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Engine rebuilding



 
 
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  #1  
Old July 13th 05, 11:44 AM
Kuebel Guy
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Default Engine rebuilding

Hi all!

Finally decided to totally rehaul my stock 1600. Reasons? 76km, oil
leaking and poor compression in 3 cilinders....

I have it all in pieces on my table, and now cleaning everything and
measuring, looking for cracks, scratches, etc....discovered a broken
camshaft bearing, will replace all.

Got a new crankshaft, conrods, pistons/cilinders. And I am evaluating
wether to keep the old crankshaft/conrods. The old crankshaft/conrods
set looks in good shape, I am measuring journal diameter and roundness,
conrod play, and conrod/shaft clearance.

If I install new, I've read that is not easy to install new conrod
bushings and that professional machining will be needed. Is that true?

If I remove old conrods, I will need to replace the old nuts?

thanks for any hint, I will be busy this summer...

cheers!

carles

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  #2  
Old July 13th 05, 12:35 PM
Jan
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Default

Kuebel Guy wrote:

> I have it all in pieces on my table, and now cleaning everything and
> measuring, looking for cracks, scratches, etc....discovered a broken
> camshaft bearing, will replace all.


Yes, replace all bearings in the engine. Also inspect the bearing
saddles in the case for wear. The surface that teh bearings rest
against, has to be perfectly smooth. No grooves or steps worn on it,
from the bearing. Usually the bearing closest to the flywheel is the
worst, it pounds grooves onto the bearing saddle. (this is caused by
very minor vibration). There can't be ANY sideways play in the big
bearing once it is pressed in place. (Do this test without the crank).
If the big bearing has end play, or if the saddles are grooved, the case
needs to be sent to a machine shop for line boring, where they machine
material off the saddles to achieve smooth, straight support surfaces
again. Then you will need oversize bearings. Ask for a correct size set
from teh machine shop, or ask them to tell you the exact size they bored
the case up to, so you know what size bearings to buy. The end play
problem is eliminated much in teh same way, they should machine the
sides of the flywheel end bearing saddle smaller, to accept a new
bearing that has a smaller flange distance. It'll be tight again as long
as the sizes match.

> Got a new crankshaft, conrods, pistons/cilinders.



Woohoo!

> And I am evaluating
> wether to keep the old crankshaft/conrods.


They make a wonderful tabletop decoration and conversation piece in the
livingroom. Or you can use them to build a "B" quality engine some
day, where you use only old (but still good) parts.



> The old crankshaft/conrods set looks in good shape,


Both can still be bad.. visual inspection doesn't reveal some of the
more severe problems they usually can have, like microscopic cracks and
slightly bent rods, even bent crank..


> I am measuring journal diameter and roundness,
> conrod play, and conrod/shaft clearance.


Good.

> If I install new, I've read that is not easy to install new conrod
> bushings and that professional machining will be needed. Is that true?


Not true. It's bolt-on, as long as you bought the right size.
The rods should be weighed against each other, to make sure there is no
weight difference across them. Acceptable tolerance is around 5 grams,
factory rejection limit is around 8 grams weight difference.
I match mine within 1g of each other.
To remove weight, you can grind off the ridges of cast "seams". Leave
the little "knob" intact on one side of the rod neck. When installed,
those knobs should all point upwards, when each rod is pointing towards
it's piston. (The rods are not symmetrical, there is a very small,
undetectable to the eye, difference)


> If I remove old conrods, I will need to replace the old nuts?


Old nuts can be reused if the threads are ok. Dry them, degrease them
(and the bolts) and use loctite thread locking glue when assembling, and
carefully torque them to specified torque value. Some rods have little
grooves by the bolt hole, and the nuts have a collar.. you are supposed
to use a sharp punch and peen that collar into the groove to prevent the
nut from loosening up.
Not all nuts have this collar, and not all rods have the groove.
Therefore a generally accepted safe practice is to use Loctite.


Jan
  #3  
Old July 21st 05, 11:13 AM
Kuebel Guy
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Default

Good!

while inspecting the case, I've discovered that the thread that holds
the
oil presure sensor is broken. In fact looks like a bronze thread insert
which
was glued to the case hole, as the case itself is not threaded at all.

I was planning to clean the hole, and glue a new insert (if I find one)
or make a thread in the case to hold the insert.

your advice...?

cheers!

  #4  
Old July 21st 05, 12:44 PM
Jan
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Default

Kuebel Guy wrote:
> Good!
>
> while inspecting the case, I've discovered that the thread that holds
> the
> oil presure sensor is broken. In fact looks like a bronze thread insert
> which
> was glued to the case hole, as the case itself is not threaded at all.
>
> I was planning to clean the hole, and glue a new insert (if I find one)
> or make a thread in the case to hold the insert.
>
> your advice...?
>
> cheers!


Thread the existing hole for an insert. Solid insert takes more room and
there's not a whole lot of meat around the boss, so I dunno... coil type
thread requires less room but I would worry about leaks.. well.. use
sealant and/or teflon tape..

Biggest problem is to find a suitable thread insert. May need to have
one made or make it yourself. Glue a non-threaded insert in there? Jeez.
No way. It's under constant pressure, and oil..

Maybe go to a pro alu welding shop and have them fill weld the hole
shut, then drill and tap for fresh threads. Alu/Mag case CAN be welded.
(if you know what you are doing)

One more idea: how about trying to find a pressure switch from another
car that already has a larger diameter thread size, then ream and tap
the case for that size?

It's just a stupid pressure on/off switch, and most car engines require
*roughly* the same oil pressure at idle to protect the bearings.
Bearings are the same basic type, with more or less same clearances,
regardless of what engine it is, so they should have the same basic
lubrication requirements. - so, it shouldn't be hard to find a switch
that opens at the same approximate pressure as the OEM VW switch, but
just has larger diamater threads. I think? Never tried.


Jan
  #5  
Old July 27th 05, 11:06 AM
Kuebel Guy
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Default

Here again...

I have inserted one of the rod bushings to test wether a 22mm wrist pin
can fit.

The result is too tight. Interference between fitted bushing anf wrist
pin is about 0.5mm.

Also the bushings I got have no drilled oil holes, although is a VW
stock part.

Whats the best action here...honing? And of course drilling the oil
holes.


cheers!

Carles

  #6  
Old July 27th 05, 11:32 AM
Jan
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Posts: n/a
Default

Kuebel Guy wrote:
> Here again...
>
> I have inserted one of the rod bushings to test wether a 22mm wrist pin
> can fit.
>
> The result is too tight. Interference between fitted bushing anf wrist
> pin is about 0.5mm.
>
> Also the bushings I got have no drilled oil holes, although is a VW
> stock part.
>
> Whats the best action here...honing? And of course drilling the oil
> holes.
>
>
> cheers!
>
> Carles
>


Do you have solid or split bushings?
I tried a set of the split type, and found them to be PITA.
Also tore down an engine where those were used (installed many many
miles ago by someone unknown), and they were loose to the rod, and spun
little, so the oil holes no longer lined up. I'm never going to buy
those again.

I also don't reuse old stock rods for high performance engines either.
New set of good rods with ARP bolts is a nice insurance.

YES they always need to be honed to perfect fit and oil holes drilled.
They are too tight probably to "force" you to hone them properly.

Jan
  #7  
Old July 27th 05, 12:21 PM
Kuebel Guy
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Posts: n/a
Default

Ups!

they are split type. so, better buy solid ones? sometimes is not easy
to select type from catalog.

I am using new stock rods for a stock 1600.

If I would like to hone bushings whats the best technique?

cheers!

carles

  #8  
Old July 27th 05, 08:12 PM
Bugfuel
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Posts: n/a
Default

Kuebel Guy wrote:
> Ups!
>
> they are split type. so, better buy solid ones? sometimes is not easy
> to select type from catalog.
>
> I am using new stock rods for a stock 1600.
>
> If I would like to hone bushings whats the best technique?
>
> cheers!
>
> carles
>



I honestly don't know. I decided to never even attempt doing them
myself. Too many things can go wrong. At the very minimum you need a
solid fixture and drill press or something for the hole so that you get
the hole absolutely straight and true, and 90 degree angle.

Buy new, or have a machine shop do them. Just don't bother.

Jan
  #9  
Old July 27th 05, 10:08 PM
Tim Rogers
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Posts: n/a
Default

"Bugfuel" > wrote in message
...
>
> > If I would like to hone bushings whats the best technique?
> >
> > cheers!
> >
> > carles

>
> I honestly don't know. I decided to never even attempt doing them
> myself. Too many things can go wrong. At the very minimum you need a
> solid fixture and drill press or something for the hole so that you get
> the hole absolutely straight and true, and 90 degree angle.
>
> Buy new, or have a machine shop do them. Just don't bother.
>
>


................My dad use to do it by hand back when I was a kid and I think
that his technique was from way back in the old days maybe even in the 20's
& 30's because he told me once that he learned from someone back when he was
a teenager. What he did though was use very fine emery paper on the wrist
pin instead of honing the bushing. It's pretty simple.

Here it is:
.....Put some masking tape on the ends of the wrist pin where it seats in the
piston. Roll the pin on an ink pad to stain the center section that's not
taped. Remove the ink on the pin with the emery paper without rubbing any
area where the ink is no longer visible. Take the rod/bushing after removing
the tape from the pin and do a trial fit. If it's still too tight, start
over. If it gets too loose, start over with a new pin. I remember that it
was time consuming and that I wasn't trusted to do it because I was an 11
year old goofball kid.


  #10  
Old July 28th 05, 04:40 AM
Grahame Rumballe
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Posts: n/a
Default


"Kuebel Guy" > wrote in message oups.com...
> Ups!
>
> they are split type. so, better buy solid ones? sometimes is not easy
> to select type from catalog.
>
> I am using new stock rods for a stock 1600.
>
> If I would like to hone bushings whats the best technique?
>
> cheers!
>
> carles
>

Honing is not the correct method. Honing follows the contours of the metal
responding to dips and highs, you can never achieve a perfect circle.
The correct procedure is to "ream" the bushes to suit your pin.
With an installed new pin of 22mm (.8661 inch) you would be after .0004 - .0008 radial play.
So you "ream" the bush to suit.
A good machine shop would be able to do this for you either using a straight or adjustible reamer.

Check here for an example of what a "reamer" looks like.

Grahame
from Aus

 




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