The New Parts: The ACE Allisons Difference

FAA Approved Repairs, Modifications, Alterations and Parts

ACE Allisons' Bud Wheeler with Thom Richards' TP-40N, American Dream. Click to enlarge
See a short video of American Dream in action.

Like all of today's builders of WWII era engines we faced a shortage of critical parts. Typically these are the high wear parts: bearings, cylinder liners, piston rings, pistons, rod bolts, valves, valve seats, seals, gaskets, etc. The ACE Allisons goal is to provide our customers with a "like new" engine, one that has every part and component in original condition and with "new engine" tolerances applied throughout. All of the above listed components are no longer available from "new old stock" and we reject the option of applying "replacement limits" when determining the viability of a part, or simply saying "it's good enough." This is a big part of ACE Allisons being able to deliver a "V-1710 with a Difference." To make this happen it has been necessary that we develop new parts for replacing those OEM worn or deteriorated parts that should no longer be in-service.

All of our parts have individually received FAA Approval. These parts are now in-service in Warbirds around the world and carry a 200 hour, unlimited calendar time warranty. To further demonstrate their viability, ACE Allisons has entered into an arrangement with Thom Richards of Warbird Adventures, Inc., and his TP-40N "American Dream," which flies daily. Thom and Bud are collaborating together to achieve 1,000 hours on his ACE Allisons V-1710-99 engine in the shortest time possible. While this project is not a requirement, it should go a long way toward demonstrating that the ACE Allisons parts equal or exceed those from the OEM.

To continue to provide our customers with the very best V-1710 possible ACE Allison's has not only undertaken manufacture of many new parts, but has developed a number of repairs to existing parts that not only returns them to service, but improves on their serviceability and reliability. So that these parts can be legally operated in aircraft engines we obtain FAA approval of the parts and repairs.

Early model coolant pumps are upgraded to the V-1710-G6 configuration for improved performance and reduced seal leakage.

Piston Rings - Allison never had a really good ring package, hence the allowed oil consumption of up to 3.5 gph at 1,000 bhp. ACE Allisons' engines use an FAA approved set of three modern rings all located in grooves above the piston pin that are far superior to what was available 70+ years ago. This new ring pack has proven to be very robust and when in appropriate cylinder liners, results in an engine with very little blow-by and negligible oil consumption.

Coolant Pump Seal - The seal in the original pumps is prone to seal leakage, while the shaft itself is often found corroded. ACE Allisons FAA approved repair upgrades the seal to the configuration of the later V-1710-G6 and the shaft is chromed, resulting in a very durable, trouble free and tight seal.

Distributor Drives are upgraded with new seal configuration to prevent oil contamination of the Distributors.

Distributor Drives - Always an issue with high time V-1710s has been leakage of oil from the valve galleries into the distributors. ACE Allisons has an FAA approved repair using new seals that resolves this issue.

Cadmium Plating - After years in service and exposure to the elements, the protective cadmium plating on external engine hardware has deteriorated or is non-existent. ACE Allison's goes to the trouble to completely replate all of the external hardware to the current standard for Aerospace applications. As plating is considered to be a Major Repair, we have obtained FAA approval and have the hardware properly plated.

Gaskets & Seals - Original gaskets and seals have long ago deteriorated, dried out or become stiff and are no longer usable. ACE Allisons has obtained FAA approval to use appropriate non-asbestos gasket material and modern seals throughout the engine. As a result our engines are known for being clean and tight.

Before and after condition of Valve Stems are reworked.

Valve Stem Repair - New valves are extremely hard to find, and expensive when they are. Old valves typically have seating surfaces that are fine, however many show effects of corrosion and wear on the stems. ACE Allisons has developed a repair for the stem surface that returns the unit to a serviceable condition and meets our goal of retaining Allison's specified clearances and tolerances for new parts.

ACE Allisons' "Orange" Valve Springs are direct replacements for Allison's "Blue" springs which no longer meet OEM specifications.

Valve Springs - An existing valve spring may have been compressed in the same "valve open" condition for more than 70 years. As such creep sets in and the spring no longer provides the proper closing force or dynamic response. ACE Allisons offers FAA approved direct replacement springs that fully meet Allison's original specifications. You will be amazed at how smooth running your engine is with these new springs.

New Valve Guides restore original clearances for both reused and honed stem valves.

Valve Guides - Experience shows that the exhaust valve guides are often badly worn and must be replaced. The only source of these is to remove the similar, but serviceable, guides from the intake side of spare cylinder heads. The result is a diminishing supply and the need for newly manufactured guides. In addition, when a guide is needed for a repaired valve stem the guide must be undersize so as to maintain Allison's clearances. The new guides are made from bronze as were the originals and are direct replacements.

Plated Silver Bearings - The V-1710 uses a number of silver plated steel shell plain bearings that require a protective overcoat to be plated onto them. These are used on the connecting rods, main bearings and propeller pinion bearings. This overcoat deteriorates over time, even on bearings in storage or in engines that are static. Application of this coating is classified as a Major Repair and requires FAA approval. ACE Allisons FAA approval assures this coating is properly applied and that the bearing is appropriate for a long service life.

Propeller Shaft Roller and Ball Bearings - While these bearings are often found to be serviceable, when they are not a problem exists as the original bearings are no longer available. ACE Allisons has obtained FAA approval to use specific new manufacture bearings as direct replacements for the originals.

Spark Plugs - These are critical to the proper operation of an engine. The OEM plugs were marginal when new, and are dangerous to use today. Modern spark plugs are certainly available, but it is critical to select the proper heat range for the V-1710, and this had not been done. ACE Allisons has received FAA approval for current manufacture plugs appropriate to the V-1710.

ACE Allisons new cast stainless steel intake and exhaust seats eliminate the need for the OEM Stellite™ seating surface for the exhaust valve while both types of seats eliminate the corrosion issues. Otherwise they are identical to originals.

Exhaust and Intake Valve Seats - Allison made these from tool steel, facing the exhaust insert with Stellite™ to provide a hard and corrosion resistant seating surface. The tool steel material itself corrodes badly due to the hot combustion gas environment and exposure to moisture. The ACE Allisons developed, and FAA approved replacements, are both cast from austenitic stainless steel and directly replace the originals, while being resistant to corrosion and erosion, thus insuring a long service life and a tight fitting valve for your engine.

New ACE Allisons FAA approved electroless nickel coated piston.

Pistons - Original Allison pistons have to have the ring grooves re-cut in order to use modern rings. Also, new pistons are no longer available, particularily oversize pistons that are required if installed in used cylinders. ACE Allisons is now using new forged aluminum pistons that take advantage of modern piston alloys, design and coatings. These pistons are slightly lighter than OEM pistons since they do not require the oil ring to be on the bottom of the skirt. Modern anti-friction coatings are used on the skirt, while an electroless nickel thermal barrier coating is applied to the piston crown and ring grooves. This coating minimizes the amount of heat entering the piston, while providing improved lubricity for the rings in their grooves

Cylinder Liners - These have become a real issue within the V-1710 Warbird community. With time and use liners become worn and must be replaced, and stocks of new liners were long ago exhausted. Allison does not allow reuse of removed liners because the "hook taper" interference fit in the head becomes undersize after their first installation, while the bore itself is honed to its final diameter after installation in the head. ACE Allisons has developed the direct replacement "Black ACE" cylinder liner that exceeds Allison's original requirements and strength.

ACE Allison's "Black ACE" steel cylinder liners feature hard Nickel-Carbide running surfaces and are direct replacements for original Allison liners, while being considerably more stable and stronger. They also allow full compliance with Allison's original installation and honing instructions. The black coating prevents corrosion by the coolant.

An enhancement to the new steel liner is the use of a black anti-corrosive coating on the exterior of the liner; this minimizes the tendency for the coolant to corrode the liner, particularly in engines using Glycol-Water mixtures for coolant. We have the interior of the liner plated with nickel-carbide by the aviation industry's leading provider of this cutting edge technology. This results in a very hard and smooth surface that can be honed and that after honing is excellent at retaining lubricating oil for the piston rings, while resisting rusting. This is a real benefit for engines being operated in humid environments. These materials and processes have been used successfully for many years in automobile and aviation engines and are proving to be a big improvement in the durability of the V-1710.

New ACE Allisons FAA approved Connecting Rod Bolts. The smaller bolt is for the Blade Rod, the larger for the Forked Rod.

Engine Mounting Studs - Allison was one of the first to use "thread inserts". Specifically, they were used for the studs attaching vibration isolating pads to the engine mounts. Allison used the "Aero Thread" design, which has a unique rounded thread profile. These inserts are often found missing or damaged on engines coming in for repair, and new inserts are not available. Furthermore, the studs themselves have often been lost and new ones are hard to find. "Aero Thread" was taken over by "Heli-Coil" and now only Heli-Coil inserts are manufactured. To this end ACE Allisons is offering an FAA approved repair that utilizes Heli-Coils and standard thread studs.

Rod Bolts - Used OEM rod bolts may appear to be in good condition, but their past history of use and the loads endured is not known, and thus they are suspect. For this reason ACE Allisons is manufacturing new and stronger rod bolts specifically designed for the V-1710 as a way to insure that this uncertainty is removed.

Reworking Crankshaft Journals - The Allison crankshaft is very robust and has no life or fatigue limit. Even so, occasionally a crankshaft will be found with a journal that has been damaged due to a bad bearing. Allison required that in such cases "all" of the like journals on the crank would be reworked to the same "undersize." This was fine when they had a warehouse full of spare undersize bearings, however, today they are very rare. With this in mind ACE Allisons has obtained FAA approval to only rework the damaged journal, thereby extending the availability of the replacement undersize bearings and utilization of the crankshaft.

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