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1982 through 1991 Porsche 944 NA and Turbo models

Page history last edited by Greg 14 years, 1 month ago

 

HOW TO CONVERT THE PORSCHE® 924 / 944 TO V8 POWER

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Driving an 80's Porsche® model 924 or 944 can be one of the liveliest and entertaining experiences anyone can have. With near perfect 50/50 weight distribution, due to the engine in the front and transaxle in the rear, these cars were very fast and nimble for their time as well as today. However, since the 80's and 90's these models have seen major maintenance bills and strife due to their four cylinder engines. Whereas one person pays these bills to keep the car stock and completely Porsche,others tend to think outside of the box.

 

The Porsche® 924 and 944 share a common feature; a four cylinder engine with a degradable rubber timing belt, and pistons that do not clear the valves if the timing belt breaks. After so many years, the timing belt must be replaced along with its tensioner, rollers and other related items. This is no small task as well as quite expensive. Nevertheless, many of these cars have been scrapped simply because of this kind of incident.

Another issue included the mere price of performance modifications. There was never a high demand for aftermarket support in the way of engine internals which made it hard or even impossible for most to compete with others such as Chevy and Ford. What's more, the Porsche® engines had a limit as to how high horsepower and torque numbers could go reliably.

 

The 924/944 series models have a 4 cylinder slanted engine mated to a driveshaft (torque tube) and then to a transaxle in the rear of the car. This set-up is also seen in the C5 Corvettes and Saleens. The weight distribution allows for easy high speed cornering with little roll as compared to other cars where the transmission is directly behind the engine. Although these cars were not designed for straight line drag-racing, they handle twisty-turning roads quite well. If you intend to drag race this car, you will be disappointed as most cars designed for that have solid rear axles or CV joints connected to a differential. Moreover, the ring and pinion in the transaxle of these models are prone to explosions from wreckless take-offs and drag racing which often costs the owner a lot of money to rectify.

 

Chevrolet eight cylinder engines are very reliable, cheap to maintain and upgrade. They have loads of horsepower and torque in their stock form, and have extremely high aftermarket support. It is no surprise that this would become the answer for some who wish to keep their 924s and 944s on the road when replacement engines are unobtainable or not cost effective.

 

The conversion is pretty straight forward and easy to accomplish by do-it-yourselfers in as little as a weekend's time. Cost is a very constant question when contemplating such a drastic move and there is no real answer. A typical conversion, assuming you already have one of these models, is roughly 5-10 thousand dollars. This also assumes that you yourself will be doing all the work. However, having a local garage do the work could range between 10-21 thousand dollars and up. This is all subjective in that different people want different things from their car. For example, where one would just want the bare essentials i.e. no air conditioning, no power steering, or stock horsepower and torque numbers, another may want all of the above as well as 500 horsepower and a supercharger. Another point is that whenever you go from a 130 horsepower 4 cylinder engine to a 300+ Chevy V8, you have to think about other changes such as brakes, shocks, coolers, etc. So the price could fluctuate quite a bit.

 

The first thing to do when considering an engine swap is to find the resources that allow you to do so.A fair amount of fabrication could be done to accomplish the transplant in a 924/931, and some aftermarket conversion parts are still available for the 924/944 Small Block Chevy conversion. Anyone wanting to do this conversion with the LSX series V8 from Chevrolet can easily source the required parts, or have the custom pieces fabricated. These engines feature aluminum blocks (as opposed to the earlier V8s that were cast iron) and are all fuel injected. These engines produce a large sum of power in stock form and with simple cost-effective upgrades (i.e. camshaft) can easily see upwards of 450-500 horsepower, which makes this engine a very easy choice for a swap.

 

WHAT TO KEEP   When converting the 944 to V8 power, several items may be retained that will simplify wiring and power steering modifications. If selling the 944 harness is not a priority, keep the DME firewall grommet and the 14-pin section of the engine harness. These will make tying into the Porsche® wiring much simpler. The 944 40 tooth cam gear may be modified to function as a reluctor wheel for VSS when installed on the rear axle flange. A GM sensor is also incorporated. The 944 power steering pump and reservoir, along with the 944 2.5L crankshaft pulley may be installed using custom brackets and slight modifications to the 944 crankshaft pulley. This will insure proper power steering system pressure compatibility. The 944 2.5L (VDO) oil pressure and water temperature senders and wiring can be adapted also (sensor wiring connects through the above mentioned 14-pin harness section, located above the power brake booster). Also, the 944 master cylinder pushrod clevis may be incorporated with a custom pushrod when converting to a manual brake setup.

 

WHAT YOU'LL NEED   If you decide you are ready to do an engine swap, you will need to obtain a conversion kit, or you may choose to purchase or fabricate the parts individually. You will also need to purchase an engine. Small Block V8 engines are still plentiful and inexpensive, as are the LT1 engines. A complete LT1 with PCM and harness can be had for as little as $500. LSX engines are also readily available for a decent price. Typically, one could find a complete (includes a long block with all accessories) pull-out for around $1,500-$3000. The 5.3L GM truck engines have also become popular, and are around $500 complete. For hood clearance, the LSX intake must be used on the 5.3L. To adapt these engines to the torque tube, you will need a special bellhousing that bolts to the V8 block, houses the clutch components, and then to the torque tube. QuickTime, Inc. offers a spun-steel bellhousing that fits well inside the 944 tunnel. As of now, the '97 up Corvette C5 bellhousing and a custom adapter for the torque tube is the most cost effective solution. Another option is the stock GM SBC bellhousing, and fabrication of an adapter plate system developed by 944Hybrids Forum members. Dimensioned drawings of the C5 and SBC adapter plate systems are provided in THE PORSCHE® 944 V8 CONVERSION MANUAL, and the C5 adapter is sold by 944v8s and 944hybrids. The SBC bellhousings are still readily available, and can be had for as little as $25. The clutch components are plentiful, cheap, and readily available from any parts house. The Porsche® 924/944 driveshaft splines match that of many vehicles including early Mopar. Basically you are going to be looking for a 1" x 23 spline 10.5" or 11" diameter disc, 153 tooth flywheel (SBC and LT1), and a pressure plate to fit accordingly. The LSX engines utilize the stock GM flywheel and clutch components.

 

MOUNTS    The mounts are pretty basic. There have been many different configurations made by lots of do-it-yourselfers. A tubular mount has been used with great success, however, you may just decide to fabricate your own that attach to the engine block and then to the OE cross-member. Technical drawings are shown in THE PORSCHE® 944 V8 CONVERSION MANUAL for those who wish to fabricate them, and are also sold by 944v8s. The motor mount 1.0" set-back plates for the LSX engines are also sold there.

 

EXHAUST   The LT1 and LSX OEM headers that may come with the engine do not lend themselves well to retrofit. They have been found to clash with available space in the 924/944 engine bay. For LT1/4 engines, the headers part number CC90 driver side and CC2 passenger side from Sanderson Headers are the perfect fit (Paul Mellor). Patriot #8052 tight-tuck headers (available from Jeg's) will also fit if the driver's side exhaust tube is routed clear of the steering shaft. The headers should run into a 3" exhaust to a 3" converter and all the way out for best performance. For the LSX, Hooker #2312 headers may be modified for an economical conversion solution.

 

The LTX and LSX engines all use OBDII computers which require 4 oxygen sensors, with the exception of earlier LT1 engines that utilize OBDI and 2 O2 sensors. However, on the later 96+ LTX/LSX engines, 2 of them can be successfully programmed out, unless your local state laws prohibit this type of modification. As well, the emissions system may also be programmed out if allowed by your local laws.

 

ELECTRICAL   The electrical system part of the conversions scares most people from attempting such a swap. However, this need not be the case. With the support of companies such as Painless Wiring, lt1swap.com, PCMforless.com, and EFILive, etc., the factory GM harnesses can be successfully modified. The factory Porsche engine harness is completely eliminated. No need to splice in here or there. The Chevy harness is close to stand alone where a mere 9-10 wire hook-up is required for fuel pump, tachometer, oil psi, water temp, AC, and other related functions. The wiring should take very little time at all with the use of the service manual from GM and Porsche® together.

 

TRANSMISSION   Many will say that the transaxle should be replaced with a Chevy transmission, or that the stock Porsche transaxle will not take the abuse of a V8. This is simply not true. However, the 924 transaxle is weak, and should be replaced with the 944 unit. The 924 torque tube is also a point of weakness, although some have used the 924 torque tube without incident. The gearing of the transaxles in these cars is very usable. The N/A (normally aspirated) and turbo version transaxles are said to hold a reasonable 400 lbs. of torque. Whereas there have been a few people who have transplanted various Chevy transmissions into their 924s or 944s, it is rare and very difficult to accomplish or justify. The N/A transmission allows for a very fast take-off with the right clutch action. For increased drivability and strength, the turbo LSD transaxle can be retrofitted with the N/A 5th gearset. For strength and driveability, the late Turbo or Turbo S transmission retrofitted with the N/A 5th gear is the best solution. A solid upper transmission mount and a fabricated transaxle case end cover reinforcement plate will add increased strength and longevity to the Audi (i.e. 944) transaxle, and should be considered part of your parts list.

 

BRAKES   Brakes should remain a great concern here. When increasing the pure power the car generates, stopping that power is just as important. The energy the engine produces is transformed to heat from the brakes. If the brake pad area is too small or the brake system is faulty, you could be looking at major damage to property or death. The 924/944 N/A brakes are considered too small for even mild V8 power and should be converted to the larger and stronger 944 turbo versions. However, the inner and outer spindle diameters on all 944s prior to 1987 are the same and became a source of minor problems (fracturing) with the heaviest brake set up from '83 to '86, which was on the '86 944 turbo. This issue became more prevalent when '86 turbo owners upgraded the front brakes to larger calipers and rotors without changing the spindle to the post '86 version. This change also requires going from the "short version" of the front suspension A-Arm to the "long version" that was stock on all 944s after 1986. However, you can simply upgrade the brake system with 993TT or 928 GTS brake calipers, pads, and rotors (requires 17" and up rims), or one of the custom brake setups developed by 944Hybrids members (such as the LS430 calipers and Boxster® S rotors).

 

COOLING   The 944 cooling system becomes less than adequate for a street driven car after the V8 conversion. Few have had satisfactory results with the 944 Turbo radiator and cooling fans, but only in mild climates, or in track-only applications where airflow is not a factor. Griffin Radiators and Thermal Products will custom build a conversion-specific radiator to application specifications, and HMR, Inc. (Heritage Motorcar Research, Inc.) offers a quality aluminum radiator that has been proven to be adequate in several 944 V8 conversions. Also worth noting is the Ford Taurus cooling fan, which supplies more than enough CFM for a street driven car. THE PORSCHE® 944 V8 CONVERSION MANUAL lists part numbers and dimensions of the most popular radiators, as well as an in-depth discussion of cooling system basics.

 

In other words, if you are going to install a V8 in your 944 / 951, read THE PORSCHE® 944 V8 CONVERSION MANUAL, and browse the 944v8s Wiki and 944hybrids Forum for the latest conversion technical information. Contact us for your conversion parts and accessories, and ask as many questions as necessary. We are here to make The Conversion fun again! 944v8s is active on the 944hybrids Forum, and the core membership consists of experienced hobbyists ready to answer any questions you may have concerning the conversion.

 

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