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#1
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Factory bore tolerance stamps
Pulled down a few engines recently that looked to be pretty original.
On the decks were stamped letters near each bore, possibly designating tolerance post hone?. S, T etc. Does anyone have any information on these tolerance stamps, if they are indeed that. Stamping looks pretty uniform, so may have been machine probed, then stamped, and assembly guy picked a corresponding piston to suit to try and close up tolerance?
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Working on going faster (and now staying dry at the same time !!) |
#2
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#3
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Those stamps indicated which piston size would go in that hole, pistons were "select fit".
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1967 Firechicken, 499", Edl heads, 262/266@0.050" duration and 0.627"/0.643 lift SR cam, 3.90 gear, 28" tire, 3550#. 10.01@134.3 mph with a 1.45 60'. Still WAY under the rollbar rule. |
#4
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What AG said. Patt Lobb is a big 409 guy(also owns a big Toyota dealership above Dallas in Allen). He has a conference table size blueprints of the 409 blocks and it has table for them what letter is for what bore size piston. And hence the term "fitted block" for factory blocks.
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Skip Fix 1978 Trans Am original owner 10.99 @ 124 pump gas 455 E heads, NO Bird ever! 1981 Black SE Trans Am stockish 6X 400ci, turbo 301 on a stand 1965 GTO 4 barrel 3 speed project 2004 GTO Pulse Red stock motor computer tune 13.43@103.4 1964 Impala SS 409/470ci 600 HP stroker project 1979 Camaro IAII Edelbrock head 500" 695 HP 10.33@132 3595lbs |
#5
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In some years they changed the letters. (SD 455 is one I believe)
I have a Craftsman Service News on one of the changes. It also showed the specs for each letter.
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John Wallace - johnta1 Pontiac Power RULES !!! www.wallaceracing.com Winner of Top Class at Pontiac Nationals, 2004 Cordova Winner of Quick 16 At Ames 2004 Pontiac Tripower Nats KRE's MR-1 - 1st 5 second Pontiac block ever! "Every man has a right to his own opinion, but no man has a right to be wrong in his facts." "People demand freedom of speech to make up for the freedom of thought which they avoid." – Socrates |
#6
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Pretty cool, would be interested in the specs if available?
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Working on going faster (and now staying dry at the same time !!) |
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