FFS Tech | B-series Piston Check

So you want some B-series Vtec piston specs, eh? Well, here it is...
I've left out the LS piston simply because I despise its low compression ratio factor.
Before you read any further, take a look at these widely known facts:

• B-series pistons can be used in any B-series block, EXCEPT the B20-CRV block.
(the CRV-B20 block uses a wider piston)

• JDM engines tend to have more horsepower than US engines. Part of this, is mainly due to the piston characteristics - a higher domed piston = higher compression ratios.

• The 'R' piston line-up:
- Have a moly coat (black coating) around the outer skirt area. This coating is suppose to reduce friction.
- Have more oil holes for optimal lubrication. The 'R' motors are higher reving than the normal Vtec engines.
- Are interchangeable with non-R type engine blocks.

• more info on the way...

	There are 2 types of B16A pistons in the world. JDM and US. All US B16A engines are equipped with the PR3 B16A piston. Which yeilds a 10.2 compression ratio. All JDM B16A's are equipped with the P30 B16A piston which yeilds a 10.4 compression ratio. That's .2 more points over the US piston. The way you can tell apart each B16A piston from each other, is by the part number stamped on the top-side of the piston. Take a look at the pics and comparisons below.... • PR3 = 89-91 B16A Piston, CR = 10.2 • P30 = 92+ B16A Piston, CR = 10.4

	B17A1 Piston... This piston comes from the rare US 92-93 GSR Integra engine known as the B17A1. The B17A1 engine was only made for the US market. What's weird is that the JDM 92-93 GSR's are (known as XSi's) come with a 92+ B16A engine rather than a B17A1. We can only wonder, why Honda put these low compression pistons in this engine. Mindboggling. However, these pistons are great for a low budget turbo setup. Btw, Project Blacksheep is based on a B17A1 engine. Notice the very teeny weeny slight dome... • P61 = B17A Piston, CR=9:7.1

	There are two types of B18C-GSR pistons in the world, JDM and US. There are B18C-R pistons too, but I'm not covering the 'R' pistons in this segment. Both are labeled with the part number of *P72*, but there's more. If you notice US GSR piston above, there's a 'A0' number right below the P72. The 'A0', I assume, is the coding number for the US market, because the JDM P72 piston has a '00' which is a JDM part. P73 pistons have these same characteristics too (see below). The JDM P72 pistons have a slight dome, which allows the JDM B18C Si-G engine to yeild a 10.6 compression ratio. In contrast, the US B18C1 engine has NO dome, and puts out a wacky compression ratio of 10.0 flat. • P72-A0 = US B18C1 Piston, CR=10:0.1 • P72-00 = JDM B18C Piston, CR=10:6

		The 'R' piston family consist of the Integra and Civic R pistons. Each of these pistons share a special 'moly' coating on their outer piston skirts for reduced friction. These 'R' pistons usually put out a higher compression ratio - depending on what engine you apply them to. The specs I have way below, are from stock compression ratios of the US and JDM 'R' engines. The US 'R' piston has a lower dome than the JDM 'R' piston. Duhhh. Which means higher compression for the JDM version. A nifty thing that I came across, when comparing these pistons, were the wrist pin oil holes. They're found on all of the 'R' pistons and GSR pistons only. Weird...I wonder why they didn't do that to the B16A piston family !? Again, the part number stamped on the top of the piston tells you if it's JDM or not. The part number for the Integra-R pistons, is P73. • P73-00 = JDM ITR piston, CR=11:1 • P73-A0 = US ITR piston, CR=10:6

These wrist pin oil holes, are fed oil by the oil spray jets
found on the underside of a B-series Vtec block.

This here, is the Civic-R piston. The part number coding on this bad boy is '*PCT', but people normally call it a B16B* or CTR piston, since 'PCT' isn't a catchy code like P73 or PR3. This piston stands out like a sore thumb when comparing to any other B-series piston (duh!). The '25' is a marking that lets you know this piston is .25 over sized. If you're planning to use these pistons, I highly suggest you DO NOT mill the head. You could run into some serious valve-to-piston slap problems, let alone the compression be too high for daily driving. Make sure you know what your getting into when building and engine using these guys.

For those that wanna use any of these 'R' pistons in/on your B16A or B17A engine, you HAVE to do the following or else the 'R' piston will NOT fit. You do not have to do this rod-mod to any of the B18C/C1/C5 rods.
(any automotive machine shop can do this)

Approximate Compression Ratios
(when using 'R' Pistons in B-series engine(s)):

• Stock B16B CR=10:8
• B16B pistons in B16A CR=11:1ish
• B16B pistons in B17A CR=11.4ish
• B16B pistons in B18C w/GSR head CR=11.8 or more
• B16B pistons in B18C w/ITR or B16A head CR=11.6 or more
• B16B pistons in yo ass CR=15:1...too high !!!
• P73 US pistons in B16A CR=10.4ish
• P73 US pistons in B17A CR=10.6ish
• P73 US pistons in B18C w/GSR head CR=10.8-9ish
• P73 US pistons in B18C w/ITR or B16A head CR=10.6
• P73 JDM pistons in B16A CR=10.6-7ish
• P73 JDM pistons in B17A CR=10.8ish
• P73 JDM pistons in B18C w/GSR head CR=11.3-4ish
• P73 JDM pistons in B18C w/ITR or B16A head CR=11.1

This JDM piston diagram are from a '99 Spoon catalog.