1971 Olds Cutlass 350c.i.d. engine build
By Grant Warner
Editors note: This five part article was originally published in the Oldsmobile Club of Southern California “Rocket Circle” newsletter in a five part series. The article below is a compilation of these five parts. if you wish to contact the author please send your emails to Info@SocalOldsmobile.com and we will gladly forward them to Grant.
Part 1
This project and technical article will cover all aspects of diagnosing, removal, rebuilding, and re-installation of the four barrel 350 c.i.d. engine and turbo 350 transmission original to the 1971 Cutlass belonging to new member Frank Gattuccio.
There will be photos to accompany this process to better portray some of the steps that will be taken during this project and I encourage any of you who may be embarking on a similar project in the near future to email or call me with any questions you may have.
To begin with this tech series, we start with the diagnosis which began a couple of months back when Frank brought his car to me to listen to a deep rattle sound coming from the front of the engine. This was a sound that when described over the phone, first lead me to consider a failing timing chain assembly. Once I heard the noise in person, it was quite evident that the sound was deeper and potentially more severe so I removed his electrical oil pressure sensor and attached a mechanical diagnostic gauge to the motor. What we found was between 0-5psi of oil pressure at idle, well below the 25psi minimum recommendation by Oldsmobile or most engine builders.
The decision was made to remove the engine and trans for a rebuild as it was suspected that the motor had never been rebuilt and there was no real history on service work on the car in general including the trans. What we found as we ( with assistance from new member Thomas Jones ) removed and stripped down the engine was quite surprising regarding the overall condition of the engine and trans and how well the car still ran.
The noise we heard was actually the harmonic balancer wobbling on the snout of a very worn crankshaft, which meant both components would need to be replaced. We also found a caved in oil pan, bent oil pump pickup, clogged oil pump pick up screen ( old timing chain debris ), well worn original bearings, leaking rear main seal, excessive sludge build up primarilly in the lifter valley, worn out rocker stands, one broken piston ring, baked hard valve cover gaskets, cracked oil filter housing, broken motor and trans mounts, caved in trans pan and a poorly done rebuild job on the trans some time in the past.
You can imagine ours and Frank’s surprise that the car still ran as well as it did. So now we needed a plan to rebuild both the motor and the trans, deciding what the primary use of the car would be so the appropriate component decisions could be made. It was decided this would be a street cruiser, built with a bit more horsepower but with drivability and fuel economy still in mind.
The goal would be to build a 370hp+ engine, based loosely on the W-31 platform, using easily acquired aftermarket parts to improve durability, and upgrade the transmission and torque convertor to handle the added power and improve driveability.
Part 2
Our second part of this article will now focus on the engine build itself starting with the steps taken at the machine shop to prepare Frank’s engine components for re-assembly. This process starts with a trip to Dougan’s Machine shop here in Riverside Ca. to have the block, heads, replacement crank, and rods all cleaned and magnafluxed to insure there are no cracks and they are sound pieces for machining.
Once all the components were confirmed to be serviceable, we blueprinted the block by having the cranks main bore housing align honed to insure the crank will be perfectly straight in the block. Then we had the deck surface machined flat and parallel with the crank centerline, then finished up with boring the blocks cylinders to an overbore of .030 to establish a straight cylinder as well as being perfectly perpendicular to the crank centerline. The cylinders are treated to a final hone to achieve the proper finish for ring seal as well as build in the proper clearance for ring gap and the new pistons. The final hone is performed with a torque plate to insure the bore will be perfectly round when under load from the torqued head bolts. Other block prep included pressing in new cam bearings, deburring all casting irregularities inside the block that may hinder oil drain back, running a bottom tap through all bolt holes, and a thorough final cleaning prior to assembly with hot soapy water and bore brushes to remove any machining residue.
The crankshaft, a used replacement salvaged from my daughter Melissa’s crashed 71 Cutlass was an interesting piece as it still had the ink date stamping on the front throw when I removed it from her salvaged engine. This crankshaft was treated to a crank grind on both the main and rod journals to establish a fresh and perfectly round surface, followed by a micro polish and heat treat ( nitriding ) to insure the bearing surfaces are as smooth and hard as possible.
The original forged steel rods were treated to a re-sizing with new high strength rod bolts to insure the housing bore ( big end ) is perfectly round and clearanced to match the crank journal size. Then the new hypereutectic ( high strength cast ) pistons were pressed back onto the rods with new tool steel wrist pins. These pistons are dish pistons of the same cc rating as the originals so we could keep the compression rating of this new motor close to the original rating to deal with todays lower octane fuels.
The final machine shop process for the bottom end was a complete digital spin balancing of the rotating assembly, using the new harmonic balancer, flexplate, pistons, rods, rings, and crankshaft to insure this motor runs as smoothly as possible to eliminate dangerous harmonics which can cause breakage as well as abnormal wear of the rotating components.
Finally we come to the rebuilding of the heads. We decided to build the original 7a casting heads to W-31 specs using the larger diameter valves along with a stiffer valve spring recommended for the cam being used and intended rpm range. The use of larger valves required some minor pocket work in the ports to properly blend the port into the wider seat area. The heads were also surfaced to insure the gasket surface is perfectly flat and parrallel to the combustion chambers to insure all cylinders are of equal volume. New stainless steel valves, chrome silicone valve springs, and chrome moly steel retainers were incorporated for durability as well as lighter weight to improve valvetrain stability. The valves were all finish surfaced on the tips to insure the installed valve height was to spec and the rocker arms were upgraded to individual adjustable units with roller tips, screw in studs, and pushrod guideplates. This design upgrade allows for more valvetrain stability as well as adjustability and reduced wear.
Now that all the freshly machined components have arrived back at my assembly facility ( ok, my garage..lol ) a final cleaning and inspection of all these parts is performed and all the other new components inspected / staged for re-assembly.
In part III of this tech article, we will go through the engine assembly process as well as discuss the choice of components used for this build. Enjoy the accompanying photos and feel free to call or email me if you have any questions.
Part 3
In this segment of our build article, we will review the choice of components used for Frank’s engine which were chosen based on the intended use / combination of the car itself as well as taking advantage of the better technology and parts durability available today.
Frank wanted a reliable, well performing, good sounding car that would see regular transportation use, be a good cruiser, and see occasional stop light action with those who needed an Oldsmobile attitude adjustment. The car was to retain the air conditioning and all other factory creature comforts but needed to get reasonable gas millage and be capable of dealing with So Cal traffic conditions. A tall order for a performance build on a forty two year old car but we were ready to tackle the challenge and so we went to work choosing the key components needed to meet the criteria.
One of the first components to consider was the camshaft type and profile. After some research, we selected a hydraulic flat tappet cam from Comp Cams with .484 lift and a split design duration with 274 degrees duration on the exhaust and 268 degrees duration on the intake. This cam is similar to the W-31 cam from Oldsmobile but with more efficient lobe designs thus the ability to make more power while being mild mannered enough for stop and go traffic use and good vacuum signal for the power brakes and transmission modulator.
Next were the oiling system components which consisted of a new 5 quart oil pan with slosh control baffles, Melling brand high volume oil pump, new chrome moly steel pump driveshaft, bolt on large volume pick up tube and screen, and modified oil filter adapter housing with bypass plugged. This modification to the oil filter housing ensures that all oil being pumped into the engine from the pan is filtered and there is no chance of debris flowing back into the engine from the pan.
Our choice for rotating assembly components included Badger brand Hyperutectic pistons of the same compression as original, single moly piston rings for better durability against detonation, ARP chrome moly assembly hardware ( rod bolts, oil pump & pickup bolts), and Clevite 77 brand main and rod bearings. This brand of bearing, specifically the main bearings, is preferred since they are fully grooved as opposed to some other brands that supply half grooved bearings. This is important as the fully grooved bearing supply a more uniform volume of oil across the entire crank journal / bearing surface which improves durability and longevity of the bottom end. With this build, we chose to reuse the original main cap bolts as they were carefully inspected and cleaned and held torque with no problem.
Next we chose a Cloyes brand true double roller timing chain set , again for durability but also for reduced friction and most important, accuracy of the timing marks. There are many different brands of timing sets out there but one has to be careful on your choice as most of these are made overseas and I have seen the timing marks off up to 6 degrees on some of these. It is critical when assembling a new engine to degree in the cam and make sure it matches up to the specs on the camshaft specification card and choosing a quality brand timing chain set such as Cloyes, Rollmaster, or Speed Pro will make your job much easier and more accurate.
We touched on the valve train in the previous article but to recap, the rocker arms were upgraded with Comp Cams roller tip rockers ( not full roller rockers ) screw in studs, and guide plates along with special length pushrods to insure the geometry of the rocker arm travel across the valve stem was correct to minimize wear of the valve guides.
Externally, the component choices included stainless steel long tube headers, Edelbrock Performer intake which Frank had polished ( looks sweet ) HEI style distributor, Holley vacuum secondary carburetor, Taylor brand 8mm low impedance plug wires, new high flow water pump, new fuel pump, new harmonic balancer, freshly re-chromed factory Olds valve covers and new stainless steel assembly hardware.
Other component and prep items included brass freeze plugs in the block and heads, new oil galley plugs, newer timing chain cover, new flexplate and bolts, and of course, fresh motor mounts. Frank prepped and cleaned all the accessory brackets and pulleys then treated them to a nice coat of high temp gloss black paint and the block / heads received three coats of gloss black engine enamel. All gaskets for this motor were either Fel Pro or Corteco which are both leading brands but Victor and Cometic as well as Detroit Gasket and Mr. Gasket make equally good products for the Olds motor.
In our next segment, we will cover final assembly and what other components of the car including the trans, wiring harness, cooling system and other components were replaced / upgraded to complete this performance build package.
Part 4
We are now going to review the process of final assembly of this Olds 350 as well as review the support items that were upgraded or replaced to better match up with this performance engine build.
Once all the engine components were thoroughly washed along with the block, and all the components final inspected, we were ready to assemble the engine. We first checked all the crank journal dimensions, measured the bore housing in the block with the bearings installed, and did the appropriate math to figure the oil clearance. The same was done with the bearings installed on the big end of the rods with the rod bolts torqued to spec. This method of establishing proper oil clearances is more accurate than the old plastigage process but that approach will work as well for the more basic rebuilds
Once we were confident we had the proper oil clearances, we prepped the new neoprene rear main seal and installed it in the block and rear main cap, offsetting the seam from the cap / block seam to better avoid rear main oil seepage down the road. The crank was dry fitted once in the block to confirm we had proper thrust ( back and forth crank motion ) clearance, was then given a generous coating of Lucas brand hi-performance assembly lube and installed in the block.
Next came installing the rods / pistons in the block but first we needed to check ring gap and install the rings on the pistons. To check ring gap, we took one top ring, placed it in the bore of one cylinder, then using the top of the piston, we squared the ring in the bore so we could measure the ring end gap. In this case, we ordered .005 oversize rings so I could file fit the ring gap to exact specs of each cylinder, much like the “select fit” process Oldsmobile used on the W cars and H/O’s back in the day. Once the rings were all file fitted to their respective bores, the rings were installed on the pistons using a special ring expander tool . The ring end gaps were clocked rougly 120* from each other on each piston to avoid all gaps lining up during the break-in process. Note; the rings do rotate in the piston grooves and can align the gaps while running but this is normal and not detrimental to normal engine operation. It is only important during break in to get a more uniform ring to bore seating.
The pistons were installed after lubing the wrist pins with 30wt oil, one cylinder at a time with a small amount of light oil on the cylinder walls and again the Lucas assembly lube on the crank / rod journals. The crank was rotated several times after each piston installation to check for binding as well as rod side clearance which is another critical oiling point for Olds motors.
We now had the basic shortblock assembly completed and it was time to now install the camshaft and timing chain assembly. The cam was coated with the special assembly lube provided with it and then the crank gear was installed on the crank snout. Next the cam gear with chain were maneuvered into place with the timing marks indicating “straight up” aligned per the factory manual / specs. The cam bolt was hand tightened for the time being while we prepared to “degree” in the cam. This process while a bit time consuming and somewhat difficult to do with the engine in the car, is an important process with a performance build to insure the cam specs, timing marks, and chain stretch are all accounted for and the cam falls within the timing specs noted on the cam specification card. Once the degreeing process was complete, the cam gear bolt, with fuel pump eccentric, was re-installed with a couple of drops of red Locktite to insure it will not come loose over the years of use. Lastly the timing chain cover was re-installed with a new front seal.
Next was sealing up the bottom end so that meant installing the high volume oil pump with its special bolt on style pick up screen, again using Locktite on the pick up bolts. At the same time the new oil pump driveshaft is installed that will fit into the bottom of the distributor gear. While fitting the oil pump, we checked the clearance between the bottom of the pickup and the bottom of the pan to insure there isn’t interference but that the pickup will always be submerged in fresh oil. Ideally you want 3/8” – ½” clearance maximum. The oil pan was then sealed to the block using the rubber front and rear seals and crush resistant steel reinforced pan rail gaskets with a light coat of black rtv sealant.
Now it was time to install the fresh W-31 spec heads, using Corteco specially coated head gaskets , making extra sure the block deck surface and head surface were completely wiped clean with lacquer thinner to make sure there would not be any possibility for improper sealing. The original head bolts were reused and the heads were torqued to factory spec using 30wt oil on the threads.
The hydraulic lifters were soaked in 30wt oil until all the air had bled out of the internal valving and were then installed in the block using more of the special cam lube on the lifter faces. Al the other valve train components ( rocker arms, pivot balls, adjustment nuts, & pushrods ) were installed after also being soaked in oil with hi pressure moly grease applied to the valve stem tips and rocker pivot rollers. The valves were then all adjusted to the cam manufacturers spec of true zero lash.
The final process to seal up the motor was now the installation of that beautifully polished aluminum intake manifold. This is a particularly important process to pay attention to as this is one area often incorrectly done by folks with minimal experience with Olds motors. You are trying to seal four different mediums all at the same time, oil, water, exhaust, and air flow so it is very important to use the right gasket combination and procedure. The factory used a steel “bathtub” gasket with the original cast iron intake but when using aluminum that expands and contracts significantly, the old “turkey tray” gasket is no longer adequate. In this case we used a “print-o-seal” type of composition intake gasket which incorporates a special bead of sealant built tight into the gasket surfaces. We also used black rtv for the end seals rather than the typical rubber seals as they have a tendancy to shrink with heat and start leaking oil. We also applied a thin layer of Gasgacinch ( contact cement ) to the intake port area of the heads and the gasket to insure a good airflow seal. Lastly we applied black rtv around the front and rear water jacket ports and set the intake into place. New stainless steel intake bolts were then torqued to factory spec and the assembly was left overnight to set before further assembly work was completed.
The final assembly phase of the motor included installing the new water pump, pulleys, harmonic balancer, a/c & alternator brackets, timing pointer, carburetor, motor mounts, flex plate, distributor, egr block off plates, spark plugs, fuel pump, modified oil filter housing and other miscellaneous items.
To complement the new and higher horsepower engine, it was decided that the cooling system should be upgraded so a new three row aluminum radiator was secured from Champion Radiator for the project. Also the transmission was completely rebuilt by Dana Sniff Transmissions with heavy duty components and a shift kit along with a new higher stall speed converter from Edge Converters to improve off idle performance . To round out the drive train upgrades, new heavy duty u-joints were installed in the driveshaft along with a new trans mount and a hi-torque mini starter for reliability with hot starts and tight header clearances.
In our final chapter of Frank’s engine rebuild, we will go through the final installation process as well as the start up and break in procedures employed to get this Cutlass Supreme back on the road and ready to do battle with our Southern California traffic and the occasional rice burner “thinks he’s fast” owner…lol..
As always, if you have any questions regarding this build or one you may be contemplating, please feel free to contact me anytime.
Part 5
In this last segment of Frank’s 350 ( now 355 c.i.d. ) build, we will now review the fun part, bringing this beast to life and rattling the neighbors windows ( yes we did have the community security patrol called on us…lol..).
The engine installation process began with removing the engine from the build stand so that we could install the rear oil galley plugs, cam bore freeze plug, and the new flex plate. In all my builds, I always replace the flex plate as this is actually considered a wear item and over time, these plates will develop cracks, not always immediately visible to the eye, from the flexing they are designed to permit during acceleration and deceleration .The new flexplate is installed with new ARP high strength bolts, torqued to spec with Locktite thread locker.
Next we installed the new torque converter onto the input shaft and front pump drive of the transmission, using a light coating of moly grease on the input shaft and front pump seal to help align the splines as well as protect the front pump seal during initial start up. We then maneuvered the transmission into place at the back of the block, seated the block locating pins in the transmission bellhousing flange and installed new grade eight bolts. It is important here to never “draw” the trans to the back of the block with the bolts, but rather seat the trans against the block and then run down the bolts. If you draw the trans to the block, you run the risk of breaking the aluminum trans housing or “ears”. The bolts were all torqued to spec and then the converter was aligned with the flexplate and secured with three grade eight bolts, again torqued to spec with Locktite.
At this point, as many accessory items as possible were installed including the trans mount, motor mounts, power steering brackets with freshly rebuilt power steering pump, a/c brackets, starter, trans dipstick tube and alternator brackets.
Just before we installed the engine into the car, knowing that we would be starting the engine within a few days of installation, I went ahead and primed the engine with a special priming tool attached to a ½” drill. With a mechanical oil pressure gauge attached to the engine, I ran the drill in reverse ( remember the distributor in our engines runs counterclockwise ) and achieved a little over 60lbs of pressure which indicated all was good with our internal clearances and galley plugs. After discovering one small external oil leak and correcting that issue, it was finally time after more than five months, to place this engine back in its original home.
The next step was to maneuver the new engine and transmission into the engine bay of Frank’s Cutlass, working around the new headers loosely placed in the engine compartment. With some grunting and groaning and yes, a busted knuckle, the engine was set in place and bolted to the crossmember mounts. This process did require the removal of the oil filter after it got a bit dented up to fit around the headers so a fresh oil filter was installed once the headers were secured to the motor and a quart of oil added to the motor since the filter we removed was full from priming. In retrospect, even though these stainless steel headers were a great price and well made with heavy gauge tubing and flanges, this particular brand does not fit that well and there were several modifications necessary to the engine compartment and overall configuration to make them fit properly. My recommendation for future builds that may be similar to this, stick with Hooker, Hedman, Doug Thorley,Flow Tech, or American Racing Headers for your Olds build. Trust me, you will save some headaches that are more than worth the extra cost of the headers.
With the engine secured in place, all the new wiring harness connections were made, the new HEI billet distributor was installed ( note: the new wiring harness was ordered to accept the HEI distributor and electric choke carb ) along with all the other belts, hoses, accessory items, driveshaft, new speedometer cable, new emergency brake cable, rebuilt Holley carburetor, radiator, fan and other detail items. The starter solenoid wiring was modified and re-routed to avoid the heat from the close fitting headers and a different bracket was needed for the accelerator cable to allow for proper throttle travel of the Holley carburetor. A new set of mechanical gauges, (water temp, oil pressure, and volts), were installed to properly monitor the new engine. Last was topping off all the fluids, using Lucas Hot Rod & Classic car oil ( 10w-30 ) with a bottle of Lucas break in additive, GM Dexron trans fluid, GM power steering fluid, and straight distilled water in the cooling system with one bottle of Water Wetter. The last finishing touch was a fresh charge of the battery and its installation and a thorough check of the entire electrical system to insure all was connected properly.
Now came the big day, Sunday afternoon, May 5th at about 1:00pm, with Frank eagerly looking on, we primed the carburetor, added a couple gallons of 110 octane leaded race fuel for good measure to mix with the slightly stale gas already in the tank, pumped the accelerator twice and turned the key. Success! On the very first crank it roared to life in all its uncorked glory and went right to the preset high idle of 1800 rpm to start the 15 minute break in period. This is always a bit of a stressful time, even for the most seasoned engine builder, but other than one shut down to fix a fuel leak at the fuel pump hose connection, all went extremely well, even with the security guy being called on us by my one of my not so understanding neighbors. He is a car guy too so when he stopped by, I was repairing the fuel leak and the car was not running. He gave his thumbs up on the project and how sweet the engine looked and just said” wait until I drive out of the neighborhood to fire it back up to finish your break in so at least it looks like I did my job when I stopped by” . Got to love your fellow car guy / gals…lol..
The remainder of the break in period went without a hitch with the motor running at a steady 190 degrees in the warm weather. We had no other leaks so we finished topping off the trans fluid and ran the car up and down the driveway a couple of times to make sure the trans was operating properly and didn’t leak. The following week we took the car to the muffler shop to button up the exhaust and the grin on Frank’s face on the drive back to the house from the muffler shop said it all! I think he was a happy camper…lol…
It is important to understand, that with any modified build such as this, there are always going to be bugs that need to be worked out and Frank’s project has been no exception. We kept the car for another week after the exhaust system was re-connected to sort out several minor issues including carb mixture and choke adjustments, loose fitting vacuum hose to the trans modulator, leaking overflow tank hose, and final timing adjustments .
Since Frank and Tonya came over the following weekend to pick up the car and start the 500 mile break in process, a couple of other issues surfaced that have since been addressed. The first issue was that the starter would occasionally grind or improperly engage the flex plate. These aftermarket “mini” starters often require shims to properly align them with the flexplate. You always want to try first not to use them which is what we did here but eventually the starter required three in order to get it dialed in just right. The other engine issue was that the 20+ year old Holley carb Frank provided and we rebuilt proved to have an excessively work front throttle shaft which was drawing air ( vacuum leak ) into the engine, creating a fluctuating idle problem and stalling at stop lights. The decision was to replace the carburetor with a new Avenger Series aluminum 670cfm Holley carb with electric choke. Bolting this carb on immediately solved the idle quality problem and feels as though it may actually have added power to the engine by being more matched in cfm rating to the motor.
The other modification problem came by way of the headers hanging too low under the car in its existing stance and scraping the flange on anything larger than an ant in the road. Since Frank had already made some upgrades to the front suspension with tubular A arms, it was decided to install some adjustable coil over shocks with adjustable valving to both adjust the ride height ( raise it ) as well as tune the ride quality and handling.
To date, Frank and Tonya has logged just under 400 miles in their revived Cutlass and will be soon doing the first oil change and final tune. Once that process is complete, they should enjoy many thousands of miles of Oldsmobile ground pounding performance.
In closing, I would like to extend many thanks to Thomas Jones for his tireless effort in cleaning, detailing, and prepping the Cutlass’s engine compartment, engine removal / disassembly as well as other details, Scott Graham for his time helping with car re-assembly including the pain in the a$# emergency brake cable, and finally my fiancé Karon, for not only documenting most of this process with her camera, but also giving up her garage parking space and time with her man while this project was being completed. And one final thanks, to Frank and Tonya for allowing us all the opportunity to share in their dream to restore and again enjoy their Olds machine.