Ideal SBC?
 

I'm looking at swapping out my 350 with an SBC 400, and was wondering what the ideal 400 to look for would be. The one that came with 4 bolt mains, etc, and which car it came in so I can check the local yards for one.

Also, I want to try to make this car emissions legal. Which is going to involve a lot of customization to make all of the sensors and stuff work, and was wondering if this was even possible, as the 400 was dropped due to emissions incompatibility.

Finally, would a HSR work on a SBC 400? I love the performance from a MPFI setup, even if it costs more to improve over a carb or a TBI.

Any help is much appreciated. :thanks:

Umm emissions legal why? 4 months and your car doesnt have to comply it will be a classic...

As far as I know, that's not true. All cars that came with emissions HAVE to continue to have emissions, and while Az is lax about their emissions laws, I am going to be moving to Tucson soon, which is one of the two places that require emissions testing in the state.

Unlike the other SBC castings, you want to AVOID the 400 blocks with the 4-bolt mains. They have a weaker main web than the 2-bolt blocks because of the extra bolt holes. If you want a good streetable 400, get a 2-bolt block. If you want an absolutely bulletproof 400 bottom end, get a 2-bolt block, and have splayed steel main caps installed. Splayed caps are different from regular (factory) 4-bolt caps, in that not all 4 bolts go straight up. The two inner bolts go straight up, the two outter bolts go in at an angle. Its a much better setup for a high performance engine.

If its going to be anything streetable though, a 2-bolt block is plenty strong. A friend of mine is running a 2-bolt 400 block, and it makes enough power to hit 11.70-ish ETs without any forced induction or nitrous. Well over 500 crank HP.

Just my 2 cents.

:thumbsup: Mmm. All throttle, no bottle. This is just the kind of information I was looking for. Other than the 4-bolt and 2-bolt mains, are there any other differences between the blocks in the 400's? Or would any 2 Bolt main 400 serve my purposes perfectly?

Okay, I just looked up casting numbers and differences between, and there is a 3030817 and a 330817 400SBC with 2 Bolt mains. Research shows one of them had a high nickel block (?) and was rated at more horsepower in the cars it was in. Would hunting one of these down be the way to go?

The high nickel thing is largely a myth, and wouldn't make a difference in a streetable application anyway.

Ahh. I was doing further research into this, and I found that most of the stock 400 SBC's had rather thin cylinder walls, especially when overbored more than .030, and was looking into the aftermarket realm of Small Block Chevy Blocks. I took special note of Bill Mitchell's Motown 400 SBC, which boasts the thickest cylinder walls of any SBC, and can come with a mighty strong billet steel four bolt mains. Granted, the block alone is like $2k, but why start with a crumbling foundation when you have fresh concrete?

One thing I noticed was they said that the block could be bored to 4.200" max, but they sell a "racing prepped" version that is bored to 4.255". Is this one more dangerous to run, due to the thinner cylinder walls, or do they make the 4.2" claim because more pistons are available in that size?

Don't use an aftermarket block for a street motor... unless you want HUGE cubic inches, and are willing to pay cubic dollars to get them, its not worth it. A block like that isn't necessary unless you want to build a 440 or 454 out of a small block, at which point you'd be better off to build a big block anyway... cheaper and more power. An aftermarket block would probably be pretty easy to spot anyway, if it has to go through visual inspection.

400's are just like almost any other factory block... .060 is possible on the 'perfect' blocks that have no core shift, but usually anything over .040" isn't reccomended. Just find a factory 400 2-bolt block that hasn't been bored, bore it if it needs it, and run it. It will be just fine. Get it sonic checked before its bored, and if its within safe limits, use it.

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Thats a myth spread by people who don't know how to build a 400 properly.

This is how you build a 400 properly... drill these holes in your heads if they don't have them already. If they are not drilled, the motor WILL have overheating issues.


You will need to upgrade the cooling system somewhat if you are going to be making more power than stock. The factory cooling system was barely adequate, if even that. Get a bigger Griffin, or similar, high performance radiator, a 180* thermostat, and a good quality water pump, and you will be fine.

More power creates more heat, and you will need an upgraded cooling system to handle the extra heat the more powerful engine will make.

It may be old, but it well never be a classic...

:lmao:

509 blocks are the ones most go with, I belive the other is a 411? anyway your casting numbers seem odd and most' 509 blocks are 2 bolt mains and are pretty common as far as 400s go


I NEVER had a cooling problem until I installed the ATI intercooler on my old firebird with the stock radiator and a/c stock fans and even then a simple home made air dam fixed that... if a stock cooling system is barely enough then your stock system has major issues

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Well, come on out to Colorado and you can meet me.

I had a factory 400 vehicle in California for several years. It sat in traffic on I-805 many, many times. The only time it overheated was when the lower radiator hose burst at the water pump end. Cut the end off, clamped it back on (used a quarter to loosen and tighten the hose clamp), and on we went.

400's started out with 3 core plugs per side, then went back to 2 core plugs per side, just like all other SBCs. Not sure what point you were trying to make there - they are there for the purpose of casting, not cooling.

If you've got a problem with a stock 400 overheating, you haven't maintained the cooling system properly.

Agreed on both points. The plugs have nothing to do with the cooling system other than the fact that they happen to come into contact with coolant. And if your 400 is overheating, its because something isn't right, not because the motor is a turd-by-design.

I've heard the 817 blocks aren't that great? I have no information to back this though. I know 509's are real popular. What are the other popular blocks?

Yes, if a 400 is overheating then there is something wrong…, in a lot of cases we’re talking about blocked or non existent steam holes in the headgasket, head deck…

As far as what to start with… 400’s are prone to thinner cylinder walls, but they can be found with good wall thickness also, it’s just a matter of getting it checked and before you spend real money on it.

As far as the main webbing… both the 2 and 4 bolt blocks have thin main webbing, the 4 bolt ones have the additional issue that you just drilled 2 more holes into that thin webbing making them prone to cracking.

If you’re really looking to build the “ideal” sbc that you’re going to push hard/beat on, you’re probably best off either starting with an aftermarket block if you really need the big bore or starting with a 350 or smaller block.

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The most important thing to do with a 400 sbc that no one has mentioned here is to get the block sonic-checked. There are some 400 sbc's out there that have never have rebuilt and they are no good. No matter how little of an overbore is needed.

No one is out to make you look bad, we just don't want to get any misinformation here.

GM does make some motors that are nothing but a pain in the coin-purse from day one, and that very well could have been the case with your truck. Not every one of the hundreds of thousands of engines GM built is going to be just right, there will be ones with ongoing problems.

But there are also alot of guys out there using 400 small blocks, both stock and modified, that don't have any cooling issues at all.

To add to that, I and other’s in this thread did not say that there was something wrong with the radiator, but something wrong with the engine (besides the fact that it’s a 400), and there’s always the chance that it’s something stupid like a water pump impeller that spins on it’s shaft a pump, block, head or intake casting that is slightly off and causing uneven flow or some RTV somewhere blocking off a passage.

In general 400’s get bad rap in a lot of cases because they’re really the only old school sbc that is significantly different and things that work on others do not necessarily work on them, so people do things like they always do and can’t figure out why something is f’ed up.

I know this post is old, but Im in the same boat with thescaryone. Im planning to swap out my 305 for a 400sbc. I found mine in a camper with 30k original miles on it. I do need to check the numbers on it, but right now Im just saving money so I can do this motor completely and properly before install. Almost there. Ive looked into this motor a good bit and bottom line, it is a great motor IMO. Yes, you do have to take care of the steam hole issue and yes, the vast majority of people say the 2bolt is better. It wont be much longer (weeks) before I build the motor and i'll keep you posted on how it goes. Also, I will be moving to Tucson in November and Im worried about emissions as well. Im registered for Merewhether Co., GA (no emissions/inspections) so I ripped off all my emissions crap. Im thinking just doing the same thing in AZ, just registering your car where there arent emissions. Not sure where though. Well, maybe I'll see you around Tucson then.

i have a 400 sbc in my camaro it ran 180 till i blew a ring then it ran 220 all i did to mine was an aftermarket high flow aluminum water pump brand new heavy duty fan clutch and a new "stock radiator" and a 160 stats even smoking it still ran hard when i can afford to rebuild it im gonna destroke it so i can rev it to the moon
:lol: :lol: :lol:

and for mpfi your gonna have to does some prom tuning im gonna have to learn to do that as well cause i just got 91 z28 thats tpi

I hope to see you around man. Gonna have to have some thirdgen days. I think there's a few others from the boards down there. AZ is emissions compliant, but the DMV won't check emissions unless you live in Phoenix, Tucson, or commute to either area on a regular basis. It's hard to cheat that. But MPFI would work, as long as I custom tuned it? Fun. I like the performance in port fuel injection over TB or carb. I think I'm gonna shell out the two grand and get a Motown Small Block 400. Build up anything from there. I dunno. If I find a 400 sbc at the right price, I'd jump on it.

Well, im going to have to find a way to get around those emissions. I may just be wasting my time and my camaro could pass right now........haha probably not. I found my 30k mile 400sbc in a camper for $550 (runs). Im down for some 3rd gen days. Are you in Tucson now?

Nah, I'll be down there in December, so you'll have a whole month on me to settle in. Also, if you check out the dual exhausts thread in the exhausts forum, you can see.... Crap. I forgot his name, but he lives down in Tucson too, and he's got a pretty sweet ride with an awesome true dual setup.

Edit: Rumour on the street is that if you won't pass a DMV emissions test, you could go to a local shop that offers the service, and instead of paying the twenty for the test, you could pay $60, and you'd pass. Granted, that's only rumours, as my car passes emissions (it's been a Cali car it's whole life except for the past three months in Az), so I don't need to worry.

I know personally a lot of local shops in tucson, so maybe one of them does emissions. ( I used to deliver parts for NAPA there in 03-04) I also found a good link to a forum that really discussed the 400 sbc. Its 400 sbc 4 bolt vs 2 bolt....anybody Know 400's [Archive] - THE H.A.M.B.
Hope that helps.

Scaryone...no one mentioned this and I hope you haven't purchased a block yet but.....have it magnafluxed, have it magnafluxed, have it magnafluxed. It would be a shame to drop a bunch of money on machine work and find out the block was junk to begin with.

As far as overheating is concerned....it's technically not a myth. Most 400's came in trucks. Back in the 70's and early 80's trucks were "second class vehicles". They were overworked and horse whipped with little maintanance performed. Antifreeze was rarely changed and water jackets/steam holes would rust resulting in overheating problems. When you have your block vat cleaned, check for rust in the water jackets. If it's bad you can install old freeze plug and use swimming pool acid (macuric?) in the water jackets to remove the rust. Do this before any machining operation as it will ruin your freshly machined bore if you accidentally spill on it. In the case of a street/strip or big horsepower motor, this will also prepare the block for water jacket filler. I don't know what your horsepower goals are but if they are over 450, I would consider a street fill of Hardblok to stabilize the block.

I know about the magnafluxing. We used to talk about it in shop all the time. Some guy bringing in like, four or five different blocks to be magnafluxed, all of them being crap. There is also this sonic checking people tell me about. Good advice on the cooling. This is swinging me back into the stock SBC 400's.

yeah they are great motors even mine after i blew a few rings was still making good power just smoke to hell and back

Re: Ideal SBC?
 

i also swapped to 400 sbc and it has been working like a charm overall. the entire thing is just pure beautiful. thanks to all the help from this forum... might go for some higher upgrades later this year.

Re: Ideal SBC?
 

Why are you ressurrecting a 4-year-old thread?