Author Topic: fitting bearings and oil seals to a G40 Supercharger  (Read 14165 times)

Offline PeteG40

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fitting bearings and oil seals to a G40 Supercharger
« on: June 01, 2011, 11:18:37 pm »
following on from the guide here,5569.msg40047.html#msg40047


All parts should be as humanly clean as possible! I use petrol in a water spritzer sprayer and lots of paper towels and an old toothbrush to brush off ground in dirt and to push the paper towel down the recesses.  To get in the apex seal grooves, use an old apex seal and in the scroll ports use cotton buds

The scroll bearing, main bearing and end bearing should be in the freezer.

1. PREPARING THE COUNTERSHAFT - (you can do this while fitting scroll bearing or outlet bearing by the way)
Put the two countershaft bearings in the oven – I normally stand them up, so the grease doesn’t run out (shouldn’t anyway). Similarly to the casings about an hour at 130degrees should do it.   Get the vice out (or a socket upside down) and get the countershaft out of the freezer – you can leave the small middle keyway in.  You need to be quick with the bearings or they’ll heat the shaft up.  Fit the first, then the counter weight and the second bearing.  Both might need a quick tap on the middle race to seat properly - I use a 15mm deep socket.  

it should then look like this

Once cooled, this needs to go in the freezer again, longer the better really.  You may need to oil it slightly to avoid it rusting. (WD40 is fine)

Ensuring the casings and scroll are spotlessly clean, fit one of the circlips to the scroll centre, put it in the oven 130 degrees with the top bearing (which isn't replaced generally - though if falling apart g-laderseite can supply - £50 ish each) facing down - so all grease in it doesnt fall out.

after 45 mins ish you should be able to take the  bearing out of the freezer and plop it in the scroll - should only take a gentle tap.  For this i'd use a 30mm socket (upside down) and an extension bar with a small hammer. If you need some support to knock it in, use a suitable peice of wood on the centre bearing support

put the other circlip on top of the bearing

Heat the outlet casing up for approx 1hr at 130degrees - if needed tap bearing in with hammer/upside down socket and 24mm socket.  Apply the circlip.

Heat the inlet casing at 130 for approx 1hr.  The main bearing and countershaft should then plop in - tapping to ensure both are down. With socket/hammer.  Apply circlips.   The main bearing one should not obscure the oil outlet hole.

Leave all casings to cool.

Scroll – supporting the centre,

i use loctite type bonder (see rebuild kits for details).

Apply to the outer of the seal and fit with your fingers till flush.  

If stubborn use an appropriate socket and tap in carefully.  Imperative that the seals need to be fully square.  I recess the scroll seals by about 1mm from the surface, feel to ensure they are recessed by the same amount all round.

Pulley side casings – fit the seals as above. The internal one is usually fitted flush, the outside casing is either fitted flush , or companies like jabba often leave it slightly protruding. I tend to fit flush.  

the outlet casing usually only needs fitting with fingers

Leave loctite to dry

Fitting the timing belt.  Fit the washer on the countershaft, with keyway and top timing pulley, belt guide inwards.

Similar to removal stop the pulley from turning with the old belt and tighten the top bolt using loctite on the thread. (careful not to slip and damage the teeth!)

Fit the main shaft as it came out with the rubber mallet or a hammer.

Using a socket or suitable soft drift refit the oil slinger (ridges downwards), long keyway and then the timing pulley.
This should be belt guide outwards.  

With both pointers north, (little nicks in each pulley) you can now fit the new belt and ensure that the inside eccentric movement is timed up.  Rotate a couple of times and check again!

Take the apex seal springs, kink on the bends to aid springyness and fit to the apex seal grooves in the casings. However not too much or you wont be able to reassemble without the strips springing out!!!

Take apex seals and fit to the grooves, the casings take longer ones and the scroll shorter. They should totally fit the seal strip grooves, it may be that you have to fit from each and and feed in to the middle.  The ones i use are exact and need no cutting but they are a tight fit.



Lube the charger.... either with Kluber grease by brushing on the walls of the charger where the scroll will be near the casings (where the swirly marks are at the bottom of the casings and scroll) or with spray PTFE grease.  I also tend to lube the top bearing in the scroll with a tiny bit of bearing grease.  Too much and it wont seat on the countershaft properly.

I tend to also lube the scroll with engine oil - to avoid corrosion.

With the oulley side with a pulley on and upright lower the scroll easing it on the shaft to seat the seals.  Be careful to avoid turning the seal lip inside out  and losing the seal spring!!!!  If the scroll is stubborn it may be due to the countershaft not seating right.  A quick push here and it often clicks into place at the top location bearing.  Rotate to ensure it does so without any issues.

Fit the small key way, followed by the balance weight and circlip.  Rotate again to ensure it rotates well. If it doesn't, then remove the scroll and try again.

Hylomar the very edge of the charger casings to ensure the two halves seal well.  

With the casings upright (to avoid the outlet casing strips falling out) put the casings together carefully and push till they meet, ensuring the locating dowels in the casings meet and the centre shaft seats in the outlet casing seal/bearing

Apply a couple of bolts at opposites and turn the charger over using a pulley.  It should turn freely with no hard spots.

Then apply all bolts. Tighten evenly corner to corner.

5.  SPRAYING – you can spray the two halves independently before you fit seals etc.  But to avoid hylomar mess I tend to mask the belt/pullies, outlet and inlets and spray together with two bolts in – then replace the bolts with nice fresh ones.

Should look like this!!

6. STARTING – before fitting to car i like to pour oil down the oil feed hole, sucking it though the drain to make sure oil is on the bearings. once refitted to the car, unplug hall sender and crank the car.  Listen for any noises.    Then reconnect the hall sender and start.  If there are any noises STOP and check it out.  Very unlucky, but occasionally you get a rogue bearing.

7. RUNNING IN – I tend to do 300 miles off boost under 3,000 rpm. Then gradually build up the boost.
IF you get excessive oil in the boost pipes, or smoke out the exhaust, it may be a seal is weeping or not seated well, sometimes there is no rhyme or reason as to why. Seals can last years or fail on startup.  Its common, not the end of the world!!!!!  Especially as you know now how to replace one.
« Last Edit: April 28, 2014, 06:27:27 pm by PeteG40 »

Offline cheys03

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Re: fitting bearings and oil seals to a G40 Supercharger
« Reply #1 on: June 02, 2011, 12:00:22 am »
Only a true G40 hero rebuilds chargers in flip-flops! Hat off to you sir!
Great guide and very useful asset.  Thank you :)

Offline Etches

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Re: fitting bearings and oil seals to a G40 Supercharger
« Reply #2 on: June 02, 2011, 12:53:57 am »
Great guide Pete


Offline xandyx

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Re: fitting bearings and oil seals to a G40 Supercharger
« Reply #3 on: June 02, 2011, 01:25:53 am »
great how to! very explicit!

also a nice way to see how's a ported charger. great for diy rebuilding and porting.


Offline Boris

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Re: fitting bearings and oil seals to a G40 Supercharger
« Reply #4 on: June 02, 2011, 08:50:00 am »
Excellent guide.  :)

Offline type-r-dunk

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Re: fitting bearings and oil seals to a G40 Supercharger
« Reply #5 on: June 07, 2011, 10:51:59 pm »
Wow that a top class "How To" thread.
Well done again Pete.

Offline budunt121

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Re: fitting bearings and oil seals to a G40 Supercharger
« Reply #6 on: June 13, 2012, 04:34:11 pm »
yes this is a top how to guide ! i rebuilt my charger with no problem with using this!! top guy thanks pete :)

Offline Jezza-7

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Re: fitting bearings and oil seals to a G40 Supercharger
« Reply #7 on: October 25, 2014, 04:35:11 pm »
Just followed this guide for the replacement of oil seals.

Class guide and very helpful.

Cheers Pete!