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401 year ?

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Category: The Garage
Forum Name: AMC V8 Engine Repair and Modifications
Forum Description: AMC-made V8 engine mechanical, ignition and fuel from basic repair to high-perf modifications
Printed Date: Feb/23/2019 at 7:19pm

Topic: 401 year ?
Posted By: htrdkd69
Subject: 401 year ?
Date Posted: Jan/10/2018 at 11:13pm
Hi I waa wondering if anyone could help me figure out what year my 401 was made the casting numbers on the back driver side of the block are 3198951the numbers in the valley are b178 and there is just a big 7 there as well thr block also has a big 7 and h on the back as well any ifo would be great im trying to figure out the year built and compression ratio thank you

Posted By: Lyle
Date Posted: Jan/11/2018 at 5:19am
I believe the b178 is month- letter, day, year.  So Feb 01 1978.
Last year of the 401's. 

Posted By: htrdkd69
Date Posted: Jan/11/2018 at 12:43pm
Ok thanks a bunch it looks like its supposed to be 8.25 to1

Posted By: SC397
Date Posted: Jan/11/2018 at 12:56pm
The part number on the heads will tell you what compression ratio it was.

Posted By: amxron
Date Posted: Jan/12/2018 at 2:12am
The 1971 high comp 401 had different pistons and heads.


Fleet/Jeep Mgr.
Orbit AMC/Jeep

Posted By: htrdkd69
Date Posted: Jan/13/2018 at 2:50am
Hi sorry it took so long the casting numbers for the heads are 3225002-2 there's also 5-13

Posted By: purple72Gremlin
Date Posted: Jan/13/2018 at 6:30am
Originally posted by htrdkd69 htrdkd69 wrote:

Hi sorry it took so long the casting numbers for the heads are 3225002-2 there's also 5-13
Sure? The last 3 should say 502. If so, 1974-77.

Posted By: htrdkd69
Date Posted: Jan/13/2018 at 1:23pm
Im sorry one to many zeros it is 502-2 would I be right in thinking its 8.25to 1 ?

Posted By: pacerman
Date Posted: Jan/13/2018 at 1:55pm
The 178 is probably the Julian date (sequential date of the year)   And the 7 probably means 1977.  The B in your case might mean second shift or perhaps a light mod to the casting/molding process.  There might be a "clock" symbol cast into the valley which also indicates the shift where the mold waste set or casting performed and the hour of that shift.  Joe

Happiness is making something out of nothing.

Posted By: htrdkd69
Date Posted: Jan/13/2018 at 2:05pm
There is a clock depending on how you look at it it reads either 1 o'clock or 7 o clock I read on another fourm that 74 to 77 was all 8.25 to 1 does that sound right ?

Posted By: htrdkd69
Date Posted: Jan/13/2018 at 8:30pm
I believe you are right about the b being for a mod to the cast a closer look shows that the driver side of the block has been machined for the push rod clearance as the right side is cast

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