Rebabbitting and Rebuilding The Model "A" Engine

The KR Wilson Way

During the 1930's Ford authorized the KR Wilson Tool Company exclusively to make all it's dealer repair TOOLS. This special relationship lead to a factory approved standard for

rebuilding model "A" engines using KR Wilson tools. Dealer rebuilt engines were known as "Wilsonized" engines. These rebuilds had the reputation of holding up better than

non-dealer rebuilds. This reputation was well earned because Ford, Wilson and the Babbitt companies worked together to make this process successful.

KR Wilson had made some of the tools that were used in the actual production of the "A" and was in a unique position to modify them for dealer use. The dealers also had been

instructed on the proper handling and installing of BABBITT and preparation of the block. This technique and information was not available to the general motor rebuilding trade. Even

to this day there is a considerable amount of confusion and misinformation on babbitting, much of it handed down from one technician to another. Wilson called the Ford/Wilson "chill

pour" method controversial by standards of his day. We do know now from hindsight that it was in fact the method that held up best. Pouring Babbitt into a cold saddle still runs

contrary to many of the books and articles, which deal with the Subject.

Some of the main points which Ford and Wilson required for block rebuilding are:

That neither the block nor jigs be heated for cast iron components prior to the Babbitt pour. They had metalurgical proof that the Babbitt had the best chemical and physical

composition if this procedure was followed. Ford Babbitt was composed of 3 metals, Tin, Antimony and copper. The melting points of each of the metals is different(tin-470 deg.,

antimony-1050 deg., copper-1980 deg.,Fahrenheit). The "chill pour" method was important because if the molten babbitt does not solidify(cool) rapidy the metals seperate due to

their diffferent liquid temperatures in the babbit rather than have a uniform composition which is so important. Wilson stated it this way "the copper could solidify while the tin

was still liquid if the babbitt didn't chill rapidly. This would cause the metals to seperate and make an unacceptable weak bearing.". The result will be a bearing which will not hold

up. Heating componets that can retain heat will contribute to this negative effect on the babbitt and adversely affect the cooling rate of the babbitt. Even today many vintage

engine restorers heat either the block or mandrels or both before they pour because they lack this information and the crystalline structure of their babbitt bearing suffer for it..

The block should not be tinned. The "A" engine block as well as any cast iron block that has been used becomes "seasoned". Its pores become saturated with oil. Heating the

block will not expel the oil it will just draw more oil to the surface as it cools. During a pour this vaporizing oil causes porosity and blowholes in the Babbitt. The plain fact is a

seasoned block is almost impossible to have its oil content removed unless it is annealed for several hours in an annealing oven at 650 degrees. Heating the block with a torch

would most definitely create a micro thin layer of oil between the bearing and the block, which affects adhesion ,the transmission of friction and heat to the block, these functions

are necessary to cool the bearings during actual engine operations. It is also for this reason you should cut out the old babbitt rather than trying to melt it out.

After the bearings were poured the Ford/Wilson method required that the bearing be peined immediately. There are two reasons for this. They had to do with the chill pour

method. Immediately after the pour the babbitt would shrink away(microscopic in size) from the cooler surface of the block

and cap. Peining stretched it back in place. Secondly it insured good contact with the bearing saddle. Good adhesion is

most important for the bearings to remain in place, to avoid being cracked during the operation of the motor and helping to

dissipate heat from the bearing into the block. The peining is done while the bearing is still warm and soft. The illustration

on the left shows both the peining tool and the rear bearing clamp. the clamp is only used on the rear bearing in the block

and rear cap not on the front and center bearings.

The front face of the rear main bearing thrust face were established with a set of jigs. When the engine was manufactured at the Ford plant the rear-bearing cap holes were used as

a reference point for the machining and boring of the engine block and the rear main thrust faces. It was and is important that any

engine which was subsuquently rebuilt had to maintain these reference points. The left pictures show the drop in jig which

establishes the front face of the rear thrust bearing.the picture next to it includes the filet cutter.

The flywheel housing case which attached to the block had to be miked to the flange of the crank. Because mis-alignment of the case to the

block will shorten the life of the bearing by causing them to crack, to pound out the bearing material, cause oil leaks, rough running and

transmission and clutch failures as well as ruined parts. The lack of understanding how important this step is, has probably accounted for

the greatest number of all Model "A" engine and drive train failures

If the above issues where observed and the procedure followed the rebuilt motor was considered to be "Wilsonized" and did in fact enjoy a longer life

than its non-Wilsonized counterparts

Steps to Rebuilding The Model "A" Engine

1. The striped block must be boiled and pressure checked and your crank magnafluxed, ground and miked. Before you send out your block check both the top surface of the block as well

as the head with a good straight edge. If they are not flat its a good idea to have them ground(decked) so they will be flat. This can help eliminate some leaking head gasket problems. If

you are having new intake seat inserts installed make sure the block is decked after the intake seat inserts are installed but before the seats are ground in. The exhaust seats will be put in

after the block surface is ground. This will be explained later under the valve seat section.

The bearing boring bar is setup on the block to remove the old babbitt material. You can use the KW Wilson setup or Kwik-way align boring equipment. However if you do use the

Wilson setup you must modify the bar to accept adjustable cutters. Originally the bar itself had fixed cutters which were made for standard cranks that were obtainable from the factory.

This is of course no longer the case.

You now need adjustable cutters. I did this simply by pressing out the pressed in cutters in the bar and using a 1/4" square broach to create a square hole for hss 1/4 lathe blanks. I

cross-drilled the bar at each hole first with 5/32""drill clear to the 1/4" square opening then I drilled with a # 9 drill almost to the opening and taped the hole 1/4-20. I dropped a ball bearing

in the hole and then screwed in an Allen grub screw. This way you can hold the cutter in either drag tight fit or solidly tight.

You can set the depth of the cutter in .001 increments with a Kwik-way bar mike regardless of which machine you use because both bars are the same diameter. The HSS cutter is ground

to the Wilson profile however a slight radius 1/16" profile is added to the cutting tip. For the babbitt removal stage the cuts should not be greater than .01 per time to prevent loading the

cutter with scrap babbitt. The bar is bolted to the block with its frame resting flat on the bottom of the block and against the dummy camshaft. The caps are fastened to the block with

Wilson quick bolts. First tightening them by hand then with a wrench another 1/4 turn, this greatly speeds the attaching and removal of the bearing caps. The KR Wilson machine is

started then the drive is engaged. The cutter will progress through the bearing at 25 rpm's. Repeat till the process is completed on the bearing. Do each bearing separately.

Finally take a small cut into the cast iron. This brings the saddle to new metal. You need to be cautious here look to see if any rebuilders have done this before. If it looks like the cast iron

saddle is too thin do not cut further. Drill out any Babbitt in the anchor holes. You can add two more dovetailed anchor holes if you like. Take a steel wire brush connected to a drill and

make sure all remaining rust is gone.

If you don't have a KR Wilson machine the boring can be done with one of the other commercial align boring machines such as the Kiwk-way. If the Kwik-way is used you will need to

locate their quick bolts and their alignment gauges for the "A". Unfortunately they are no longer in production. Thus unavailble from Kwik-way.

You are now ready to pour you bearings in the block. All the oil holes must be plugged with damtite, a material which will not melt, it is pliable and will stop the molten Babbitt from

entering the oil tubes. For this step use the KR Wilson jig with the pouring blocks. The saddles should be clean but not tinned as explained previously. Each bearing should be poured

and peined separately even though you could do all three at once. I find it easier to remove the jig that way. You will also need at

least one set of Wilson Babbitt casting dams for the mandrel. Prior to placing the mandrel on the block I heated the jig with a torch to

get all the condensation out of it then I smoked it with my torch and let it cool back down.

Place the mandrel on the block. Raise up the cross arms a little with hollow washers. This is done for two reasons, first the bar was

made for standard size bearings on a standard crank and the new size bearing will be oversize, secondly the babbitt will be able to fill

the space quicker with the larger opening. Now bring the first set of collars up to the block where you will pour the first bearing. Place

the dams on both sides of the mandrel. Repeat this procedure as you pour each additional bearing.

Wilson sold a gasoline tin melting rig but I would not use it because of the danger it posed. Originally I was going to use a propane plumber's pot but I was also concerned about the

dangers it posed. Finally I got an electric Babbitt pot which I feel much more comfortable with. The Babbitt is poured from two ladles one on either side of the saddle or cap diagonally

across from each other, quickly and as forcefully as possible. Don't overfill the dams as they will then be very difficult to remove. Preheat the laddles before you dip them in the babbitt. If

laddles are cold or damp you stand a chance that the babbitt will explosively splatter out. A word about safty here is necessary. If moisture comes in contact with molten babbitt it will

splatter with great force, Therefore you should always wear a clear full faceshield as well as insulated gloves and a welders apron when handling molten babbitt.

The Babbitt is heated to cherry red and checked with a pyrometer to be between 950-975 degrees. Don't use the "pine stick till it chars" method as it is really not hot enough nor a really

good indicator. The idea here is one to have the babbitt hot enough to guarantee it will flow and fill the whole bearing space, provide some extra heat to compensate for the cooling that

takes place during the transfer from the pot to the bearing saddle. It will also chill rapidly enough to get the proper crystal structure when it is surrounded by cooler metal. While you

need a high heat avoid temperatures higher than 1000 degree's as this can have as bad an effect as too little heat. Too high a heat will alter the crystal structure of the babbitt as it won't

be able to "chill" at the proper rate. Put your warm laddles in the molten babbitt and stir in a figure 8 pattern. Push aside the oxide skin on top and get clean babbitt in your laddles. Do not

continue to skim the oxide skin as you will see a new skinning coat keeps reappearing. The heating constantly creates this oxide which over a period of time depletes the chemical

composition of the babbitt. The result is that the tin content and antimony content will change in the babbitt.The only preventive measure to be taken is to use a dross reducer to

minimize the oxidation process.

Originally the service bulletins suggested chiseling off the excess Babbitt sprue's. I prefer to cut them off with a hack saw and then vixen file the babbitt flush with the block surface.

Make sure the file is flat and flush with the block surface. You do not want to cut into the block especially at the rear main as this can create a permanent rear main leak. Now is a good

time to check both the block and caps for flatness with a straight edge. If required carefully mill file the high spots on the block always making sure the surface remains flat. The caps

should all be milled flat by rubbing them on sand paper which is laid on top of a 1/4" piece of plate glass.

The next step deals with the caps. In the 30's and 40's the caps where supplied to dealers rough babbitted from the factory on an exchange basis. Today this is no longer an option.

Because of the then Ford policy it was unnecessary for Wilson to make provisions for molds to re-babbitt caps. Today however we need to use aftermarket molds. I have purchased

Babbitt molds made up after the kwik way style at Hershey.

After seeing another type in a book on bearings which seemed more efficient I fabricated my own. One for the front and center

caps and one for the rear. It has the cap stand on end, which is then bolted to a flat surface around a half round mandrel plus end

pieces which act as dams. This allows for good venting of the gasses as the Babbitt is being poured. After having explained that

the cast iron parts are not to be tinned there are two items which can be tinned. They are the front and center caps. This is because

they are forged steel and the oil can be removed by heating with a torch till the cap begins to turn blue. Let them cool and wire

brush them back to clean metal.

4. The procedure for the tinning is as follows: the tinning compound I use is a paste that is spread on the caps with a cloth then heated with a propane torch till it melts and wire brushed

till it shines. While the cap is still hot and the tinned surface is plastic in consistency it is placed in the jig which is heated a little hotter than the cap. The Babbitt is poured into the cap

and is then misted with a spray bottle filled with water to cool it. The cap is then quickly removed and peined. The rear cap has a different jig it is neither tinned nor is the jig heated it is

poured and peined. The special clamp is only used to reinforce the thrust faces during the rear main peining. If any of the bearings ring hollow after peining and can not be tightened with

the peining hammer they must be cutout and redone as they are not making good contact with the block or caps. Both the front and center caps as well as the rods are also exempted from

the rule of preheating. However the mandrels should always be 50 degrees hotter than the parts to be babbitted. These are steel items which can be rapidly cooled with a water mist and

therefore the crystal structure of the babbitt will not be compromised .

5.The Wilson boring frame or Kwik-way system is again setup on the block. Either follow the instructions in the Model "T" service bulletins for 1927 or in the case of the Kwik-way in

their setup instructions. The caps are now installed on the block. New shims (1/32") are placed between the caps and the blocksand the quick bolts are tightened. The front and center

caps should have their casting marks face the camshaft side. The boring bar is set with the bar mike to take the cut to .005 of the

finished size as determined by your crank journals.. Do your cutting in .01 increments to avoid tearing at the Babbitt. The bar is then

removed and the oil holes are located exposed and drilled and cleaned out. Be careful not to break thru when drilling out the oil holes.

If you are lucky enough to have a KR Wilson oil groove set you can cut the groves on the caps and block and if you have the side oil well cutter you can do that too. If not they can be

cut by hand with a dremel type tool and a 3/16" carbide rasp cutter they just may not look the same as the factory ones but will work just as well.

6. A straight surface cutter is now inserted into the bar and the front bearing face of the front bearing is faced off flat. Now a radius edge cutter is installed. The rear face of the front

bearing, the center bearing and the rear bearing faces are all finished with a radiused edge. The last part of the process involves cutting the bearing thrust surface (filet). Again as stated

above this is the defining position of the crankshaft in relation to the piston bores and will determine what if any back and forth motion the crank has. Improperly set it can create rod

problems, piston rubbing on the cylinder walls ,blowby as well as rear main oil leaks. Before the actual cutting starts a measurement must be taken with an inside micrometer of the

distance between the two flanges on the rear main bearing surface of the crankshaft.

Now to the actual cutting of the filet. To aid in this critical setting Wilson made a two piece jig set which helps the rebuilder establish the front thrust bearing face. The jig fits in the

two-rear cap bolthole without any free play it has a milled face which is exactly where the face of the thrust face should be. A second jig is bolted to the block and has an arm, which

swing up and down. It is lined up with the jig face and the first jig is removed and the arm swung up.

Either the Wilson filet cutter jig is now installed and the cuts are made and constantly checked till the cutters meet the swing arm face.

Or with a boring bar setup a fillet cutter is placed in the boring bar itself the cutter is moved as close to a bearing face as possible the

arm is swung down, a feeler gage is used to determine the gap between the two and a stop which has been loosely installed on the

boring bar at the center bearing's front surface. Is moved up to the bearing. The feeler gage in placed between the stop and the block.

The stop is clamped tight and the bar is rotated and pushed from the forward end. Thus cutting and positioning the filet (thrust) surface

at the same time. The cutter is now moved to the rear side and the process is performed again cutting the bearing face to a distance that

is .004 undersize of the actual distance between the two flange faces of the rear main bearing surface on the crank.

Now the boring bar is reinserted and the finally cut is taken .002 short of the finished size. In the case of the Wilson equipment the

finishing is done with a reamer made for this purpose. Again during the Wilson time there was only one reamer and it was standard size.

Today you need at least 3 reamers in your rebuilders kit. Each reamer should be ground down to increments of .010 undersize of

standard i.e. 1.613(-. 011),1.603(-. 021),1.593(-. 031). The extra .001 is the allowable clearance. The smooth faces of the reamers need to be .006 smaller than the cutting edges i.e if the

cutters are 1.613 than the smooth areas need to be 1.607. It is for this reason I prefer using the kwik way bar which has three speeds and you can get a fine enough finish without reaming

and you can cut right down to the finish size at the slowest speed. Regardless of which machine is used the finish cut should leave the bearing .001 oversize.This completes the Babbiting

phase of the block rebuild.

A few words on the rods

Rods just like the caps were on an exchange basis. There are no KR Wilson tools for their rebuilding. At the present time I

purchase rods myself on an exchange basis. However I will include a picture of a rod pouring jig I made. Wilson does have a setup

for checking and straightening rods(pictured left). The greatest limitation to rod rebuilding is you

need a rod lathe(not a rod hone). I have seen a jig to bore out crank bearings after they are poured

which can be setup in a milling machine or large lathe but I think the setup time is too great for each

rod and I am not confident of the result. In the illustration on the right you can see the 3 piece set I

made. The small item on the left fits in the piston pin end and keeps the rod parallel to the rod end

mandral. the tube behind it is used as a centering device and fits between the pouring mandral and

the rod. In fact you can see the space the babbitt is poured into.The cover over the crank end acts as

a clamp and a babbitt dam. Remember the rod is steel so it should be tinned before the babbitt is

poured and the mandral heated

The next phase is the piston boring.

At some future date when time allows I will describe and illustrate the Wilson method of piston hole boring. Again Wilson equipment was dedicated to just Ford engines. Because of that

it paid special attention to bore to crankshaft positioning.

I will however include some illustrations and text from the Wilson catologs of 1927 and 31.

"The boring bar is placed in the cylinder and accurately located by means of two tapered (2-piece) locating plugs, one plug from each end of

the cylinder. This is the most accurate method known, for there is very little wear at the lower end of the cylinder and none at the extreme

top, due to the fact that these two extreme points are not worn by piston ring travel.The two permanent guides are then positioned and

securely fastened in place, the crankcase end and the cylinder head end by four cap screws. The temporary tapered locating plugs are then

removed through the openings provided, then the boring bar pushed forwards until the cutter head is about 1/4" from the bottom end of the

cylinder. Now the split bearings in each of the permanent guides are tightened up until they show some "drag" on the boring bar which one

can feel by using a 10-inch Crescent wrench I on the square end of the boring bar. This operation, on the K. R. W. Combination Machine, insures a perfectly straight hole, absolutely free

from taper and prevents the boring bar or the cutter from resisting or pushing away from hard spots or "digging-In" to the softer metal. The universal joint is connected, feed lever thrown

in and eight, minutes later the cylinder is bored. The machine requires absolutely no attention and stops automatically, unless stopped by operator. The boring bar is very rigid and is

made from 1 1/2inch, special, heat treated,. machinery steel accurately ground to a perfect fit. The bearings in the two permanent guides are accurately reamed and polished and designed

to take up wear after boring each cylinder. The table and motor bed plate and raising plate which holds the cylinder block, automatically aligns and positions each cylinder in its exact

location for reboring (no mechanical skill necessary) by means of two No. 5 taper pin holes and another for 7/16 cap screw, opposite the center line of each cylinder. Corresponding holes

are drilled in the bed of the machine. Thus by moving the motor plate with the cylinder block attached, the cylinder is brought into exact location, whenever the two No. 5 tapered pins will

fit into place. It is FOOL-PROOF and eliminates all other complicated methods and the necessity for an experienced operator."

Now to the valve area.

This area of rebuilding has significantly improved over the era that the "A" was built. Therefore there is no Wilson method to be dealt with. However with today's unleaded gas

consideration should be given to new exhaust seats in any good motor rebuild. I normally don't advocate many of the motor upgrades available today. I don't recommend a balanced

crank. I also don't condemn the practice. It's just that I like the "feel" of the "A". Some people think for as little use as an "A" gets now, exhaust seats should not be upgraded. When the

"A" was built the gas of the day ran cooler than unleaded gas. With the advent of unleaded gas the exhaust gas is running a lot hotter and can burn up the cast iron valve seats which

were not built for the higher heat.

The solution is to replace the exhaust seats with chromium insert seats they are made to withstand the higher heat loads. This does not apply of course to the intake seats which are not

subjected to this heat when they are open. Make sure when you have inserts installed, that the chromium seats will be 1/32" below the surface of the block. So they will have both a

resistance fit and the 1/32" rim on the block can be peened over onto the insert. Otherwise the chromium insert has a different coefficent of expansion than the cast iron, when the block

gets hot they can come loose. This does not effect the intake seats as they should be cast iron too. Both the intake and exhaust seats should be ground to a two or three angle

combination thus giving the valve face a contacting surface of approximately 1/16th of an inch. The seat angle is 45 degrees and the top angle 30 degrees and the throat angle is 60

degree's. The top angle is used to reduce the seat face to bring it to the 1/16 size. You may need to throat the seat to accomplish this with a 60 degree stone. A finished valve should

stand proud with its lip about 1/32" above the surrounding surface. Because the engine may have had its valves rebuilt many times you must take care that the valve lip still extends

above the surrounding surface. If not the seat whether it is exhaust or intake it should be corrected or replaced.

It will all be for nothing if.....

After the bearings, crank, rods, pistons ,cam ,tappets and valves are in place we come to one of the final items to "Wilsonize" our engine. Often the rear engine flywheel housing is simply

bolted on at best. The housing shims may or may not be installed but without verifying if the housing is really parallel to the crank flange we 've wasted our time. Without properly

checking this item all of our rebuilding work can simply go for naught. A housing which is out of parallel by more than .005 will ruin the rear bearing , create a leaker, put undue stress on

the transmission, ruin the pilot bearing, cause hard shifting, cause premature gear wear, and cause shaking just to mention a few problems. All of this can be solved with a three-way test

and a fixture that Wilson made. You can adapt a dial micrometer to do the job if you don't have access to the fixture. The first setup has the fixture bolted to the crankshaft face through

an arm and dial micrometer. It is attached with the dial plunger resting on the bolt face of the housing and the arm securely fastened to the crank flange. The crank is rotated and the bolt

face height needs to be parallel within .006, if not shims need to be installed or removed under the mating bolt areas till it is brought into tolerance. In extreme cases the housing may be

warped and should be replaced. The next step requires the flywheel be checked using the micrometer dial. The arm is now attached to the housing and the plunger rests on the flywheel

face and then on the flywheel hub and the flywheel is rotated for each test. Both the side and top runout should to be checked. If they are within limits, .005 you and can move on in your

restoration if not the necessary steps must be taken to correct the problem.

Congratulations you have now "Wilsonized" your rebuilt engine.

A note on thrust face repair.

For one reason or another(most often excessive endplay) a thrust face on the rear bearing may crack or otherwise become damaged. This can be repaired and or built up with great care.

You must have some flux, a large soldering iron and some homemade repair babbitt. It is made with 50% babbitt(#2) and 50%, 50/50 solder. This material will work on the thrust faces as

the lead content is less likely to be beating out with the side forces then on the bearing surface. It is important when building up the bearing that the final result is brought back to the

.004 undersize. Obviously this will require some hand scraping. Remember this is only a repair not a cure. The only proper repair is to recast the bearing.

Useful Tip

If you have the bad luck of having a stud break off when you are removing them from the block. Very carefully center punch the broken stud. drill into the punch mark with an 1/8" drill

about 1/8" deep. Then re-install 2 or 3 studs. Put the head back on. Use an 7/16" extra long center drill (5") in the hole where the stud is broken. drill down 1/2" and no more. The two

pitfalls in drilling out a stud is you either use too large a drill when the centered drill hole is slightly off center and end up ruining the threads or you drill too deep piercing the water jacket

at the base of the stud hole and as a result the stud will leak when the engine is assembled and running. Using the head as a guide will give you a well centered hole to drill from. In the

final phase start with a 1/4' drill bit for the bottom piece of the stud and work up in size being careful not to go too deep and pierce thru the water jacket. Careful drilling will permit you to

remove the old stud piece without damaging the threads in the block. Now chase the threads with a good quality bottoming tap stopping every turn or so and removing the tap and

cleaning it, going down a little deeper each time. If this does not work you'll have to redrill and tap the hole for a helicoil insert but at least the stud will be centered in the head hole after

you are done.In the event you have pierced the water jacket at the base of the stud hole plug the pierced hole with two part plumbers epoxy this will act the same as the dentists filling

contact me Steve Ross