the best way to bump up the compresion is to get pistons there are alot of good aftermarket companys out there putting out 11.1 compresion ratios in 84mm bore i meen you are already there with the 2.0 so you dont have to go crazy with boreing it out just get the machine shop to hone out the cylinders and slap the pistons in but that is just my 2 cent good luck with the build

Ok, is there going to be any big difference by raising the compression with let's say 11.1ish pistons instead of let's say 10.13ish pistons? My goal is 160 whp only.

Yes there will be but with 402 cams you will be under cammed a little for that CR. The 10.1 will be a good match for the 402 where as the 403 or 404s will be better for the 11.1 CR. If you are looking for 160whp 10.1 with the 403's, a good header, 2.5-3inch exhaust, 68-70mm TB, ITR style intake mani and a good tune will get you 160-170whp no problem. A little port matching will always help as well. Also if you are looking for decent mid range power not just top end then a 4-2-1 header with a 2.5inch collector is a better choice then the ITR style 4-1 it is best for 8-10K performance. Best would be a Hytech style, big gains with these headers 10whp at least with gain from 5-10K+. I went with a 4-2-1 on my LS Vtec because it is a DD and I wanted to keep and increase some low end as well as top end and the header did its job nicely. If I was going all out NA I would have gotten a Hytech rep header.

I changed my ITR 4-1 replica headers for an Edelbrock 4-2-1 header a few months ago because of the stance/fitment/dent/road/scraping/annoying issues with the roads here while driving my car lol , but the collector in the edelbrock is ''2 . I remembered seen in a forum that you could cut the collector and weld a 2.5 collector in it but can't find it. I just want to know where to cut and weld it exactly.

As for as the cam project is going, i put it on hold because of the new headers i got. But thank you for the input. I have everything you mentioned:
ITR Throttle body (63mm) that i could port bigger if necessary.
BLOX ITR style intake manifold . (installed)
2.5 test pipe and exhaust. (done a while ago)
walboro 255 fuel pump (installed)
Arp rod bolts (installed)
crower valve springs and retainers. (not installed yet)
sk2 cam gears (not installed yet)
crower 403 cams (not installed yet, but im considering trading them for the 402 so that i could just shave the head .020 or just throw a one layer gasket and be good to go after a good tune of course).

The header thing is my issue now, well mid-term exams too.
Any input, reference is well appreciated.
Thank you.

You are over fueled with the 255LPH pump, you could have just kept the stock pump or a 190LPH would have been plenty for a NA. I am not a big fan of the Ebelbrock header but it will do the job, you could have gotten a Hytech rep header for around $160 and it would way out perform a 4-2-1 or 4-1. You would cut off the flange that goes to the cat/test pipe and replace it with a 2.5 inch collector/flange. DO NOT shave the head to increase compression and always use a OEM style 3 layer head gasket unless you are planning to O ring the block. If you want to increase compression do it by changing the pistons to higher compression pistons like CTR or P30 in a 84mm bore for the B20.

Regarding the walbro pump, i have a fuel pressure regulator.

Thank you for the input, I found the post and the pictures on where to cut it ( i will do this in a few weeks or so). However they do mentioned that nowadays there are plenty of headers that would outperform this modification. My problem was that with the 4-1 itr replica i was scraping and denting the headers badly (ground clearance issue). I been looking on the Hytech replicas today and the ground clearance will be an issue again since my car is dropped (please correct if i am wrong or recommend me a good tri y header with better ground clearance). With the headers i have right now the ground clearance is perfect, so that if a extend the flange and add a 2.5 collector it will be a good mod (wannabe toda header) but not as good as a Hytech.

and yes sir i will do my best regarding raising the compression with pistons. Just thought it wouldnt be necessary since i am not looking into crazy power just 160whp or close. I been doing a lot of research on the one layer head gasket with copper spray.... but that will be later on. Now my main concern is headers and cv joints.... then saving for pistons maybe
Thank you.

The Hytech and rep headers dont have the ground clearance issues that a 4-1 header have so you will be fine. Common issues with a lowered Honda and a 4-1 header is smashing the crap out of it. Another reason my I alway go with a 4-2-1 or Hytech Tri Y style headers. The header collector mod in the pic is a very nice one and a perfect example of what ned to be done to a 4-2-1 to add a larger collector.
If all you want is around 160whp just do a Vtec head. My stock LS Vtec is at 161whp.

Look what i have found for $300 o.b.o. + shipping, instead of the $60/$80 collector mod on my current header.... hummm tempting.
B20/Vtec would require getting a bunch of other parts, like oil pan, water pump, vtec head, oil lines, vtec conversion kit, etc, etc which makes it more expensive, instead of just using the parts i bought already, plus i like this forum otherwise i will be on b20vtec instead hehe

i have an ITR 4-1 replica w/ 2.5 collector and it fits just like oem. granted my car isnt lowered, but the clearence between the header and oil pan is just like factory. I guess it probly depends where you get it from..

FPR is not needed, stock will do the job just fine. It is good for around 500-600whp. You are only shooting for 160whp.
Your planned build will be good for at least 160 if not a bit more.
Get that header, that is the one. You can find them on Ebay for around $160+shipping though so dont buy that one. Most knock off headers fit and perform just fine but the ITR/4-1 has ground clearance issues because the runners under the oil pan are lower than other due to the way the 4-1 is designed.
No oil pan is needed for a B20 Vtec or Ls Vtec. A P72 oil pumps is a very good idea though, some motors can with them though so check first before replacing.

Forget Crower, look into colt cams!!! People you need to believe me when I say these cams will outperform any crower cam available. He can do a custom grind for you if you know exactly what you want. Contact him at http://www.coltcams.com He will explain his cam theories to you and offer you a grind that would be best for your set up.

I tend to stay away from regrind cams like Colt. Crower cams for the non Vtec B series have been proven to make good power NA and boost. The end all for LS heads and cams is just to go LS Vtec and open the door to nearly unlimited cam choices.

i have my tune set up for the beginning of June with my BC stage 2s. Itll be interesting to see what they make. Keep ya posted

Nothing wrong with reground honda cams as they use the best materials. Geoff has tested it vs a billet custom cam he custom ground from 1 billet piece and the honda regrind outperformed. Plus he gives a 5 year unlimited warranty! Crower and any other company don't back their products up like that. My car with the colts outperform many vtec turbo setups in Canada and the car literally has a surge of power from 5500rpm all the way to 9000rpm via the tri-flow technology. Car still makes power after 8000rpm dyno proven. The only reasn I don't shift to 9k is bc of the geometry of the ls head. Plus car idles like stock no problems. Plus cost is half the price of crower cams.