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BIPSBug Samba Member
Joined: June 02, 2007 Posts: 257 Location: Arlington TX
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Posted: Sat Mar 07, 2009 7:15 am Post subject: Piston Size Question |
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Just a quick question. I'm messing out in the garage this morning before I'm dragged off to an Irish festival (ugh) for the day, and I was looking at my new Cylinder and piston I picked up to replace in my older engine I'm rebuilding for my dune buggy.
The engine is an H, and the old pistons(Mahle) read size of 86.93. My new pistons read 85.44. Now I'm wondering if the engine was bored. Will these work? Are the Mahles slightly bigger than the Brailian pistons and cylinders? _________________ '74 Superbug
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Mark33563 Samba Member
Joined: November 13, 2005 Posts: 1667 Location: Tampa Bay. FL
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Posted: Sat Mar 07, 2009 7:36 am Post subject: |
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you need to measure the bore in the case and the ouside of the jug (cylinder). _________________ -—--------—-------
"That's an ultra-rare Dung Beetle... in reverse, it rolls up giant balls of crap. " - Dave24 |
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BIPSBug Samba Member
Joined: June 02, 2007 Posts: 257 Location: Arlington TX
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Posted: Sat Mar 07, 2009 8:12 am Post subject: Measurements |
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Okay, the bore in the case measures exactly 90mm.
and the outside of the the jug is 87.5, so....
guess I'll be taking these back next week to get the next size, right? if the bore is 90mm then what size do I need for the piston and cylinders? 90mm?
What those that equate to in horspower? I thought this was a 1500. Its got sp heads that came with it... _________________ '74 Superbug
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Cusser Samba Member
Joined: October 02, 2006 Posts: 31378 Location: Hot Arizona
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Posted: Sat Mar 07, 2009 8:29 am Post subject: |
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The sizes on the pistons are the piston diameter in mm, so the ones you purchased were stock 1600cc size (original 83mm pistons for 1500 not readily used these days). Your "H" case was originally a 1500 single port. But if the bore in the case is too large for those, then it's been bored out, like for the 87mm you had in there before, not that uncommon. In other words, someone else already built that engine up for a little more power. So you need to get a replacement 87mm set to fit in the bores you already have.
The 90 and 92mm sets go into larger bores yet. _________________ 1970 VW (owned since 1972) and 1971 VW Convertible (owned since 1976), second owner of each. The '71 now has the 1835 engine, swapped from the '70. Second owner of each. 1988 Mazda B2200 truck, 1998 Frontier, 2014 Yukon, 2004 Frontier King Cab. All manual transmission except for the Yukon. http://www.thesamba.com/vw/forum/album_page.php?pic_id=335294 http://www.thesamba.com/vw/forum/album_page.php?pic_id=335297 |
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Mark33563 Samba Member
Joined: November 13, 2005 Posts: 1667 Location: Tampa Bay. FL
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Posted: Sat Mar 07, 2009 10:36 am Post subject: Re: Measurements |
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BIPSBug wrote: |
...i guess I'll be taking these back next week to get the next size, right? if the bore is 90mm then what size do I need for the piston and cylinders? 90mm?
What those that equate to in horspower? I thought this was a 1500. Its got sp heads that came with it... |
Take them back and get the ones that will fit the case.
As for the horsepower, it depends more on just the displacement. What cam are you using? Carb? Fuel injected? Turbo? have the heads been reworked? What are the valve sizes? What exhaust? Compression ratio? That is just a few of the questions....
Dual port heads will breathe better. To convert over you will need to replace the two inside case bolts on both sides of the case (total of 4) plus the heads. Everything else is the same with the exception of the intake manifold system and a larger carb (I am using a carb adapter and an early/smaller carb). _________________ -—--------—-------
"That's an ultra-rare Dung Beetle... in reverse, it rolls up giant balls of crap. " - Dave24 |
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BIPSBug Samba Member
Joined: June 02, 2007 Posts: 257 Location: Arlington TX
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Posted: Sat Mar 07, 2009 8:50 pm Post subject: Bores and Cylinders |
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At least theres no additional cost with 1 step up. Now I can still get those tools I wanted. The heads I'll check tomorrow to see if there looks to be anything special about them. _________________ '74 Superbug
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kreemoweet Samba Member
Joined: March 13, 2008 Posts: 3899 Location: Seattle, WA
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Posted: Sun Mar 08, 2009 8:47 am Post subject: |
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90 mm is the stock spigot hole diameter on the 1500 and 1600 cases. Your
85.5 mm P&C set should fit fine. _________________ '67 bug: seized by the authorities
'68 bug: seized by the authorities
'71 kombi: not yet seized by the authorities
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