Swapping

* Brakes
* Differentials
* Engines
* Exhaust Manifolds
* Heads
* Steering Boxes
* Suspension
* Transmissions

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



Brakes

[ Notice: ]This information is contained in the Brakes section.
[ Notice: ]Please see the Steering section as well!
[ Notice: ]Please see the Suspension section as well!


Differentials

[ Notice: ]This information is contained in the Differential Swapping section.


Engines

[ Notice: ]Please refer to the Engines section as well!
[ Notice: ]Please refer to the Automatic and Manual Transmission Swapping sections as well!

General

The big and small block Olds motors use identical mounting provisions, so you should be able to simply bolt the 330 motor mounts to the 455 and drop it right in. In addition, the 455 is externally identical to the 400 used on the 1965 to 1967 442s.

Assuming the car [or other Olds] already has an Olds V-8, and you are not changing the accessories (e.g. using the late model power steering pump), you don't need any of the accessory mounting hardware from the 455. The big and small block accessory mounts of that era are all the same and all the blocks and heads have the same holes drilled and tapped. All you have to do is install the longer belts required of the big block because of the higher deck height.

Most of the Olds brackets either have two sets of holes or will fit either block, but you certainly want to get as much as you can from the donor car. You certainly need the 455 exhaust manifolds (unless you plan to use headers), but you need the correct ones for an A-body (for example, Toronado manifolds won't work).

The transmission will also bolt up. As noted above, the block mounting locations should be the same. This puts the motor in the same location, so the transmission bolts right up. The bellhousing bolt pattern is also the same. Note that the 455 uses the newer-style flywheel bolt pattern, so you will need the flexplate or flywheel for a 455. With 400 CID or more, the car probably already has a TH-400. Ignore that if you have a 4-spd, as it will certainly bolt up, assuming your 455 crank is drilled for the pilot bearing.

You may require some fabrication for your throttle linkage, depending on your choice of carb. Also, you may have clearance problems with the PB booster. Get the A body valve covers which have the "notch" for clearance. This may also be a problem with the A/C unit, if your car is so equipped.

[ Thanks to Joe Padavano, Bob Handren, Doug Ahern for this information ]

Big Block to Big Block

This entails swapping an Olds 400, 425 or 455 big block in place of the existing Olds 400, 425 or 455 big block.

[ Thanks to for this information ]

Small Block to Big Block

This entails swapping an Olds 400, 425 or 455 big block in place of the existing Olds 260, 307, 330, 350 or 403 small block.

Un-bolt the 350, remove the 350 motor mounts, install 455 motor mounts, and then in-bolt the 455. Everything fits, and when you're done, if you keep the 350 decals, no one short of an Olds expert will notice the difference.

If you have a 350 and want to change to a 400, 425 or 455 you can use the 350 motor mounts, only drawback is the engine will set at least 1 inch higher than normal. The other option is to use 400, 425 or 455 frame mounts with the matching motor mounts and the engine will set normal. You will not need to drill holes for the BB frame mounts. They are direct bolt in. The 350 mounts only pose a problem with hood to aircleaner clearance. If you run a stock intake, no problem. If you use a Torqer or Performer than you may have trouble

455s fit nicely into Cutlass' designed for small blocks. The clearance problems are minor. One note: you won't be able to bolt on headers to a big block in that chassis without cutting through the wheel wells and affecting turn radius. Headers on small blocks don't have this problem.

The other modification you should consider is a bigger radiator. Get one as large as you can find, with as many rows as you can find. Order the largest 4-row core you can get out of an 88 or 98 with all the options. You will need to modify the top and bottom brackets on the core support to accept the wider tanks on this unit.

[ Thanks to Joe Padavano, Bob Handren, Doug Ahern, Cliff Feiler, Mark Prince for this information ]

Small Block to Small Block

This entails swapping an Olds 260, 307, 330, 350 or 403 small block in place of the existing Olds small block.

Externally all Olds small blocks are identical. The carb may have to be modified to work with the extra cubes, however. And you'll have to keep the computer-controlled distributor, assuming you want to keep the computer. All Olds distributors will fit into any Olds block.

The 330 water pump shaft is shorter than the 350, so the pulleys wouldn't line up. To solve the problem, I purchased a 350 water pump and installed that.

[ Thanks to Bob Barry, Rob Turner for this information ]

Diesel to Big Block/Small Block

This entails swapping a an Olds big block (400, 425, 455) or small block (260, 307, 330, 350, 403) in place of the existing Olds 260 or 350 diesel engine. It would also apply to swapping in place of an Olds 263 V-6 diesel engine.

One list member has experience installing a number of 350s, 455s, and one 403 in place of Olds diesels. He used all the accessories that originated on the diesel cars. Never had a water pump problem (probably luck), and discovered that the accessory brackets were the same by the useful imperial method of using them.

On a 1979 Cutlass that originally had a 260 diesel, the hood wouldn't close after installing a 455. Changing to a set of 455 motor mounts solved the problem. There was never any trouble with any of the full size cars, regardless of the engine that was being used.

The only engine parts that will not work on the gasoline engine is the cable between the throttle pedal and the carb. You need to get the gasoline one, replacing the diesel cableit. The diesel cable is a different length. Diesel engines are shut off by closing a fuel valve. The wire to the fuel shut off valve has the same end fitting as required with the spark ignition system. Only the wire is longer, so you coil it up, attach the end, and go. The glow plug wiring is not used with the gasoline engine.

[ Thanks to Cliff Feiler for this information ]

GM V-8 to Olds Big/Small Block

This entails swapping a an Olds big block (400, 425, 455) or small block (260, 307, 330, 350, 403) in place of the existing Buick, Pontiac, Cadillac or Chevy engine.

You need the motor mounts and accessories from an Olds powered car.

Using the mounts from a 6.6 liter (403-Olds) powered T/A, and you can have any Olds engine of your wish in a second-generation Firebird or Camaro. Come to think of it, given the fact that X-bodies used 350's, pickups came with diesels, and the large FWD cars at GM were pioneered by Olds, is there any body style that you can't swap an Olds engine into?

[ Thanks to Bob Barry for this information ]

GM L6, V-6 to Olds Big/Small Block

This entails swapping a an Olds big block (400, 425, 455) or small block (260, 307, 330, 350, 403) in place of the existing Buick, Pontiac, Chevy engine L6 or V-6 engine.

You need the motor mounts and accessories from an Olds powered car. Front springs also need replacing depending upon the amount of front end droop that the car is now experiencing from the added weight.

[ Thanks to Bob Barry for this information ]

A/C Brackets

Since all the A/C stuff bolts mostly to the heads, and the dimensions are the same, then the A/C brackets should be the same.

The A/C brackets rarely line up with aftermarket manifolds. This is a very common problem. What you have to end up doing is to notch out the section of the bracket where the bolt goes through on the top of the manifold. You literally have to cut the bracket so the bolt hole is a "U" shaped notch. This will allow a bolt and flat washer to allow you to clamp the top of the bracket down. It won't be original anymore of course, but then, an aftermarket intake isn't anyway.

When A/C brackets don't line up, it usually means soneone has cut (milled) the heads. If the intake is not cut to match, you will develop this problem.

The newer R4 compressor was never offered on a big block, so that bracket is unique. You'll need to find a 455's A/C setup to get the proper brackets for your application.

[ Thanks to Jim Chermack, Steve Kenny, Charley Buehner, for this information ]

Accessories

Get the accessory brackets that go with the 455 also, as the big block is about an inch taller and 1½" wider than the small block. Alternator will bolt up, but you may have a problem with the old style PS pump. Alternatives are get a newer style pump (as in from the donor car) or get brackets from a 1965 to 1967 400 or 425. If you do change to the later model power steering pump, add A/C, etc., then you do need to switch entirely to the setup on the 455 donor.

You have to watch the AC bottom brace (long straight piece.) You have to change holes when fitting it to an Olds big block. Belts must of course be changed due to the width expansion when going from a small block to a big block.

All Olds engine blocks are drilled and tapped at the same points, small block and big block. As long as you use all the same pulleys, brackets, etc. from the small block, all that needs to be changed are the belts.

Now, if you decide to mix the pulleys and brackets, while the pulley grooves will line up (as far as I know anyway) you can easily run into problems trying to run, for instance, the '70 power steering pump with the later model brackets/pulleys.

Far and away the easiest method is to transfer all the pulleys, brackets, accessories, etc. already in the car to the new engine. There might be a problem with the water pump. Again, keep the one you have in the car already - after swapping it for a rebuilt one of course!

Your only concern would be an accessory bracket that bolted to both the head and the water pump.

Both big and small block use the same brackets for the PS pump. The P/S brackets bolt to the side of the block and to the timing cover area, and again, that area being the same dimensions for big and little Olds V-8s, it should work (save for using the other hole on the side bracket that bolts to the head).

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

Alternator Brackets

The alternator position on Olds cars varied depending on whether it had A/C or not.

[ Thanks to Bob Barry for this information ]

Belts

The only REAL difference between the exterior configuration of the small block and the big block is the deck height. Which means the big block is a little wider, requiring longer A/C and alterator belts, and a tad taller.

[ Thanks to for this informatiton ]

Brakes

Be sure to upgrade the brakes and suspension at the same time. The 1969 to 1972 disc brakes are a bolt-on. Aftermarket kits are available with even larger brakes (and price tags!).

[ Thanks to Joe Padavano, Bob Handren, Doug Ahern for this information ]

Crankshaft

If you want a 4-spd, the bellhousing and original trans should bolt up. Just get the correct flywheel as noted above. Also, if the engine was not from a manual trans car originally, it will likely not have the crank drilled for the pilot bearing.

[ Thanks to Joe Padavano, Bob Handren, Doug Ahern for this information ]

Drive Shaft

The stock driveshaft will work, unless you are also swapping transmissions. You will likely need a different yolk if swapping transmissions. The Jetaway is shorter than the TH-400. So your original driveshaft will also be too long. You can try to find a correct one (good luck), or just have yours shortened and rebalanced at a driveline shop. The Jetaway is the same length as a TH-350.

[ Thanks to Joe Padavano, Bob Handren, Doug Ahern for this information ]

Engine Bay Clearance

There might be hood clearance problems if you use small block motor mounts with a big block.

[ Thanks to Cliff Feiler for this information ]

Exhaust Manifolds

As for exhaust, I don't recommend using the restrictive manifolds of a small block on a 455, but the passenger side will fit OK with no frame inteference. The drivers side will interfere with the frame. Do not cut the frame to make it work! I've actually seen this done! Crazy.

[ Thanks to Joe Padavano, Bob Handren, Doug Ahern for this information ]

Engine Power

Most 455s are smoggers and have low compression, so you might want to watch for pre 1972 engines. You can run the low compression 455 pistons, and in a light weight 1979 cutlass, they will make lots power.

[ Thanks to Joe Padavano, Bob Handren, Doug Ahern for this information ]

Hood Clearance

Problems with A/C pump clearance under the HOOD might be attributed to using small block motor mounts with a big block.

[ Thanks to for this information ]

Motor Mounts

Small block and big block Olds frame mounts mount in the same position. The difference is in the size of the frame mount. Both BB and SB have two bolt holes on top and on on the bottom. Now this applies to 68-72 A body cars (Cutlass's) as long as you match BB motor mount to BB frame mount and SB motor mount to SB frame mount, no problems will arise.

In order to put a big block in place of a small block, all you need to do is put the small block motor mounts on the big block. The location of the motor mount bolt holes is the same on both motors. True, the factory did use different mounts on the big block. However, the big block will go in with no almost problems so long as you use the corresponding motor mount with the correct frame mount (e.g. small block motor mount with small block frame mount.

All conventional Olds Big and Small block motor mounts will interchange on the blocks, as far as I'm aware. There are six mounting holes (three per side, two used per application) to choose from. In the late 60's, early 70's they had the single bolt going down to the frame mount, somewhere along the line they switched to the crossbolt that runs front to back. I'm not sure when that change took place, or how it relates to BB vs SB.

An easy way to tell is if the engine goes right in and the fan is centered within the fan shroud then the motor mounts and frame mounts are correct. Note that there is a difference between big block and small block motor mounts.

Confused? Call 1-800-442-PART or see Oldsparts.com for the Correct big and small block motor mounts and frame pads.

The Delta 88 & 98 frame pads are the same as Cutlasses from '71 to '76.

The 350 part number is 404752 and fits 69 to 72 cutlass. The 455 part number is 402953 and fits 69 to 72 400-455 cutlass. A giveaway to the difference is that 2 different motor mounts are used so there has to be 2 frame mounting brackets were used. A big block can be installed in place of a small block, but only if the small block mounts are used and the big block will set about an inch lower, usually causing interferance with the fan shroud.

A frame is sagged a little when the holes for the motor mounts don't line up perfectly with the holes in the frame mounts. The holes might overlap just enough to stick the tip of a pencil in.

One solution is to loosen the two bolts holding the mount to the block, slip the bolt through the frame mount and motor mount, and then tighten the motor mount bolts.

This problem seems to be caused by frame sagging. Believe it or not these cars were not designed to hold 455s (as evidenced by the spark plug next to the A/C box). After 30 or so years of holding up the engine weight the frame will sag just a bit.

[ Thanks to Scott Jerdan, for this information ]

Power Steering Brackets

The power steering pump brackets are identical (same part number). The brace that goes to the exhaust manifold bolt has both holes drilled in it already; simple line up the correct hole at installation.

The difference is in the small "link" bracket which bolts to the PS bracket and then to the front bolt of the exhaust manifold. This bracket has two holes, one for the small block and one for the big block. The use of headers won't matter, as I've installed this bracket on several big and small block Olds motors with headers before.

The other thing which you should look out for is the small spacer which goes between the bracket and the block. This spacer is about ¾" thick and goes between the PS bracket and the drivers side of the engine block, under the bottom-most bolt. Note that there is also a tubular spacer between the PS bracket and the stud which passes through the front cover. If either or both of these spacers is missing, the bracket will not fit properly.

As most people here know, there are two styles of PS pumps, the 67 and earlier large reservoir pump and the 68 and up small pump. The early pumps were mounted high above the driver-side head (except on the Toro), and the brackets bolt only to the head and intake manifold (thus making them independent of engine deck height). The parts book lists only one set of brackets for all 66-67 V-8 engines. I'm assuming from the drawings that 64-65 are the same also, but as I noted above, the book doesn't go back that far. The bracket is a two-piece affair, with the front bracket bolting to the front of the pump and picking up fasteners on the end of the head and the front exhaust manifold bolt. The rear part of the bracket bolts to the rear of the pump and the front bracket and picks up the head bolt over the first exhaust port (that bolt must have the threaded stud coming up off of it) and a tapped hole on the intake manifold.

The 68 and up configuration mounts the PS pump low on the driver's side and uses a three-part bracket. Again, the parts book only lists one set of brackets for all V-8s. The front piece is called a link, but is the bracket which bolts to the front of the pump and has the curved adjusting slot. This piece picks up a stud on one of the water pump bolts. The rear bracket (imaginatively called a bracket) bolts to the back of the pump and the front link bracket. This rear bracket picks up a stud on the timing cover bolt (second from the bottom on the driver's side) and the front-most tapped hole on the vertical side of the block. This latter may be used for the engine mount attachment in some chassis configurations also. In all cases, a tubular spacer about ¾ inch long is used between the bracket and the block.

Since all of these mounting points so far are on the block, the relationship between them is the same for either deck height. It is the third bracket (this one is referred to as a brace) which is the problem. This brace has a hole at the front end which attaches to the front link bracket and two holes at the back end, one of which will line up with the front most exhaust manifold bolt hole. The factory service manual indicates that the lower of these two holes is to be used for small block Olds motors, and the upper hole for big blocks.

There you have it. Both big and small block use the same brackets for the PS pump.

The bracket will fit with headers, there are no differences at the bolt holes. Just get a longer bolt, about 1" will do.

The PS pump will work without the bracket, but you should use it if you can for extra rigidity. Always remember, GM looked at things like this: a part left out needs no maintenance and can cause no warranty problems. So if GM thought it was needed, it was in there. If you don't use it, there is a potential for pulley misalignment when you tighten the belt. An Olds V-8 PS bracket from virtually any car should work. They have 2 bolt holes in them and you use whichever lines up with the header depending if it's a small or big block. Just remember to shim the bracket against the header flange because the exhaust manifold flanges are somewhat thicker than the header flange.

The power steering pump is mounted high on the non-A/C 400's and 425's before 1968. 1968 and after, the PS pump is mounted low.

[ Thanks to Joe Padavano, Paul Rousseau, Mike Rothe, Bob Barry for this information ]

Radiator

One potential problem is the radiator. I've never owned a 64, but I seem to recall that 1964's used downflow radiators (tanks on top and bottom of core), while 1965-up used crossflow radiators (tanks on sides). If your car has the latter, get the largest 4-row core Delta 88 or 98 radiator you can find. If you have a downflow, you will either need to fabricate mounts for the crossflow, or have your original radiator modified for a thicker core.

[ Thanks to Joe Padavano, Bob Handren, Doug Ahern for this information ]

Suspension

Be sure to upgrade the brakes and suspension at the same time. The 1969 to 1972 disc brakes are a bolt-on. Aftermarket kits are available with even larger brakes (and price tags!). Similarly, add 442 anti-sway bars as a minimum, or if money permits, step up to the larger units from such places as HO Racing or Global West Alignment. You will likely not need new springs unless yours are weak, as the difference in weight between the two motors is less than 100 lbs.

If you want a 455, I don't think weight should be a factor as they are all about the same. Are you going to be drag racing, or is this going to be a street machine? If its street machine, any of the 455's will do. You can get hi-po parts for them if you are doing basic street engine rebuilds or hi-perf. bolt ons. All make lots of power and have good low-end torque.

An Old big block does not weigh much more than a small block. You do not HAVE to change springs at this time. But, the added weight will take its toll eventually.

Make sure your Cutlass's sunspension is up to snuff for whatever engine duties and applications it will see. If your Cutlass was originally a V-6, a 455 will add at least 225 lbs directly over the front wheels, not to mention weight increases if you switch to a TH-400. You might want to consider a TH-350 if this is going to be a street car, or if you are planning to stay under 350hp. They are lighter, deplete less hps, and can be built to hold up (upwards of 500-600 hp!!).

[ Thanks to Joe Padavano, Bob Handren, Doug Ahern, Mike Rothe for this information ]

Transmission

Be sure to get a short tailshaft version for a Cutlass. The transmission should bolt in, as the frame should have two sets of crossmember bolt holes.

As for the TH-350 mount, the crossmember will stay the same unless you change to a TH-400. With the TH-400 the rubber mount is different, so you will have to buy one and move the crossmember backwards to the second set of holes. It is pretty easy to do.

Transmissions come in two flavors (ignoring the B-O-P vs. Chevy bolt pattern on the bellhousing), long and short tailshaft. The short version is used on the A-body cars, while the long version is used on the full-size cars. You will need the short version. In addition, the TH-400 is longer overall than the TH-350, so you will need the correct driveshaft as well (or you will have to have yours shortened). I seem to recall that the front yoke on the driveshaft is different between the TH-400 and TH-350, so you definitely want the right driveshaft.

[ Thanks to Joe Padavano, Bob Handren, Doug Ahern, Mark Prince for this information ]

Water Pump

Water pump lengths are different, so you would have to be careful here. Just make sure you have the correct water pump (dimension from mounting surface to pulley flange is different between A/C and non-A/C applications).

[ Thanks to Mike Rothe, Joe Padavano for this information ]


Exhaust Manifolds

[ Notice: ]Please refer to the Exhaust Manifolds section as well!

As for using big block exhaust manifolds on a small block, the right side big block manifold will hit the oil filter adapter. On the left, the manifold might hit the starter (standard A-body manifolds).

I can attest to the fact that a big-block dual-exhaust RH manifold will NOT fit on a small-block, due to the interference between the exhaust manifold and the oil filter mount. The good big block dual-exhaust manifolds don't clear the oil-filter housing (at least they didn't on my 403; maybe certain configurations would, or they would with a custom remote oil-filter hose adapter on the block).

And the big block LH manifold hits the starter!

The crossover pipe will be different between a SB and BB on account of the fact that the BB's heads are about an inch or two higher and farther apart than are the SB's. Bolt pattern is the same, and 403/455 port size is close enough to not worry about. So, put 'em on, then get a crossover from a SB car that fits the manifolds' holes; an early 403 application; or maybe an older 350 application. If you HAVE to, you can weld the correct size manifold flare onto a crossover which is bent to fit correctly.

As for the J pipe, if you are talking earlier BB exhaust manifolds, you might find that the RH outlet, like where your present J pipe connects, is at quite a different location and angle. The later, three-bolt flanges point about straight down, whereas, the earlier exhaust manifolds exit down and back about 45 degrees, and has a 2-bolt flange. In which case, just get the headpipe from a similar bodied car that did use those exhaust manifolds, or have one custom bent.

The Toro exhaust manifolds would bolt on to any Olds head, but since they point up and back, the only practical use for them is in a Toro, or maybe a boat or tractor installation. What you want is Cutlass-body exhaust manifolds, like the ever popular W-Z pair, or an X-Y pair.

Small-block manifolds would fit on the big-block, but there would be no advantage to that; smaller ports, and the outlets are in slightly different positions. The fit is close though. In fact, a number of single-exhaust 455 applications used small block exhaust manifolds, so the big-block manifolds that will give you an advantage won't fit, and the ones that will fit won't give you any advantages.


Heads

[ Notice: ]Please refer to the Heads section as well!

Yeah, you could bolt them on, but what do you hope to gain by putting a head with an 80cc combustion chamber (BB) onto and engine that thrives on heads with 65cc chambers (SB)? What would that do to your compression? Not to mention the larger ports and valves would enhance WOT performance at the expense of low-rpm response. I.e., if you wanted an all-out, race, on-or-off type engine, that MIGHT work. Otherwise, keep your SB parts on a SB and BB parts on a BB. There's also the intake port size at the head/intake interface discrepancy.


Steering

[ Notice: ]This information is contained in the Steering section.
[ Notice: ]Please see the Suspension section as well!
[ Notice: ]Please see the Brakes section as well!


Suspension

[ Notice: ]This information is contained in the Suspension section.
[ Notice: ]Please see the Brakes section as well!
[ Notice: ]Please see the Steering section as well!


Transmissions

[ Notice: ]This information is contained in the Automatic and Manual Transmission Swapping sections.



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