Antonio,
All is not lost if the pistons don't exactly match the 0.030 over bores. If
the bore for a particlar piston is too small you should hone it to fit.
Assuming you have no bore mic. the time honored method of checking bore
size is with a long feeler inserted at 90 deg. to the wrist pin along the
skirt of the piston. When it requires a 3 to 4 lb. pull to remove, the
clearance is as etched on the feeler.
If the piston is too small for the bore, have it knurled and carefully file
the knurling until you get the result with the feeler as above. Many racers
used to knurl new pistons as a matter of course claiming that
irregularities in the surface trapped oil and prevented scuffing of the
skirt and improved the sealing.
As long as you're building the engine, you might look into "Total Seal"
piston rings. I have had good experience with these. The will reduce
cylinder leakage to so close to zero that you can't tell the difference.
They're a little spendy however.
Don't forget to balance the parts and the crank, you'll be glad you did.
-Tom Allen
51 3800
At 07:40 AM 8/20/99 -0600, MIKE RAHL wrote:
>Antonio,
>
>Standard bore for a 235 is 3-9/16". If your block has already been bored 30
>over, then you would order 30 over pistons. Your machinist should have
>miked the bores first, then decided which overbore size pistons that will be
>needed, assigned each piston to a bore, and then bored each cylinder to fit
>that specific piston. The pistons are not necessarily going to be exactly
>the same dimensions. When you assemble the engine I would check the piston
>to cylinder wall clearance to ensure that it is within spec.
>
>Mike
>
>-----Original Message-----
>From: Antonio R. Tijerino [mailto:antonio@innercite.com]
>Sent: Thursday, August 19, 1999 11:17 PM
>To: MIKE RAHL
>Cc: oletrucks@autox.team.net
>Subject: Re: [oletrucks] Engine questions
>
>
>Oletruck list members.
>
>Thanks for the replies about my shims questions. I guess the general
>consensus
>is that shims are required before '56 to adjust the main bearing caps. My
>'56
>does not require the shims, so I should be ok. One more question and I will
>be
>done. Does anyone have a '56 service manual? Can you check what is the
>original
>standard Bore size for a '56 235 engine?. I need to order new pistons and
>rings
>(blocked bored to 0.030) and need to know the standard bore size to be able
>to
>order the new pistons for the new overbore.
>
>Thanks,
>
>Antonio
>'53 3100
>
>MIKE RAHL wrote:
>
>> The 55 235 I just recently dissassembled had shims under the main bearing
>> caps. According to the shop manual they were used for bearing adjustment.
>> My crank was ground 10/10 and I don't plan on using any shims on
>reassembly.
>> The 56 shop manual supplement states that the bearing shims were
>eliminated
>> for that year.
>>
>> -----Original Message-----
>> From: Allen L. Jones [mailto:ALJ@hartcrowser.com]
>> Sent: Wednesday, August 18, 1999 9:04 AM
>> To: oletrucks@autox.team.net
>> Subject: Re: [oletrucks] Engine questions
>>
>> However, there are shims installed at the factory under the main bearing
>> caps in a lot of 235s and 261s. Ever notice those really, really thin
>> sheets of metal under the mains? Typically under the rear bearing cap?
>> It's critical to keep track of these guys during disassembly and put them
>> back in the exact same spot. If you lost or forgot where they go,
>wouldn't
>> line boring the block take care of things? If you talk to some Inliners,
>> they always line bore their block anyway. I suggest you talk to a
>machinist
>> that is more familiar with your situation. Good luck!
>>
>> Allen in Seattle
>> '50 3100
>> Inliner #2235
>>
>> >>> "jack halton" <safesix@worldnet.att.net> 08/18/99 04:32AM >>>
>> Either this guy is confused, or you have an older motor. The older babbitt
>> rod motors used shims on the rod bearing caps, but later 235s use insert
>> bearings - no shims required.
>>
>> Most "production" machine shops don't want to work on older engines, as it
>> takes more time away from their more profitable operations. It's usually
>> better to contract with them for just the major machining operations and
>do
>> the assembly yourself. Or else find a shop that specializes in older stuff
>-
>> but be prepared to pay more.
>>
>> Jack / Winter Park FL
>>
>> ----- Original Message -----
>> From: Antonio R. Tijerino <antonio@innercite.com>
>> To: Ole Trucks <oletrucks@autox.team.net>
>> Sent: Wednesday, August 18, 1999 1:26 AM
>> Subject: [oletrucks] Engine questions
>>
>> > I have a question for the engine rebuilding experts. I am getting a '56
>> > 235 cid engine that has been recently bored 0.30 and the crank has been
>> > ground 0.10/0.10. New cam bearings installed. I have read the 6 part
>> > engine rebuilding article posted on the oletrucks list and does not
>> > mention anything about the main crank bearings "shims". I took the block
>> > to the machine shop and the machine shop guy told me that installing the
>> > "shims" was a job on itself and that it make the price of putting the
>> > engine together more expensive. Can anyone tell me more about these
>> > shims, how to install them and what is the story? is this guy trying to
>> > pull my leg? can I install the shims myself?
>> >
>> > Thanks,
>> >
>> > Antonio,
>> > '53 3100
>> >
>> > oletrucks is devoted to Chevy and GM trucks built between 1941 and 1959
>> >
>>
>> oletrucks is devoted to Chevy and GM trucks built between 1941 and 1959
>>
>> oletrucks is devoted to Chevy and GM trucks built between 1941 and 1959
>> oletrucks is devoted to Chevy and GM trucks built between 1941 and 1959
>oletrucks is devoted to Chevy and GM trucks built between 1941 and 1959
>
Tom Allen
Seattle, WA
oletrucks is devoted to Chevy and GM trucks built between 1941 and 1959
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