[Consumerwh0re]

Hey guys

I've been thinking about picking up a 69 LeMans which according to the owner currently has a 400 olds. Unfortunately I don't know much about them or even if its worth going for from a performance point of view.

So, is this engine worth spending time on? If so are there any specific things I should be looking for?

Much appreciated

[Valkyrie5.7]

Originally Posted by Wikipedia

The 400-cubic-inch (6.6 L) version was the second tall-deck "big-block" Olds. Two distinct versions of the 400 CID engine were made:

- 1965 through 1967 Early 400's used a slightly over-square 4.000 in (101.6 mm) bore and 3.975 in (101.0 mm) stroke. All the pre-1968 engines used a forged steel crankshaft.

- 1968 and 1969 400's shared the Olds big-block standard 4.25 in (108 mm) stroke with the 455 but used a very undersquare 3.87 in (98 mm) bore to comply with GM's displacement restrictions in the A-body cars and reduce tooling costs.

This later 400 is considered by many enthusiasts to be less desirable because of the powerband characteristics induced by this exceedingly undersquare format, and the fact that the crankshafts were now made of less durable cast iron material.

Early 400's used the same forged steel crankshaft as the 425's, while the Later 400's used the same cast iron crankshaft of the 455's, with rare exception- some 1968 and later Olds 400/455's were produced with forged steel crankshafts. These rare cranks can be readily spotted by the "J" shaped notch in the OD of the rear flange; cast iron cranks have a "C" shaped notch. All 1965 through 1969 Olds 400's were painted bronze.

I wasn't completely familiar with the Olds 400, so I searched wikipedia for this info. Basically, the 65-67 motor sounds like a decent platform for a build. The 68-69 motors having less than a 4" bore with the 455 stroke sounds like something right out of the 366 BBC smogger playbook. I'd say it's not worth your time.

[cobalt327]

I had a '68- nothing to build on, but good enough in stock form to pull its weight.

More on ID'ing what you have HERE.

Good luck- maybe it's a 455!

[handymann3]

I know your not gunna wanna hear it but your better off going to realoldspower. com. I am not taking anything away from hotrodders but the only thing the guys at ROP do, is work on these engines LOL. They will be able to tell you EVERYTHING you need to know. I have heard good things about these engines though.

[cobalt327]

Originally Posted by handymann3

I know your not gunna wanna hear it but your better off going to realoldspower. com. I am not taking anything away from hotrodders but the only thing the guys at ROP do, is work on these engines LOL. They will be able to tell you EVERYTHING you need to know. I have heard good things about these engines though.

Good things about the '68-69' Olds 400's?

[handymann3]

sorry, I have read good builds on them is what I ment. I dont have one so I never really bothered to look into them, but when I stumble apon a olds 400 build they seem to push fairly good numbers. Thats just me though.

[Valkyrie5.7]

Originally Posted by handymann3

sorry, I have read good builds on them is what I ment. I dont have one so I never really bothered to look into them, but when I stumble apon a olds 400 build they seem to push fairly good numbers. Thats just me though.

As I stated earlier, there's two completely distinct Oldsmobile 400 engines. One that would make a great platform for a build and one that I think would be a waste of money to put performance parts in. If you've seen some healthy 400's I'd put my money on them being of the 65-67 persuasion.

[joe_padavano]

What everyone else said. The 65-67 400 motors have the forged short stroke crank from the 425 and can be made into screamers. The 68-69 motors used the cast long stroke crank from the 455 and are not Oldsmobile's best effort. These motors have about the worst bore/stroke ratio of any modern V8. In any case, pretty much any external parts (headers, intake, etc.) that fit a 455 will also fit either 400 motor. One thing to be aware of with the early 400s is that there was some variability in lifter diameter and lifter bank angle. Most Olds motors use the common 0.842" lifters. Some motors in the mid-1960s used the 0.921" lifters. These are somewhat more difficult to find (at least at a decent price). The lifter bank angle is a bigger problem, since obviously the cam must match the bank angle. Most Olds motors (and nearly all aftermarket cams for them) use the 39 deg bank angle. Again, some mid-60s motors used a 45 deg bank angle. You can get cams for this, but you need to specify it up front.

One last thing. There is actually a third "Olds" 400 motor. In the 1975 model year, the full size Olds cars actually used a Pontiac-sourced 400 motor as an option. Many people are confused by this and call it an Olds motor. Be certain of what you have.