Questions Regarding Replacing the Mangusta Jackshaft Bearings

Terry,

if you need new ones, I bought a set from these guys in the UK and they arrived in Texas in two days!  very reasonable pricing too

https://www.qualitybearingsonline.com/

Here's a text clip from an earlier thread with dimensions.  Worked perfect in my case

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Front bearing: 47mm OD x 20mm ID x 18mm Wide. #62204-2RS1 (SKF). $22 (I had a 14mm wide bearing here and a spacer behind my pulley!)

Middle and Rear bearing: 47mm x 25mm x 16mm. #63005-2RS1 (SKF) $20

Rear bearing for LATE cars: (not sure where cutoff is, but if a 47mm is too small.....
52mm x 25mm x 15mm #205-SZ3 MCH? $16

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

MH

FWIW, I'm of the school that says the center bearing is the source of most Mangusta drive bearing problems. If you're worried about the shaft whipping from the combined alt/AC load (that from an alt alone on a shaft that size is almost non-existent), use a home-made nylon support bushing in the center position. I suspect that heat-related expansion/contraction of the engine castings causes more distortion in the long, spindly bearing holder than the center bearing can compensate.

Good to see you're working on the old  'Goose, Terry. Let us know when it makes it around the block on its own power and I'll hoist a drink for you!

MH...

Thanks for your info.  I had my jackshaft at a shop who disassembled it and he said there were no spacers in the front, that the pulley was up to the bearing.  He still has all the parts as I sending it out for clean up (media blasting).   Markings on the shaft seem to indicate no sign of a spacer.  That bearing sits next to a shoulder on the jackshaft itself.  It was only 14mm.  I need to talk to him again to make sure there was no spacer but he said there was not when I did talk to him before.  The middle and rear bearings were 12mm with thin spacers inside the clips that are on the outside of those bearing races.  I have been told to not put in the middle bearing and have decided to follow that.  Johnny Woods does replace them but note that said that they are "normally spun" and he has to repair the jackshaft.  Indicates a problem.  Steve Liebenow says definitely to not replace the center one siting problems.  I did place my shaft carrier on a flat counter and found that the center to bosses that are to meet the intake manifold are about a mm+ short of the length of the outer two.  Either the stock intake manifold has that slight step up or thin spacers are needed there.  Have you checked this?  Also, my shaft is bare metal, not painted black like I think earlier ones.  My car is #700.  I have considered thinning the rear spacers to accept a slightly wider bearing like 14 same as the front.  If I don't have a spacer on the front as I was told, I am reluctant to trim the shoulder on the shaft to accept a wider bearing.

Bosswrench...Re "whipping problems or just for appearance, I considered taking a bearing and making the inside diameter slightly larger such that it does not contact the center shaft bearing race but could put a damper on potential whipping if the tolerance was not too big.  Seems it would have to be out of balance to do any whipping.

Is there any choice between double or single row bearings in this application?  Is double better?

Terry     

Has anyone fabricated a complete jack shaft assembly? I have a pantera and I'm considering running a jack shaft to a super charger if one can be fabricated

@Bell3156 posted:

Has anyone fabricated a complete jack shaft assembly? I have a pantera and I'm considering running a jack shaft to a super charger if one can be fabricated

Fred Terry did exactly this about 10 years ago . He installed twin Eaton M90 superchargers on his GT5-S . He made everything ,including the pulleys.

There is an article in a past issue of POCA Profiles .

Ron

Magnuson did a Jack-shaft setup on their SSR supercharger kit.
https://simple-engineering.com...ete-kit-for-the-ssr/

Denisc

I don't know if that's relatable other than trying to buy just the jack shaft and bearings..

pacton novi2200 super charger rear mounted is what Im contemplating

Ok simplified version. If Magnusen can make a similarly built Jack shaft turning high rpm. We should be able to replace the bearings with the same thing that was there (read numbers on the old bearings) and run our old shafts.

I have found that if I put a straight edge inside the aluminium casting where the bearings sit it's nice and straight. If I then bolt it onto the engine without the jack-shaft in place it distorts. So I shim the casting until the straight edge sits on all 3 bearing surfaces, then remove and install the bearings.  Maybe this is why the centre bearings fail? I am no expert on shafts or bearings. I still install all 3 bearings. I'll let you know if I have any fail. Maybe the factory did this and the shims got lost over time?

We had to fabricate a new jackshaft when we tried 4 x Webers.  Wasn't that involved.  Used x 2 bearings only as worked out (with chrome moly tube) that whip unlikely below 7000 rpm, short shaft and tubular. Brackets attached either end.   If you know the thickness and material there are plenty of critical speed calculators on web to work out where / if it stock jackshaft likely to whip although they thought it would under full load / off load situation.  Sounds like Johnny has hit on why centre bearing often fails.  We had thought of doing what BW has suggested and having a nylon bush that would control the whip but give clearance at centre.  Never got round to it as we replaced the Webers so went back to stock jackshaft.

Johnny has some good photos on his "harleywax" website dealing with jackshaft refurb.

cheers

Larry

This is at mock up stage, no bearings.