Engine bearings early vs s4
01-11-2013 | 06:16 PM
#32
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Getting a crankshaft turned undersize, correctly, is a really tough thing, at least in my area. (Turned undersize, not polished, inspected, and cleaned.) Not many crank grinders want to spend the time to correctly shape the edge of the stone to match the different radius requirements of various crankshafts (and the ones that do take this time want to be paid to do it.....so getting a grinder that takes the time to do this, is usually expensive....more than $250.)
01-11-2013 | 07:50 PM
#33
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From: Irvine, CA
Just for grins here's the repair that Greg had Taylor Machine do on my trashed GTS crank back in 2011:
Straightened (it was 0.008 out of spec), jpurnal welded up, re-radiused, polished, and had all the shrapnel damage welded and cleaned up. Not sure whether any additional heat treating was done, the receipt doesn't say. All main and rod journals are within 'new' spec for a GTS crank. Total shop bill was $600. Not cheap, but I'd guess I could sell it for at least that, so it seemed worth 'saving' it.
Old n' busted 2-6 journal:
The 'new' hotness:
thrust surface and 2/6 journal:
Closeups on the welded-up 2/6 journal:
And another.
[/QUOTE]
And just for S&G's here's a TBF crank that Mark had in the junk pile, to illustrate exactly how hard the steel in the thrust bearing is once you get through the copper. This is the 'rear' face of the #3 main journal:
And the front face, for comparison:
Straightened (it was 0.008 out of spec), jpurnal welded up, re-radiused, polished, and had all the shrapnel damage welded and cleaned up. Not sure whether any additional heat treating was done, the receipt doesn't say. All main and rod journals are within 'new' spec for a GTS crank. Total shop bill was $600. Not cheap, but I'd guess I could sell it for at least that, so it seemed worth 'saving' it.
Old n' busted 2-6 journal:
The 'new' hotness:
thrust surface and 2/6 journal:
Closeups on the welded-up 2/6 journal:
And another.
[/QUOTE]And just for S&G's here's a TBF crank that Mark had in the junk pile, to illustrate exactly how hard the steel in the thrust bearing is once you get through the copper. This is the 'rear' face of the #3 main journal:
And the front face, for comparison:
Last edited by Rob Edwards; 01-11-2013 at 08:15 PM.
01-18-2013 | 08:24 PM
#34
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From: Baltimore,MD
main bearings
just for the record....i stand corrected, the early pre 87 crankshafts are not exactly equivalent to the s4 87+....although all the diameters of the mains and rods are exactly the same, the counterweights are different.
i found this from the instructional video on 928 engine building. they mentioned that the only differerence between 4.7l and 5l cranks are the counterweights. i.e. the s4 has heavier counterweights on the crank.....
i found this from the instructional video on 928 engine building. they mentioned that the only differerence between 4.7l and 5l cranks are the counterweights. i.e. the s4 has heavier counterweights on the crank.....
01-18-2013 | 08:43 PM
#37
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From: Baltimore,MD
so there you have it. just by looking at diameter specs, doesnt tell the whole story....
the early pre 87 crankshafts are different from the s4 crankshafts 87-95, and the GTS crankshafts are different from the s4 cranks
however, the bearings are a different story.....is diameters are same etc and we found from earlier posters about the #1 bearing the early cars have a 2 piece, while the later '84? and later have a one piece on the #1.....
the early pre 87 crankshafts are different from the s4 crankshafts 87-95, and the GTS crankshafts are different from the s4 cranks
however, the bearings are a different story.....is diameters are same etc and we found from earlier posters about the #1 bearing the early cars have a 2 piece, while the later '84? and later have a one piece on the #1.....
01-19-2013 | 05:25 PM
#38
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From: Mount Mort, Ipswich , Australia
Actually recently I had both the cranks on the workshop floor and weighed both , the early s crank came in about 200 grammes heavier than the s4 .
I am currently accessing if it will balance up with the later reciprocating gear .
I am currently accessing if it will balance up with the later reciprocating gear .
