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0311htp Frugal11 Z

The casting number is the one on the top. The last three digits, 081, tell us that these are the good heads. There are too many casting numbers to list, but Mortec.com has quite an extensive list and a brief explanation of each one. Many TBI-equipped cars use a swirl port head, which has a large obstruction in the intake passage. Stay away from those if possible.
1989 Pontiac Firebird Formula TPI Head Work - Rocking and Rolling

 The casting number is the one on the top. The last three digits, 081, tell us that these are the good heads. There are too many casting numbers to list, but Mortec.com has quite an extensive list and a brief explanation of each one. Many TBI-equipped cars use a swirl port head, which has a large obstruction in the intake passage. Stay away from those if possible.  View Related Article

 

 

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