3198951 x 2 Block Castings

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   I am currently working on 2 x 3198951 401's. One a 71 and the other, a 74. They are quite different castings. The 71 has at the bottom end, approximately 0.100" more cylinder wall but there is more:

I first noticed when cleaning out the cast flashing. The right side of the 71 was very restrictive at the front with a more work to clear the right front oil return from the head. 

The 71 has extra casting "tabs on 1,2,7,8 cylinders and all are heavier.

The 71 has a #2 only in the valley, not on the block.

The 74 has a very open oil return on cylinder #1 and no casting "tab".

Very little cylinder valley tabs on the 74.

The 74 has a 5 cast in the block. Same casting # on back.

Edited by Trader - Jan/08/2019 at 9:29pm

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Trader Members Profile Send Private Message Find Members Posts Add to Buddy List AMC Addicted Joined: May/15/2018 Location: Ontario Status: Offline Points: 6909	Post Options Post Reply Quote Trader Report Post Thanks(0) Quote Reply Topic: 3198951 x 2 Block Castings Posted: Jan/08/2019 at 9:26pm
	I am currently working on 2 x 3198951 401's. One a 71 and the other, a 74. They are quite different castings. The 71 has at the bottom end, approximately 0.100" more cylinder wall but there is more: I first noticed when cleaning out the cast flashing. The right side of the 71 was very restrictive at the front with a more work to clear the right front oil return from the head. The 71 has extra casting "tabs on 1,2,7,8 cylinders and all are heavier. The 71 has a #2 only in the valley, not on the block. The 74 has a very open oil return on cylinder #1 and no casting "tab". Very little cylinder valley tabs on the 74. The 74 has a 5 cast in the block. Same casting # on back. Edited by Trader - Jan/08/2019 at 9:29pm

easydean Members Profile Send Private Message Find Members Posts Add to Buddy List Supporter of TheAMCForum Joined: Sep/26/2010 Location: West Fargo, ND Status: Offline Points: 1591	Post Options Post Reply Quote easydean Report Post Thanks(0) Quote Reply Posted: Jan/08/2019 at 10:41pm
	I was told the casting number on a 1971 block faces the front of the car while all others face the firewall. I have a 71 401 block that faces the front of the car. Had a call from a guy looking for a 71 block and he informed of that and I do have one of them in my stockpile. FYI.

BassBoat Members Profile Send Private Message Find Members Posts Add to Buddy List AMC Addicted Joined: Aug/29/2008 Status: Offline Points: 1719	Post Options Post Reply Quote BassBoat Report Post Thanks(0) Quote Reply Posted: Jan/09/2019 at 8:09am
	Yes, I have heard that the casting number orientation was different and the early blocks had more "beef".

Trader Members Profile Send Private Message Find Members Posts Add to Buddy List AMC Addicted Joined: May/15/2018 Location: Ontario Status: Offline Points: 6909	Post Options Post Reply Quote Trader Report Post Thanks(0) Quote Reply Posted: Jan/09/2019 at 10:25am
	As a crude way of measurement, going though the frost plug holes with a scale measuring from center of cylinders to the block face. The 71 averages 2-1/2" and the 74 2-3/4". The 71 seems quite a bit beefier on the cylinder walls. Found an upside down #2 cast quite a bit smaller on the opposite side of the 71 block, found it wire brushing some crud off. No #2 on the front face.

PHAT69AMX Members Profile Send Private Message Find Members Posts Add to Buddy List AMC Addicted Joined: Jul/07/2007 Location: West Virginia Status: Offline Points: 5926	Post Options Post Reply Quote PHAT69AMX Report Post Thanks(0) Quote Reply Posted: Jan/10/2019 at 10:40am
	Don't know 1st hand, and hindsight being what it is, seems the early 1971 401 with the stock higher compression would be an awesome original engine to have... No Smog Pump or EGR... Those early '71 Humpsters with a 4-Speed and some gears had to been pretty fast and a blast... other than the AutoLite Carb maybe... but it was a Square Flange and easy enough to change out. Edited by PHAT69AMX - Jan/10/2019 at 10:43am
	Link to a Short YouTube Burnout Video