455 CID Engine Detail

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General Information

Note: The information contained in all of the "Engine Detail" sections should be read before proceeding with modifications, etc., because some information that applies to all engines, or all small blocks or all big blocks, might not be duplicated in every section.

The 455 was built from 1968 through 1976, produced from 210hp to 400hp, and were installed in just about every car Olds built in that period at one time or another, including the Cutlass/442, Delta 88's, 98's and Toronados (not the Omega, though). You can get a quick estimate of the year of the engine by looking at the 1" high casting letter on the lower-left corner of the block and/or head.

If the engine is one of these high-performance motors, it's pretty easy to identify where it came from. If not, it's a little tougher.

Other clues for identifying the engine, especially the later engines, are the carb numbers (stamped on the driver's side of the carb, usually something like 7040251), as the emissions regulations required carbs calibrated for the specific requirements of a particular model (basically 1973 and later), whereas all models before 1973 used the same carb numbers (again, aside from high-performance and Toronado engines). Likewise, the distributor number might be specific to the model it was installed in.

The exhaust manifolds would also provide a clue as to where the engine was originally installed. If the passenger-side manifold has two openings, it's a single-exhaust application, and likely from an 88 or 98.

Year Differences

According to my trusty Olds engine book, the 455 was available in 310 hp, 320 hp, 365 hp, 370 hp, 390 hp, all street engines, with full manufacturers warranties. The 455 is a very forgiving and long-lasting engine. To eek out more HP you can go with higher compression, which will prevent pump gas usage (highest stock 455 comp. was 10.5:1). To achieve this, use flat top pistons (butterfly cut), milling heads, and decking the block. This will yeild CR in the 14 range. However, you have to pay for it in wear and tear.

455 engines through the years have some differences. Some have lower compression pistons, not an issue if you are getting new ones anyhow. Later blocks, typically with an Fa casting ID have lost the boss where the clutch z-bar used to mount, which affects only manual trans applications. If you are using it in AT car, all 455 blocks are pretty much fungible for street use. Rumors of rear-face "F0" etc. codes having more nickel, but no one can seem to document that. Some are more likely to have a Nodular crank, might even have a forged crank. Not likely though.

[ Thanks to Bob Barry, Joe Padavano for this information ]


455 Application Comparisions

1969 - 1970 Toronado 455 vs 442 455
I know 365 horses is the stock rating for the 442, but what about the Toronado. I have an F block and E heads. What is my engine out of and what is the horsepower rating for the 69 & 70 Toronado?

The Toronado engine (1969 and 1970) was rated at 375hp, but in point of fact, it was a more mild engine than the base 442 engine in 1970. Aside from the intake and a slightly different camshaft, a '70 Toronado engine was identical to the small-valve big-car L-31 455, and in 1969, the only difference was the larger intake valves.

OTOH, the specs on the 400hp W-34 motor was identical to the 390hp W-33 and base 365hp 442 motor. So the factory hp rating doesn't mean much.

[ Thanks to Bob Barry for this information ]


Buildup

Cams
Put a W-31 cam in it if you want to drive it with power brakes. Makes a load of power and still has a nice sounding idle without effecting the power brakes. Pulls hard past 6000 RPM with lots of bottm end torque.

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Cooling

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Crank
If you drop the late 400/455 crank (4.25 stroke) into the early E-block 400 block (4.000 bore), you get a 427 Olds. If you go 0.060 over, you get a 440 (unfortunately, you need a custom set of 4.066 pistons to get it to 442 cu in).

[ Thanks to Joe Padavano for this information. ]

Differential Gears

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Exhaust

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Heads

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Induction

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Ignition

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Oiling

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Redline

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Short Block

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Transmission, Torque Convertor

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Valvetrain

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Buildup Examples

W-30 455
I have a 1972 455 that I bored .030" over with torque plates. I took the crank and had it cross drilled and chamfered, and the counter weights were deburred. I am using the stock piston rods with F2323 TRW pistons with file fit plasma moly rings. I have a Toronodo 5 quart oil pan with windage trays and a crank scraper. The oil pump is a Melling HV with Toro pickup from Mondello. I am using a Cloyes double roller timing chain. My cam is a Comp Cams and the specs are as follows at .050" duration: intake 234°, exhaust 244°. The lift is 523" intake and 518" extake with a 110° degree center line. Advertised duration is 292°. Don't use the Mondello cam button. It just causes premature wear.

I am using Mondello 7400 roller rockers, and standard TRW pushrods and lifters. I set the cam in at O° or what is called straight up.

Back to the block, I had the block decked so that I have .017" piston to deck clearance. Using Victor brand head gaskets that measure .028" when compressed. Felpro gaskets are .038" when compressed.

I am using GA heads the have been milled .060" on bottom and intake side to give me 73cc of head volume. The valves are Milodon stainless steel 2.072" intake and 1.710" exhaust, with a 5 angle valve job. The center divider on exhaust side was welded and milled smooth and #3 and #6 heat risers were welded instead of using Mondellos Heat Block Mix. The heads have been ported to remove the EGR bump and the bowls and exhaust polished.

I recommend not polishing intake side for better atomizing of the fuel. I am using the stock GM valley tray and the stock W-30 aluminum intake.

The carb is a W-30 Q-jet that I had a local shop bore the bottom .050 and put in new shaft bushings. I am using #69 jets and 48b primary metering rods with AX secondary metering rods with a K hangar. The CFM rate is 795, and the carb is #7042253. I am also using the paper filter in the carb. For fuel delivery I am using a Holley Blue electric through stock fuel lines and using the stock pickup and the regulator is set at 6.5 PSI.

For exhaust I am using Hooker headers with 1 7/8" primary tubes with a 3" full exhaust with Flowmaster 3" mufflers with 3" tail pipes.

For ignition, I am using the MSD pro billet distributor and the MSD Blaster coil and the MSD 6A box with NGK 5670-6 spark plugs gapped at .040". The wires are just Accel black 8mm wires. I am still using power steering and the GM thermo clutch fan and a 160° thermostat. I am using 20w50 Vavoline oil and a K&N 3.5" air filter.

It is also important how you set up your car. I'm using the stock posi rearend but with 4:10 gears, and the TH-400 with a shift kit. I am using an ATI Treemaster torque converter that stalls at 3500 RPM. I shift at 5600 RPM when I race this car. If I drive the car without hot dogging it I get about 10mpg.

This motor was built for street and strip. I drove the car to Norwalk dragway which is 130 miles from my house and ran it that night with times of 12.67's consistently. At the NMCA event at Norwalk in September I ran a best et of 12.47@108.23mph.

By the way, at idle, which is 1000 RPM, I pull 15 inches of vacuum. So you can run power brakes, but my car is manual. You can use a 460 Ford rear main seal which is same size as Olds but is a two piece rubber lip seal (as opposed to the stock rope seal). It is much easier to install than a rope seal, especially with the crank in place, and I feel gives a more reliable seal. It's easier to install properly.

For the oil pan gasket, use a 350 Olds diesel because it has a steel shim or fiberglass core to prevent squashing.

[ Thanks to Mark for this information ]

Marine 455
The Olds is a good jet boat engine although you really need to fix the short block. Need to turn the crank journals down and put different rods in it. Cost sneaks up a bit but the rpms are good up to 7000 or so. Good for when that prop comes out of water!!!

A super charger puts pressure on the two bolt main crank. Yes you can get the kits to strengthen it, but lets face it - the Olds was not meant for it. It was meant to haul those 4000 lb cars around. Not push a race car with a blower. Some engine are a narural for a blower, 426 Hemi for example.

Run a blower if you wish, but you probably shouldn't overdrive it more than 10% or so. Just run the juice, use when you need it.

With the tunnel ram, run 2 390cfm Holleys, and you will get better fuel distribution than with a single Holley. You will get better throttle response for pullling those people up out of the water.

I like the Offy Port O Sonic better than the Torker, simply from a design standpoint. The Offy manifold is a little bit more up to date in airflow characteristics.

Nitrous 455
I ran a 455 with nitrous in a 1971 Cutlass. The engine was a PAW kit with 10.5:1 forged pistons, stock heads, and a relatively mild cam. The intake was a long-out-of-production Edelbrock dual-plane low-rise dual quad setup with two 500 cfm Carter AFBs. The engine had Kenne-Bell headers. This ran through B&M TH-400 with a Kenne-Bell switch-pitch torque converter setup and into a Type O 12 bolt with 3.42:1 gears.

At my one and only trip to LA County Raceway, the car (on 10" slicks and with open exhaust) ran a best of 13.5 without the nitrous and 11.95 @ 115.5 mph with the nitrous. I used the nitrous right off the line, and with the slicks and the 3.42s, the car would still bog due to insufficient rear gear. I suspect that I could have put it into the low 11s or high 10s with proper tuning and 4.11s. See the car in the Oct. 1985 Car Craft (stuck way in the back with a single page b&w feature).

[ Thanks to Joe Padavano for this information ]

Cheap High Compression 455
Buy TRW forged Chevrolet 396 +.060 pistons. The bore is 4.155 perfect for your +.030 455 Olds. Piston height is like +.020 more than Olds, which will give you 0 deck or there abouts. The Olds connecting rod wrist pins will have to be reamed out (like $20). The good part is the Chevy pistons sell for $220 or so. A machine shop will mill off the big domes for $50 or so. Doing this you can get around 11.5:1 compression with unmilled heads and a stock type head gasket. Compare the $290 price tag with a set of $600 custom flat tops.

[ Thanks to Dave Brode, Ken Rotten for this information. ]


Rebuilding

General
I think new bearings, oil pump, gaskets, timing gears, timing chain, and a head job are mandatory if the engine has many miles (you didn't mention how many this motor has). If the crank and rods don't have any signs of damage then leave them alone. I would replace all the lifters and any damaged or suspect pushrods, rockers, and bridges. The deeper and more vital the part is in the motor, the greater the incentive to replace it now.

Because of the high cost of Oldsmobile pistons the big question is to bore or not to bore. You will not be able to answer that until you have the engine tore down and have a good machine shop measure the bores. Of course good machine shops want you to bore if there is much wear at all. For one thing they know that an engine they bore should seal tighter and last longer than a honed one. This makes them look good. It's also my understanding that the oval shape of a worn bore causes stress on the rings causing them to break earlier. In addition the wear on the piston sides and the bore are cumulative so worn pistons in a worn hole may clatter more and break skirts.

Block
When you have the block bored, try to find a shop that has a torque plate for an Olds motor (but don't be surprised if you can't find one). A torque plate is a thick (about 2") chunk of cast iron which is intended to look like a cylinder head with holes where the cylinders are. This plate is bolted to the block and torqued prior to boring the block to mimic the distortions in the cylinder walls when the real heads are installed. This ensures that the cylinders will be as close to round as possible in the assembled motor. Again, this is not mandatory, and I'll be surprised if you can find a shop with such a plate for an Olds.

Do a good job of deburring the block, paying particular attention to eliminating stress risers. In addition (since this is what I was doing earlier this evening), enlarge and clean up the four oil drain back holes at the top corners of the valley. These pass through the deck surface and connect with the drain back holes in the lower corners of the heads. I found that the ones in my block were close to half their intended diameter due to mismatches in the drilled holes.

Block cleanliness cannot be stressed enough. Clean the block and components thoroughly before assembly.

Use a high volume oil pump and a Toro pan if you can find one. Get a heavy duty oil pump drive shaft from Chris Witt. (US$10)

Cam
Cam technology has come a long way since the 70s. Due to the poor exhaust ports on Olds motors, dual pattern cams are preferred. I suspect that Mondello has some of the best. I'd call his shop for a recommendation with your particular setup. I selected the 20-22 for my 69 442 (455 with stock converter and A/C), probably on the conservative side for me, but this will be a driver. Use a roller timing chain.

Beside boring the next toughest question will be what cam to use. Unless yours is in really good shape you will want a new one. Modern grinds are said to be much superior to the old ones but beware of cams that make big power by ruining your idle. The best cam depends on the gearing, torque convertor, intake, heads, pistons, driving style, and so many other things it's tough to figure out exactly what you need. I have always had too much cam in my Olds engines so I'm leaning toward a mild one this time. Lack of power for brakes, idling at 1500, and lurching when you put it into gear are not cool for a daily driver. Get lots of opinions for the people who have actually built Oldsmobiles and drive them. Supercars Unlimited can help you out and Mondello's probably will too.

Exhaust
I'm also a big fan of headers (unlike others on the list), but I suspect that W and Z manifolds will come close without the hassles. Use an HEI if it fits, or a stock distributor with an electronic conversion if it doesn't. I'll take a properly set-up Q-jet over a Holley any day, with a Carter as second choice.

Heads
The heads will provide the greatest performance improvement; if you can at all afford it, get the heads ported. At a minimum go with the big valves.

If I wanted to do the heads I would have a shop grind the A.I.R. bumps down, debur the runners, and polish the exhaust ports. Anything more than that requires someone who knows exactly what they are doing and a flow bench. The FAQ talks about working the oil flow area on the heads to help get the vital juice back where it belongs and I think this is a good idea even though I haven't done it (yet).

Intake
I'll always use a two plane intake for the street, either the original or a Performer. Stay away from the Torker or other single plane units (despite what Car Craft says).

Pistons
Most aftermarket pistons for big block Olds motors carry a compression rating based on a 72cc combustion chamber and a thin, OEM style head gasket. Most big block heads run combustion chambers closer to 80 cc, and as you've pointed out, the aftermarket head gaskets run thicker than stock. Taken together, these effects tend to drop the compression ratio about a point from the advertised rating.

A 10.5:1 piston will really yield about 9.5:1 as installed, if you don't mill the heads or use thin gaskets. Obviously this is a generality, and you should run the numbers with actual measurements on your specific parts if you want to hit a certain compression ratio precisely, however I've found that just assembling this combo is more than adequate for a street-driven motor (I'm doing just that right now).

If the machine shop says you're within tolerances for a hone only and you do not plan on putting on high mileage (just hard miles) then skip the pistons. If you need to bore then remember that forged pistons are not much more expensive than cast for an Olds and they are superior (stronger and better heat dissipation).

Since you're changing the pistons, I strongly recommend balancing the reciprocating components. Use forged pistons.

[ Thanks to Cliff Simpson, Joe Padavano for this information. ]


Tuning / Power Boost



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Submit corrections and additions to this information to The Olds FAQ Compiler.

Cams

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Cooling

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Differential Gears

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Exhaust

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Heads

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Induction

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Ignition

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Oiling

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Redline

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Short Block

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Transmission, Torque Convertor

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Valvetrain

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