Rocketing the 455 Oldsmobile Engine into the Future

By Joe Mondello

Rocketing the 455 Oldsmobile Engine into the Future using
Today’s Gasoline & Oils

For this article I am drawing on the more than 50 years of experience dealing with automotive gas and oils with their ever-declining zinc and phosphate contents. This will show the effects on the high performance engine. I will also cover Ethanol as a fuel and other additives.

Many engine component manufacturers have moved their operations to, or purchase materials or entire parts from, foreign countries. Speed Pro, Federal Mogul, Sealed Power, KB Pistons, Accel, MSD Ignition, Pertronics, PEP, SBI Professional Products, Erson, Probe, Moon, Doug’s and Hedman Headers, Mr. Gasket, Hooker, even some of the cylinder head companies are just a few. I feel we all need to purchase more of our components and products that are totally manufactured right here in the United States from our own materials and using United States citizens in their factories. If we stress this enough we will see more and more products on the shelves that again say “Made in the U.S.A.” And I don’t mean the area in China renamed Usa or USA to fool us!

The days are gone when you could purchase your parts from Jegs, Summit, PAW, Aetec, and other wholesalers and WD distributors with confidence that you have quality U.S.A. made components to install in your engines. You can no longer have the block bored .030” over, have the crank ground .010” under and install. All the parts may no longer fit right out of the box. You can no longer trust what is stamped on the part or written on the packaging. You have to inspect and measure EVERYTHING. Remember what our parents used to tell us, “Don’t assume anything”. The last set of pistons for a 361 Mopar I purchased varied in weight 18 grams and the sizes varied from .0025” to .003” within the set of eight pistons. I had to purchase three more of those “sets” before I found eight that were a matched set that I could balance.

The timing chain sets out there aren’t very good either. The ones coming from underdeveloped countries have cheap chain material, out-of-round gears, with timing marks and keyways that are in the wrong location. Be especially cautious of the True Roller Chain set for $19.95. I spent three days checking all the chain sets I could get my hands on and some, like the one mentioned above, were 9º to 11º off the timing specs. I only use Cloyes True Roller Chain Sets in all my 455 engine builds and even then I do check each one before installation. So far the Cloyes has been within ¼ of a degree in total timing events. The factory 455 engine was one of the closest machined and fitted engines of its time in the entire GM line. Every 455 Olds was completely blueprinted, unlike most of the Buick, Pontiac, and even Chevrolet of that time. Cylinder bores were precision honed, pistons were weighed, mic’ed, and matched in .0002” increments, then marked with A, B, C, D so they would fit perfectly in their respectively marked cylinder bores. All the deck heights were machined to 10.625” give or take .005”, all connecting rods were checked for center to center lengths, housing bores measured and matched to correct bearing size and the small ends were mic’ed for correct press fit on the wrist pins of .001” to .002”. Each engine had all the rods, pistons, pins, and cranks balanced. Oldsmobile cast, nodular, and steel cranks were heat treated and had hardened bearing surfaces right from the factory. In other words, they were blueprinted. The 1964 through 1967 330, 400, and 425 forged steel cranks have a different flywheel flex-plate crank bolt pattern than the 1968 and later engines. We manufacture billet steel flywheels and flex-plates for Olds and other hard to find engines.

After being align-bored and matched to a crankshaft, the blocks were matched to within tenths with variable sized main bearings. All engines had Morain rod, main, and cam bearings. The cams were degreed-in for all engines, rings were end-gapped and de-burrred. Some of the SB and BB engines had lifter bores .010” over and were marked with “.010” on top of the lifter bore pad. All of this machining, fitting, and balancing was done in a custom built machining and assembly facility built in 1948 by GM’s Oldsmobile Division. It was dust free, air conditioned and maintained year round at 70º. This facility allowed Olds to build a smooth-running engine that would go hundreds of thousands of miles with only a possible timing chain replacement. In the 455 engine, Olds used a chrome plated steel or plasma moly, ductile top ring, a reverse taper second ring and three piece, hard chromed stainless steel oil ring with medium to high pressures. These rings were Perfect Circle, Dana, or Hastings. The only weak link in Oldsmobile’s engine was the aluminum timing cam gear with Teflon coated teeth. It was used to quiet the engine noise in all GM engines and usually had to be replaced at about 100,000 miles. It is my opinion that Olds really built the best engines in the industry since the first Rocket over-head valve engine in 1949.

Since the introduction of all the big blocks, 400, 425, and 455 cubic inch motors, I have been associated with Oldsmobile and my dear friend, D. Dale Smith. Dale persuaded GM to hire me as an outside vendor for testing, design, and modifications of stock and performance oil systems, engine parts, and suspension pieces. Because of GM Corporate, Oldsmobile never had a Motorsports or Race Division or produced performance aftermarket parts. Well, guess what? Dale Smith and Dave Maurer, along with myself and others like Marv Thompson and Machine Shop Richard decided to sneak everything we needed to go racing out the back door to do our R&D. We made Olds famous in virtually all facets of racing, NHRA, IHRA, NJBA, AHRA, Pike’s Peak Hill climb, Mexican Baja road race, circle track and even a stab at NASCAR.

Ever since the first V-8 Olds engines left the factory many of them have been rebuilt, some incorrectly. The reason for this? Olds engines are not the same as small block Chevy, Ford, or Mopar. If everyone in this industry knew how the factory built our Olds engines they would pay more attention to their OEM quality. Remember, Olds engines were built to cruise down the highway between 18 and 26 hundred RPM. When the W30, 31, and 32 442’s along with some specialty cars were built, the red line was 5000 RPM and nothing was changed in the engine except installation of stronger valve springs and lighter steel retainers. Dual Exhaust manifolds W, X, Y, and Z were added; they are divided into two muffler systems plus a slightly higher RPM torque converter and Stifer Clutch for 4 speed cars.

There are several modifications that must be made to the 455, like re-hardening cranks after a grind, cross drilling mains, and converting from a rope rear main seal to a Neoprene seal. We suggest oil restrictors between the cam bearing and main bearing, oil galleys along with restricted cam bearings must be used. You have to open up the oil return holes in the block, cylinder heads, use a bronze camshaft thrust button, .041” bronze cam spacer and .041” steel crank timing gear spacer. You must install a rear left oil galley 3/8th pipe plug located in front of the rear 29/32 soft plug. This plug must have a .040” hole to oil the cam and distributor gear. Believe it or not, a lot of good engine builders leave this plug out and the result is 0 to 5 pounds of oil pressure when the engine is started. The only way to install it is to R&R the transmission flywheel or flexplate, remove the 29/32” soft plug and install the 3/8th pipe plug with the .040” oil hole in it. If you use a 3/8th pipe plug without a hole you will have cam and distributor gear failure.

I see a lot of rod bearing and connecting rod failures when builders install aftermarket ARP rod bolts and don’t put a 65-70º chamfer in the I-beam portion of the rod where the bolt contacts the flat portion of the rod. This should be checked very closely with a .001” feeler gauge or a close look to see if the rod bolt is perfectly seated in the rod. This is one reason rod bolt nuts come loose, the other is failure to torque cycle or torque rod nuts properly. The use of a rod bolt stretch gauge is highly recommended.

The 455 Olds, 400 and 425 big block, and 330, 350, 403 small block engines have very poor oiling systems. This problem, plus the use of aluminum babbit rebuilder type bearings and not nitriding, heat treating, or cross drilling the crank, will cause quick and premature lower end failure to crank, rod, and main bearings. Another major problem of piston skirt scuffing and failure is engine builders who press the piston pins into the rods instead of using a rod heater. If you cannot put your hand through the big end of the rod, hold it next to your leg and rattle the piston on the pin. It is too tight if you have to apply any force to rotate the piston on the pin. That engine will fail.

A lot of what I am mentioning also applies to many other engines. The best way to control oil to the upper end in the valve covers is to use Mondello .100” restricted cam bearings with the R-104 oil restrictors in the numbers 1 through 4 galleys leading up to the camshaft. Also, a big help is restricted 5/16 or 3/8 push rods using a .040” restrictor in the push rod itself. When installing a mechanical roller cam a .040” lifter bore restrictor must be installed. With mechanical or roller hydraulic cam you must use my TB740 bronze cam thrust button and CS120 .041” cam thrust washer with a CS40 steel crank gear spacer. I highly recommend this set-up in all hydraulic and mechanical flat tappet cams. Nearly all cam manufacturers use a Chevrolet style hydraulic roller tappet which comes out of the lifter bores causing uneven lifter preload, low oil pressure, lifter noise, and a rough idle. I have redesigned a true Olds hydraulic roller lifter and flat tappet lifter that doesn’t come out of the bores. Be careful when shopping price in this area, it can ruin your entire rebuild. Just because a cam manufacturer states Olds products ask questions before you believe it because some manufacturers use Chevy lifters and cam profiles. If you order Mondello parts they all fit and have been engineered to make your Olds engine perform better and last longer. Most engine builders who grind cranks will tell you they can’t and don’t reheat or nitride them. But the biggest thing I can’t believe is they say you don’t need it! An Olds engine is not small block Chevy with its small rod and main journals, a killer oiling system, and limitless choice of size of rod and main bearings to fine tune your clearances. Olds rod journals sizes are 2.500 & 3.000 mains. This is a lot of bearing surface to get oil to, especially when the best oiling system by Mondello still isn’t as good as a Chevy’s! This is why nitriding, cross drilling, re–heat treating, shot peening, and ultra micro polishing is needed. Clevite’s H series or ACL’s Tri Metal performance rod and mains with a good coating like our Tech Line Poly Dyne or Calico should be used. We modify the thrust bearing and numbers 2, 3, and 4 main bearings in the main saddle drilling the center oil hole 17/64 and also elongate it towards the centerline of the oil restrictor for better oiling. All the bearings we sell at Mondello Tech Center for cams, rods, and mains, regardless of manufacturer, are cryogenically frozen. With the very aggressive flat tappet cams we nitride the wear surfaces when possible. These cams are a special order item.

On my higher end engines I cryogenically freeze and stress relieve shake all moving parts. I highly recommend you also have the heads, valves, pistons, cam, bearings, crank, rods, intake manifold, lifters, wrist pins, and oil pump gears coated with Tech Line products when blueprinting as it helps the engine live longer. We use chromed steel or moly ductile top rings, Napier second rings, and stainless steel chromed three piece oil rings (on some we use Total Seal tops or 2nds); high volume oil pumps with 3/4 to 7/8 pick up tubes; 7-8 quart oil pans; neoprene rear main seals, cork/steel reinforced pan gaskets. This, along with chromoly oil drive shaft and a steel roller mechanical or hydraulic cam using a bronze or nitrided, heat treated distributor gear and a Cloyes timing chain set, is a great set up. When using an electric fuel pump do not remove the OEM fuel pump eccentric as the cam drive pin will come out. I install my clearances as follows: cam to cam bearing .001” to .003”, rod bearing .0022” to .0026”, main bearing .0024” to .0028”, and cam thrust bearing .000” to .005” with front cover gaskets in place. I end gap my rings wider than most rebuilders. The top ring on a 4.125” to 4.155” net bore is .020” to .022” top .022” to .024” second oil ring rails .020” to .022”. I lap all top rings, Napier rings, and oil ring rails to eliminate any coating build up. You cannot lap RBT taper style second rings. The sharpest ring ends in your engine are the stainless oil ring rails. I designed an oil-filled half-round very fine hard de-burring stone to clean up all rings (RS103). On the oil ring rails I use a 150 to 180 grit 1” belt sander to chamfer the end edges at about 30-45º angle from the face of the ring to the end gap, then lap the rings on both sides to remove all sharp edges. On Total Seal’s I use the same end gaps. On rod bolt stretch torque cycling, ARP has made it a lot easier with their moly-free Ultra-Torque fastener assembly lube. I tested it over a year’s time at the tech center and now use it daily.

Let’s talk more about heads, intake and exhaust manifolds, headers, and roller rocker arm systems. I will also touch on carburetors and distributors.  I like up to 9.5:1 compression with iron heads and Tech Line coatings; 10-1 with aluminum heads and coatings using the correct cam choice and lobe separation. The best factory built heads as far as flow and performance were the A, B, and C, D, E, F, and H were second best. The A and B heads need the push rod holes bored to 9-16 because they were designed for a 45º lifter bank angle. The G, Ga, and J heads were built for low compression, unleaded fuel smog engines and had induction heat treated exhaust seats. Today all these heads need replaceable exhaust seats installed but beware in this area. Do not use any seat deeper than .214”. Years ago I helped Dura Bond design some seats with their powder metal material at .188” deep using .005” – .006” press fit. I have thousands of the 3000 Series seats out there and never had one fall out! I use Goodson and K-line bronze guide liners, stainless steel hard chromed stem valves broached and diamond honed with a Goodson or Sunnen diamond hone tooling to correct size and finish. I prefer .0016” to .0018” intake and .0018” to .0022” exhaust clearance. Because of dual heat riser crossover ports I fill them with my ZA12 zinc alloy to allow even size center exhaust valve bowls and keep the excessive heat away from the intake manifold surface, eliminated warping and leakage. Valve bowl and short side radius porting, removing exhaust EGR bumps, widening the exhaust throat .100” to .12”, raising intake and exhaust roof .10” if the manifolds allow you to do so.

When using W, X, Y, or Z Olds manifolds or headers with the exhaust center divider, we braze them and resurface the gasket surface. The stock Olds heads all have a .080” to .150” gap on the center exhaust divider below the gasket surface. I make the divider .100” to .200” wide (usually .125”) for better gasket seal. If you don’t do this procedure, you will always blow exhaust gaskets when using headers or divided manifolds. The valve stem tip length is very critical when using a stock type non adjustable valve train. This is where most shops ruin Oldsmobile heads. Back in the ‘60’s Burroughs designed an aluminum gauge that fit from the valve cover surface to the valve tip; it’s no longer available but I have made one (HG455). You can’t measure from the spring seats because Olds engines have both shallow and deep and a combination of these on some heads. If you mess up in this area because you don’t have my HG455 tool the engine won’t start, will idle rough, and/or backfire. The solution is adjustable push rods. If they are even but too long, shim the rocker stands or use an adjustable roller rocker arm system like my SAR-455. Now you have rocker arm to valve cover clearance problems. Use my .250” to .375” thick valve cover gaskets or my extra tall Mondello valve covers with baffles. They are 1” taller than stock. Ask for part number VC-468.

Air conditioning and power steering brackets must be shimmed. If this is a stock rebuild that’s a real pain unless you follow my instructions and do your valve job right the first time. If you are building a performance street engine there are all kinds of roller rocker kits available. I like the Edelbrock 6041 aluminum heads but they need to be cleaned up, or fully ported if you want to make the maximum power. All the heads I have mentioned need a multi- angle valve job 89% intake and exhaust valve bowl throat dimensions and a full radius exhaust seat below the 45º primary valve seat cut. If you are building a set of high performance heads, valve tip length is not as critical because you will be using roller rocker arms. All my valve jobs are similar among a lot of different heads but I insist on the 89% to 89.5% throat dimension. I use my signature series Joe Mondello Goodson valve seat cutters designed after much wet and dry flow testing.

The A, B, C, D, E, F, G, H, and J heads are all for the 455 and can utilize the seat angles. The stock 455 heads with large 2.072” intake valves were 30º but by changing to 45º you will get 8 more horse power. Small block 403 and all early 350 heads had 45º intake seats. Some of the SB and BB heads had 30º exhaust seats. My favorite big block cast heads are B and C. All Olds iron heads regardless of year need the heat riser passages filled with zinc alloy ZA12, the center exhaust port dividers brazed, and mild clean up porting if you are using headers on the street. You need my street strip or bracket porting job for a street strip application. With filled heat risers an electric or manual choke is necessary. On all Olds heads including Edelbrock’s, I recommend the following Mondello Signature Series valve seat cutters by Goodson. Remember the 89% throat dimensions on intake and exhaust. The IFT-4539B-HP intake cutter is 39º 1.77mm top cut 45º primary seat 1.1mm 60º bottom cut. Make this .085” to .090” wide narrow with a 75º IFT-75R6B-HP then hand blend below 75º, cut into the valve bowl leaving all angles sharp to shear incoming fuel. Use this on all small and big block Olds heads. If you need to clean up chambers for un-shrouding or sunken valve seats into combustion chamber floors, use the IFT-1556-HD cutter. Scribe cylinder bore with the head gasket in place. Do not go bigger than the gasket, usually 4.200”. On the exhaust side I like to use a 45 º primary cut then a full radius below it. I like Goodson Cutter IFT-4524-HD 39 º top cut 1.5mm 45 º primary cut 1.4mm wide and R10 full bottom radius. If you have to open up the exhaust throat dimension to 89% do not use a straight blade cutter; use my SF5-11 round nose tree shaped 24 tooth regular cut carbide in a die grinder to achieve your 89%. Reface valves 45 º undercut 30 º the same width of your 45 º primary seat angle. On the upper edge of the 45 º next to the margin set your valve re-facer to 50 º and break the edge .005” to .007” wide. This helps to accelerate the air around the valve into the chamber. On the top side of the intake valve exposed to the chamber, machine a 15 º cut .015” to .020” wide. This helps eliminate reversion on the high lift race cams with over .700” lift. All the above information will work on all performance V-8 engines regardless of make. Follow these instructions to the letter.

Always use a run-out gauge for seats and valves. Do not assume your equipment is good and true, even if you just installed new stones, chucks, mandrels, bearings, drivers, or pilots. A premium re-facing diamond for your valve re-facer is highly recommended. When buying Mondello Signature Series cutters from me or Goodson a highly detailed instruction sheet comes with your order. Always make sure all your machines and equipment are level; check this monthly.

On engines making up to 400 HP, chromoly straps and studs are needed to help keep the main caps from walking. If you make up to 500 HP, a chromoly main stud girdle is needed to prevent cap walk. Any engine over 500 HP will need three billet steel center main caps plus the girdle. On all of my high end engines that make 475+ HP, I use steel main caps and a girdle. This is just a good insurance policy for longevity. You cannot install 4 bolt main caps on a 455 Olds engine.

I have been modifying all my connecting rods especially between the mating surfaces on the big end to enhance oiling and cooling of the rod bearing surfaces. I make the notches .375” wide and .010” to .012” deep on the inboard side of the rods for street and mild bracket street side clearance .010” to .014”. On engines for all out racing it’s .018” to .022” side clearance. For 500+ HP engines I do both sides but only .375” wide. If you notch the rods you can reduce your side clearance about .005”. Remember, Olds engines are not like the rest. Good blueprinting consists of balancing; correct rod, main, and cam bearing clearances; precise ring end gapping and lapping; cam degreeing; use of oil restrictors; correct piston to wall clearances and correct installation of connecting rods. When using either stock or aftermarket rods the bearing tangs on the rod go towards the camshaft, not the oil pan rail like most other V-8’s. I suggest my V-8 Oldsmobile Engine Tech Manual to find other answers; it contains all my knowledge to date and took me over two years to complete. GM Motorsports liked it so much they gave me the official GM part number 12480027 and sell it worldwide through dealers and the net. You can purchase it from me or my California store where Lynn Welfringer at 805-237-8808 can assist you with the parts and all special Olds gaskets you will need.

I haven’t mentioned head, or intake and exhaust gaskets. I work mostly with Fel-Pro. Cometic, Detroit, Rol, and Corteco. I really like the Cometic MLS multi layer steel gaskets to adjust compression ratios on engines, especially in muscle car rebuilds where the builder puts in a 10.5 to 1 piston because that was stock in ’69 and ’70 W-30 442’s. A lot of engine builders don’t know any better and still today just order a rebuild kit for the proper year. We fix this with coated chambers along with installing a .060” thick head gasket instead of the .041” and it drops your compression to a little over 9.5:1; perfect on today’s 10% Ethanol junk gasoline. If you want 9-1 use the .080 MLS gasket and you will be fine on 93 Octane gasoline containing Ethanol. These calculations are rated on a 14cc dish piston, .020 deck height, and 80cc cylinder head.

Now, I will talk about oils, cam break-in, and zinc maintenance levels to keep your flat tappet cam engines alive. When buying today’s gas try to get it without the ethanol. Sunoco has ethanol-free fuel. Beginning in October 2010, the shelf oils will again reduce the zinc content to 600 or 700 PPM in each quart. The racing oils for off road use only have between 1200 and 1500 PPM of ZDDP. The serious problem on proper break-in for flat tappet cams is that 2000-2500 PPM of ZDDP is needed. I recommend you leave your oil break-in additive in for the first 500 miles. After break-in you need the 1500 to 2000 PPM of ZDDP to keep the cam from going flat. Camshield zinc additive is the best I have found. One eighth to one fourth oz will raise the ZDDP 800 to 1600 PPM per quart. I recommend racing oils or synthetics with 1200 and 1500 PPM of zinc plus 1/4 oz Cam Shield per quart of oil in older engines and you will see no more cam failures. 1/4 oz Cam Shield gives you 800 PPM zinc; 1/2 oz adds 1600 PPM per quart of any oil. Remember the engine has to be built right in the first place. I use torque plates, same gaskets as final assembly, plus cycled aftermarket fasteners like ARP and Milodon.

I properly blueprinted from 750 to 850 OEM, QuadraJets by SMI with electric chokes, Edelbrock AVS-800 cfm electric choke carbs, Edelbrock 2151 Performer, 2730 Torker, 57026 air gap professional products Cross wind, Mondello stainless headers 1-3/4 Hooker, 1-7/8 Doug’s headers 1-7/8 for performance street use and all out drag racing, 2” Hooker headers. Mondello or Pertronics performance HEI’s, the new Pertronics billet flame thrower distributor with MSD discharge and adjustable rev limiter should also be used. Call me for further details.

In my next article I will cover all machining, blueprinting, and correct assembly of all engines.

Fel-Pro is designing an MLS gasket for the Olds and I’ll let you know when it’s available. I hope this article will help you build the best, most reliable power producing engine you’ve ever completed.

If you need further assistance, phone and I will be happy to discuss your project with you.


Joe Mondello has been involved in quality head porting and R&D at a time when Ed Iskenderian, and a few others started a high performance industry. Joe has been so successful that his tech manual was given a GM part number. Joe is an innovator and educator of the highest order. When he could have sat on his laurels, Joe chose instead to start a Tech Center in Crossville, Tennessee holding classes for any who desire to learn air flow secrets that took Joe a lifetime to find out.

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