Volume 6 - Engine Displacement

The power of a Volkswagen engine can be increased relatively easily by replacing the pistons and cylinders (increasing the bore) with a set having a larger displacement or CCs (Cubic Centimeters). The vast majority of VW engines these days are the stock 1600cc with a bore of 85.5mm. During an engine rebuild, this can easily be increased to 1776cc or even 1915cc. I mentioned that this can be done during a rebuild because the crankcase and heads require a modification for the larger cylinders to fit.

Case and Head Boring

For those of you who want big horsepower, replacing the crankshaft with one having a longer stroke (referred to as a "Stroker" engine) is the way to go and results in an engine displacement up to 2.4 liters. Of course this comes at a significant cost, a stroker engine can run anywhere from $2 to $5K depending on how exotic you want to go. The chart below outlines the various combinations available. The blue indicates a stock 1600cc engine.

     

    83mm
    Bore

    85.5mm
    Bore

    87mm
    Bore

    88mm
    Bore

    		 90mm
    Bore    		 90.5mm
    Bore    		 92mm
    Bore    		 94mm
    Bore
    64 mm.
    (Stroke)     		1385 1470 1522 1557 1629 1647 1702 1777
    69 mm.
    (Stroke)     		1493 1585 1641 1679 1756 1775 1835 1915
    74 mm.
    (Stroke)     		1602 1699 1760 1800 1883 1904 1968 2054
    78 mm.
    (Stroke)     		1688 1791 1855 1897 1985 2007 2074 2165
    82 mm.
    (Stroke)     		1775 1883 1950 1995 2087 2110 2180 2276
    84 mm.
    (Stroke)     		1818 1929 1997 2044 2138 2161 2234 2332
    86 mm.
    (Stroke)     		1861 1975 2045 2092 2188 2213 2287 2387
    88 mm.
    (Stroke)     		1905 2021 2093 2141 2239 2264 2340 2443

    Note concerning case boring -

    When cutting a case for late 90.5 or 92mm cylinders there's very little left of the ledge that the cylinder must seat on*. It depends upon the individual casting, but in many cases (pun intended) you need to "deck" the seating surface clear down to the side of the block to establish a flat area of sufficient width. Spacers will be needed to regain any deck height lost by that process. The difference in compression height (wrist pin location) between an "A" and a "B" piston is ~ 5.6mm. This means that all other things being equal a "B" piston would yield the same deck with an 80.2mm stroke as an "A" would with a stock 69mm stroke. An additional 1.8mm stroke is going to require .9mm in shim thickness to maintain that same deck. You may not be able to achieve your desired compression ratio without additional deck height, either.

    It's safe to assume that you'll need some cylinder spacers - but you really can't accurately predict how much until you mock-up the engine.

    *this absolutely MUST be done in all cases with 94mm cylinders, and their "out-of-the-box" deck height takes that into account.

    Topend Calculator (Excel Spreadsheet Download)

    Links to sites with more information on increasing your engine's displacement

    Aircooled.net - Building a performance engine.

    Chirco Engine Tech - Opening up the case and heads for big bore.

    Chris R.

    This club is not affiliated with or endorsed by Volkswagen AG or Volkswagen of America, Inc.  All Volkswagen trademarks herein are used under license from VWoA.

    BACK TO TECH TABLE OF CONTENTS BACK TO MSGCVWC HOME PAGE