Perkins 3.152 rebuild - Bearing size

[WombleNo8]

Hi,

Can anyone identify these big end bearings? I'm rebuilding a 3.152 but can't find any markings to show if these are oversized bearings or not.

 

[Netherfield]

Google search suggests 20 thou conversions shows 20 thou as 0.508mm which is probably what's marked on yours, possibly made abroad or for foreign market.

AECO EngineeringCo.MASSEY FERGUSON \ PERKINSEngine-P-3.144/3.152Model-REAR MAIN BEARING PERKINS P-3.144/3.152 (THICK TYPE) AL/Sn (STD) 1 PAIR=2 HALVESITEM DETAILOEM # 0050117 (STD)OEMP-3.144/3.152MODELITEMCODER011P03070860NALT OE#GLA. # GS7861LINTERMEDIATE MAIN BRG PERKINS P-3.144/3.152/4.192/4.203/4.288/6.288/6.305 (THIN TYPE) AL/Sn (STD)ITEM DETAILOEM # 31121221OEMP-3.144/3.152/4.192/4.203/4.288/6.288/6.305MODELITEMCODEC121P03070869NALT OE#GLA. # GS8943SACONNECTING ROD BEARING PERKINS P-3.144/3.152/4.192/4.203/4.288/6.288/6.305 (AL/Sn) 0.020''ITEM DETAILOEM # 31131173 (0.020")

 

[startinghandle]

I see 050 but does it mean oversize bearing??

 

[Netherfield]

I see 050 but does it mean oversize bearing??

Well yes, or properly that the crankshaft has been ground down by that amount.

 

[startinghandle]

On another site an engine expert said
0.030 should be max for grinding,any
More won't leave enough depth hard
Service causing excessive wear

 

[Netherfield]

On another site an engine expert said
0.030 should be max for grinding,any
More won't leave enough depth hard
Service causing excessive wear

I think you're getting confused with Metric and Imperial, They look to be Perkins Genuine parts and I can't see them making something not fit for purpose.

And it might depend on the engine, you can get bearings for Gardner 6lxb engines at 90thou

 

[Ley253]

Just one thing. Pistons, etc are oversize, Bearings are UNDERSIZE, would rattle a bit if larger than the originals, and fitted to a regound(now smaller=under size) shaft.
Two ways to be sure, check Perkins part number, or measure crank. If being reground, grinder will provide correct bearings in any case.
I would think these are fifty thou undersize, which is getting close to bottom limit I feel. I will see if I can find more info for you, I have some books, but they are not here at the moment.

 

[agrimax]

I think they're 0.50mm undersize,which is 0.020'' in old money as Netherfield's post suggests.

 

[Ley253]

I think they're 0.50mm undersize,which is 0.020'' in old money as Netherfield's post suggests.

Now all we need is to find out when Perkins went metric, as these seem to be genuine parts. Twenty thou makes more sense, but there is not enough space between the 0 and 5 for there to have been the decimal point.
Best get the micrometer out methinks!
Edit.
Book mentioned is near useless! Its for the 3D152, of around 1972, but makes no mention of the crankshaft or bearings! It does however give all measurements in imperial, so as those are genuine parts, its unlikely that the marking would be metric.

 

[TheTallGuy]

A quick Google on the part number and they are 0.5mm/20 thou undersized.

 

[WombleNo8]

Thanks everyone, I seemed to be going round in circles. I actually spoke to Perkins who referred my to a reseller, even they couldn't confirm what they are. Most logical answer seems to be that they're 0.5mm/20 thou undersized.

 

[MrNoo]

When I did my Perkins engine there was an excellent manual online (it may have been the Perkins factory one?) and went right up to the modern versions of this engine.