so i just picked up a chevy 396. It's a "basket case" motor, but a good start and the price was right. the plan with this build will be pretty stock, maybe a cam and some bolt ons...going in a 1960 Apache. i was running numbers on everything (something i should have done before i paid the guy but anyways,...the block and crank check out and are in great shape. the heads aren't bad looking,...but here's the kicker... when i ran the head numbers....they're later model 454 heads... this is my first big block build, but my understanding would be that running 454 heads on a 396 (***uming all stock) would give me some really low compression....is this a correct statement? this is also a normal budget build...not gonna cut corners, but money is all a concern. what i DON'T want, is to end up spending more money on some "off" combo than just a normal stock set up. give me some advice...and what would be a good head choice with some decent, but drivable compression? stock 396s? i've got a line on some stock heads, but wanted to make sure that i'm not jumping the gun and already have a decent set-up. thanks everyone Chris
My 396 was a low output (265hp) out of a 69 Impala, but it turned out to have truck heads on that had some tiny little exhaust valves. Rather than rebuil it with those I opted for the Merlin II cast iron oval port heads. In my opinion they're the best bang for your buck if you are going to spend money on new heads. Otherwise my motor is nearly a stock rebuild I'm running a smaller Comp cam in the car, I believe it's a rv/truck cam. It's very torquey but doesn't have much top end. By the way, good luck doing a budget build on a big block. You could build 2 small blocks for the same price.
Go to Mortec.com and run the numbers on the heads you have and find out what the CC of the combustion chambers is. There were some small closed chamber BB heads that would give a flat top piston motor a 9:1 comp. ratio howerver most BB heads are in the 112-116 cc range which will completely kill compression with out some domed pistons. Also, make sure they are not peanut port heads which are great on an enging that won't be spun over 4000RPM but completely run out of legs past that. BB are more exspensive to build than a small block but its a fair trade off for the torque and sheer presence if you ever plan on raising the hood.
heh, i hear ya on the "budget comment", just want to make sure i'm not doing any spending that NOT needed. thanks for the input
cool, thanks for that info.<?xml:namespace prefix = o ns = "urn:schemas-microsoft-comfficeffice" /><o></o> yea, they are more expensive, but will be WELL worth it. i use the word "budget" loosely...haha i'm not looking for high rpm, just a streetable motor with some punch.
Take the block to a machine shop that can mill the rear cam bearing journal to oil like the later big blocks. It will be worth your time >>>>.
i found a set of heads and the numbers are coming back with this according to Mortec: 3964290....69-70...oval..CLOSED..396, 402, 427, 454, 101cc chamber Large or small hex spark plugs used would these be decent to run....or worth buying? thanks for the help. Chris
anything would be better than the newer peanut port heads. If you can go to the junk yard and try to find a set of oval port heads with the 781 casting number. they have a 119cc open chamber, but flow pretty damn good. honestly with the money you would have in rebuilding a set of junk yard heads ontop of the initial cost/time invested you could buy a decent set of iron heads from Summit or Jegs. You usually have an option on what springs they are ***embeled with so you can taior them to suit your cam which also saves you money on the big end. I believe they have their own brand for something like $800-900 which is super cheap if you think about it. it is all in what you want the motor to do though. if you are using it for simply transportation i would keep it fairly stock, but nothing is gayer than a big block in a rod with no grunt. pm me if you have any other questions, im always happy to help if I can.
I'm not sure what year they changed the oiling on the BBC, you may or may not have the early block. Check the bell housing extension for the date code. The thing about open chamber vs. closed is that the open will drop compression about a point, but if still over say 9.0:1 will be worth 25-30 h.p.! If you use the stock style pistons with the short domes (which are about 0.100" tall) and closed heads they were 10.25:1 I believe. In this case the open chamber would be a good choice. As far as cost for getting the heads done, a lot depends on the condition of the valves and guides. There is no way to know this without a comeplete dis***embly and inspection. If the price is right on the heads, who knows, you may get lucky. I did, but then I had two sets of heads to source valves and a good set of springs came with one of them and I only needed to fix three or four guides. Another suggestion; befriend a machinist! I cannot stress this enough!
Using stock replacement 3/16" tall dome 396 pistons, you would probably not notice any difference at all in performance between the two sets of heads you listed. I did the same head swap way back when on the 396 in my truck....no change in 1/4 mile times or mph.
I would also like to add (since someone brought up the cost compared to a small block); the 396 will make as much power with stock heads as a 400 small block would with after market heads. And; the big block comes with a bullet proof bottom end, especially in the short stroke 396/427 versions. Another point; the 396 is so under stressed that it can be expected to live virtually forever. And; it's not a sbc, which you see everywhere (not that there's anything wrong with that, I happen to love them too). The only drawback to the big block is weight/size, but in most cases; who cares? P.S. Thanks to squirrel for chiming in, always value his opinions, as they are always backed by real world experience.
I 100% agree with you, my comment was aimed at his intent to do a "budget" build and usually small blocks fit that bill a lot better.
keep in mind, i'm well aware of how much it takes to build a big block...just want to make sure i'm not spending $$$$ where i don't need it. but i do appreciate all the input and advice. Chris
I was wondering that too. The "peanut" heads easily support 500hp and would be plenty for a 396 as long as compression can be worked out.
nothing more than what i found out here. project has kinda taken a backseat, i'm in the middle of moving houses right now... pretty much where i left off was trying to see if those late 454 heads are worth having rebuilt or should i shop for different heads...
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