| Author |
Message |
jslew
Samba Member
Joined: March 03, 2008
Posts: 55
Location: Trinidad, CO
|
 Posted: Tue Sep 22, 2015 10:27 pm Post subject: Spare 94mm piston anyone? |
 |
|
I recently got a 79 FI bus which had been sitting for 7 years. Took the engine apart to check clearances & see what kind of shape its in. Crank play & rod/crank clearance are excellent, and 3 out of 4 piston/cylinder clearances are excellent (.0017-.0019). One piston is .001 larger in diameter than the others, and the clearance in that cylinder is .0006!! No evidence it ever seized... maybe it did and that's why it was parked??
I was wondering if anyone out there for whatever reason has ended up with a spare 94mm piston in good shape? I need one that measures (as per bentley) anywhere from 3.6965" - 3.6972". I would also be interested in a single 94mm piston/cylinder combo if anyone has one laying around, but would want to know the clearance.
Thanks! -Jeff
_________________
Current Garage:
'67 Cal Look Bug
'70 Westy
'73 Baja
'74 Spec Ed Love Bug - my first car bought in '86!
'89 Vanagon GL
'92 Corrado SLC |
|
| Back to top |
|
 |
cliveawn
Samba Member
Joined: December 07, 2010
Posts: 481
Location: Southern Sweden
|
| Posted: Wed Sep 23, 2015 12:34 am Post subject: |
|
|
I have a full set in good condition.
_________________
---------------------------------------------------------
Green 78 Westfalia Helsinki,
2056 with 41 x 34 valves,ported heads
Fully balanced
8,5:1CR
JPM Custom made cam
JPM 7075 dual taper pushrods
IDF 40's with 28mm venturi's
Python CSP 42mm exhaust.
115 HP
Daily driver 2017 Volvo V60 D5 hybrid
Rica stage 2 tune 345hp.
''Funny thing about common sense is that its not very common''
Seismic gun mechanic |
|
| Back to top |
|
|
jslew
Samba Member
Joined: March 03, 2008
Posts: 55
Location: Trinidad, CO
|
| Posted: Wed Sep 23, 2015 9:08 am Post subject: |
|
|
New ones are easy. But I'm a cheap VW owner  , and would rather not pay $400 a set just to get one piston! Especially not when the other 3 are excellent.
_________________
Current Garage:
'67 Cal Look Bug
'70 Westy
'73 Baja
'74 Spec Ed Love Bug - my first car bought in '86!
'89 Vanagon GL
'92 Corrado SLC |
|
| Back to top |
|
|
SGKent 
Samba Member
Joined: October 30, 2007
Posts: 41031
Location: Citrus Heights CA (Near Sacramento)
|
| Posted: Wed Sep 23, 2015 9:31 am Post subject: |
|
|
take it to a good machine shop. Also when you measure it. Do so just below the wrist pin 90 degrees to the wrist pin. Do not measure them on the skirts as skirts collapse, or bend outwards sometimes if dropped.
Another option is measure all 4 cylinders and match them by clearance because it is possible someone swapped cylinders when it was built. Once you are done matching them by size, you will want to have them honed on a sunnen cylinder honing machine to even them up. If you are still tight on one or two, the shop can hone a little more out to give you the correct clearances. If you try to find a matching piston you will have other issues where the wrist pin to deck height can vary, weight differences can be excessive etc. Normally pistons don't wear out for a long time, it is the ring lands that wear away, and skirts collapse inwards. Before you decide those are good, make sure you measure the ring land clearance, and how much the skirts have collapsed.
_________________
“Most people don’t know what they’re doing, and a lot of them are really good at it.” - George Carlin |
|
| Back to top |
|
|
my59
Samba Member
Joined: August 13, 2003
Posts: 3790
Location: connecting the dots
|
| Posted: Wed Sep 23, 2015 3:36 pm Post subject: |
|
|
I have a set out of 79 that has one piston with a broken section between the rings. It was the second piston i was de-ringing and after that i said screw this and bought a new set. They came out of an engine with low/no oil pressure.
Send me a box postage paid for the weight of 4 P&C big enough for pistons out of the cylinders and I will put em all in and send the box back.
It will save me from dragging the milk crate to the dump and hurling everything into the scrap metal bin.
_________________
my59: Well son, my grandfather died before I got to drive it, so does that answer your question?
our79: sunroof bus w/camper interior and 2.0 FI
Other:'12 Jetta, '77 Benz 300D, and a 74 MG Midget. |
|
| Back to top |
|
|
jslew
Samba Member
Joined: March 03, 2008
Posts: 55
Location: Trinidad, CO
|
| Posted: Wed Sep 23, 2015 3:51 pm Post subject: |
|
|
| my59 wrote: |
| I have a set out of 79 that has one piston with a broken section between the rings... |
PM sent
_________________
Current Garage:
'67 Cal Look Bug
'70 Westy
'73 Baja
'74 Spec Ed Love Bug - my first car bought in '86!
'89 Vanagon GL
'92 Corrado SLC |
|
| Back to top |
|
|
jslew
Samba Member
Joined: March 03, 2008
Posts: 55
Location: Trinidad, CO
|
| Posted: Wed Sep 23, 2015 6:55 pm Post subject: |
|
|
| SGKent wrote: |
take it to a good machine shop. Also when you measure it. Do so just below the wrist pin 90 degrees to the wrist pin. Do not measure them on the skirts as skirts collapse, or bend outwards sometimes if dropped.
|
My neighbor runs a machine/speed shop. He questioned if taking .001" out of a cylinder might be too much? The cylinders are all the exact same diameter, so moving pistons wont really help.
I actually measured the piston in several places. No more than .0003" difference in roundness. I swear someone stuck in a bigger piston!
_________________
Current Garage:
'67 Cal Look Bug
'70 Westy
'73 Baja
'74 Spec Ed Love Bug - my first car bought in '86!
'89 Vanagon GL
'92 Corrado SLC |
|
| Back to top |
|
|
Tcash
Samba Member
Joined: July 20, 2011
Posts: 12844
Location: San Jose, California, USA
|
| Posted: Wed Sep 23, 2015 7:20 pm Post subject: |
|
|
| jslew wrote: |
He questioned if taking .001" out of a cylinder might be too much?
You can hone .001 out of the cylinder no problem. Oversize pistons came in .020".
I would be more concerned about the weight. Balance if necessary.
|
Good luck
Tcash |
|
| Back to top |
|
|
airschooled
Air-Schooled
Joined: April 04, 2012
Posts: 12721
Location: on a bike ride somewhere
|
| Posted: Wed Sep 23, 2015 7:31 pm Post subject: |
|
|
| Tcash wrote: |
I would be more concerned about the weight. Balance if necessary.
|
Pistons came in several weight groups. It's hard enough to effectively take one piston down an entire weight group, let along three…
Good luck, seriously!
Robbie
_________________
Learn how your vintage VW works. And why it doesn't!
One-on-one tech help for your Volkswagen:
www.airschooled.com |
|
| Back to top |
|
|
jslew
Samba Member
Joined: March 03, 2008
Posts: 55
Location: Trinidad, CO
|
| Posted: Wed Sep 23, 2015 8:06 pm Post subject: |
|
|
I still need to weigh what i've got. I'll do that & go from there. Sounds like easiest fix (if weight is close) is to just take .001 out of the cylinder. We can adjust piston weight.
So, at some point maybe just that piston got replaced? I wonder how many miles it did w/ .0006" clearance!!
Thanks guys.
_________________
Current Garage:
'67 Cal Look Bug
'70 Westy
'73 Baja
'74 Spec Ed Love Bug - my first car bought in '86!
'89 Vanagon GL
'92 Corrado SLC |
|
| Back to top |
|
|
Tcash
Samba Member
Joined: July 20, 2011
Posts: 12844
Location: San Jose, California, USA
|
| Posted: Thu Sep 24, 2015 9:42 am Post subject: |
|
|
| jslew wrote: |
So, at some point maybe just that piston got replaced?
|
More likely that it came with the set. Someone just missed it or let it go.
You have to imagine a worker with a pile of pistons in front of him and miking them and sorting them by size and weight. .001 would be easy enough to miss or they just did not give a ?hit.
Tcash |
|
| Back to top |
|
|
SGKent
Samba Member
Joined: October 30, 2007
Posts: 41031
Location: Citrus Heights CA (Near Sacramento)
|
| Posted: Thu Sep 24, 2015 1:51 pm Post subject: |
|
|
| jslew wrote: |
I still need to weigh what i've got. I'll do that & go from there. Sounds like easiest fix (if weight is close) is to just take .001 out of the cylinder. We can adjust piston weight.
So, at some point maybe just that piston got replaced? I wonder how many miles it did w/ .0006" clearance!!
Thanks guys. |
the problem I have with this when I think about it is that .0006 is almost an interference fit. I'd make all my measurements again at room temp and make sure I was holding the mic properly so my hand did not warm it. Then I would use a good quality bore gauge to measure the cylinders.
Regardless, the machine shop can sort it all out when then hone the cylinders. Use a Sunnen Cylinder hone and not one on a drill or a bottle brush. The stones in the Sunnen will keep the cylinders straight. You'll just have to rig a way to hold them down and use light pressure when honing.
_________________
“Most people don’t know what they’re doing, and a lot of them are really good at it.” - George Carlin |
|
| Back to top |
|
|
|
