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#1
09-16-2002, 04:06 PM
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78 WS6 TA.On the block where the cubes would normaly be is XXX on the back of the block XX with date code 481S88 serial # Z8N150787(which matchs the VIN) heads are 6X8s.Would any body be able to tell me what the h311 I have here I realy dont want to tear it down,it runs fine.I am assuming this is a 455 due to the heads.Please help,I know head gaskets are cheap but why mess with some thing if its not broke.
Thank you, Dave |
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#2
09-16-2002, 04:06 PM
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78 WS6 TA.On the block where the cubes would normaly be is XXX on the back of the block XX with date code 481S88 serial # Z8N150787(which matchs the VIN) heads are 6X8s.Would any body be able to tell me what the h311 I have here I realy dont want to tear it down,it runs fine.I am assuming this is a 455 due to the heads.Please help,I know head gaskets are cheap but why mess with some thing if its not broke.
Thank you, Dave |
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#3
09-16-2002, 10:51 PM
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More than likely it's an 400, assuming the heads are the original for that motor. 6X's came on 400's and some 350's.
I could be wrong on this , but I don't believe the 455 made it to 78'. Thinking 76' was last year for the Big Guy.. [img]smile.gif[/img]
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#4
09-17-2002, 01:10 AM
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the engine CID tag is not where older pont. engines have it on your 78. it is toward the front of the block on the side. looks like an oval with 400 cast on it. its is rotated to face north - south. the 6x-8 heads are from a low compresion 400. they are not the w72 heads which are 6x-4. i just rebuild a w72 motor and this is how all teh info appeared on mine. i believe the blocks are the same.
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1972 HO Trans Am auto White/white 1974 SD Trans Am 4 spd, no a/c dk blue/ white & blue 1978 Trans am gold/ black ,T56, t tops, EFI 474, Build: http://www.pro-touring.com/showthrea...1978+g+machine 1999 30th Trans Am 6 spd, T top |
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#5
09-17-2002, 09:16 AM
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The number 481S88 should be 481988 and is the block casting number not a date code. All W72 engines used in 1978 & 1979 Trans Ams and Formulas have the XX 481988 block. This block number was also used on earlier 1971-1975 400 blocks, however those did not have the XX letters. The date code which is 4 digits will have one letter and three numbers, is to left or driver side of the distributor. To date no original W72 engines used in 1977-79 Trans Ams or Formulas have been found with a date code later than Nov 1977 (K307).
Original W72 400 engines were suppose to have 6X #4 cylinder heads from the Pontiac 350 engine. What are the date code from the cylinder heads? What is the engine block code from this engine which is located on the front passenger side of the engine just below the cylinder head. The codes used on W72 engines for 1978 were X7(auto) and WC(4-speed). John Witzke POCI/NFTAC Tech Advisor 1977-79 W72 Performance Package |
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#6
09-17-2002, 12:56 PM
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Thanx for the replies guys.
TAKid,the pad you mention is where I found XXX no cubes cast in. John,You are correct on the block #481988,looked like an S.Dug into the grunge by dist and found K087 and on the front for the eng code I found X7 which says auto which it is.I have not pulled a vlv cvr yet,but a # just below the vlv cvr is 8138.I assumed they were 8s because they both have a GM8 cast on the outer exh port(dvr rear frnt pass)How do you tell 4s from 8s? Thanx again guys  .
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#7
09-17-2002, 12:56 PM
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Thanx John,I found the 4 where you said.Is there any significance to there being 3 Xs stamped with the 4?Also is there any reason why there are Xs where the cubes sould be (dvrs frnt of block)?There is a pad where the cubes should be but only has XXX cast into it????It probably is a 400 but one of my buddies thinks it may have been somthing special (NASCAR,EXPERIMENTAL).Or could it be just a glitch when they cast the block?
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#8
09-17-2002, 12:56 PM
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Also, forgot to add, the date code 8138 should be B138 or Feb 13 1978.
John Witzke POCI/NFTAC Tech Advisor 1977-79 W72 Performance Package |
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#9
09-17-2002, 12:56 PM
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The 6X #4 cylinder heads can be identified externally by the number 4 stamped on the topside of a flat machine boss pad located towards the top front of the driver side head and the top rear of the passenger side head. This boss pad is just below the rocker cover and between the end and center exhaust ports just above the brass temperature gauge fitting. Hope this helps.
John Witzke POCI/NFTAC Tech Advisor 1977-79 W72 Performance Package |
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#10
09-17-2002, 04:01 PM
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The XXX 481988 400 blocks were used for all W72 engines in the 1978-79 cars. Nothing special. All engine blocks used for the W72 Performance Package, 500557 (1977) & 481988 (1978-79) were 2-bolt main block that utilized spring pin dowels in place of the solid dowels used on the base L78 400.
John Witzke POCI/NFTAC Tech Advisor 1977-79 W72 Performance Package |
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