Lotus Elan

oversize small end wrist pin bushings

PostPost by: dgym » Wed Aug 07, 2019 3:57 am

is it a possible thing to aquire oversize small end bushings? my con rods have been enlarged but oversize bushings don't seem to get listed.
cheers-Jim
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1967 S3 Coupe (left the factory in 66)
original rego PPC 8E
original owner B.M. Wetherill ..are you out there?
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PostPost by: 512BB » Wed Aug 07, 2019 7:12 am

You will probably need to get an old school engineer to make up some new bushes from scratch and ream to size.

Might be cheaper to buy new rods :? Others may know different.

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PostPost by: dgym » Wed Aug 07, 2019 7:16 am

yes i was suspecting the same.. :cry:
36/6612
1967 S3 Coupe (left the factory in 66)
original rego PPC 8E
original owner B.M. Wetherill ..are you out there?
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PostPost by: el-saturn » Wed Aug 07, 2019 7:58 am

you just need a bit of brass-alloy (?) the self lubricating stuff and a lathe owner - it just takes a good artisan! sandy
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PostPost by: nmauduit » Wed Aug 07, 2019 11:11 am

dgym wrote:is it a possible thing to aquire oversize small end bushings? my con rods have been enlarged but oversize bushings don't seem to get listed.
cheers-Jim


some people may use that kind of trick for offsetting pistons... as mentioned above cost are likely to rise when some machining is required: have your conrods been enlarged true and square, or is it the result of an incident? if the former the cost should remain reasonable (Si Bronze, or possibly Al Ni Bronze - clearance will likely need to be larger than with the factory backed bushings so that tolerance is proper at operating temperature - 1 thou or a bit more would be my guess) .

Bill Bradford, one of the Denver, Colorado, based engine builders has developed a scheme where he machines the connecting rod, small end bushing bore to accept an oversized bushing. After installation of the oversize bushing, he machines the bushing ID off center, towards the connecting rod big end, and gains additional piston to deck clearance. Bill says that up to .015" can be gained using this method. Although not sanctioned by the SCCA, as an approved modification, it has become the preferred method of gaining additional deck height in Rocky Mountain Vintage Racing. It is the opinion of RMVR's and Bradford's that the .015" shorter connecting rod effective length provides no performance advantage.
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