Hi, im currently building a b20 VTEC motor with jdm b20 block, kings bearing, stock rods and 85mm F20B piston with a p30 b16a head and y21 trans. Will be tuning the p30 chipped ecu when the engine is done. Need some of the recommendation or experience with people who ran with this similar build.

Questions:
How much rpm can this build withstand or should i set while tuning?
How many hp will this build approximately get?

 

Doesn't the F20B have a larger diameter wrist pin than the B20B does ?

You didn't specify the cams you intend to use, but if they will be stock B16A cams, you will likely make peak wheel HP around 7K RPM... and peak wheel HP should be around 160. Without adding a girdle to the bottom end, I would not spin the engine beyond 7200 RPM very often.

 

I will be boring the smaller end of the rod to 22MM in order to fit the wrist pin, i’ll also be using fully stock B16A5 VTEC head. Will the girdle really be necessary as I intent to set my rev limit to only 8000 RPM? Also, will it be better for me to slap in the CTR/ITR cams?

 

I looked it up and the install height of the F20B piston is an additional mm over the typical "B" series choices... so how do you deal with the F20B piston sitting proud above the block deck about 25 thousandths ? I think your piston choice is a REALLY BAD idea. Why are you making things so difficult ? Press the easy button and order a set of cast Nippons with an ITR dome contour at 84.50mm and run them... no connecting rod modifications necessary and they will sit in the bores at least a few thousandths... leaving you a more manageable compression ratio and a decent quench area for proper combustion... not to mention WAY less potential for valve-to-piston contact.

Yes, a set of ITR cams will be MUCH better for making power.

 

Advice taken, bought the b16b CTR style piston, coded PCT with 84mm. What the compression ratio will it approximately be and will it be much different comparing to the F20B piston. Will the piston to valve clearance be better than the F20B, and will the oem 0.8mm head gasket be enough for the clearance?

 

Usually when you replace pistons, you go .25 over, bore and hone the block to create the correct piston to wall clearance to fit the new piston correct. If you order a same size piston, you may end up with too much piston to wall clearance. And you can't add material, only remove material, so then the pistons would be useless, or incorrectly installed, too loose. Unless you measure first, that's a gamble.

You don't need to change headgasket thickness with a ctr style piston, run an oem-spec or stronger gasket, like a speedfactory gasket.

I'd say the popular go to is the Nippon pistons and Scat rods. Guy has been selling them on ebay for a loong time. Cast pistons modified for c-clip floating wrist pins.

 

I said ITR... not CTR. Genuine CTR (PCT) pistons have a taller install height... not quite what the F20B piston has, but they will still sit proud in the block about 15 thousandths. Some aftermarket pistons have a more generic install/compression height of 30mm, which will create lower compression numbers, and less of a chance of valve-to-piston contact. You can check the description of what you purchased to see their particulars... or you may have to measure them to be sure. Running a .030" head gasket will also reduce the compression slightly... and with those pistons, every little bit will help considering that the combination that you have stated could be as high as 14.90:1 !!!

 

Definitely don’t wanna do ctr pistons in that motor lol. B16 ot itr reps in 84.5mm would be best. If it’s a pump gas motor around 11.5 to 1 is great for making power without being knock limited. Allot of power can be found in the cams, itr and ctr cams can make about 200whp, some skunk2 tuner 2’s in that could push it closer to 220whp if it’s a happy setup with good bolt ons that work together well.