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Old 09-02-2007, 07:52 AM
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Engine builders/ Machinists question

Just had my 406 block done .030 over decked and my rods (pressed onto the wrist pins and pistons).

And I am starting assembly.

My question is That the machinist put the rods on the wrist pins off center, meaning that if you push the rod to one side fully the wrist pin is just about to the piston skirt(maybe .010 in ) and if you push the rod the other way the wrist pin just goes slightly past the lock ring groove.

My question is will this affect the balance or is this something thats done for a reason ,as all the pistons were done this way.
By the way they are speed pro hyper flat tops 4 valve reliefs and 5.7" scat I beams.

I will call him but hes not back in untill next Thursday,
Thanks for any help ,

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Old 09-02-2007, 08:04 AM
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It won't hurt a thing. His fixture is off center a little bit. But it will work just fine.
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Old 09-02-2007, 02:30 PM
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Quote:
Originally Posted by RPM
It won't hurt a thing. His fixture is off center a little bit. But it will work just fine.
Agreed. Nothing to worry about.

Now get 'er together and light it up!
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Old 09-02-2007, 02:52 PM
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While I agree that it is unlikely to create an issue, it does show sloppy workmanship by the machinist. I know that I always make sure the pins are centered and I know many machinists that do also. I would be looking for another machinist for my next job. If he cares so little about something like that I would guess he has little concerns about anything.
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Old 09-02-2007, 04:00 PM
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Thanks guys I feel better now
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Old 09-02-2007, 07:30 PM
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We build a lot of performance engines and don't se many press fit pins but the ones we do they are centered and on every set of pistons tha goes through our shop we ALWAYS measure the wrist pins and the use a bore gauge the check the clearance and from what we have seen over the years we have had to hone the pin bores in the pistons for the proper clearance.

Over the years we seen problems with pin gauling do to tight wrist pins and most wrist pins are not .927 but .9275 or even bigger as most shops just push them in and call it good because they don't have the proper measuring equipment to check the clearances.
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Old 09-02-2007, 08:05 PM
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Well the pins come in the pistons when new , each one slid in and out of the piston like butter, my concern was when he heated and installed the rods onto the wrist pins , the pins were not centered to the rod, and I was worried about balance issues.
Thanks
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Old 09-02-2007, 09:41 PM
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When I install that type piston I put a clip in the groove on one side of the piston and put the pin in after heating rod up in the rod furnace, centering the pin on the rod, then I remove the clip.
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Old 09-02-2007, 10:28 PM
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Would they still be able to be centered now, or is there no going back since they cant be heated now with the pistons on them??
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Old 09-02-2007, 10:43 PM
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pins not centered

Quote:
Originally Posted by 66sedanman
Would they still be able to be centered now, or is there no going back since they cant be heated now with the pistons on them??
hi, we always center the pins, we also have to hone the pistons for proper clearance. you could press the pins to center them, but i would not recomend doing this as you could crack the piston. i don't think you will have any problems using them this way. as suggested in another post i would look for another machine shop. i would certainly check all the work that was performed by this machinist on your engine. sam-missle
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Old 09-03-2007, 06:44 AM
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Quote:
Originally Posted by 66sedanman
Well the pins come in the pistons when new , each one slid in and out of the piston like butter, my concern was when he heated and installed the rods onto the wrist pins , the pins were not centered to the rod, and I was worried about balance issues.
Thanks
Wrist pins will slide through at .0002 clearance and in most cases we find wrist pin clearance is only around .0005 which I feel is not enough form what I have seen and maybe on a stock engine this will work but not on a performace engines as we shoot for .0009 to .0012 and we see the problems that other shops have had by not clearancing the pin bores.

As I have posted before if the pins were .927 like they are suppose to be there would be any issues.

Its like guys buy new floated rods and think there ready to install never seen a set yet.

We use the Sunnen rod heater to install wrist pins and we also have a fixture for pushing out wrist pins with out damaging the pistons as the pressure is put on the rod instead of the piston so if your dealling with a good shop thay could center tnem with out damaging the pistons.

To do this type of work there are a lot of shops out there that don't have the correct equipmnet to do it right but get by with what they got.
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