many people ask the quest of what is the difference between the crappy AMC head vs the bmw head. well some say the ports are different sizes and such.
when i pulled my head off my mtech i found that it was an AMC head so i replaced it with a 87 bmw b25 head. i was very surprised to find very little difference. the AMC head is very poorly cast. many rough spots and the top side of the head is ~3-4 mm shorter and makes it difficult to fit the seals in.
as for the intake and exhaust ports. they are both the same size. though there is about 1mm deviation between the ports on the AMC head. meaning they arent all the same size. the intake side of the AMC head was cut smaller to fit an ETA engine, the bored for an "I" head. the chamber was also rebored to "I" specs. the BMW head has a better design on the intake ports, being a smoother line into the valve.
please see the pics bellow to see the differences.












thx, any questions? ill try to answer as i can.
when i pulled my head off my mtech i found that it was an AMC head so i replaced it with a 87 bmw b25 head. i was very surprised to find very little difference. the AMC head is very poorly cast. many rough spots and the top side of the head is ~3-4 mm shorter and makes it difficult to fit the seals in.
as for the intake and exhaust ports. they are both the same size. though there is about 1mm deviation between the ports on the AMC head. meaning they arent all the same size. the intake side of the AMC head was cut smaller to fit an ETA engine, the bored for an "I" head. the chamber was also rebored to "I" specs. the BMW head has a better design on the intake ports, being a smoother line into the valve.
please see the pics bellow to see the differences.












thx, any questions? ill try to answer as i can.
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