Early 400 vs 455

Old October 13th, 2018, 10:59 AM
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Early 400 vs 455

I have a 400 and would like to get in the 400-500hp range. I am being told to think about going 455 because of parts are more Accessible. I am not against going with Aluminum heads route
Have seen post on here about using 455 crank in my 400 but could use some advice
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Old October 13th, 2018, 11:07 AM
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The only "less accessible" parts I can think of are lifters (if it's a .921" lifter bore engine) or camshaft (if it's a 45º cam bank angle engine). Both of those are readily available through several vendors on this site, though, as are very good forged pistons.

I think it really depends upon what you want out of an engine. The 455 can make monstrous torque at moderate RPM, the 400 can rev much higher.
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Old October 13th, 2018, 12:14 PM
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The 455 will allow you to reach your goal with less effort $$$ but both are capable of making 400 to 500 hp.
Pick up a copy of How to build a Max performance Oldsmobile by Bill T.
Also check out realoldspower
Edelbrock heads are a good investment. Make sure you research who to buy from and who not to, this also goes for machine shops!
There are enough horror posts to lead you to the right sources for parts and machine work.
Take your time and do your home work.
Good Luck

Last edited by Bernhard; October 13th, 2018 at 12:22 PM.
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Old October 13th, 2018, 12:28 PM
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Which 400 do you have? Those blocks are worth money to a stock restorer, whereas a 455 could come in anything and is worth less.
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Old October 13th, 2018, 01:45 PM
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Early 400

Its a 65 400,
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Old October 13th, 2018, 02:22 PM
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Whats the 400 going in?

Here is a link to a 400 E build
https://www.hotrod.com/articles/0906...mobile-engine/
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Old October 13th, 2018, 02:31 PM
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Its going in a 65 cutlass conv it was out of my recently departed 65 442. Its amazing how fast 20 years go really
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Old October 13th, 2018, 02:42 PM
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Welcome to the group... JMO, but I would stay with what you already have and use the 65 400...
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Old October 13th, 2018, 02:52 PM
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Well I am the new owner of 72-76 455 so now I have a choice.
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Old October 13th, 2018, 03:00 PM
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Originally Posted by Mcolabella View Post
Well I am the new owner of 72-76 455 so now I have a choice.
I'm in the same situation. I have a '67 400 and a '72 455, along with a set of 12cc dish 4.057" forged pistons for the 400 and a pair of ported G heads for the 455.

And one more option: use the 400 forged crank and rods in the 455 block for a 425 cid engine. Decisions, decisions.
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Old October 13th, 2018, 03:53 PM
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Did the 400 have the issues with the 39 and 45 degree cam angle and lifter bore size? I thought that was only the 425.
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Old October 13th, 2018, 04:42 PM
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Originally Posted by Fun71 View Post
I'm in the same situation. I have a '67 400 and a '72 455, along with a set of 12cc dish 4.057" forged pistons for the 400 and a pair of ported G heads for the 455.
Why can’t you use the ported G heads on the 400?.
Op- do you want 400 or 500hp? Big difference.
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Old October 13th, 2018, 05:27 PM
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I would like 500 but I think and would be happy with the 400-450 range considering budget. I am really trying to get a direction now
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Old October 13th, 2018, 08:25 PM
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My thought is the 455 will give massive low end torque (maybe too much and cause traction issues?) whereas the 400 will have less torque at low RPM (for fewer traction issues) but have higher peak horsepower RPM. Kinda depends upon what your overall goals are for the car.
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Old October 13th, 2018, 08:29 PM
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Originally Posted by cutlassefi View Post
Why can’t you use the ported G heads on the 400?.
Definitely a possibility, but with the choice of 400, 425, and 455 cubic inches, I'm leaning towards 425 to get the same benefits of short stroke, long rod of the 400 with more displacement. Plus that would mean your new pistons for the 425 vs. the set of 400 pistons on my bench (heavy L2320F with 12cc dishes milled into them).
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Old October 13th, 2018, 09:21 PM
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Originally Posted by Fun71 View Post
Definitely a possibility, but with the choice of 400, 425, and 455 cubic inches, I'm leaning towards 425 to get the same benefits of short stroke, long rod of the 400 with more displacement. Plus that would mean your new pistons for the 425 vs. the set of 400 pistons on my bench (heavy L2320F with 12cc dishes milled into them).
Bernhard wrote:
I would build it once and use light pistons with a modern ring pack. The Mahle piston and ring package looks like a good deal.
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Old October 14th, 2018, 08:24 AM
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Are you cloning your "Cutlass convertible" into a 442? If not, someone with a non 400 B block engined true 442 will pay a decent price for the 400 engine. To make 500 hp will be a lot easier using a 455 engine as a starting point. Jmo
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Old October 14th, 2018, 10:19 AM
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I am not against selling the 400 to someone that could use it, and I am not cloning the car
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Old October 14th, 2018, 10:55 AM
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What Kenny said. 455 is cheaper and probably will get you more, and there's a 442 out there needing an E block 400.
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Old October 14th, 2018, 01:46 PM
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He said it was a 1965 442 400 so it should be a B block, one year only engine. A heads, great flowing heads but a one year only rocker pedestals. They look like there adjustable but are not. I have a set "somewhere."
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Old October 14th, 2018, 01:53 PM
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Originally Posted by Mcolabella View Post
I am not against selling the 400 to someone that could use it, and I am not cloning the car
Could be a tribute car nothing wrong as long as you don't sell it as the real deal.
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Old October 14th, 2018, 01:58 PM
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Originally Posted by Kennybill View Post
He said it was a 1965 442 400 so it should be a B block, one year only engine. A heads, great flowing heads but a one year only rocker pedestals. They look like there adjustable but are not. I have a set "somewhere."
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In Bill's book he said they had the largest ports untouched it would be interesting to see how they flowed compared to the other big block heads.
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Old October 14th, 2018, 02:26 PM
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Originally Posted by Bernhard View Post
Bernhard wrote
In Bill's book he said they had the largest ports untouched it would be interesting to see how they flowed compared to the other big block heads.
They’re all within about 5% of each other. No major difference just cuz they’re bigger.
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Old October 14th, 2018, 03:18 PM
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It is a 400 B block I do still have the A heads also, it was in my sadly departed 65 442. I was just going to use it in my 65 conv to replace the non running 330, but thought I would try and get a little more hp but have been told by several that a 455 might be a better route so I bought a running one yesterday and going to work with that for now
I just dont have the 10,000- 15,000 to do a build with using the olds gurus, but am looking to start gathering parts and may build it myself which I have done before
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Old October 14th, 2018, 04:51 PM
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Originally Posted by Bernhard View Post
Bernhard wrote
In Bill's book he said they had the largest ports untouched it would be interesting to see how they flowed compared to the other big block heads.
I suspect this is due to most of the A heads not having the factory bump where the A.I.R. holes would be drilled. I know people grind those out in other heads, but with rare exceptions the A heads didn't have these bumps to begin with. So factory they would likely flow a little better than other heads.
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Old October 14th, 2018, 04:54 PM
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Originally Posted by Mcolabella View Post
It is a 400 B block I do still have the A heads also, it was in my sadly departed 65 442. I was just going to use it in my 65 conv to replace the non running 330, but thought I would try and get a little more hp but have been told by several that a 455 might be a better route so I bought a running one yesterday and going to work with that for now
I just dont have the 10,000- 15,000 to do a build with using the olds gurus, but am looking to start gathering parts and may build it myself which I have done before
As previously mentioned the B block 400 was only used in the 1965 442. Also one of the A heads would have the application code stamped into the end starting with the letter V, designating 442. If you decide to sell these be sure and post the casting dates for block, heads, and if you have the intake. someone building a 1965 442 needing these parts would likely want casting dates in a range that fit the data plate on their car.
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Old October 15th, 2018, 02:07 AM
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Originally Posted by Mcolabella View Post
It is a 400 B block I do still have the A heads also, it was in my sadly departed 65 442. I was just going to use it in my 65 conv to replace the non running 330, but thought I would try and get a little more hp but have been told by several that a 455 might be a better route so I bought a running one yesterday and going to work with that for now
I just dont have the 10,000- 15,000 to do a build with using the olds gurus, but am looking to start gathering parts and may build it myself which I have done before
If you have a running 455 you could try and build a low dollar engine using cast off parts from others.
If the 400 engine is a runner their is nothing wrong with using that as well.
The best bang for the dollars is a gear set at least 3.42
There is nothing wrong with the small block Olds 330 and good basic engine mods.

Last edited by Bernhard; October 15th, 2018 at 02:10 AM.
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Old October 15th, 2018, 02:11 AM
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Would you mind posting pictures of the 400 B 1965 valve train rockers and studs?
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Old October 15th, 2018, 02:15 AM
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Originally Posted by cutlassefi View Post

They’re all within about 5% of each other. No major difference just cuz they’re bigger.
What does a 5% increase look like in terms of HP increase?
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Old October 15th, 2018, 04:37 AM
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Originally Posted by Bernhard View Post
What does a 5% increase look like in terms of HP increase?
Depends on whether or not you’re using their full capacity to begin with.
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Old October 15th, 2018, 06:28 AM
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Originally Posted by Bernhard View Post
If you have a running 455 you could try and build a low dollar engine using cast off parts from others.
If the 400 engine is a runner their is nothing wrong with using that as well.
The best bang for the dollars is a gear set at least 3.42
There is nothing wrong with the small block Olds 330 and good basic engine mods.
the 330 is currently not running, was told it was blown when I bought the car, have not really messed with it
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Old October 15th, 2018, 07:20 AM
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A shop named Mid-Am Performance or Mid-American Performance use to have a website with the flow numbers of the various Oldsmobile stock heads. As I recall A's were the best flowing. "If" the heads are the "bottleneck" then a plus of 5% could mean 5hp per every 100hp. Aka, 390 hp engine could turn into a 410 hp engine, hypothetically. I bought a 1965 425 (A block) twenty five years ago. It was a perfect running 4 barrel engine "except" previous owner didn't put proper amount of antifreeze and it had a crack in the block, near a freeze plug. The plug was seated perfectly. The heads were big valved and I sold the heads because I wasn't familiar with the pivot setup. As I recall the exhaust ports did not have A.I.R. bumps from the factory. That was always the first thing I use to do back then was grind them off. Anyway that's thoughts on A heads. Jmo
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Old October 15th, 2018, 10:17 AM
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Originally Posted by Kennybill View Post
A shop named Mid-Am Performance or Mid-American Performance use to have a website with the flow numbers of the various Oldsmobile stock heads. As I recall A's were the best flowing. "If" the heads are the "bottleneck" then a plus of 5% could mean 5hp per every 100hp. Aka, 390 hp engine could turn into a 410 hp engine, hypothetically. I bought a 1965 425 (A block) twenty five years ago. It was a perfect running 4 barrel engine "except" previous owner didn't put proper amount of antifreeze and it had a crack in the block, near a freeze plug. The plug was seated perfectly. The heads were big valved and I sold the heads because I wasn't familiar with the pivot setup. As I recall the exhaust ports did not have A.I.R. bumps from the factory. That was always the first thing I use to do back then was grind them off. Anyway that's thoughts on A heads. Jmo
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That would be a nice increase in HP for a non modified head.
I know once you start porting the heads it maters little among the top factory heads what you started with.
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Old October 15th, 2018, 10:42 AM
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Wasnt the Mid-Am numbers considered to be inaccurate and without any proof of numbers.
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Old October 15th, 2018, 10:45 AM
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Originally Posted by Kennybill View Post
A shop named Mid-Am Performance or Mid-American Performance use to have a website with the flow numbers of the various Oldsmobile stock heads. As I recall A's were the best flowing. "If" the heads are the "bottleneck" then a plus of 5% could mean 5hp per every 100hp. Aka, 390 hp engine could turn into a 410 hp engine, hypothetically. I bought a 1965 425 (A block) twenty five years ago. It was a perfect running 4 barrel engine "except" previous owner didn't put proper amount of antifreeze and it had a crack in the block, near a freeze plug. The plug was seated perfectly. The heads were big valved and I sold the heads because I wasn't familiar with the pivot setup. As I recall the exhaust ports did not have A.I.R. bumps from the factory. That was always the first thing I use to do back then was grind them off. Anyway that's thoughts on A heads. Jmo
Why anyone in there right mind would use this as a reference is beyond me!!! I know the guy who was mid am! He didn't know squat!! Never built a set of heads and went down the track or performed as he advertised. He did have a couple cool cars and that is it!!!
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Old October 15th, 2018, 10:53 AM
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Originally Posted by wr1970 View Post
Why anyone in there right mind would use this as a reference is beyond me!!! I know the guy who was mid am! He didn't know squat!! Never built a set of heads and went down the track or performed as he advertised. He did have a couple cool cars and that is it!!!
Also what flow bench i was there many times!!!I bought some blocks and rods from him. He never had any ported heads to show me.But he was selling heads to others out of state as performance heads!! I suspect because he could take advantage of them! JMO
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Old October 15th, 2018, 10:58 AM
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Originally Posted by wr1970 View Post
Why anyone in there right mind would use this as a reference is beyond me!!! I know the guy who was mid am! He didn't know squat!! Never built a set of heads and went down the track or performed as he advertised. He did have a couple cool cars and that is it!!!
Thanks for the insight into MID AM
We are going more by Bill T. His comment that in stock form un- touched, he found the A slightly better than the rest with having the largest ports.

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Old October 15th, 2018, 11:38 AM
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Originally Posted by wr1970 View Post
Why anyone in there right mind would use this as a reference is beyond me!!! I know the guy who was mid am! He didn't know squat!! Never built a set of heads and went down the track or performed as he advertised. He did have a couple cool cars and that is it!!!
Btw, I was just commenting on personal experience and yes, things I've read on various Oldsmobile sites over the years. The difference isn't much but they aren't all the same flow. I explained the exhaust port as I remember not having the "bumps." Imo, that would make a difference. We're talking street engines not national record holder stuff. Btw, I believe I'm in my "right mind." You seem a little worked up over my comments. I always put jmo because what I write is jmo. Hopefully the following won't get you upset.

https://redirect.viglink.com/?format...2Fheadflow.htm
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Old October 15th, 2018, 12:11 PM
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Originally Posted by Kennybill View Post
Btw, I was just commenting on personal experience and yes, things I've read on various Oldsmobile sites over the years. The difference isn't much but they aren't all the same flow. I explained the exhaust port as I remember not having the "bumps." Imo, that would make a difference. We're talking street engines not national record holder stuff. Btw, I believe I'm in my "right mind." You seem a little worked up over my comments. I always put jmo because what I write is jmo. Hopefully the following won't get you upset.

https://redirect.viglink.com/?format...2Fheadflow.htm
Yes i guess you missed my JMO!! LOL☺
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Old October 15th, 2018, 02:15 PM
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I saw your JMO in the second post but it wasn't in the first post that you commented about "right mind."
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