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Re: Looking for advice on ground up rebuild Posted by 900 Aero [Email]  (#425) [Profile/Gallery]
(more from 900 Aero) on Thu, 22 Nov 2012 17:37:16
In Reply to: Looking for advice on ground up rebuild, BT, Wed, 21 Nov 2012 22:08:23 Members do not see ads below this line. - Help Keep This Site Online - Signup |
You'll find that Saab as well as most other manufacturers machine their crankshaft journals to small standard spec. and then have coded bearings to get the clearance just right. The way I've accomplished correct bearing clearances as long as the crank is in spec. is re-size the connecting rod housing bore accordingly. In other words if the crank is small spec. size the rod to small spec! We go a step further and calculate the exact housing bore needed for the bearing clearance we're looking for. Just add both bearing thicknesses (at their thickest mid point) to the journal size plus clearance. We do the same thing with the maim bearing housing bores when we align hone the block. I always use ARP main bearing studs, nuts and washers so by the time I hand touch up the caps and their block surfaces along with the extra clamping force of the ARP studs all I have to do is a very light align hone to get the bearing clearance just right. Otherwise with just plain standard bearings and a standard spec. crank you end up with around .0035" clearance and I like to see it come out more like a loose .002" on the mains and a tight .002" on the rods. As far as installing bearing shells just make sure that your bearing housing bores are de-burred at their parting lines so the back of the bearings are not scuffed as they're placed all the way into the rod or block. Some oil control rings are more difficult to install than others so just take it slow and you'll be okay. By the way we don't use plastigage, we use vary accurate micrometers! If you have questions along the way you can give me a call, I've been doing performance engine machining/building for right at 50 years now and I like helping people to get things right the first time! Dave at Precision Turbo Works 805-235-3951
, Thu, 22 Nov 2012 17:37:16 <-- Viewing This Message, Thu, 22 Nov 2012 05:57:59
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