#3 Main Bearing Trick- thrust bearing reuse tip- BUY 2 SETS OF MAINS!Normally, one will mic the crank, order 1 set of mains bearings in the appropriate size and slap it together, and if done properly (probably not very often) they adjust the amount of lash on the sides of #3 bearing by removing material from the almost always too thick thrust portion of the bearing.
One of the things I do when rebuilding is to buy 2 sets of main bearings and throw away the supplied collar style #3 main bearings. Or you can buy a set of Glyco mains which are just like the factory ones, if you need a set - email me at
[email protected])
I then use the regular non - thrust bearing and the original detached thrust bearings on the #3 main journal. This means that if they are not worn, lash is already adjusted for for that crank / block from the factory! You also only have to buy one set the next time... and you get 3 more "upgrades". :wink:
360 Degree edit: #4 Main - Improves Head / #3 Rod Oiling Circuit Performance!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
I SCREWED UP MY DIRECTIONS BELOW - APPARENTLY I'M DYSLEXIC.
SORRY IF I MADE EXTRA WORK FOR ANYONE (IE. YOU HAVE TO PULL THE PAN AND SWAP #4 and #3 CAUSE I GAVE YOU ***TY DIRECTIONS.:oops: :oops: :oops: )
BTW: Doing this according to my initially crappy directions doesn't screw anything up - it basically behaves as stock (denies you the benefit of an improved circuit) to fix it, simply swap the lower halves between 3 & 4 main.
The Corrections are in bold, basically anywhere it said "#3 main", it now says
edit:#4 main.!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
You can make a 360 degree slot bearing on
edit: #4 main (2 'top' halves like
this ) instead of a 180 degree slot (one slot , one solid) which promotes full lubrication of
edit: #4 main 100% of the time instead of 50% of the time. IMO
edit: #4 main supplies oil pressure to not only rod #3 but also the head.
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Intermediate shaft bearings-
Aside from just letting the shop deal with this part, one thing worth noting is that the German bearings almost always need sized where the federal mogul & Duro brand ones are almost always right on and need no additional modification after simply (hehe) installing.
[fspGTD edit: Title changed from "Full Rebuild tips / gotchas / FAQ / HOWTO?"]
gotta agree,2 sets of mains,,i did same thing,,,,,,,,wanna try a new lube for your cyl bores????total seal has a dryfilm lube for installation on a rebuild,,,,dont be scared,,if its good enough for a top fueler,its good enough for me,,,it looks like pencil shavings,,grey,,good stuff, rub it on thats it,,, :wink: ,,,dont know how many times i gotta say it,,if you are reusing pistons,,never never beadblast, baking soda is ok in a pinch,or walnutshells,,glassbeads gets trapped in pores,,comes out with heat and pressure(like whenyou finally start it),use gasket remover,in a can,,or that cold carb dip,,be careful w/ that stuff,it can stain some metals,,,,,,,i dip em,,scrub a little rinse,,inspect,and repeat if neded,tilli can see the orig machine marks in the pistons,,,,,,heh,,i been sayin i got like almost 5k in my tdi build?,,yea thats used pistons too,whew,they mic'ed up nice,,,,,,,,,,,,,,,,,make a priming tool also,,i can post a pic of that too if needed,,,,,,,,,just ask,i wont bite,,,, :wink:
My engine rebuild tip is to never forget any bearings & seals.
As for intermediate shaft seals & ebarings I reccomend checking the clearance for the bearings before changing them. they may still be within specifications BUT they are extremely vital. If they don't look brand new - replace them.
Also, always remember that the rod & main bolts are torque to yield.
Another good rebuild tip is that an oil pan baffle can be had for very cheap and is an extremely easy piece of insurance to install.
Always prime the engine periodically even while rebuilding to prevent errosion with everything exposed. Fresh bores can surface rust very quickly especially in a coastal location.
Compressed air is always a good idea to blast your bottom and top ends with before install and all mating surfaces need to be surgically clean to ensure no leaks on that ever so monumental start up!
lastly, never run new bearings or rings on synthetic oil. The surfaces need to wear to mate fully against each other. Switch to synthetic after a couple thousand Km.
If you've got a lot of money invested in your build another good thing to do (very cheap piece of insurance again) is to change the oil and filter after the engine has ran for only a couple hours to make sure no machining dust or fillings damage the parts.
for the price of 4L of conventional oil and an $8 bosch filter it's never a bad idea.
Also, always remember that the rod & main bolts are torque to yield.
Always remember not to use absolutes
. Sorry Smokey Eddy, the older engines ( Mk1) do not have torque to yield rod or main bolts or crank pulley bolts either. In fact, I don't think there's a torque to yield bolt anywhere on my Mk1 Caddy.... That's not to say that it's not worth replacing 30 year old stressed parts that can blow up your engine, if you have the bread, and can find new stuff that you are sure is better than the old stuff...
Hey, bumping up an old post.
As some know the main bearing sets come with 4 flat bearings and
6 with an oil hole and groove.
Well there are only 5 mains so that grooved bearing has to fit in one of the caps.
I'm rebuilding an engine and while putting the main bearings in,
there is the old question of where the grooved main cap bearing goes.
It seems like 2,3,4 and 5 mains supply oil to the rods through a hole in the crank.
While #1 supplies no oil to a rod.
And I remember Jack, the former vwdieselparts.com owner and engine rebuilder,
telling me the grooved one goes on #1.
I looked at the MK2 bentley page 41 picture of the oil passageways
and the idea that the #4 main bearing somehow supplies oil to the head
doesn't seem like any more than a rumor.
It almost seems like VW intended for the rod to start getting oil pressure halfway down the downstroke
and halfway back up.
Before the flat cap bearing acted like a check valve at the top of the stroke
to keep oil from being pushed back toward the main when it fires.
I'm pretty sure I'm going to use the 2 grooved main bearings on #1
unless someone can convince me otherwise.
