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#1
04-02-2007, 07:49 PM
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455 questions
I have a 455 with block code YX. It has 4x heads on it but I can't find anything stamped on the little pads for the other code. assumng they are the originals which 4x would they be? What size chamber? what compression ratio on a stock 455? thanks for any help on this
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#2
04-02-2007, 09:17 PM
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The YX code made in 1971/72 was a "400" engine(automatic).
265hp 8.2:1 comp 2bbl. If you think you have a 455 and you've misread the code,check drivers side of engine and look for 455, it will be legible.Sorry to be the bearer of bad news. 
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65 GTO 4 spd Tri-power Convert 13.64 @ 104.94 2.23 60' 3920# bias ply tires |
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#3
04-02-2007, 09:18 PM
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The YX code made in 1971/72 was a "400" engine(automatic).
265hp 8.2:1 comp 2bbl. If you think you have a 455 and you've misread the code,check drivers side of engine and look for 455, it will be legible.Sorry to be the bearer of bad news.
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65 GTO 4 spd Tri-power Convert 13.64 @ 104.94 2.23 60' 3920# bias ply tires |
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#4
04-02-2007, 09:28 PM
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I think there is a YX 455 in 1974.
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#5
04-02-2007, 09:49 PM
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You may be correct..my Chilton's only went to 1972 !
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65 GTO 4 spd Tri-power Convert 13.64 @ 104.94 2.23 60' 3920# bias ply tires |
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#6
04-02-2007, 09:48 PM
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yea it is a 455 cast in the side of the block. and the yx is the only code i can find on the front
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#7
04-03-2007, 08:04 AM
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What's the date code by the distributor?
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#8
04-03-2007, 08:27 AM
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PunchT37 is correct..it is a 1974.. 455 250hp 8.0CR auto 4Xheads casting #485428 4BBL..came with carb#7044262..good luck.
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65 GTO 4 spd Tri-power Convert 13.64 @ 104.94 2.23 60' 3920# bias ply tires |
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#9
04-03-2007, 08:29 AM
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I had a 1974 455 YX code 455, it had 4X-1H heads on it. The 1H appears on a squared off cast-in hump on the exhaust side of the head near the valve cover land area. There should be 2 of these cast in humps on each head, approx. located between the center and end exhaust ports on each side. Look at the head so you are looking at the exhaust port exits, than look at the fase of the squared off humps I described above, on one of them you should see a little punch type stamp of a number and letter.
Like I said mine was 1H Hope this helps, Mark
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1965 GTO: 467 (Built By Dan Willever), 400 Block, Eagle 4.25 Stroke, Eagle 6.8 Rods, BRC Pistons, Custom Grind Hydraulic Roller Cam, Edelbrock 72cc Heads Ported, HS Rockers, Doug's Headers, Edelbrock Victor 4150, QTF 850 Carb, AutoGear M22 4 Speed, SPEC Clutch and Pressure Plate, 12 Bolt 3:73 Posi. 
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#10
04-03-2007, 05:58 PM
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thanks 65gto69 that was what I was looking for. I can see the little spots where they are supposed to be stamped but mine arer completely blank.
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