Some people try to get 1.9-2.0 L displacement from a B18 by mixing and matching with other B Series Honda parts.

I. General Rules To Remember

I'd like to thank my friend Tony who helped me sort out the "rules" for the various parts which can be mixed and matched.

a) Rule 1: Any B series Honda crankshaft will fit in any B series block (with minor machining or notching to allow for adequate clearances in some cases).

b) Rule 2: Any B series rod will fit any B series crank, EXCEPT the B18C's and B16B (CTR) { i.e. "R" family: ITR, GSR, CTR}.

The B18C1, B18C5, and B16B rod are 1.96-2 mm narrower (0.858 in. vs. 0.935 in. in non-R rods) at the crank end (or rod "big end") and will not fit on the other Honda B series cranks or pistons.

On the small end of the rod (from FF Squad):



Rod Small End Widths:

B18C1, B18C5 17.9 mm (0.705 in.)
B16A, B17A 18.0 mm (0.710 in.)
B18B 19.9 mm (0.785 in.)
B20A 23.7 mm (0.935 in.)

Here are the Strokes for each B Series Crank :

B16A and B16B............77.4 mm

B17A.....................81.4 mm

B18C1 and B18C5..........87.2 mm

B18 A/B and B20B/Z ......89.0 mm

B20A.....................95.0 mm

Remember, rod ratio is the connecting rod length divided by the stroke.

One way to get a higher rod ratio (i.e. get higher revving ability safely without sideloading the cylinder walls too much or getting more vibrations) is to reduce the stroke ( by swapping to a crank with a shorter stroke) .


The other way to get a high rod ratio is to use a longer rod. Three of the longest stock Honda rods are:

B18A/B or B20B/Z 137 mm

B18C's 137.9 mm


However, using a longer rod or increasing the stroke usually means you have to add deck height.

LS owners who were wondering which rods fits their crank without any machining needed? Answer: B16A, B17A, B20.

The B17a rod length is the shortest of the three at 132mm.

The B16a is next at 134mm and the B20 rod is 137 mm in length.

The longest B-series stock rod is from the B21A (early 90's Prelude) with a 141.7mm rod length.

c) Rule 3: Any B series piston will directly fit onto any B series rod without milling or machining , EXCEPT the B18C's and B16B {i.e. the "R family" of rods} .

The connecting rod bearing width on the B16A,B17A, B20B/Z, and B18A/B is apporoximately 19.5 mm. The connecting rod bearing width for the B18C1, B18C5, and B16B is approximately 17.5 mm (ca. 1.4-2mm narrower at the crank). The same narrower width happens at the small end of the rod. The B18C small end width is approx. 2mm narrower than the other Honda B series rods' small end width.

LS owners who want more compression, you can this from a B16A and B17A piston and it is a direct fit at the piston pin to your rod.If you want to put a narrower B18C piston onto your rod, you must mill 1 mm off each side of the rod at the small end to fit.

d) Rule 4: Block Deck Height

is the main reason you cannot go for a "drop-in only " longer rod or stroke. You can calculate whether your new rod length or stroke will exceed the deck height from these numbers:



Block Deck Height = (Stroke/2) + Rod Length + Compression Height + Stock Deck Clearance



B18A/B and B20B block deck height = 211.84 mm

B18C1 and B18C5 block deck height = 212.39 mm

B16A block deck height = 203.37 mm


Rule 5: OTHER USEFUL DIMENSIONS TO KNOW AND USE ->

e) Piston to Deck Clearance


B18A/B, B18C1, B18C5, B20Z/B = 0.76-0.84 mm ( 0.030 -0.033 in.)

B16A/B = 0.5-0.9 mm (0.020-0.035 in.)




f) Piston Compression Height


B18A/B (PR4) 29.97 mm

B18C1 (P72AO) 30.05 mm


B18C5 (P73AO) 30.23 mm

B16A (PR3) 29.97 mm


B16B (PCT) 30.73 mm


B20B (P3F) 29.59 mm




g) Piston Dome Height


B18A/B (PR4) - 1.397 mm

B18C1 (P72AO) 0.00 mm


B18C5 (P73AO) + 1.78 mm

B16A (PR3) + 2.49 mm

B16B (PCT) + 6.43mm


B20B (P3F) - 0.89 mm


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Now that the rules are known, what can we do to mix and match to get 1.9-2.0L (i.e. more displacement for power)?

You cannot use a B16A or B16B crank to achieve 1.9-2.0L. Even if you bore out to 87 mm, the displacement is only 1840 cc.

This leaves us with the remaining cranks:

I. B17A Crank (IF you can find one)

You will need to bore out to at least 86 mm to get close to 1.9L (1891 cc). Boring to 87 mm (max.) will get you 1936 cc but reduces your reliability. Using a compatible, direct-fit LS B18A/B rod onto the B17A crank, the rod ratio will be a very good 1.68.

II. B18A/B or B20B/Z Crank

For the B18A/B block, you will need to bore out to at least 84 mm to get close to 2.0L. If you do not want to re-sleeve, then a bore of 82 mm will give you close to 1.9 L (1880 cc). Most people opt for 84.5-85 mm bore to get 2.0L (1996-2020 cc) . You can do this by boring and sleeving a stock LS block or honing a stock B20 block (stock bore is already 84 mm!!!) to 84.5 mm (cheapest way to go).The rod ratio remains stock with 137 mm long stock rods at 1.54. There is no advantage to using a B18C rod, since this only increases the rod ratio to 1.55 and you'd need to add 0.9 mm deck height.

III. B18C Crank

You will need to bore out to at least 85mm to get close to 2.0L (1979 cc) and 83-83.5 mm to get close to 1.9L (1887-1910 cc). You'll have to re-sleeve anyway, so you might as well go whole hog with 85 mm. The rod ratio remains at 1.58.

Tooken from MD's Swapping Engine Parts For Power..