  
  OPTION 1 - Leave the 390 crank at 3.574" and run a 5.85" SBC 2.100" journal Rod with a Keithblack 1.561" compression height SBC 305 flattop piston (5cc reliefs), which makes a ZERO deck at 9.198".  Yields 10:1 compression with 63cc heads.  This would be a 323.6 CID stroker (3.796" bore 304 block).  Note:  Rods & pistons would be matched, so no bushing work would be needed.
  
  OPTION 2 - Leave the 390 crank at 3.574" and run a 6.125" SBC 2.100" journal rod with a Keithblack 1.261" compression height SBC 305 half-dome piston (-2.8cc top), which puts the piston at 0.025" below deck.  Yields 9.8:1 compression with 63cc heads.  Same 323.6 CID stroker and rods/pistons are matched ... no rod work needed.
  
  OPTION 3 - Offset grind the 390 crank for a 2.00" SBC rod, stroke to 3.75" and run a 5.7" SBC 2.000" journal rod with the Arias forged 232/258 domed pistons (1.595" c/d) I picked up.  This combo puts the piston 0.028" below deck and yields 10.1:1 compression with 63cc heads.  NOTE: The Arias pistons have 0.931" AMC pins, so the SBC rod bushing would need to be slightly reamed from SBC size of 0.927".  This would be a 342 CID stroker (3.81" bore x 3.75" stroke).  NOTE:  To get my crank offset ground would be $200 (as opposed to the $100 for a regular regrind on option 1 or 2).  FYI, I would run H-beam rods for stroker clearance.
  
  While I am leaning towards option 1 or 2, option 3 at least looks promising.  Since I have already had my NOS 390 crank cross-drilled (years back) ... would there be any issues with offset grinding a cross-drilled crank?  OR for that matter, grinding down from 2.249" AMC journal to a 2.100" SBC journal?
  
  Thanks all for the feedback ... and ... good night!


Sincerely,
Greg Taylor :)  <><
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