Subject: Need help with bearing size selection: I think all sorted!
bajachris88
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posted on September 2nd, 2013 at 07:57 PM
Need help with bearing size selection: I think all sorted!
Good evening guys,
I need help. I bought a set of STD rod and main bearings, given it was a new CB case, and a new CIP1 crank. Little did i know until months after
delivery its a dirty empi crank. Anyways...
The whole bottom end is balanced, so I want to stick with it so far.
Crank is meant to be 55mm when new, but it appears the chinese factory was trigger happy and polished the main and rod journals between two standard
crank grinds (55mm or 54.75mm). See table below. And this isn't consistent across the crank. I really don't want to get the crank grinded down,
otherwise i'm worried i'd have to rebalance the whole thing, don't I? What can I do?
What sizes do you suggest for bearings? Can i get bearings for 54.75mm for rod and mains, and polish them down to suit 54.8ish to 54.9ish?? whats the
best way to do that? I just want longevity at the end of the day and a safe bearing clearance.
During blue printing, i used a micrometer and telescopic bore gauges, excluding main bearing 4, i used vernier calipers instead (didn't have small
enough mic)
Thanks guys,
any help gravely appreciated!
Chris.
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69' baja: kombi box, thing spindles, irs, disc front, type 3 rear drums, 2 inch lift kit, 31x10 rears.
New engine in process: 94mm p&bs, 74mm C/w chomol Crank, 35.5x39 SP heads, turbo. Wierd combo, hopeful torque monsta!
bajachris88
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posted on September 2nd, 2013 at 08:03 PM
on the other note,
if i were to crank the new crank grinded, i won't have to rebalance again? will i need to reharden/nitride the surface?
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69' baja: kombi box, thing spindles, irs, disc front, type 3 rear drums, 2 inch lift kit, 31x10 rears.
New engine in process: 94mm p&bs, 74mm C/w chomol Crank, 35.5x39 SP heads, turbo. Wierd combo, hopeful torque monsta!
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posted on September 2nd, 2013 at 08:28 PM
Give the guys at Crankshaft Engineering a call at Browns Plains, talk to Craig as he has had years of experence with vw engines, you should be able to
have it ground .010" undersize, it is the perfect oportunity to get the correct clearence for the mains, i had Craig fit the new bearings and grind
my crank to suit after i had it nitrided, you could get them to check the balance if they think it is neccessary
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dangerous
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posted on September 3rd, 2013 at 05:39 AM
You should not need to grind that new crank,
unless you want to get an exact oil clearance,
or want a better nitride, and journal surface, as Shayne has had done.
Those crank measurements are not as bad as you think.
Check the journal sizes in your specifications books.
Looks more to me like an issue with your rods.
Typically, yes, the Chinese cranks do not have perfect journal surfaces, but
The rods' bores may be your issue, not torqued properly,
or not clean at the parting faces.
Cleanliness is SUPER important when doing this, as is correct lube on all fasteners.
The correct procedure is to mount all bearings in the rods and case, by themselves
and torque to specifications.
You then measure what clearance you have, based on each individual journal.
Snap gauges are better than nothing,
but a bore gauge is the best way to do this.(with 'ten thousanths of an inch' or 'thousandth of a mm' gauges)
I can double check your numbers if you like, but I think Crankshaft Engineering is closer to you.
Do as Shayne suggests and get Crankshaft to have a look at it.
0.1mm is a very loose journal, so unless you are running grease for oil you are not going to want that!
Generally an engine will like .05mm plus or minus .025mm, depending on 'application' and journal diameter.
A good rule of thumb is one thou per inch of journal diameter.
(about.025mm per every25mm of journal, eg 50mm journal would be .05mm clearance)
Quote:
Originally
posted by westi
That's mad Alan.
bajachris88
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posted on September 3rd, 2013 at 06:12 PM
Quote:
Originally
posted by dangerous
Generally an engine will like .05mm plus or minus .025mm, depending on 'application' and journal diameter.
A good rule of thumb is one thou per inch of journal diameter.
(about.025mm per every25mm of journal, eg 50mm journal would be .05mm clearance)
Thanks Dave,
I just had a go at Rod #2 again, and getting 0.086 mm clearance now. Cleaned it up really good, lubed the fasteners and torqued appropriately. Yea
i'm at Cornubia, i'll hit up Craig in a fortnights time next pay packet.
Many thanks for the advice though.
In the mean time, i will play with the others and maybe even swap bearings. see what happens.
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69' baja: kombi box, thing spindles, irs, disc front, type 3 rear drums, 2 inch lift kit, 31x10 rears.
New engine in process: 94mm p&bs, 74mm C/w chomol Crank, 35.5x39 SP heads, turbo. Wierd combo, hopeful torque monsta!
bajachris88
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posted on September 4th, 2013 at 06:52 PM
Just an update:
Tonight I thought i would investigate further.
I put the new rod bearings on an old original con rod, and was achieving correct clearance in my measurements. Then all of a sudden, i vaguely
remember CIP1 commenting on different bolt torque specs for these hyper rods. So I went onto their website, and they were saying to torque to 30 ft
lbs for these rods http://www2.cip1.com/ProductDetails.asp?ProductCode=C18-1254.
I torqued one, and retrieved an average clearance on this one at 0.06mm YAY!
This might be the solution.
Next question... now that i have rubbed telescopic snap bore guage on teh rods about 30 times or so... is the surface still okay to use or do i need a
new set of bearings? Its got marks as a result.
thanks guys...
I'll have to check the other 4, then will check the main bearings. I'm not out of the mud yet, but may have found an easy way out.
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69' baja: kombi box, thing spindles, irs, disc front, type 3 rear drums, 2 inch lift kit, 31x10 rears.
New engine in process: 94mm p&bs, 74mm C/w chomol Crank, 35.5x39 SP heads, turbo. Wierd combo, hopeful torque monsta!
dangerous
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posted on September 5th, 2013 at 10:23 AM
Very light marks will cause no problems,
but this is very hard to judge without looking and feeling the surface in person.
I would say that if you can feel the marks at all,
a good insurance would be replace.
This is where a woman can be handy,
most have soft fingers, so get them to rub gently and check for lumps.
An then if they have time they can check the bearings too.
Quote:
Originally
posted by westi
That's mad Alan.
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posted on September 5th, 2013 at 08:07 PM
HAHA..........I asked my wife to run her soft hands on my rod and feel for lumps.........................insert slap
bajachris88
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posted on September 5th, 2013 at 10:46 PM
!
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69' baja: kombi box, thing spindles, irs, disc front, type 3 rear drums, 2 inch lift kit, 31x10 rears.
New engine in process: 94mm p&bs, 74mm C/w chomol Crank, 35.5x39 SP heads, turbo. Wierd combo, hopeful torque monsta!
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posted on September 6th, 2013 at 09:58 PM
Lol Dave good advice...
bajachris88
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posted on September 8th, 2013 at 09:04 PM
Yay! I torqued the rods as per cip1.com (30 ft lbs).
Now we are talking. no worries. I will buy a new bearing set of mains and rods given the learning curve has been a little harsh on them. The snap
gauges have had quite a few passes.
Whats your opinions on these? Not tooo tight? Im planning a thinner oil anyways because of the 26mm oil pump gears planned.
Thanks to all,
Chris.
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69' baja: kombi box, thing spindles, irs, disc front, type 3 rear drums, 2 inch lift kit, 31x10 rears.
New engine in process: 94mm p&bs, 74mm C/w chomol Crank, 35.5x39 SP heads, turbo. Wierd combo, hopeful torque monsta!
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posted on September 8th, 2013 at 09:14 PM
Use some oil on your rod bearings next time when you use the telescopic guages. The oil greatly reduces bearing scoring and will not affect your
measurements.
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bajachris88
A.k.a.: Chris Leete
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posted on September 9th, 2013 at 09:13 AM
Thanks for the tip!
Will do, the dry scraping didn't do em any good thats for sure. Well... one or two were worse than others.
(ô_!_/ô) (ô_!_/ô)
69' baja: kombi box, thing spindles, irs, disc front, type 3 rear drums, 2 inch lift kit, 31x10 rears.
New engine in process: 94mm p&bs, 74mm C/w chomol Crank, 35.5x39 SP heads, turbo. Wierd combo, hopeful torque monsta!
posted on September 2nd, 2013 at 07:57 PM
