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Bad bug
Samba Member
Joined: March 11, 2006
Posts: 1160
Location: Jamaica
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 Posted: Mon Dec 05, 2011 10:27 am Post subject: 85.5mm pistons by 76mm stroke |
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| Good day has any ever tried a 85.5 x 76 mm engine using 5.3 inch rods, can you tell if the piston skirts made contact with the crank throws. |
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SRP1
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Joined: January 06, 2007
Posts: 4342
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| Posted: Mon Dec 05, 2011 10:36 am Post subject: |
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Biggest I have gone is 85.5 "A" pistons, 311b 5.395" rods, on a 78.4 stroke.
However that took some creative mill work on the piston.
I see where your going with this, and I like the idea.
Your going to have to do a little measuring on your own using a stock crank,
rod, and piston, then subtracting the differences for your new combo.
I would say worst case you would need to do some minor clearencing
on the piston skirt, and below the wrist pin. |
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DarthWeber
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Joined: November 24, 2007
Posts: 7542
Location: Whittier,CA
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| Posted: Mon Dec 05, 2011 10:46 am Post subject: |
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Where do you find 5.3" rods? CB Performance, and probably a few others, sell 5.325" H beams.
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| Mitey62 wrote: |
| Swapped the Compufire for a Bosch blue and some points I had sitting around, started 1st crank. Took her out for a drive, pulls harder, more RPM, and runs smoother. I think I'll be sticking with points from now on. |
| RockCrusher wrote: |
JB weld the case halves....that'll keep the fretting to a minimum.  |
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Bad bug
Samba Member
Joined: March 11, 2006
Posts: 1160
Location: Jamaica
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| Posted: Mon Dec 05, 2011 11:45 am Post subject: |
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| Darth that's what i should have written 5.325". |
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Bad bug
Samba Member
Joined: March 11, 2006
Posts: 1160
Location: Jamaica
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| Posted: Mon Dec 05, 2011 11:48 am Post subject: |
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| SRP1 wrote: |
| Biggest I have gone is 85.5 "A" pistons, 311b 5.395" rods, on a 78.4 stroke. |
SRP1 i am thinking of using the 85.5A forged piston with 5.325" rods and 76mm crank should go together nicely, what do you think. |
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Alstrup
Samba Member
Joined: July 12, 2007
Posts: 7952
Location: Videbaek Denmark
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| Posted: Mon Dec 05, 2011 12:06 pm Post subject: |
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| Bad bug wrote: |
| SRP1 wrote: |
| Biggest I have gone is 85.5 "A" pistons, 311b 5.395" rods, on a 78.4 stroke. |
SRP1 i am thinking of using the 85.5A forged piston with 5.325" rods and 76mm crank should go together nicely, what do you think. |
It will work. You may have to do minor clearance for the piston not bottoming out. I build several of the type, but with 5,4" rods. I have built one with 87 mm pistons and 5,350" rods. It juuust cleared, in that case.
T |
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Kalen1970
Samba Member
Joined: October 18, 2004
Posts: 356
Location: Tallahassee, Fl
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| Posted: Mon Dec 05, 2011 12:44 pm Post subject: |
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| Bad bug wrote: |
| SRP1 wrote: |
| Biggest I have gone is 85.5 "A" pistons, 311b 5.395" rods, on a 78.4 stroke. |
SRP1 i am thinking of using the 85.5A forged piston with 5.325" rods and 76mm crank should go together nicely, what do you think. |
I haven't run the math on that combo. But 76mm + B pistons + 5.5 rods is about 1.09mm longer then stock and should put you at .043 deckheight.
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1970 - Separated from the Pan again for a proper rebuild *fingers crossed* |
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UK Luke 72
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Joined: September 07, 2011
Posts: 2875
Location: Little Britain
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DarthWeber
Samba Member
Joined: November 24, 2007
Posts: 7542
Location: Whittier,CA
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| Posted: Mon Dec 05, 2011 12:59 pm Post subject: |
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Bad bug, the forged 85.5mm pistons are absolutely the way to go. Much less (if any) clearancing needed than on cast "A" pistons. Only problem is finding forged A's, they are about as rare as hen's teeth now that Mahle has deserted the air cooled VW market. Don't know if AA will take up the slack or not as there's very little demand for that type of piston. I hope they do though.
_________________
| Mitey62 wrote: |
| Swapped the Compufire for a Bosch blue and some points I had sitting around, started 1st crank. Took her out for a drive, pulls harder, more RPM, and runs smoother. I think I'll be sticking with points from now on. |
| RockCrusher wrote: |
| JB weld the case halves....that'll keep the fretting to a minimum. |
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VWporscheGT3
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Joined: September 01, 2006
Posts: 2203
Location: Gardnerville, NV
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| Posted: Mon Dec 05, 2011 2:25 pm Post subject: |
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did mahle finally tell the VW world to screw off?
_________________
If you have any questions about Forged ICON 4032 VW pistons just shoot me a line. |
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Alstrup
Samba Member
Joined: July 12, 2007
Posts: 7952
Location: Videbaek Denmark
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| Posted: Mon Dec 05, 2011 6:44 pm Post subject: |
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| VWporscheGT3 wrote: |
| did mahle finally tell the VW world to screw off? |
I´m afraid so. we have been told "in 3 months time" twice now. Still nothing. The AA cylinders arent bad. I´m not too fond of their pistons. Too many woopsies. And its impossible to tell until you get them running. -Well, if you Xray them you can see it. But how many have a dentist lab next door to sneak in and borrow ? 
For the larger bores there is always the Wiseco and JE upgrade. But for the smaller bores there arent many choices.
T |
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