So I picked up a 2bbl small block 400 last Saturday out of a 73 impala and don't know much of anything about them other than what I've read on here and what I already know about other SBCs that carries over. The first thing that has me scratching my head is that this is an 817 block, I've read that there are 3 castings of the 400 and I've seen the 817 listed in best, worst, and second best position in various posts and web write-ups so I really don't know what to think about building this particular engine. The other thing I've been wondering is how much of a difference I'd see in this engine with a few bolt ons thrown at it, right now I have a set of headers, an msd hei distributer, an edelbrock performer intake and a 725cfm road demon carb sitting in my garage, would it be worth putting that stuff on now or should I run it stock until I can throw a cam and some heads at it? Any help would be great, thanks.
If it has 882 heads its not gonna scare anyone. Put all your bolt ons on the 400,it will have some good torque.If you change the heads with the cam it should impress you. The age of the engine will determine how hard to push the engine considering reliability,,,
So I picked up a 2bbl small block 400 ... 817 block... headers, an msd hei distributer, an edelbrock performer intake and a 725cfm road demon carb sitting in my garage, would it be worth putting that stuff on or a cam and some heads at it?
I think the 817 is the early 4 bolt mains block, which initially looks strong, until you notice the mains webbing is usually windowed and not as strong as the later two bolt mains webbing... but, strong enough for your purposes...
Headers are usually the best performance for the buck buy when used with dual 2 1/2" - 3" exhausts... the Eddy Performer intake wouldn't make a seat of the pants difference over a stock 4 barrel intake, but will make a big difference over the stock 2 barrel intake/2 barrel carb. which gets asthmatic by 3,000 RPMs when combined with the 4 barrel carb... won't be able to tell any difference powerwise with the MSD distributor except for maybe better starting/idling... this gets you to about 250 HP...
SBC 400's started in 1970 at 9:1, 2 bbl. carb., and 265 HP... compression ratios dropping after that to about an actual 7's:1... despite the low compression ratios, dropping the pistons down in the bores created horrible "engine quench" effects and pinging and caused these wimpy stock engines to be spec'd for Premium gas... the later engines, even with their then standard 4 bbl. carb.s, but overly advanced cam timings, torque peaked way down at 2,000 RPMs and HP peaked at 3,600 RPMs... like an ancient B&S lawnmower engine...
New flat top or mini-dome pistons with correct 'compression height' that get the tops back up in the bores for higher compression ratio and better engine quench effects along with a budget very mild 214/224 performance cam (Summit K1103) basically gives you a very low cost 1960's-style muscle car engine with 375 HP even with the much-maligned stock -882 heads... more power is readily available, easily a mild-mannered 500 HP, with different pistons/heads combos, but at much higher cost...
Thanks for the input everybody, I'm pulling the oil pan and valve covers today to check for either 2 or 4 bolt mains and head casting numbers, every site seems to have different info on the mains, most say it's 2 bolt, some say it's 4, lots say an 817 block always has 2 freeze plugs, but mine has 3, etc the more I dig the more confused I get about these small block 400s lol. I think my route right now will be a quick regasket and throw those parts on, if the heads are a super junky casting I'll probably throw on some cheap camel humps since I have head gaskets anyway and pick up some aluminum heads down the road with a nice cam and bottom end setup.
Doesn't matter if 2 or 3 freeze/core plugs... but be glad yours has 3 because I think only some 400's have 3 and that verifies the first step: it really is a 400... 'Cheap camel humps', if there is such a thing, prolly won't flow any better than the stock 76cc open chamber heads on there... but if they have 64cc chambers, can help bring the compression ratio/torque/MPG/HP up...
There's a few sets of camel humps up on some local buy and sells here for $100-$200 so they're not overly pricey but since I'll eventually be going aluminum it sounds like the performance bump might not be worth taking the time to do it right now. I'm not sure of the mileage on the engine, but it didn't burn oil and ran pretty smooth for needing a tune up, when I actually do get the time to do a proper build on this engine if it's worth it, it'll be getting stripped down to the block and sent to the machine shop, etc.
Buzz...the #817 casting was the last 400 casting, used from mid '73 thru 1980, and is always 2-bolt main. Three freeze plugs per side.
Early castings, were '70-72 #511, which is the only 4-bolt casting....and all '70-72's were 4-bolt and have this number.
For 1973 to about 1977 there were two more numbers, the #509, considered to be the best 400 casting, three freeze plug bosses but the middle one is typically not bored and is cast shut This block is always 2-bolt main. The other casting is the #512, also 2-bolt main but typically has all three freeze plugs bored out. both of these are the most desired for conversion to splayed aftermarket 4-bolt main caps.
There were no factory 4-bolt 400 blocks after 1972.
I'd throw the intake and headers on it when you re-gasket it, and just keep it below a 5100 rpm limit. The tired old valvesprings probably will be lucky to let it turn over 4600 rpm anyway, thus protecting the stock connecting rod bottom end.
The other casting is the #512, also 2-bolt main but typically has all three freeze plugs bored out. There were no factory 4-bolt 400 blocks after 1972.
Thanks, Eric, for the detailed info... I thought there was some overlap between two and four bolt blocks coming from different foundries... The reason for two or three 'freeze plugs' isn't because they just happen to be bored out... but because the tricky sand casting cores for 400's with their siamesed cylinder bores were expanded to 3 core supports from just 2 for better, more accurate sand core support and fewer scrap castings... the 'freeze plug' holes are actually where the sand pegs supporting the glued sand cores come out through the iron block... once the molten iron is poured in and cools, then the sand core is sonically disintegrated into grains of sand, and removed/poured out. The 3 as cast rough holes remain, which are then machined smooth, and "core plugs" added to seal the block/coolant in...
Thanks, some good info there, is there anything inherently flawed with the 817 block? Or is it more internet rumors than actual fact? I've seen posts about it being a weak block, and posts saying that it's perfectly fine and those people just had a bad core. I'm just basically planning on getting this engine in the car and running within the next month and from there stockpiling parts for a proper build, just not sure if I'd be wasting my time and I should just find a different block to build.
Talk about the #817 block is mostly just that....talk. It may or may not be a slight bit weaker than the most desired #509 casting, but in general most 400 block failure come down to either bad casting, core shift that is not visible, or just flat overpowering a stock block.
About like any SBC stock block, once you start venturing into the 600 hp area and above you are rolling the dice.....and that is why the aftermarket has stepped up with several different varieties of performance blocks that are much stronger.
that's great to know Eric, i have the 509. been trying to sell forever. anyway. i'd third or fourth just throwing the intake and headers on it for now, but i HATE EDELBROCK carbs. my gas never evaporated out of my Holley, and because of this my cab smells like gas everytime i get in it. (and no, my tank isn't in the cab anymore either). biggest pile ever! but that's just me. if there is ONE part on my truck i wish i never bought, it is that junk carb. if there was one thing i wish i never DID to my truck, it would be having my rear carrier welded up. BLAH!
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