The 2.2L Long Rod Drag Racing Engine

[ Theory | Block | Crankshaft | Rods | Pistons | Top End ]


This page describes the concepts behind the 2.2L long rod engine.  I first discusses the theory behind it and then it describes how to build one.  Much of these concepts are credited to Ed Peters, while other, more specific data is credited to Garry McKissick Jr.  To see the specifications for Garry's engine and the method he used to calculate it, see his Ultimate Engine Specs page.  To see some pictures of his project, check out his Ultimate Engine Pictures page.  Special thanks have to go to Garry for helping me with many of the details on this page.

The Theory

I'll start with the big question, "why bother".  The reasoning is all in the "rod ratio".  The rod ratio is the measurement of the length of the rods versus the length of the engine's stroke.  It is calculated by dividing the length of the rod by the length of the stroke.  For example, a stock 2.2L Turbo I engine has a rod length of 5.945 inches and a stroke of 3.622 inches.  This gives a rod ratio of 1.64.  If you look at the 1989 and later 2.5L engine, it is much worse.  It also has a rod length of 5.945 inches, but a stroke of 4.090 inches.  This gives a rod ratio of 1.45, which is quite bad.  It has been generally accepted that a good four cylinder drag racing engine should have a rod ratio of 1.80 or more.  The argument for this is discussed below, but 1.80 has been determined to be the ideal ratio.  Luckily, the 1986 - 1988 2.5L non-turbo engine has an unusual tall block that has the room needed for longer rods.  By putting a 2.2L crankshaft into this block, a rod ratio of 1.8 or more is possible.

So why is rod ratio even important?  Well, it has to do with how the rod moves as the crankshaft rotates.  A longer rod will have a smaller angle if deflection than a shorter rod at the same stroke.  This is most apparent when the crankshaft is half way between TDC and BDC.  The smaller the angle, the less the rod has to rotate on the wristpin axis, and the more force from the piston is applied downward on the crankshaft.  See the illustrations below:

Here you can clearly see that the long rod engine on the right has more force from the combustion directed through the rod to the crankshaft and less thrust force pushing the piston against the side of the cylinder.  By reducing this piston trust force, you are also reducing the amount of friction between the piston and the cylinder.  The maximum angle of deflection shown is for the standard 2.2L rod ratio of 1.64 (left) and the 1.80 rod ratio of our tall block 2.2L engine (right).  While this difference is not that significant for many performance applications, it is significant for an all out drag racing performance engine.  It is of great significance when compared to the short rod 2.5L engine with a rod ratio of 1.45.  Here, the maximum angle of deflection is 20.12 degrees.  Consider this when decided between a 2.2L and 2.5L engine!  The 2.5L crankshaft that is normally put into the tall block has a rod ratio of 1.51, which is slightly better than in the short block, but still worse than 2.2L short block.

The reduced angle that the rod has to travel reduces the rotating intertia of the crankshaft and rod assembly.  This reduces the parasitic drag of the rods and sends more power to the output of the engine.

Another advantage of the increased rod ratio is the amount of dwell time of the piston at TDC.  While technically, the pistons are at TDC and BDC for an infinately small amount of time on both engines, the effective amount of time they stay at TDC is increased on a long rod engine.  For example, if you consider 5 degrees before and after the actual TDC on the crankshaft to be the effective TDC, then in a long rod engine the piston will move less during this 10 degree sweep than in a short rod engine.  This is again because the long rods have a lower change in angle for any given change in angle of the crankshaft.  At BDC however, the dwell time is actually decreased with longer rods, though this is not as big of a concern on forced-induction engines.  So, there is a "happy medium" for the rod ratio here, which seems to be about 1.80.  Increasing dwell time increases the amount of time that the valves can stay open, which increases the volumetric efficiency of the engine (the effectiveness of the engine to move air in and out of the cylinder).

The Block

As you can see, there are a lot of good reasons to increase the rod ratio of an all out drag racing engine.  To accomplish this, we need an engine block that has a long enough bore to accomodate the longer rods.  There just happens to be an odd-ball engine block that was used from 1986 through 1988.  It was the 2.5L "tall block", which was used for the 2.5L N/A (naturally aspirated or non-turbo) engine.  It has a deck hieght (distance from the center of the crankshaft to the top of the block) of 9.83 inches, relative to the 9.36 inches of the standard 2.2L blocks.  Although this block has a few differences from the standard 2.2L block, it is capable of using the 2.2L 3.622" stroke crankshaft and other components.  The original crankshaft and rods in this engine give it a rod ratio of 1.51, which is quite low.  If a 2.2L crankshaft is installed, more room is available for longer rods.

The 2.5L tall block is actually a stronger block than the 2.2L Turbo I block, even though it is a non-turbo block.  Because of the increased torque output of the 2.5L engine, the tall block was given stronger main bearing supports and slightly thicker cylinder walls.  The 2.5L tall block should be less prone to the block torquing of the early 2.2L Turbo I block.  The trick is to find an early 2.5L N/A engine, which are a dying breed.  It's best to take a trip to the local salvage yards and keep an eye out.  If you get the block from a salvage car, be sure you get the oil pan, front bearing support, dip stick and tube, and all timing belt sprockets (they use the round-tooth belts).  These parts are specific to this engine, so be sure to get them all.

Since the block is a non-turbo block, some modifications have to be made to it to accomodate the turbocharger.  First, a 23/32" hole has to be drilled in the back of the block for the oil drainback from the turbo.  According to Garry McKissick Jr., the tall block has the boss needed in the back of the block for the oil drainback tube, but it is not at the correct angle.  So, the hole has to be drilled perpendicular to the boss provided, but some modification of the tube is necessary to get it to mate properly to the turbo.  Also, the hole for the coolant supply line has already been drilled and tapped.  All that is required is the pipe-to-flange adapter for the turbo coolant supply line.

It is important to have the block bored and honed with a torque plate to remove any disformity in the bores.  The torque plate allows the bores to be honed round while torque is applied to the head bolt holes, since this torquing actually disformes the shape of the bore.  It's always a good idea to give the machine shop the pistons that you are going to use so that they can hone the block as close to the piston-to-wall spec as possible.  Another good thing to do is to cross-drill the block between the bores, which allows coolant to flow between the bores and keep them from disforming from the heat.  O-ringing the block also helps maintain a positive seal between the headgasket and the block as the block expands from the heat.


The best crankshft to use here would be a cast 2.2L turbo crankshaft.  While there is a forged version available, it is unnecessary on an 8 valve head which won't be revved past 6000 RPM, since the 8 valve heads generally don't generate much power there.  The increased mass of the forged crankshaft does not warrent its use for this engine (or most other 8 valve engines, really).

Connecting Rods

The connecting rods on this engine have to be custom fabricated.  To achieve a rod ratio of 1.80 with a stroke of 3.622", a rod length of 6.520" is necessary.  You can order rods from Cunningham or Venolia, though it is unknown if Venolia makes steel rods.  Cunningham will make steel rods, however, and they need to know the type of engine these are for, the center-to-center length of the rod (6.520" for our 1.8 rod ratio), the type of rod bearings used and the bearing part number, diameter of the wrist pin, and the estimated weight of the rod.  The diameter of the wrist pin depends on what type of pin you will be using with the pistons.  If you are having custom pistons made, then you can choose any size you like.  The 0.936" Chevy pin or the 0.912" Ford pin are popular choices.  Make sure that your pistons are made to accomodate the same size pin.  The estimated weight of the rod will determine its strength.  You can discuss this with the representative at the custom rod manufacturer.  Typicially, you would want to go with at least the stock weight for these rods (669 grams for the 2.5L N/A rods).  You may want to go stronger.


A set of custom pistons from Venolia or J&E is usually the best way to go.  Venolia is usually significantly cheaper than J&E and the quality is at least as good, if not better.  If you go with custom forged pistons, they need to know the type of engine you have, the diameter of the piston, the compression height of the piston (distance from the center of the pin to the top of the piston), the volume or dimensions of the piston dish, the wirst pin bore diameter, and the piston ring groove size.

The diameter of the pistons depends on how large you are going to have the cylinders bored out.  Stock bore size (A size) is 3.440 inches.  Typicially, a high-mileage block needs to be bored 0.020" or 0.030" oversized (most go with the 0.030", just to be safe).  So, a 0.030" oversized bore requires a piston diameter of 3.470".  Be sure to give the pistons to the machine shop that is machining your block.  This way, the correct piston-to-cylinder-wall gap can be achieved (these specs are supplied by Venolia).

The compression height of the piston determines where the pin bore is placed.  This is calculated based on the stroke of the engine, the length of the rod, and the deck height of the block.  For rod ratio of 1.8, a rod length of 6.520" is required.  With the 9.83" deck height of the block and the 3.622" stroke of the crankshaft, a compression height of 1.499" is required.  This is slightly less than the stock 2.2L Turbo piston (1.604"), but more than the later stock 2.5L Turbo piston (1.370").

A stock 1986 and later Turbo piston has a dish volume of 14cc.  When overboring a cylinder, the piston dish volume has to be increased to maintain the proper compression ratio.  You can give Venolia the dish volume, and they can determine the best way to implement it.  Otherwise, you can calculate the diameter and depth of the dish you desire.

As stated in the above sections, two pin diameters are popular: the 0.936" Chevy pin or the 0.912" Ford pin.  While the Chevy pin is stronger, the Ford pin is lighter.  The stock Turbo II pin is 0.900" in diameter, but is known to flex in high output applications.  Also, Venolia forged pistons use spiral locks to retain the pin instead of the stock cir-clips.  The spiral locks sit in a square-shaped groove and they can't be pounded out by the wrist pin like the cir-clips can.  A pin length of 2.500" is required.

The stock ring groove dimensions are 1.5mm x 1.5mm x 4mm.  Just tell the piston manufacturer that you want to use the stock ring dimensions.  This is by far the easiest route because they have all of this information on file.

If you would rather go with a stock piston, the you should go with a Mahle cast piston.  They are the best cast pistons that you can get for your engine.  Two types are available.  The stock Turbo II piston has a compression height of 1.604", which limits your rod length to 6.415" and your rod ratio then becomes 1.77.  Better than stock, but not quite 1.80.  If you go with 2.5L Mahle cast pistons, they have a compression height of 1.370", which allows a rod length of 6.649" and your rod ratio then becomes 1.84!  Better than the desired rod ratio, but the 2.5L cast pistons have shorter skirts and higher rings.  The shorter skirts provide less support for the piston to guide it across the bore and the higher rings encounter more exposure to the high temperatures inside the combustion chamber.  If you are going to be running this engine hard and hot, go with forged pistons.  Exposing the ring to very high temps can blow the moly coating off of the ring.  Also, Mahle's floating pin retainer clips are prone to failure.  They use the cir-clip design, which can be pounded out by the pin.  Venolia forged pistons use spiral locks, which can't be pounded out.

There are several types of rings available.  Companies like Sealed Power, Total Seal, and Hastings sell gapless ring sets that have a double ring for the lower compression ring to greatly reduce blowby, which is important in any performance engine.  They also have high performance rings for the upper compression ring that can take high temperatures and even detonation.

The Top End

Here you have as many options as you desire.  The 2.5L tall block is compatable with any 2.2L/2.5L head that is available.  For different options for the top end of your engine, see the Upgrading The Engine's Top End page.  Also see the other performance options in the Performance Guide.
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This page is maintained by Russell W. Knize and was last updated 05/17/99. Comments? Questions? Email

Copyright © 1996-2003 Russ W. Knize