Hello gearheads my name is john bishop. age 20 learning bout these wonderful motors trying to be a gear head myself. I had bought a 400sbc for $250 from a 74 caprice the guy said i could have put it in my car as is, but i was goin to rebuild it anyways to make sure everything was fine.i have a 88 caprice with a 305. and i wasnt planning to put the 400 in 88 caprice but my rear main seal went out on the 4th of july and i was really upset. So my moms boyfriend and i thought it would be a good idea to get the 400 together. well the last 2 days we took it apart and he ran into problems. they ran the motor with no oil it looks like. the cam looks bad. crank needs to be turned. anti-freeze was in the oil pan. im taking it to the machine shop to get the crank and block hot tanked and magnafluxed (how ever u spell it) so hopefully the block and crank is in good hands and im goin to get the heads looked at. Is there anything i should know about 400sbc when redoing this motor and do u know any good parts i should use with out changin the heads. i want to atleast get 400 or more out of the 400sbc i only got 1000-1500 to use and bout 350 -400 is goin to get it hot tanked maganafluxed and bored .30 over. anything info would be appreciated thank you

                John Bishop

First things first if there is coolant in the oil more than likely something is cracked, which is very common with 400 heads and blocks. Better get the results back on the magnaflux tests before ordering any parts.

Even if your block is fine, without changing heads you won't meet your 400 Hp goal.

                                                                                     ~Gibs

well i pray it aint cracked. so how much hp u think i can get out of it? and what parts u think  

You're in the process of learming lesson 1 which is most guys that sell used engines and tell you they're great as is are selling junk. Not to worry, you'll buy a lot of junk if you stay a hot rodder, you just learn not to pay top dollar for it and to some extent how to see it before dissassembly. One of the first things is to look at the oil, never trust a dry engine cause you can't learn anything untill you open it up. The other is try to get the seller to let you open it up before buying it. Unless you're buying a late model engine that comes with a guarrantee of serviceability, always assume your buying nothing more than (hopefully) rebuildable castings.

GM castings and Chevy is  no exception are crack prone, always have been and going to thin wall casting in 1972 didn't help an already iffy problem. Add to that, the 400 has siamised cylinders, that is down the middle of each side's cylinder block, all the cylinders are co-joined. This causes an area of stress concentration which leads to cracking if the engine is overheated. The heads are very sensitive to cracking and this is commonly found in all castings from the early 70's to the present. The 400 heads are unique having 6 drilled holes located in pairs between the inboard cylinders. These allow the passage of coolant up and out where the cylinders are co-joined. You can use non 400 heads on a 400 but you have to drill these holes in those heads to prevent steam pockets from forming at the tops of these cylinders. No big deal this is done a lot.

Coolant in the oil could be the result of cracks in the block or heads, or a gasket leak, intake into the valley is common as are blown head gaskets. This needs to be checked out as you need to know if its a gasket leak or crack allowing coolant to get into the pan.

Cracked heads can be replaced, a crack in the block is simply the kiss of death as there is no reliable and inexpensive way to repair cast iron. Simply welding a crack in cast iron results in more cracking from the uneven heating and cooling welding causes. To properly weld cast iron, the whole item has to be carefully heated into the transition region, then welded and carefully allowed to slowly cool over several hours if not a day or two. After all this it's less than 50-50 crap shoot that the item won't continue cracking.

400 hp from a 400 engine while possible, doesn't make for a reliable engine. First 2 bolt 400 blocks are right on the structural edge, 400 blocks are heat sensitive leading to thermal stress cracking and 400 hp put out more dynamic and thermal stress. The short rods of the 400 place a lot of side load on the piston skirt leading to skirt and lower cylinder wall breakage.

Your 88 Caprice is a some what different beast. First off it's fuel injected and computer controlled including the transmission. It's Federally SMOGed so changes to a 400 are technically illegal. A 400 using factory EFI will be struggling for air and fuel requireing expensive changes to the fuel injection and computer for adaquate performance. there's aways a carb if you don't have to pass an inspection.

The 88's engine uses a one piece rear crank seal and is internally balanced; the 72 400 uses a two piece seal and is externally balanced. This means the 400's crank will not mate to the Caprice's flexplate. An aftermarket flexplate that remakes the connection between the old style crank and new transmission and provides balance for the 400 crank will be required.

This swap gets more and more complicated and expensive as you dig into it. You could swap the transmission, but your current speedometer is fed electronically which is something an old TH350 isn't set up to do, so you get into changing the speedo drive or changing the speedometer, it's stuff like this that proves the devil's in the details and what appears to be a simple swap gets to be very complex rather quickly. So make sure you're up this level of difficulty and expense.

Bogie

I am very happy there are people that know what they are talking about when it comes to these engines. i been learning alot in the past few days. I do have some bad news tho. After looking over my block and talking to my moms bf (gearhead) we have discovered that my block is not a 400 its a 350 2 bolt main. i guess there's suppose to be 3 soft plugs on each side of the block and mine only as 2. and the diameter of the piston hole is not i think 4.5 or close to that. so im pretty bumed about that. but i called up one of my other friends and he says he got a 72 350 4 bolt main with a 350 trans for a grand so im goin to look at that today or tomorrow because i have to get my caprice in order. but the 350 is out of a motor home but its still a chevy motor. and it only has 26,000 miles on it and im gettin it from my other mechanic if i decide to get it. and his cousion has a rebuilt 350 but i dont kno much about that motor but i miss my chevy and i need to get it running so hopefully i can get a good motor. the good thing about the 350 from the motor home i can hear it run. well i will ttyl thanks for all the help i appreciate it. i know this wont be the last time i will be on here

John Bishop

John a 350 is proabably a better base to build from, not that 400's are bad; the 350 doesn't have the center cylinder cooling issues and their resultant stress, nor the short rod problem of high lower cylinder wall loading. Then there is the issue of external engine balance, there are folks who for good techncial reason have the opinion that it doesn't matter whether an engine is balanced by the cylinder or whether that balance comes in total with the necessary trimming hanging on the ends of the crank beyond the oil seals. And there's plenty of engines like that. However, when it comes to high power engines, especially those with 2 bolt mains or aftermarket conversions of 2 bolt blocks to 4 bolts, I REALLY like a crank that has each cylinder in mass balance. This really helps to unload the bearing webs and caps from mass induced crank flexing. These items have plenty to do just reacting the the force variations put into the crank by the cylinder cycles; and these you can't balance out. Well to some extent you can but that gets into balance philosophy on under balance, netural where I'm at here, or overbalancing. Overbalance of a competion engine has some value in absorbing the high loading that hits the crank on the power strokes. This is good at high loads and speeds but causes a lot of shake at low to medium revs, not recommended for street engines.

Anyway, where was I going with this, oh yeah, um, 2 bolt blocks. With a well balanced bottom end a 2 bolt block will reliably handle upwards of 500 horses on the street. A 4 bolt block upwards of 6-700 before you have to get real tricky to things together. Oh  yeah, by stuffing a 400 crank into a 350 with a .030 over bore you get 383, which is a real popular swap. So now you've got two "junk yard engines" with great possibilities to make an interesting motor for yourself. 

Bogie 

John !! Nobody talks about it much , but it' extreeemly important to keep things clean ! Think of working on your motor as surgury !! A grain of sand in a bearing cap , or under a head gasket ,or in a bolt hole is your enemy !! Good luck with your rebuild !! Tom  

The funny thing is i work in surgery so i know all about that but i got my 350 out of the motor home. 350 4 bolt main. i just been short of money i got about $400 of parts to buy. i bought a nice dress up kit painting the block blue. i got summit racing headers. using my 700r4 instead of the TH350 because of electrical issues. Plus i have an extra gear. i Got a Comp cam Maganam Cam 270 and lifters. B & M shift kit for high performance. about to get new timing chain, trans lines, all the gaskets, trans mounts, rear main seals and fronts for engine and trans. Synthetic oil(valvaline) Trick shift trans fluid. and i got other lil things to buy but things are looking good so far. this weekend i get paid so i should be able to buy the rest of the parts if not im taking out a loan lol! but it should be fine. i will post pictures when i get it done. Ive had some people say this build wont work. Im pretty sure it will. after i get it running and i get some extra money im goin to chrome it out a little more. Pullys intake and carbs all the good stuff. well take care i will post more next week.

John B aka TRU