i bought headers for my 91 integra(b18a) and i was wondering if they fit all bseries blocks and heads

 

yes the header is interchangable with all b-series motors

 

All B series heads have the same exhaust manifold flange, so it will technically bolt up to all of them. However, there are other differences that might cause fitment issues when used on an application other than the B18A/B. For one, B16A's have a shorter deck height than the rest of the B series blocks, so a B18A header might sit lower than desired on a B16A. Two, the collector end of the header will be cocked one way or the other to meet up with the cat. Which way the collector flange is cocked tends to vary between different models. When I compared the 99-00 Si cat I had to my B18B cat, the flanges were cocked in different directions.