ignition and carburetor settings, a good performing valve train and non-

restrictive air cleaner and exhaust system.

Stock distributors on each of the W-Machines have mechanical advance curves which parallel best spark timing. The mechanical advance curves, vacuum advance curves, and initial timing settings on all models are selected to give best performance with the normal carbon build-up and street equipment. For off-road use in a car where the amount of idle and low speed operation will be held to a minimum, higher timing settings may be used. However, precautions must be taken:

1. Disconnect vacuum advance hose at the distributor and plug the hose.

Leave the distributor vacuum connection open. This will preclude road

load detonation which must be avoided for long engine life.

2. Use super premium fuels to further avoid detonation.

3. Be conservative. Increase timing in small steps, listening for any

detonation ("knock")

The important area to watch in changing timing is the advance above 4000 RPM (with vacuum disconnected). For off-road use, timing should be set to give 35 degrees advance BTC above 4000 RPM. Advance beyond 35 degrees should be done in small steps against a timer and in conjunction with changes in carburetor jetting, slight richening until ultimate potential is realized.

To set timing accurately above 400 RPM, a new set of scribe marks will have to be added to the balancer, since the normal timing tab stops at 15 degrees BTC. These marks must be made on the balancer below the present mark (clockwise from the front of the car). Timing can then be read using the 0 degree mark on the tab and the new marks on the balancer, while revving the engine to 4000 RPM momentarily.

CAUTION: DO NOT LOOSEN THE DISTRIBUTOR HOLD DOWN BOLT AND ADJUST WHILE

REVVING THE ENGINE. MOVE THE DISTRIBUTOR A SMALL AMOUNT, TIGHTEN, AND

REV TO 4000 FOR 2-3 SECONDS.

Scribe the marks clockwise from the present mark per the following chart:

Degrees BTC 350 Engines 400 & 455 Engines

30 1 7/8 inches 1 11/16 inches

35 2 3/16 inches 1 31/32 inches

40 2 1/2 inches 2 9/32 inches

The timing indicator (tab) is marked (in degrees) -4, -2, 0, 2, 4, 6, 8, 10, etc. The top edge of the tab is 14-15 degrees BTC.

To insure against point bounce with high RPM usage, double springing of theproduction point springs may be done. The best method is to use Corvette Delco points No. 1966294. These points are good to 7000 RPM.

Carburetors are calibrated for best full throttle as best part throttle mixtures and street performance. The best starting point for off-road use is production specifications. However, because of varying climactic conditions and the fact that exhaust headers will be used and part throttle driveability need not be considered, a number of changes may be tried.

Normal Driving up to 1/2 throttle is done with the primary side of the carburetor. Fuel is controlled by the size of the primary jet and large end of the tapered primary rod.

At full throttle, the fuel is controlled by the primary jet and small end of the primary rod plus the addition of fuel through the secondary jet and rod.

The position of the secondary rod relative to the jet is controlled by the angle of the secondary air valve. Therefore, the full throttle fuel rate as well as air flow is controlled by the air valve.

Air valve position or angle is controlled by air flow pulling against the air valve spring. Air valve wrap is the term that describes the amount of pre-load adjusted into the spring. Earlier opening of the air valve naturally allows more air flow; but if opened at too low a RPM, might give might give improper fuel mixtures and distribution, resulting in a loss of low end torque or a "bog".

Production setting allow the air valve to begin opening at approximately 1500 RPM full throttle and reach full open at approximately 3500 RPM.

The dashpot or diaphragm located at the right-front corner of the carburetor effects the air valve as well as choke operation. It provides a smooth opening of the air valve rather than the popping open when the secondaries are reached. It is used mostly for less than full throttle maneuvers, but can also be a benefit for full throttle operation, especially with the intake manifold heat crossover blocked. By delaying the opening rate of the air valve, less spring wrap may possibly be used.

Variations of all the above should be tried; primary jets and secondary rods for fuel mixture, and air valve wrap, with and without the dashpot for low and mid-range power and feel.

The following chart compares various rods with the AU:

ROD END DIA. DESCRIPTION

AU #2033655 .053 inch

AT #2033658 .067 inch Same below 3500 RPM as AU

4.5 percent richer above 3500 RPM

AX #2033549 .042 inch 5 percent richer below 3500 RPM than AU

3 percent richer above 3500 RPM

AG .030 inch 3.5 percent richer below 3500 RPM than AU

5 percent richer above 3500 RPM

Production rods can be machined to a smaller diameter, but must be done only with precision machinery. Only the small straight portion of the rods should be changed. Remember, the distance from the bottom of the hook to the top of the straight portion must be 2.5 inches or less.

Full throttle fuel rate can also be altered with changes in primary metering jets. Each .001 inch jet size change is equivalent to 1.5 percent change in full throttle fuel mixture. Since the primary jets affect part throttle operation and since the top of the carburetor must be removed to reach the jets, changing the secondary rods should be done first.

Richening of the primary jets could give a more responsive off-the-line feel.

SECONDARY BLEED TUBESThe secondary bleed tubes are air bleeds into the secondary wells, which aidsecondary tip-in response in normal driving. Though they also help control the fuel mixture, they are not an especially good tool to use. They are small brass tubes that protrude out of the top of the carburetor beside the secondary rods. Plugging these tubes with toothpicks will greatly enrich the mixture, approximately 10% to 20%, but the exact change is unpredictable and could affect distribution.

The necessary enrichment on a stocker can be easily achieved by use of available jets and rods without using the bleed tubes. However, if a highly modified engine is used, and further enrichment is needed, the bleed tubes do have a great effect.

PRIMARY METERING RODSThe primary metering rods should NEVER be changed. All Rochester primary rods have the same .026 inch diameter on the small end. Changing to another rod can only affect part throttle operation. Since the large end of the rod is a tapered surface, which is pre-set at the factory, any change would give an unpredictable effect.

This rod holder is also known as a hanger, yoke, or lever. It holds and positions the secondary metering rods in the secondary jets. Changing the height of the holder by bending should NEVER be done. Any change would definitely be unpredictable, with no way of returning to the baseline. Also if one side is bent more than another very poor distribution will result.

Raising the holder raises the secondary rods during their travel. This will richen the mixture below 3500 RPM, while not affecting the mixture above 3500 RPM.

Lowering the holder will lean the mixture below 3500 RPM and will lean the mixture drastically above 3500 RPM. Again, the change is unpredictable.

If experimentation in this area is desired, the holder can be raised by placing narrow shims under the holder, one in front of and one behind the mounting screw.

Better yet, a new holder can be used. The holders are letter coded A, B, C, etc. Each letter size indicates a .005 inch change in rod height, with A being the highest or richest, Z the lowest and leanest.

The hanger is selected at the factory to make the carburetor flow properly.Therefore, a carburetor with a D holder is not richer than a carburetor with anM holder.

If a particular carburetor has an N hanger the secondary rods can be raised .010 inch by using a K hanger, and lowered .010 inch by using an O hanger.

You can see that this is a very touchy area.

The air valve wrap is the amount of pre-tension applied to the air valve by theair valve spring. The spring is located at the right end of the air valve shaft

(passenger side). An adjusting screw can be found on the right side of the

carburetor, with an allen head lock screw below. The wrap 1/2 turn or 3/4 turn

is the angle the adjusting screw is turned BEYOND the tension required to just

close the air valve with vibration.

Before adjusting or changing the air valve wrap, note and scribe a mark where

the adjusting screw is at present.

To check wrap as received:

1. Place a narrow screwdriver in the adjusting screw.

2. Loosen the lock screw.

3. Back off, by turning counter-clockwise, the adjusting screw while

"tapping" on the casting with the handle of a larger screwdriver.

Note the number of turns or part of a turn before the air valve

begins to open.

To set the wrap: 1. Loosen the lock screw and back off the adjusting screw until air valve opens. 2. Begin closing the air valve by turning the adjusting screw clockwise while tapping on the casting until the air valve just

barely closes.

3. Turn the adjusting screw an additional turn, 1/2, 1/4, etc.

clockwise.

4. Tighten the lock screw.

TEST PROCEDUREFirst runs should be made with the carburetor in stock form. Subsequent runs may be made with the following changes:

1. Disconnect the vacuum hose from the choke diaphragm and plug the hose. Leave the spout on the diaphragm open. 2. Decrease air valve wrap in 1/4 turn steps. Make runs with connected and

disconnected. The wrap should be decreased until a loss in performance or

bog off-the-line is felt. Less wrap may be possible with the diaphragm

connected. The automatic transmission cars may need more wrap than

synchromesh.

3. After a particular wrap, with or without the diaphragm, is determined

change secondary rods and make more runs. Try going richer first, but also don’t hesitate to try a step leaner. To be sure the proper mixture has been

found, it is best to find a mixture that is too rich as well as too lean. 4. Changing wrap will affect fuel mixture in the low and mid-range engine

speeds, so additional changes in air valve wrap settings should be tried

after secondary rods have been changed. 5. Further changes in fuel mixture can be made by changing the primary jets, plugging or restricting the secondary bleed tubes with a piece of wire, or using a new secondary rod holder.

IMPORTANT: Production "W" car camshafts are developed on a dynamometer with cold air induction, exhaust headers, and blocked carburetor head. Indexing these camshafts to other than stock positions is not recommended. Additional performance increases here are highly unlikely, since all "indexing" has already been done on the dynamometer.

• This cam is the ultimate for street usage on cars with power brakes and air conditioning and production exhaust. Idle quality is okay.
• It is also recommended for jet boats with water cooled exhaust manifolds.

Special assemblies 404729 and 398247 and 1972 production springs 411225 have special heat-set wire that will not lose load after repeated high RPM usage.

It is not recommended to shim rocker arm stands to get near zero lash in thehydraulic lifters. This will upset valve train geometry. It is advisable tochange springs and lifters if high RPM cannot be obtained.

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B. BLUEPRINTING

For all out racing internal specs and clearances should be checked. A very

important item is piston to bore clearance. With production pistons it should be .003 to .004 inches.

If forged pistons are used, additional clearance is needed since forged

pistons expand more than autothermic production pistons. Use clearance

suggested by piston manufacturer.

To hone the bores for increased clearance the following is recommended:

1. Insert the piston upside down in the bore and check clearance

between the piston skirt and the bore.

2. Hone the block with a Sunnen rigid hone with a 200 grit stone to reach

the desired clearance.

The crankshaft should be ground to obtain .002 - .0025 inches connecting rod

clearance. .002 - .0025 inches main bearing clearance on 350 engines and .002

inch maximum main bearing clearance on 455 engines should be used.

Most production engines will be very close to these recommended clearances. In that case a good engine break-in is all that’s needed.

For increased main bearing clearance, the following method should be used: insert the bearings in the connecting rod or main bearing cap and torque tospecifications. Check the I.D. with a micrometer. Grind the crank for desired

clearance on a crankshaft grinder. The crank should be polished after grinding.

Connecting rod side clearance should be increased to .018 - .020 inches. To check side clearance the rods should be installed on the crankshaft and torqued to specifications. Install a screwdriver between the rods and gently pry apart. Be careful not to damage the thrust face when prying apart. Insert a feeler gauge between the rods to check clearance.

As an example, assume that this clearance is .010 inches. Then remove only one

rod and surface grind .005 inches from each side. This will total .020 inches

clearance.

Piston-to-deck clearance minimum specification is .002 inches. Naturally, allpistons can't be made to this exacting tolerance. Pistons should be purchased

with .006 - .008 inches deck clearance. Check this clearance when assembling.

For all out performance, modifications should be made to the oiling system.

Oil pump pressure should be about 60 psi at 2000 RPM. If more pressure is

needed then a heavier oil pump bypass spring is needed or else the old one

can be shimmed.

It is also important that oil pump gears be of equal length. They should be

surface ground to equal length. The amount that they project out of the oil

pump body should be .009 inches. The oil pump body may need to be surface

ground to get this dimension. Doing the above will insure that you have a

"perfect" pump.

Main bearing oil holes should be enlarged to 5/16".

The fitting at the front of the block that squirts oil on the timing chain

should be plugged.

Toronado oil pan and pump are recommended. The Toronado pan has one more

quart capacity and a skimmer baffle.

The oil pump pick up tube should be enlarged to 5/8" I.D.

Oldsmobile W machines are produced with excellent clutch disks, pressure

plates and flywheels; and they have good durability for street and strip.

For maximum protection in all out competition, the stock bellhousing should

be replaced with a Lakewood Industry 1/4 inch thick steel housing (model P01.)

In 1971-72 there is one four speed synchromesh transmission available at Olds.

Ratio is:

GEAR Muncie Wide 1st 2.52 - 1
2nd 1.88 - 1
3rd 1.46 - 1
4th 1 - 1

All floor shifters are made by Hurst. They are the same basic construction

as the aftermarket Hurst competition shifter except there are no stops and

there is a sound insulation on the production shifter.

Oldsmobile started manufacturing their own differentials in 1968. The

following performance ratios are available for 1968, 1968 and 1970 for

Cutlass and 4-4-2s -- 3.42, 3.91, 4.33, 4.66, and 5.00.

The 4.33, 4.66 and 5.00 are dealer installed only. The reason for this is

cooling considerations.

Differentials with ratios of 2.56, 2.78, 3.08 and 3.23 are of different

design and the above ring and pinions will not interchange.

If you have a car with a 3.42 or numerically higher ratio then the

performance ratios will interchange from 1970 on back to 1968.

In 1971 a new differential was designed and is common to Olds, Pontiac, Buick and Chevrolet. Axle shafts, ring and pinion and case assemblies are different to pre 1971 differentials and parts will not interchange.

The 2.56 differential is different from all other ratios. But all parts are interchangeable with 2.73 or higher numerically axles.

Production ring and pinion ratios are 2.73, 3.08, 3.23, 3.42, and 3.73. Dealer installed ratios are 4.10, 4.33, 4.66, and 5.01.

The G.M. axle shaft is made from 1038 material and has doubtful durability in higher classes of Super Stock competition. Summers Brothers is making a high grade shaft for the G.M. differential and is better than production.

Their address is:

Summers Brothers

530 S. Mountain

Ontario California 91761

There are four ways to modify the Turbo Hydra-matic 400 for quicker shifting.

The methods are:

A. STREET PACKAGE - Quick Shifts

1. Rework spacer plate

a. Open 2nd clutch feed orifice to .110" dia.

b. Open 3rd clutch feed orifice to .125" dia.

2. Replace 2nd clutch wave plate with flat plate P/N 8623150.

3. Replace 3rd clutch wave plate with flat plate P/N 8625197.

4. On steps 2 and 3 be sure there is adequate clutch pack clearance.

B. SEMI BONZI - Hard Shifts

1. Open 3rd clutch feed to .180" dia. in spacer plate.

2. Replace 2nd clutch wave plate with flat plate P/N 8623150.

3. Replace 3rd clutch wave plate with flat plate P/N 8625197.

4. Replace forward clutch wave plate with flat plate P/N 8625197.

5. On steps 2 through 4 be sure there is adequate clutch pack clearance.

6. Remove the following 4 ball checks: a. RND b. 3rd clutch c. 2 - 3 Dr (2 balls)

NOTE: DO NOT remove modulator / intermediate and reverse / low

ball checks.

7. Remove front accumulator spring and install piston upside down in valve body.

8. Remove center seal from forward and direct clutch drums.

9. Plug reverse clutch feed in center support with 1/4" dia. cup plug.

10. Rework 1 - 2 accumulator system as below: a. Remove trim spring at bottom of the valve body bore. b. Install 1/4" dia. copper tubing .95" long for 1 valve

or .82" long if there are 2 valves. This should block the

valve(s) out against the plug.

11. Install modified governor to get a higher W.O.T. rpm.

C. FULL BONZI - Maximum capacity, hard shifts, shifts only at W.O.T.

1. Items 1 through 10 on SEMI Bonzi plus:

2. Block vacuum modulator valve in by installing a 5/16" dia. ball in the neck of the modulator can.

3. Plug reverse boost with 1/4" dia. cup plug in pump cover.

4. Vent reverse boost with 1/16" deep flat on large O.D. land of

boost valve.

5. Install 30.4 lb. pressure regulator spring. (1.372 checking height)

6. Remove detent solenoid. NOTE: no vacuum or electrical connection is needed.

7. Install modified governor to get a higher W.O.T. rpm.

D. MANUAL SHIFT - Low=1st, Intermediate=2nd. Left in drive it's 2nd gear start and shifts 3rs at 20mph. (For use with packages B or C)

1. Block detent valves apart with 5/16" dia. copper tubing .41"

long.

2. Remove 1 - 2 modulator - regulator valves and spring.

3. Plug 1 - 2 valve body bore vent with 3/16" dia. cup plug.

4. Electrical connection not needed for manual shift package.Note: Packages B, C, and D should be reworked only by an

accomplishes transmission technician.

Low range can be engaged at any speed with packages C and D.

Additional welds at outer corners of converter weld nuts are

recommended for speeds over 6000 rpm.

There are axle shaft differences in 1968, 1969 and 1970 differentials.

1968 shafts have 31 tooth spline 1969 shafts have 28 tooth spline and shafts are smaller but metallurgy is better. 1970 shafts have 28 tooth spline but a change was made from a ball

to a higher capacity roller bearing.

The 1971-72 shafts have 28 tooth spline but have a 30 degree spline angle.

The 1968-69 & 70 have 45 degree spline angle.

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FRONT SUSPENSION
The following suspension modifications have proven successful for

dragging.

A. Springs

442 No. 400870 (Pontiac) Both sides. An Olds No. 400360 spacer under the left front spring

Cutlass No. 400870 left front (Pontiac)

No. 400868 right front (Pontiac)

These springs are selected for their low rate and controlled load. They allow the car to lift more on acceleration.B. Shocks Cure ride 90/10. Available from speed shops

and auto parts houses.

C. Front Stabilizer Ream out hole to 1.0". This decreases

shaft bushings effectiveness of front stabilizer bar.

This hole can be reamed with a 1" stone

and electric drill.

D. Upper control arm Cut off top of bumper so that base is

bumper 3/8" thick.

E. Tires 2-ply polyester cord with narrow tread.

8.15 X 15 non-low profile

REAR SUSPENSIONA. Springs No. 9793915 OldsmobileB. Shocks ProductionC. Control arm bushings Replace all (8) with No. 388266 (Olds)D. Helper Springs Use Air Lift H-D type

Start with 4psi on both sides. Add air in

2 psi increments on the side opposite the

sideways motion of rear end until car goes

in a straight line. For off the road use, a

likely starting point is 5psi left and

20 psi right.

Lakewood industries is marketing traction bars that have proven

successful on some top running cars.

10