3A Bottom end rebuild suggestions

[mardak at cogeco.ca (Mark)]

> -----Original Message-----
> From: scirocco-l-bounces@scirocco.org [mailto:scirocco-l-
> bounces@scirocco.org] On Behalf Of stetson
> Sent: March 19, 2004 8:54 PM
> To: scirocco list
> Subject: 3A Bottom end rebuild suggestions
> 
> Should I get new keepers and seats too?


Not usually necessary unless there's visible wear.  But if you're like
me, it's one of those things where if you're going new with everything
else, why stop there, right?  And so on, and so on, until you realize
you just called your local VW dealer, tied up their parts guy for an
hour and ordered $500 worth of new BOLTS just for stuff that's attached
to the engine!  Been there done that - but it really hurts to use old
crappy looking hardware to bolt up your brand new waterpump, and
alternator, and CPR, and, and, and...  :)


 
> I'm thinking that since the bank account is hemmoraging already that
maybe
> I should want to rebuild the bottom end too since it will be out and
> convenient and I'll end up w/ nearly a brand new mutant engine for
under a
> grand so maybe I should shoot the wad and go for it.


I say shoot your wad and go for it. (did I just say that... :D )  Unless
of course the block has under 60K or so on it.

 
> Haven't done a bottom end rebuild since my dad and I rebuilt a Honda
Trail
> 90 (looks like a girls bike!) engine when I was in jr. high. I know
I'll
> probably need rings and crank bearings.


Yup.  I'd rip the engine apart (make sure you label/mark where
everything went, mark the same side of each connecting rod to make sure
you put them back in the right way), and bring the rods, crank and block
to a machine shop to check out.  Have them check the crank for run-out
and wear.  If it's still straight and close to size just get them to
polish it.  If it needs grinding it might be a good idea to get the shop
to order the bearings - that way they're responsible for matching their
machining to the new bearings.  (On the topic of bearings, it's been
recommended to source a bearing kit with a multi (3) piece thrust
bearing rather than the one piece.)

Have the machine shop check the big end of the connecting rods to see if
they're still round and close to size.  If they're out, the cap and rod
can be ground down a bit and the rods resized.  After that's done make
sure they check if the rods are straight (ie: the little end is parallel
both vertically and horizontally with the big end) - they can be
"tweaked" in a vise if they're not...

Now's a good time to install some quality rod bolts and nuts - can't go
wrong with ARP IMHO...

As for the block, the machine shop (make sure you find a good one you
can trust!) should check the cylinders for wear and roundness.  Most
(reputable) shops will shy away from doing a "re-ring" job if the
cylinders are anything less than perfect.  If you decide to bore it to
the next size you will have to buy new pistons though.  If there's
minimal wear a quick hone (or even deglaze) and new rings will do.

Before you bore/hone the block install the crank (reground or polished)
with the new bearings and lube, torque it down, and see how easy it is
to spin.  If it's stiff the bearings might just need to be "seated" by
using a brass drift and a hammer on the crank as close to each bearing
as possible, top and bottom.  If it's still stiff you may have to get
the block "line bored".  You want to do this before you machine the
cylinders because the boring/honing process machines perpendicular to
the crank journals.

You can save a bit of cash by assembling everything yourself, but the
shop might not guarantee the work if you do.  If you know anyone with
the proper measuring tools it might be wise to check the shops work
before you assemble the engine.

Good luck Tim!  Let us know how it goes...

Mark.
75
80 S
81 S  2.0 ABA/JH/4K


 

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