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building a 400 BB ( shortblock info)
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61sene
Posted 2015-06-22 5:36 PM (#482401)
Subject: building a 400 BB ( shortblock info)



Member

Posts: 43
25
Location: temperance, MI
I'm posting this for the reason that when I was building my engine I couldn't come across any useful information on building a 400 as a 400. Lots of people asked in threads about doing so and everybody that had responded was"build a 451", "build a 470", or "build a 498" with no info or regaurds to the op's original question. I realize that your not gonna get the power out of a 400 that you can get out of a 451,470,498, or a 500+ inch stroker but it's a driver and how much power do you really need to cruise, this may even be over killl to some. so hopefully this helps someone with questions in the future.
if you want to build as a 400 your choices for pistons are limited, extremely limited. The three options I found was 1)cast- low compression deck 2) hyper piston-taller compression deck 3)custom made slugs from say wiseco or diamond-between 750 and 900 bucks. I tried to find a street forged piston with no luck, no shelf units, custom only Don't care for hyper pistons, have my own reasons so i'm not using them. So looks like I'm going cast even though it wasn't my first choice. first we square decked the block down to factory specs, it was .012 to tall. the STOCK 400 piston was .130 in the hole and at supposed to be around 8 to 1 comp. I want a little more fun but the car still has to be able to go long distances, like east coast to west coast, so it has to be reliable and run on 93 octane or less. So we went with an oversized 440 pistion. The compression deck was just over a .100 taller so the pistons were an average of .021 in the hole. my heads measure at 80.5cc so with a head gasket that crushes to .039 I have an engine that is 9.45 to1. Not gonna set the world on fire but should be more fun on the streets and on the expressway.
This is what I used.
1) 3.375 stroke cast or steel crank, I had a steel crank from a 65 383
2) 6.358 rod. Stock reconditioned +arp rod bolts will do
3) #SEA424NP.040 cast .040 over 440 piston
4) #SEAE424K.040 moly ring set
5) #fel2947 felpro rear main seal
6) your preferred rod bearings
7) your preferred crank bearings
8) your preferred cam bearings
I used stock rods that were reconditioned because the engine Will most likely never see anything above 5000 to 5500, so these will work fine. I had the steel crank otherwise I would have used the cast one
with this setup I can accommodate the .484 purple shaft cam with no worries about needing valve reliefs, other setups may vary. I'm running the .455 p/s cam because of the less overlap so I'll have better vacuum signal for my power brakes. With the .455 cam there was .160 of valve to piston clearance with the thick head gasket. Plenty of room
your dimensions may change somewhat with the consistency of production parts being pretty awful. Get everything balanced, I had two rods that were just over 30 grams out from the others and they were out of that engine originally.

*also note: if you are not real familiar with mopar big blocks, a 400's stock bore is .020 larger than a 440's. so you would only take out .020 from your 400 to accommodate a .040 over 440 piston**

Hope this is useful to someone out there and will save someone some headaches when planning out a rebuild. If you have any good info to add please do so, most of us are always learning and want to know more, if you have question post em, there's Lots of good info from the folks that use this site. Thanks -Joe
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zrxkawboy
Posted 2015-06-24 7:26 AM (#482614 - in reply to #482401)
Subject: Re: building a 400 BB ( shortblock info)


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Posts: 168
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Location: SD
Good info - thanks for sharing!
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61sene
Posted 2015-06-24 2:57 PM (#482646 - in reply to #482401)
Subject: Re: building a 400 BB ( shortblock info)



Member

Posts: 43
25
Location: temperance, MI
Hey guys, I also forgot to add this, valve to piston clearance was with the cam being installed strait up, but when I degreed my purple shaft cam in, it was 4.5° advanced ground so the valves start opening sooner than if it wasn't advanced ground, this Will be better for low end power but if your goin for higher compression and tighten all your clearances up more or a larger cam this could result in ur valves tagging the top of your pistons.
That's why it's important to degree your cam in, some are right on, some are advanced and a couple companies retarded grind there cams. They're mass production parts so there's bound to be things out of spec.-Joe
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Tragic Wagon
Posted 2015-06-24 7:59 PM (#482679 - in reply to #482646)
Subject: Re: building a 400 BB ( shortblock info)



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Posts: 35
25
Using your numbers and an assumption of a 4.4" gasket bore, I come up with a CR closer to 9.75:1. Still not Earth (or piston) shattering, but I'd recommend you stay with pump premium only. It will probably knock pretty easily on 87 unless you run fairly conservative timing.

If you're looking for low-end grunt, the smaller cam was a good idea. Starting about the MP .474" lift (Hemi grind) cam, the low-deck engines start behaving a lot more like 340s, with all the fun happening up high. A friend of mine with a '69 'Cuda 383 put the .509" cam in it and lost every stoplight Grand Prix he entered. He was shifting at 5,500. I told him to wait another 1,000RPM before shifting, and suddenly the car had a big local rep. I ran the .484" in a 400 Cordoba with a similar shift point and results. Pulled like a beast above 4,000 and didn't want to end the party anywhere near the factory redline. Both cars had single-plane intakes, 750CFM or bigger carb, and headers.

As a side note, people REALLY hate losing to rusty beige Cordobas.
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61sene
Posted 2015-06-25 2:26 AM (#482716 - in reply to #482401)
Subject: Re: building a 400 BB ( shortblock info)



Member

Posts: 43
25
Location: temperance, MI
Good call on that. I just refigured it and I'm getting 9.66 to 1? Hope I'm leaving anything out. We figured originally the pistons would be .030 in and they ended up being an average of .021 in the hole. At .030 it ends up being right around 9.45to 1. feel like a dope for not thinking of that. Only plan on running 91 to 93 so I'm prepared to run better fuel, it just needs to be something I can get while traveling. I went down from the .484 I was originally gonna run. I didn't think that engine had enough stroke to utilize it. So I'm hoping the .455 with the 2.14/1.81 valve combo I'm running will still be fun. If not I can always upgrade to the .474 -Joe
hell yeah to the rusty Cordoba, we built my buddies 54 210 Chevy gasser with a 468 bb, and get all sorts of fools in their smog era vettes and mustangs with a cam and intake wanting to run it cause it's missmached paint and rust holes. You hang wth em a bit to play with em then open it up. when you start to freight train them they just let off the gas and turn into a parking lot or down a side street. Love it

Edited by 61sene 2015-06-25 4:22 AM
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Tragic Wagon
Posted 2015-06-26 10:18 PM (#482897 - in reply to #482401)
Subject: Re: building a 400 BB ( shortblock info)



Member

Posts: 35
25
Well, my numbers came up a little closer to 9.75 but it's kind of splitting hairs at that point. I don't know what gasket you're using so I had to make an assumption on the bore of the gasket. Those 440 pistons don't have any valve reliefs, if memory serves.
The 400 has enough stroke to use the .474" but you've got to enjoy a higher-RPM playground. It doesn't exactly become a 6,500RPM screamer, but you are giving up some bottom end with the hotter cam. Even the stock 383/440 Magnum split-pattern cam is a good choice, especially for a cruiser. Since that's what my '61 Suburban will be, that's the cam I'll probably use (possibly a slightly-more-modern grind of it, though). I have a couple of other projects that are much lighter and more speed-oriented anyhow... both Mopars, of course.
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