Ken Cates' Hudson Stepdown Restoration Resources



Engine Casting Decoder

To translate Casting Codes - Dates are determined by the last digits - thus D122 translates
as April 12th 1942 or 52. C234 is March 23rd, 1954. (Single digit for year) Month is determined by the first letter - A = Jan., B = Feb, C = Mar., D = Apr., etc. This is true for all CWC (Campbell Wyant and Cannon) engines. The "unknown "foundry uses the full date, 1-15-54 no code involved. Translation of date codes = MO/DAY/YEAR

Hudson Engine ID Codes1

7X 308 Hudson Engine

Engine is displayed on Factory Provided Stand


The 'ead with the bigger 'ole

by Doc

Extracted from July 1975 WTN - Bernie Siegfried and I were sitting under a tree at Indian Caverns back in the early Hershey Meet day, talking as you might guess about Hudsons. Bernie told me this story which I realize should have been an item for the WTN years ago, but wasn't due to procrastination and a miserable memory.

According to Bernie, during the 1949 model run, the rear main bearings started to go our on the 262 engines after some little usage. Naturally the boys at Hudson went to work on the problem with a panicky zeal. Everything possible was checked out.The break-in oil, the bearing material, the oil supply, crankshaft, seals, Everything! Nothing was overlooked, but in spite of all their efforts the trouble was never found.So, what did Hudson engineers do to make continued production possible? Well, these degree knuckle-busters simply made the combustion chamber of number six-cylinder larger to reduce the compression ration, thus taking some of the strain off the rear main. I asked Bernie about motor balance with this uneven compush and he told me the motors being electronically balanced after assembly, this was no problem. Now, it seems to me, thought I didn't get Bernie's opinion on this, that replacing this larger hole head head with one of equal dimensions would upset the motor balance and also cause the bearing trouble. Fortunately not many 262 motors ever had head trouble except the few that came through with aluminum.

When the aluminum head cracked on my '49 C6, I went to Greely SHOPWASH"S Place for a replacement. He had a '50 parts car, but remembering Bernie's story. I had check out the head on my car and found it and the over-size chamber on number six I found a '49 in Greely's lot and pulled the head, Sure enough, it was the larger hole type so I took it.

Probably few have ever noticed this difference, and if so may have thought the head defective. I've shown the head off my car to many Hudson nuts, asking if they could see anything wrong. No one has so far. So, it is evident the difference isn't evident.

The bearing trouble? Bernie said it disappeared as mysteriously as it came. They never knew what happened.

The Original Hudson 7X Engine - Created by Bernie Siegfried

Starting with the block, .015" was milled off the top deck, intake ports were enlarged to take 2 1/16" valves with 30 degree seats, exhaust ports to take 1 3/4" valves. All ports were polished. The block was fully contour slope relieved to the Hornet gasket shape. The slope finishing about 3/32" below the block top. Head bolts were 1/2" diameter. A Pacemaker Aluminum head was drilled to for 1/2" bolts and relieved to accommodate the larger valves. Bores were honed to "C" size. Pistons were "A" size. Piston heads were sloped at the valve facing side the width of the block relief and the relief depth. Piston pins were finish ground on the inside diameter and this diameter tapering from the enter to the pin ends. A set of the lightest of the 40 weights of connecting rods were used by Hudson had .020 straddle milled off both sides of the big end. A rods were semi polished as was the crankshaft. Crankshaft bearing surfaces were made to allow .001" - .0015" additional bearing clearance. The tappet oil holes were plugged. The rod squirt holes were closed. This was done to permit a continuous flow of oil at pressure from the relief valve through a copper coil oil cooler. As an after thought I removed the upper ring pin and cut the pistons off at the lower ring groove. Overall I reduced the weight of each piston and rod assembly by slightly more than 1/4 pound. All pistons, pins, rods and crankshaft were microbalance. I semi polished the inside of a Twin_H manifold. "Somehow" word of what I was doing got our to the various suppliers at Hudson and all the vendors got into the act.

The Carter representative supplied me with two carburetors with increased CFM capacity, Federal Mogul provided precision heavy duty bearings, and the MacQuay-Norris man with a set of low friction quick setting rings.

With the exception of the block deck milling and the crankshaft balancing, all the work was done on the engine was accomplished by me in the basement of my house with tools acquired in the 20 years I had been tinkering with racing engines.

With the added relief area in the block, the head and the piston slope, the Pacemaker head produced a compression ration of 8.25:1 which I knew would work well with the 92 octane fuel Pure Oil Company provided.

Bernie Siegfried - Hudson engine test engineer

JC Whitney
Sold left over Hudson engine stock

INTEVIEW (excerpt) Stuart G. Baits Chief Engineer 1928-1934 - By Guy Folger, 1974 (then editor of North Texas Hudson Dealers Chapter newsletter.

One of the questions asked of Mr Baits by Guy was:

Q. Can you tell us anything about Hudson's role during the racing era of the 50's? Did Hudson make changes in construction of their cars based on information given to them by race car drivers such as Teague, Thomas and Mundy?

A. Racing, This started with Ira Vail and the Super-Six way back. THen we raced at Indy with the Straight 8 and various ventures with Buddy Marr, Miller and others. Teague picked up the Hornet engine on his own and got us going again. We worked closely with him, developing new camshafts, pistons manifolding and cylinder heads. Howe ever the basic engine was not changed much. Credit must be given to Dana Advertiser, who was our engine designer on the Hornet, for producing the outstanding design. Teague was a fine driver and mechanic, very modest as are all the good drivers I ever knew, easy to work with and jointly we produced cars that dominated stock car racing for some time. Alas, Teague was killed on the track, not in a Hudson, Alas we could never see that racing success did anything for our sales.

Bernie Siegfried at 1975 Youngstown National Meet...

"...stressed that the Hudson automobiles Marshal Teague and others first started to compete in were strictly stock. He used examples of the development of Hudson engine improvements as a reaction to Teague's experimentation."

Hudson Engine Heads: provided DJ Kava

The July, 1951 Hudson Service Merchandiser notes the following about 1951 heads: "Beginning with the 1st production, an aluminum head of 7.2:1 compression ratio was standard.  The marking on top of cylinder head was H-145 Super Power Dome-304632 (this is casting number).  The optional cylinder head was of cast iron, 6.7:1 ratio, with marking H-145 Power Dome-304630.

Later, a cast iron cylinder head, 7.2: ratio, was used as standard-marking H-145 Super Power Dome-305923, and a metal tag with the imprint USE PREMIUM FUEL.  The present and final change for standard head 7.2: ratio is of a new casting with marking H-145 Super Power Dome Use Premium Fuel-305854."

The metal tag head was simply standard equipment.

Hudson Big 6

Mark Hudson

My son Joseph with Smoky @ 1999 Nashville HET National Meet

Stroker Crankshaft and Rods


When replacing the timing chain cover make sure the crankshaft Spacer is not worn. The diagram above shows how the seal wears the spacer. The spacer can be reversed to provide an unworn surface on which the new seal will ride.

Tips for Trouble shooting compression problems

(Park W. July 2004 – Hudson Chat) Try a pressure test to see exactly where the compression is leaking: Take the plugs out, and put the one to be tested near top dead center on the compression stroke (just have the dist. rotor pointing to that cylinder's position on the cap). Then apply an air hose with a rubber tipped nozzle and about 40 psi pressure to the spark plug hole and listen for air leakage. You'll hear it out the adjacent cylinder spark plug hole (head gasket sealing problem), out the breather pipe (ring blow-by), through the carburetor throat (intake valve) or out the exhaust (exhaust valve). If the engine's cold, you'll usually get a little blow-by into the crankcase, audible at the breather ... to see how that normal leakage sounds, do the test on a good cylinder first.


Front Crank Seal - Sealing the leak

Sealing the front crank may require more than changing the timing the timing cover gasket and the crank seal. HUDSON crank seals are known to cause groove cutting into the crankshaft spacer. The crankshaft spacer rides on the font of the crank just ahead of the crank timing gear sprocket. This spacer is what keeps the oil seal lip in place and the oil inside the timing cover. When replacing the crank seal remove and clean the spacer. It is a good idea to make sure you mark the side, which is toward the front of the engine when removing the spacer. Upon reassembly REVERSE the spacer so that a new and unblemished surface is provided for the crank seal



 R.V.Blake provides a systematic set of checks to assist a Hudson owner diagnose and solve a starting problem with a Hornet engine

Now that we have established that the engine will crank freely, let's be sure of timing, first the valve timing, then the ignition. If the crank gear, timing chain and cam gear were not disturbed during your rebuild, then the valve timing should be OK any of those were apart, it's time to double check their relationships. The ignition timing would possibly be affected if you had the distributor out while doing the re-ring job. If not, there's really no reason for the ignition timing to be so far off that she won't fire, but check it as follows: With the plugs out, crank the motor while you keep a finger over the first plug hole. When you have compression, the air will rush past your finger. That should be when the timing mark shows in the flywheel peephole. It should also correspond to the rotor being just about under the #1 plug post on the cap. The fact that you have a weak spark sounds like either a bad coil or condenser, or even points really out of adjustment. Swap in another coil if you've got it, but remember the set up the positive and negative correctly (which is to say 'wrong') for the positive ground system. It's possible the coil wires got reversed if apart. Funny thing with my total rebuild, using all new ignition parts too, the d--- thing wouldn't start and it puzzled me for days. The new condenser was NG right out of the box. The old condenser went back it and she ran fine. Remember compression will probably not be peak until the rings re-set. I always start the balky ones with a 12-volt battery (set up with positive ground) and never have hurt the starters or any electrics. Once it starts, switch to 6 volts. You can use a jumper pack to get the same results, or just jump off a newer car. It sounds like an ignition problem to me from this distance, so just go through each item systematically and you'll have a running car again!

He continues:
  Just one more area which you may look at. Is the distributor timed correctly? In relationship with the firing order? A quick guide find compression stroke set flywheel on marker at top dead center. (You can have top dead center on exhaust stroke. So be sure it is compression stroke) At this point rotor button should be pointing to no 1 lead on cap. If this is all correct. Turn on ignition loosen distributor and rotate distributor by hand in opposite direction of shaft rotation if all is correct there will be a discharge of current at the points at this position lock distributor if all is working it should start at that setting any further adjustment to timing can be done later. Some cars can be for what appears there is no apparent reason, very hard to start even when all is OK if this fails try 12 Volts or try starting whilst being towed. Good Luck.

The problem turned out to be a dragging starter that was found when 12 Volts was put to the starter, so it pays to look closely at the things we least expect to be at fault. NOTE ALL THE DIFFERENT TESTS that were recommended ... take the time to do all the tests thoroughly and REPAIR the items found defective after all the last Hudson STEPDOWN was built over 60 YEARS AGO!

HOW TO BUILD A "7X" ENGINE By Sloane F. McCauley

Sloan died a number of years ago, but his talent and love for Hudsons lives on in this paper. He was A.H.R.A. National Record Holder Formula 4, B/A and D/A racing a Hornet powered Jet.

Most Hudsonites have heard of the magical 7X engine, but a great many of them do not really understand what it is nor what modifications have been performed to make it a true 7X In this article we will show you what is required to 7X your own 308 engine. Of course, it will be necessary to remove the engine from the car and completely disassemble it so at rebuild time would be a good time to 7X your engine. The basic differences in the 7X engine and the stock Twin-H power 308 are the larger valves, the wider and deeper relief area, the hot cam, the dual exhaust manifold, and the high compression head. The 7X engine has 2" intake valves and 1 11/16" exhaust valves. These valves can be easily installed in the stock 308 block. The valve pockets must be enlarged and then hand ground to achieve the venturi /effect under the valve seat which is so important to obtaining max flow through the valves. These oversize 7X valves are available from Jack Clifford as is the 311040-7X cam, which is reasonable in price and affords a good performance boost over the stocker. The 7X cam is set at .016 H and the timing specs are intake opens 14 degrees BTDC, intake closes 62 degrees ABDC, exhaust closes 56 degrees BBDC, exhaust opens 20 degrees ATDC Gross lift is .390. The 232 head is used on the 7X engine, giving a compression ratio of 8.7 to 9.2-1, depending on the variance in hand machine work in the relief area. Horsepower of the 7X engine is rated at 180 and torque is 305 ft-lbs. at 3,000 rpm. The 7X dual exhaust manifold helps in the back pressure-relieving department but these are becoming very scarce items. The stock exhaust manifold can be split and dual exhausts installed if a genuine 7X dual exhaust manifold cannot be obtained. The stock Twin-H power intake system is also used on the 7X engine. Of course, the heart of any good 7X engine is the relief area. This is the area of the block across which the mixture must flow from the valves to the cylinder. This area must be deepened and widened to achieve full 7X status. The first thing to do is get a head gasket and some machinist's dye. Paint the block surface with the dye and put the head gasket on the block. Now take a scriber and scribe a line, following the head gasket. This will show you what must be removed in order to widen the relief area all the way out to the head gasket. Also, the edge of the relief area should be radiused where it meets the head gasket to afford greater flow. The relief area should be deepened right down to the edge of the valve seat and cut all the way out toward the bore. The counter bore that the valve sits in will be eliminated and you will have a flat plane surface from the edge of the valve seat to the cylinder. The best way to cut the relief area is to use a milling machine such as a Bridgeport along with an end mill tool. This is the easiest way to remove the bulk of the material and then the block can be hand finished and smoothed. It is possible to grind the complete 7X relief by hand, but I would not recommend it. I believe you would be better off paying a machinist even at $10/hour because the work is not precision type work and can be roughed out quickly and easily on the machine and then hand finished and polished. I would estimate that I have nearly 100 hours work in the block in my race car, mostly hand finished This is only my second block in five years of racing this car, and is far superior to The first one, which was lost when a piston exploded and the rod wiped out the cylinder wall and went right out through the side of the block. Needless to say, if my present block were damaged beyond repair, I would cry a lot. The block is the critical part of a flathead racing engine. Unlike an OHV, in a flathead, all the power is produced by the breathing ability of the block in which the valves are located, as opposed to the easily replaceable head of an OHV engine. One thing to remember, however, is that just because an engine is advertised as being a 7X does not mean that it really is. It has become fashionable to call any mildly souped 308 a 7X engine. In reality, the 7X engine was a dealer-installed option (which means built by the factory racing team) the specs of which were set forth in a Hudson factor3~ technical bulletin dated 2/2/52. The true 7X engines were generally hand built for racing purposes and it is doubtful that many of these original 7X engines are still around. A high altitude engine was produced by the factory, which included some 7X parts, such as the oversize valves, 232 head, and hot cam, but were not true 7X's in that the relief area was not deeply machined and hand finished. The later model '55 and '56 blocks have deeper stock relief areas than the earlier blocks which make them more desirable for a stock engine, but if the relief area is to be machined to 7X specs, it makes no difference which block you use. The second-generation 7X engines, such as mine, are also hand-built units utilizing Clifford parts. Don't let anyone pawn an engine off on you as being a 7X without First pulling the head and checking for sure, as a tremendous amount of hand preparation goes into creating a genuine 7X engine. Well I hope this gives everyone a general idea of what a 7X engine really is, and if you are planning on rebuilding that tired old 308 anytime soon, l'd definitely recommend 7X mods as the performance increase per dollar spent is fantastic. Now we will discuss how to 7X your block and we will delve further into proper block preparation as applied to a racing engine.

Correct block preparation is a very exacting science, the details of which are often overlooked by the amateur hot rodder. The major rule in block preparation is "cleanliness is next to Godliness." I assembly my engines in hospital like surroundings, and if you want your engine to last, I'd advise you to do the same. The first thing to do with an old block after disassembly is to have it placed in a hot caustic solvent tank to clean out the din and sludge The cam bearings must be installed after caustic cleaning because the vat would devour them for its dinner. The block should be milled about .020 to insure a straight and level deck. The top edge of the cylinder bore should then be chamfered in order that the rings will go in easily without breaking. Many hot rodders advocate align boring the main saddles of the block but I have found this to be unnecessary on the old Hudson blocks. The Hudson engine was a precision product and all tolerances were very closely held. Besides, align boring is a very difficult operation which requires extremely expensive equipment to perform correctly. Some of the cheaper align boring rigs are nothing but junk, and they can really butcher a block.

The lifter bores should be smoothed and polished with fine emery cloth. On other engines, a brake cylinder hone can be used for this job, but the Hudson lifter bores are too narrow. The head bolt holes in the block should be slightly chamfered at the top of the block surface to allow for any distortion caused when the head bolts or studs are torqued down. .. The block should be honed on a Sunnen CK-10 honing machine. The old hand-held drill-operated corncob hone is junk and can never deliver a professional ring seal. For best results, a honing jig should be made from an old head, which can be torqued down, on the block to distort the cylinders. The hone can then be passed through the holes cut in the old head and hone the block with it distorted as it would be with a real head installed. Cylinder wall distortion can and will run as high as .003 to .004 so this is the only way to get a topnotch professional quality ring seal. The block should now be completely de-burred and smoothed. All edges should be chamfered, the rough spots in the ports should be smoothed out, and any loose casting slag should be ground away. The inside of the Hudson blocks is already painted orange with special paint which is good, in that tiny nicks and cracks are sealed and the oil can flow back to the pan easier. The main oil gallery is plugged with welch plugs at each end of the block. When oil pressure is raised above 50 psi, these plugs tend to go away, so the fix is to thread the oil gallery front and rear and install pipe plugs. This prevents any chance for oil leakage, and the pipe plugs can be easily removed for cleaning at rebuild time. Another little tip I can pass along to you is that the front main bearing cap should have another oil return hole drilled in it to allow for greater flow of oil from the timing cover back into the pan. I experienced an oil buildup problem in this area early this year due to increased oil pressure, which was causing the front timing, cover seal to leak. After we drilled the second oil return hole on the other side of the main cap, we had no more problems. Now we come to the most important part of block preparation: cleaning. Simply vat cleaning the block is not good enough. The best way to really clean a block is to take it to the 25-cent car wash and soap the hell out of it. Stick the sprayer in all the oil gallery holes and blow detergent through them until the flow is clean. Also clean the entire block inside and out. Splurge and spend a couple of bucks here, as it will pay off in the long run. The next step is to get some small bristle brushes, such as gun cleaning brushes, and run them in and out of all the oil passages in the block and crank, using soapy water as a cleaning solvent. You'd be surprised how much dirt you can still get out of the block with these brushes, even after it has been cleaned in a vat and soaped at the 25-cent car wash. You will need to use an extension in order to pass the brush through the main oil gallery, which runs the length of the block. Brush all the oil galleries until they come clean, then rinse off the block and crank. You are now ready for assembly. I do not have the space to elaborate on proper assembly methods, as this article deals with block preparation. However, the main thing to remember is "keep it clean". This does not mean a disorganized, hurried assembly on a dirty garage floor. I like to assemble my engines on a pair of sawhorses upon which the block can be placed. This gets the engine off the ground and can easily be wrapped up in cellophane after assembly is completed to protect from dirt. Take your time in assembling the engine. Be sure all the parts are operating room clean and wash your hands often

Don't get in a big hurry, and above all - THINK!


Note: This procedure requires a correctly installed flywheel.

1. Pull the plugs to take compression off motor.

2. Turn the engine by hand until the UDC 1-6 appears on the flywheel in the area where the timing pointed in installed on the engine. (Opening above the starter).

3. Clean and paint this area as it will be necessary to see to properly time your engine.

4. TOP DEAD CENTER is the next long line as the motor is turned in the normal direction of rotation. (Rotation is counter clockwise looking at the water pump on the engine). Each line represents approximately 2.8 degrees of advance in timing. For best performance of a stock engine 2 marks or ~6degrees advance is recommended.

5. When using a timing light to time your HUDSON, lay the light on top of the starter. If you don't use this method the sight angle will cause you to set time timing incorrectly. Peering over the top of the radiator will allow you to view the timing light flashing on the flywheel.


SPACERS on Conventional Hudson Mechanical Fuel Pumps:  Hudson used a variety of fuel pumps to complete the fuel delivery to the various carburet ion systems used.  This variety and the need to use existing non-special parts created parts interfaces, which required the pumps to be "adapted" to the particular use.  Adaptation takes the form of a gasket stack which spaces the fuel pump out or away from the block . These gasket stacks are usually misunderstood when the new Hudson owner is confronted with a fuel pump failure. If the owner is lucky they already know of the existing HETers who provide rebuilt pumps or kits to fix the failed pump.  When the pump arrives it usually comes with a single fiber gasket, which can easily be MISTAKEN as the ONLY gasket needed to reinstall the new pump.

The owner can determine if the gasket stack is needed by a careful measurement of the fuel pump drive arm length. If it is the same as the length of the arm on the failed pump and a gasket stack was part of that installation. REPLACE THE GASKET STACK with the new pump. If the arm is about 1/2 inch shorter then the stack is not needed.

What is this all about?

The camshaft of the engine is used to drive the fuel pump.  If the arm is improperly spaced it will in fact "go past" the cam (it is 1/2 inch too long/ the cam shaft eccentric is not engaged and the cam will push a minimum stroke on the fuel pump arm Vis a vis the end.  Improper installations will result in weak fuel pump pressures and POOR engine performance.

If you do not have a gasket stack all is not gloomy. You can make the spacer from suitable gaskets or if you take your fuel pump to a machine shop they can make a metal spacer. To install a metal spacer adds gaskets to each side and bolt on the pump. Careful measurements will keep your fuel pump happy, DO NOT THROW THOSE SPACER GASKETS AWAY!


Gasket Making  - Ken Cates

Hudson gasket sets are often hard to find. When you cannot find a proper gasket one method for overcoming the immediate need is to make your own. One method often overlooked in the use of the original part to make your new gasket. There are several methods, but the following two methods have been used successfully. 

One: purchase sheet stock gasket material of the same type as the original gasket being replaced. Cut a piece of gasket about 1-2 inches larger than the dimensions of the surface for which the gasket is to be placed once manufactured. Examine each half of the two surfaces to be gasket-ed, select the half that has the deepest inner cavity as a template /tool for making your gasket. Now while firmly holding your gasket material against the selected surface, use a small metallic tool to carefully tap around the edges of the object to be gasket-ed. Your will find that with care you will outline the part (template) and the gasket material will be cleanly cut. Continuing to hold the gasket in place, tap at the interior surfaces of the part, again the gasket should outline the inner edge. If your are successful a completed replacement gasket will be your reward. 

Two: Again purchase a proper sized piece of gasket material as well as a stamp pad inking stick. Using the stamp pad stick quickly ink all of the surfaces of the part to be gasket-ed. Once ink has been applied, place that surface onto the gasket material, taking care to not smear your impression. Remove the part and you will have a gasket positive that can be cut out with a craft knife or razor blade.

These two methods have been used successfully on STEPDOWN WA1 carbs, 3 spd. and overdrive transmissions, Timing cover and valve cover gaskets, Rear end housings, and Water pumps.

Providing this web site is an ongoing cost to it's owner. You can defray some of those costs by moving your mouse cursor over the word DONATE above and clicking. . It will provide you with an immediate easy and safe method to donate, THANK YOU!

This page was updated March 2017

© 1998 - 2017 Klassic Concepts Consulting all rights reserved