400 vs. 455 differences

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Old Jun 17, 2022 | 11:46 AM
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400 vs. 455 differences

I'm considering buying a 67 Cutlass 442 that would need full restoration. The seller has 2 blocks, both would have to be gone through. I know 67's came with the 400 but see a lot of them have had 455 installed. I've heard the 400's have a higher rev limit and I assume less HP but is there a benefit either way?
thanks,
Steve
Old Jun 17, 2022 | 11:57 AM
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Parts for the 455 will be easier to find and cheaper.
Old Jun 17, 2022 | 12:08 PM
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If the 400 is original to the car that would be my choice.

Which 400 an E block or a G block? Look at the #'s next to the oil fill pipe. What letter heads are on them?

455 will likely make more power for less $$$ as long as it isn't a late smog engine that would require extensive work.

Good luck!!!
Old Jun 17, 2022 | 12:10 PM
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The E-block 400 motor used in the 1966-67 cars used a 4.000" bore and a 3.980" stroke. The crank was forged (and was the same one used in the 425 motors). The 455s used a 4.125" bore and a 4.250" stroke. With very, VERY few exceptions in the 1968 model year, all 455 cranks were cast. The longer stroke, cast vs. forged crank, and heavier reciprocating mass all conspire to limit the RPM of the 455. Note that the 1968-69 G-block 400 used the same same cast crank and 4.250" stroke as the 455. To stay under GM's 400 cu in limit in A-body cars, Olds reduced the bore in the G-block motors to 3.890". This grossly undersquare design is one reason why the G-block motors are not well thought of, but obviously that doesn't apply to the 1967 motor (assuming it has an original E-block).

Externally, all big block Olds motors are identical. All take the same manifolds, brackets, distributor, timing chain, oil pump and pan, etc, etc.
Old Jun 17, 2022 | 01:11 PM
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In addition to what Joe posted above, the 400E and 425 use 7" long rods whereas the 400G and 455 use 6.7" long rods.
Old Jun 17, 2022 | 01:22 PM
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If the 400 is an E-block you should go for that, especially if it's original to the car. If it's a '68-9 G-block, you might as well get the 455 and enjoy the extra displacement, all other things being equal, of course.
Old Jun 17, 2022 | 01:32 PM
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Originally Posted by Fun71
In addition to what Joe posted above, the 400E and 425 use 7" long rods whereas the 400G and 455 use 6.7" long rods.
And different compression height as a result.
Old Jun 17, 2022 | 01:42 PM
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1966 and 1967 400s and 425s are Oldsmobiles best engine's. They are better than any 455. Cost effectiveness is not part of the equation.

1968 and 1969 400s are the worst of the big blocks. Any 455 should be considered above them unless it's a numbers matching concern.

455s are the easiest route across the board.

Old Jun 17, 2022 | 02:15 PM
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The 67 400E I put in my 64 F-85 Club Coupe was a sweet motor. I loved it. Go for it. CutlassEFI-Mark has some good stuff for the early 400's I would bet it would not cost a whole lot more to build a 400E. They do rev!
Old Jun 17, 2022 | 04:35 PM
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Originally Posted by therobski
I would bet it would not cost a whole lot more to build a 400E.
Agreed, the only real difference would be the pistons and maybe the lifters if it's a .921" lifter bore block. Other than that, everything is the same as any other Olds big block.
Old Jun 17, 2022 | 04:49 PM
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If it's an E block 400, use it. If it's a G, go for a 455. Engines do not numbers match in 67 and very few people have the protectoplate, so there is less concern about it being the original block. Do not put a G block 400 in there.

Everyone put 455s since they are plentiful since they were in a lot of cars from 68-76 or so, versus the E 400, which was only in 2 years of 442s and the few Turnpike Cruisers.
Old Jun 18, 2022 | 05:58 AM
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Originally Posted by Phoenix8990
I've heard the 400's have a higher rev limit
Just to touch on this statement for a minute, the max RPM is irrelevant unless it matches the gearing, trans, and how you plan to use the car. The classic example of this is the original Honda S2000. 9000 RPM limit, but the engine only made power between 8000 and 9000 RPM. Do you REALLY want to drive that way on the street? Interestingly, after a couple of years Honda redesigned the engine to move the power band down a lot. Funny thing about that.

As far as RPM vs HP, it all boils down to how much air the engine moves, which directly related to HP. At 5,000 RPM, a 455 cu in engine moves about 660 CFM. A 400 cu in engine needs to rev to 5,200 RPM to move the same amount of air. A 350 needs to rev to 6,500 RPM. Assuming all else is equal, those three different engines should produce about the same HP at those RPM levels. Of course, all else is never equal. Even assuming the same cam, same timing, same carb, the manifold geometry, internal friction, etc, will be different in each.
Old Jun 18, 2022 | 07:13 AM
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Thank you all for the info. Always glad to know a bit more about Olds.
Steve
Old Jun 18, 2022 | 08:09 AM
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I raced a 1967 4 speed W30 car (E block) and never had any oiling problems or bearing problems going to 6200 routinely with the stock oil pump. On the other side I have seen many of the 1968 and newer 400 and 455 motors with spun rod bearings! Yes, the Olds connecting rods are "soft" and the big end will go out of round over time but built with adequate bearing clearance they will live just fine; or use aftermarket rods if desired.
Old Feb 24, 2025 | 03:54 PM
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Joe, in this thread you say that ‘externally , all big block Olds motors are identical. All take the same manifolds, brackets, distributor, timing chain, oil pump and pan, etc, etc, etc’.
Two questions, is the water pump body/mounting the same as a 400? Is/are the a/c mounting bracket(s) the same?
Where I’m going with this…..it has to do with me trying to ad AC to my 66 442 E bloc. Car wasn’t built with AC. Companies like March make front engine kits with p/s pump, alt, ac compressor, brackets, pulleys, belts for 350’s and 455’s . If what you say is true, would those kits work on a 400? The only unknown for me is if the water pumps and damper are an issue.
I posed this question on another thread this morning. I’m thinking I should have sent this in a pm.

Tom
Old Feb 24, 2025 | 06:33 PM
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Originally Posted by TOC
Joe, in this thread you say that ‘externally , all big block Olds motors are identical. All take the same manifolds, brackets, distributor, timing chain, oil pump and pan, etc, etc, etc’.
Two questions, is the water pump body/mounting the same as a 400? Is/are the a/c mounting bracket(s) the same?
Where I’m going with this…..it has to do with me trying to ad AC to my 66 442 E bloc. Car wasn’t built with AC. Companies like March make front engine kits with p/s pump, alt, ac compressor, brackets, pulleys, belts for 350’s and 455’s . If what you say is true, would those kits work on a 400? The only unknown for me is if the water pumps and damper are an issue.
I posed this question on another thread this morning. I’m thinking I should have sent this in a pm.

Tom
Tom, all BBO motors of any displacement are dimensionally identical on the outside. As for the water pump mounting, every single second gen Olds V8, from 260 to 455, uses exactly the same front cover. All of the water pumps built for those motors interchange (and yes, even the one-year-only 1964 pump will bolt up). The accessory brackets are specific to year and model, not engine, but all BBO brackets interchange as a set onto any other BBO. Yes, any March kit that fits a 455 also fits a 400 and a 425. Just be aware that there are three different Olds water pump lengths, so you need to use the one that fits the kit.
Old Feb 24, 2025 | 06:39 PM
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Originally Posted by joe_padavano
Tom, all BBO motors of any displacement are dimensionally identical on the outside. As for the water pump mounting, every single second gen Olds V8, from 260 to 455, uses exactly the same front cover. All of the water pumps built for those motors interchange (and yes, even the one-year-only 1964 pump will bolt up). The accessory brackets are specific to year and model, not engine, but all BBO brackets interchange as a set onto any other BBO. Yes, any March kit that fits a 455 also fits a 400 and a 425. Just be aware that there are three different Olds water pump lengths, so you need to use the one that fits the kit.
Toronado 425 uses different intake and exhaust manifolds does it not?
Old Feb 24, 2025 | 06:48 PM
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Originally Posted by ourkid2000
Toronado 425 uses different intake and exhaust manifolds does it not?
Which doesn't change the fact that the hard points where the water pump and accessory brackets bolt up are still in the same place.
Old Feb 24, 2025 | 07:02 PM
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Originally Posted by joe_padavano
Which doesn't change the fact that the hard points where the water pump and accessory brackets bolt up are still in the same place.
Ahh, I see.....so everything still bolts up, I get it sorry
Old Feb 24, 2025 | 07:27 PM
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The Toros had issues due to their aggressive styling and the fwd, so the manifolds and oil pan are different. Bracketry did not change. The issue is 1, using stuff as a system, and 2, not losing any of the spacers.
Old Feb 24, 2025 | 08:47 PM
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Originally Posted by Koda
The Toros had issues due to their aggressive styling and the fwd, so the manifolds and oil pan are different. Bracketry did not change.
Wanna bet? 1966 Toro vs 1966 Delta 88. Note that the Toro PS pump bracket is different and the pump is further outboard and lower to clear the hood. The Toro had room to move the pump because the engine was offset to the passenger side. By the way, the Toro exhaust manifolds are different to clear the transmission.




Last edited by joe_padavano; Feb 24, 2025 at 08:50 PM.
Old Feb 24, 2025 | 08:59 PM
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And before someone points out that the Toro in my photos above has A/C but the Delta does not, here's a 1966 Delta WITH A/C. The alternator isn't even on the same side of the car.



Old Feb 25, 2025 | 10:41 AM
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Are the B bodies and A bodies bracketry the same?
Old Feb 25, 2025 | 12:30 PM
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Originally Posted by Koda
Are the B bodies and A bodies bracketry the same?
Usually but not always. Depends on the year.
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