first of all, please do a search next time. There are WAY too many ls/vtec questions being asked. The topic has practically been done to death by now. There are MANY posts out there with TONS of good info. I’ll give you some answers, but not all of them, please, do some research… do a search, read through old posts, scour the search engines on the net… all kinds of stuff. This board (and the internet as a whole) is a tool, use it. When you get stuck, come back and ask about the details.
first off, there is no such thing as a b16a1. Its a b16a. The jdm engines didn’t come with a number at the end. What you’re probably getting is a 1st generation b16a from an 89-91 jdm integra xsi or civic sir. there is also a 2nd generation jdm b16a (produced 92+), which has 10 more hp. But in almost all cases it came with a hydro tranny.
The b16a rods WILL NOT fit in your b18a. However the b16a pistons will fit on the b18a rods (no modifications needed). But before you start thinking of using the pistons you need to figure out how high of a compression ratio you want to run, and what compression ratio the b16a pistons will give you. Depending on your situation it might be too high… or might be a little lower than you’d like. So, look into that.
buying a b16a swap to do an ls/vtec is a very good way to go about it (this is what i originally had planned for my engine swap). Like you said, you have almost all the parts you need.
Please don’t think that you can just slap a vtec head onto the ls block and expect it to behave like a vtec engine. The ls can’t rev as high as vtec really needs. You can build the ls block to rev higher, but it takes money, time, and effort.
If you’re on a budget, i’d suggest you forget about the ls/vtec plan (that is if you want the engine to last). Expect a full ls/vtec to cost you $2300-$3000 (that does not include any labor for removal or installation of anything, the only labor it includes is bore/hone/deck/balance, so if you would be paying labor, tack on a lot more $$$).
However if you are planning on spending that amount on the engine, i suggest you look into making a poorman’s itr. It costs just about the same, but will probably last longer and be more reliable. Basically do like you plan with the ls/vtec. The only difference is that you use a b18c1 block instead of a b18a/b block. The b18c block is a lot better designed for vtec, so you don’t have to pay for all the extra stuff that the b18a block would need (shot peen rods, arp rod bolts, block girdle), plus its already made for a vtec head so you wouldn’t have to pay for the oil line and fittings or have the head’s oil hole plugged. True, the b18c1 block does cost more, but it makes up for it since you don’t have to pay for all that other stuff.
Like i said, do a search, beef up your knowledge base a little, familiarize yourself with the ls/vtec and other stuff. If you get stuff, or have any specific questions just post, i’m sure somone will be able to help you.