whats my Horsepower gain with these mods?
you should be up around 146 HP
Why do V8 guys insist on commenting with such venom on slant threads?
Not everyone wants/needs a V8 swap.
To the OP, you have to understand, you're probably dealing with a tired, worn out slant with very low compression. Specific parts don't equal "x" amount of horsepower, everything works together as a package. If you're working with tired bones, the 2bbl and exhaust improvements will
help, but they won't be doing their best.
I'd say a FRESH slant six with a 2bbl, nice exhaust, some increased compression (9:1), and a some cam will make 175-200 hp at the crank easy. A well-worn slant with stock 7:1 compression, a 2bbl and decent exhaust would sound and feel better, but it won't be night and day.
My suggestion is to pull the cylinder head, take some measurements, have it milled to increase compression to 9:1 or so, THEN bolt on the new intake/exhaust upon reassembly. Much more worth your time and effort, and I think you'd be pleased with the results.
But like I said in your other post, if you want/need to run with V8's, don't waste your time. Put your money towards an engine swap.