Volvo Penta Cylinder head Twin Cam AQ171 A – AQ171C B234 DOHC Engine 16 Valve & 89-90 740 & 940 1991




Secondhand, perfect for modifying your Volvo car engine into a twin cam, see below blog for more information

Very good condition

Volvo Penta cylinder head assembly including twin solex carburetors

Suit Volvo Penta 171A/C

This cylinder head will suit the B234 double overhead cam

AQ171C aka ‘251DOHC’ – summary

– 16V DOHC head
– twin Solex carbs
– distributor mounted at rear of head
– interference engine., therefore camshaft belt must be changed on or before schedule
– uses Penta-type timing belt tensioner with p/n 855506-2 timing belt (not used on cars = 146-tooth belt)
– PZI and PZA cams (desirable)
– uses B230 blocks (& blocks are marked ‘B230’)
– may be either centre-trust or rear-trust bearing, depending on year model (later year and rear thrust is preferred)
– may have skinny rods or 13mm rods depending on year (later the year, the better)
– 2.5 litre capacity (B230-sized bore with longer stroke)
– forged crank
– mechanical fuel pump
– high-volume oil pump (as fitted to turbos)

Can be a tight fit in a 240, although it’s been done.

16V head responds well to turbocharging, however mid-thrust bottom ends are known to be weak.

Building up a more powerful 2.3 litre 4 cylinder turbo engine is an alluring thought. Good news is the 8V head can be replaced by a free flowing 16V normally aspirated B234 double overhead cam (DOHC) head that will bolt onto the red B230 ET/FT turbo block.

Volvo didn’t combine a 16V head with a modern 2.3 litre B230 Turbo block, probably due to high cost, however, a 16V head can be sourced from a production non-turbo Volvo B234 engine, or from a few Volvo Penta marine engines particularly the sterndrives eg AQ171C = ….532 head casting number.
History wise, between 1989-94 Volvo did manufacture
in limited numbers two red ‘B’ turbo engines of 2.0 litre capacity, being a 16V 2.0L B204FT unleaded for eg. Italian and French markets, and a leaded fuel version; B204GT model with lambdasond for other markets. Both had 8.2:1 compression ratio. These engines are not readily obtainable secondhand. Neither engine was sold in Sweden.

Desirable performance 16V conversions are not straight forward, and may require additional components such as custom pistons to lower compression or use modified B230FT units (see pic of valve relief in B230 style dished pistons), programmable engine management, turbo exhaust manifold, hi-flow turbocharger, hi-flow injectors, B234 camshafts x2 or custom camshafts, adjustable timing gears x2, timing belt and tensioner, labor costs for engine building, reconditioning, assembly costs plus gaskets, etc. On RH (right hand drive) 740’s it can be done but RH drive 240’s don’t really have enough engine bay room. Serious commitment and money are required to complete related project issues, but it can and has been done.
If using a B230FT block you will need advice on
Timing Belt and Tensioner ->Sales info

For a successful conversion, the starting point is seeking out a non-turbo 740/940 GLE (Sweden 740GLT) with a 16V head. With a second hand head/engine, beware of bent valves or broken cam carriers – a sign of belt breakage (typical comment – I have the head off now and at least 12 of the 16 valves are bent, so the head will be going to the machine shop), note the B234 is an interference engine, so be buyer wise. Replacement components (new) are typically sold in sets and are expensive. Remember to obtain all related components such as sensors, (some) wiring, inlet manifold, cams, ignition distributor, brackets etc.

The correct choice of a mating engine block is most important to avoid longer term problems. A 1995-on B230FT turbo block is the ultimate match. However, a 1991-on B230FT turbo block will suffice. From 1993, blocks featured oil squirters for piston cooling. 1991-on engines feature bigger main bearings, a relocated axial thrust bearing, stronger conrods and stiffer blocks. Recent advice is the normally aspirated B234 engine blocks is also suitable, a drawback being it doesn’t have a turbo oil drain hole.
All red B230 blocks feature an internal oil pump. The B234 block/engine has an external belt driven oil pump. Recent advice is the external pump supplies a larger volume of oil for items like hydraulic lifters, dual cams and dual balance shaft lubrication, items not found on B230 ET/FT.

If using a B234 block for high performance purposes, people recommend removing the balance shafts. Link for Cam and timing belt information. Additionally for high performance, hydraulic lifters should be replaced with solid lifters.

Year Make Model Trim Engine
1991 Volvo 940 GLE Sedan 4-Door 2.3L 2316CC l4 GAS DOHC Naturally Aspirated
1991 Volvo 940 GLE Wagon 4-Door 2.3L 2316CC l4 GAS DOHC Naturally Aspirated
1990 Volvo 740 GLE Sedan 4-Door 2.3L 2316CC l4 GAS DOHC Naturally Aspirated
1990 Volvo 740 GLE Wagon 4-Door 2.3L 2316CC l4 GAS DOHC Naturally Aspirated
1989 Volvo 740 GLE Sedan 4-Door 2.3L 2316CC l4 GAS DOHC Naturally Aspirated
1989 Volvo 740 GLE Wagon 4-Door 2.3L 2316CC l4 GAS DOHC Naturally Aspirated

Additional information


Volvo Penta