mx5cartalk.com

Yesterday I was working on the engine and got up to the stage of checking the big end clearances. All of the documentation I have is a Haynes manual and so I had a look at the front which documented what the clearances should be. If I remember correctly, one spec was listed as 0.000xx to 0.00yyy inches. There was also a figure listed with that spec - I can't remember the description but from memory it said 0.004 inches or something to that effect.

I see that there are about 3 different thicknesses of plastigauge - I believe 0.001in to 0.002, 0.002 to 0.003 and 0.003 to 0.004. None of these will measure the 0.000xx to 0.00yyy range. So am I reading something wrong here? Should I be using the second number instead?

Does anyone know which texts contain the clearance specs for the mains and bigend journals that I can crossreference with?

I've left a message with the Mazda parts people @ Centenary Mazda to get a price on the factory workshop manual, too.

Not sure what you're after but, from Haynes:

Main bearing oil clearance
Standard.............0.0007 to 0.0014\"
Limit..................0.004\"

Connecting rod oil clearance
Standard.............0.0011 to 0.0027\"
Limit..................0.004\"

Aha, those are the figures I was talking about.

No plastigauge (that I could see) could measure as low as 0.0007. The only figure I can match is the Limit figure.

Hmmm. I must admit to putting complete faith in the crank, rods and bearings supplied and never checked clearances hen I've done a re-build.

Warpspeed wrote:I have fitted replacement bearings purchased from Repco. I did check the clearance with plastigauge and they were all around .002 to .0025 which is ideal.

For B6 engine part numbers, mains 5M8353, big ends 4B8351

If the clearances are not what you want, there is not a lot you can really do about it.

Those are the exact ones I have. Where did you get those clearance figures from? Is that the figure on the end of the part number (as seen below) ?

\"-.25\" is the undersize in mm

ACL bearings catalogue PDF has recommendations on bearing clearance.

Ta for the link, Daz. If those are any indications I'll wait til I an get the PDFs. That way I can print them out and it won't matter if I get grease or oil on them.

Matty - ta. I have a copy of the catalogue but can't see anything on recommended clearances?

sabretooth wrote:Matty - ta. I have a copy of the catalogue but can't see anything on recommended clearances?

Catalogue AB04,
page vii for general recommendations
and p351 for the B6/BP motor specifically:

Conrod: .0006-.0026
Mains: .0006-.0028

Doh. Thanks. I looked at catalogue AG05 (from checking the valve stem seals). I'll check AB04.

<-- stupid.