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.

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?

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

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)

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.

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.

HAHA..........I asked my wife to run her soft hands on my rod and feel for lumps.........................insert slap

!

Lol Dave good advice...

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.

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.

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.