I did a search, but only came up with limited info...
I was given a complete '71 400 small block, 4 bolt main engine, with flywheel, and harmonic balancer, less intake, and carb.
With all the talk about "stroker" motors, I'm not sure which way to go. :confused:
Why don't more people build 400s? (other than they're a little harder to find)
Is there any great advantage to a 383, or a 377 over the 400?
I would think the more CID the better....
I also recall something about Steam holes in the 400 heads. Can a guy use "normal" heads on a 400 block?
it will end up in a 68 Camaro.
Any other pros, or cons?

Thanks in advance graemlins/beers.gif

Nice job scoring the 400. I think you should build the 400 rather than go the 377 or 383 route. A 377 would rev quicker but the 400 would make as much or more power and have more lower end than both the 383 and 377. 450 HP should be easy to make with the 400. You'll need to choose what fuel this thing will drink before choosing pistons, heads and cam. Even a dished piston with 64 cc heads makes respectable compression in a 400. The weak link in a 400 is the connecting rods from what I've been told, they are shorter than all the other smallblocks chevy produced. The aftermarket pistons available from most suppliers offer them for use with longer rods which supposedly helps reduce side loading on the piston skirts. The steam holes will need to be drilled in any non400 type head you plan to use but this is no big deal, a 20 minute job. I'd go with the longer rods, bore it .030-.040 over, use flattops or dished pistons, 64cc heads, 280-290ish solid lifter cam, aftermarket heads with 180-200 cc intake port volume, have the crank cut if needed and assembly balanced, zero deck the block, rpm airgap intake, 750 Holley. With the right alluminum heads and flattop pistons and cam I bet she'd run on 93 octane without a problem.

Build the 400.

Throw the heads that are on it away, if they came on it from the factory.

There is no advantage to leaving out any of the cubes. The reason people build 383s is because they don't have what you've got (a 4.125" block). The reason people build 377s is either class rules, or not understanding the HP/$$$ equation. In neither case does it produce a "better" motor than one with all 400 inches.

I wouldn't worry so much about the rods, if it's a street application, below 6000 RPM or so. Alot of your decisions will depend on what you intend to do with the engine. The one thing you should do, however, is to replace the rod bolts, no matter what, if you use the stock rods; that's the weak link, not the rods themselves.

I'd say you could install the steam holes in 20 minutes, if you stopped for lots and lots of beverage breaks. 5-10 minutes should do it, with a good sharp drill bit. All you do is lay a head gasket on the head as a template, mark the missing holes with a center punch, and drill about 3/16" holes. 6 per head. Angle the ones on the intake side over toward the exhaust if you're working on aftermarket heads, because on alot of them, the head bolt hole that you'll be drilling right next to, is very thick, and you'll miss the water jacket if you go straight in.

Use small chamber heads and "reverse dome" pistons (where the dish is roughly the same shape as the chamber) if at all possible, rather than large chamber heads and domes or even flat-tops. Choose heads with LOTS OF FLOW. Heads that seem too large for a 350, are probably about too small for a 400. You can also use about one step larger cam out of any of the typical mfr's lineup in a 400 than you would in a 350, for otherwise equal results as far as RPM range and idle quality and all that.

I agree with everything that's already being said. MUST do the steam holes and for sure it's RECOMMENDED to goto a 5.7" rod as the stock 5.56" rods are anything but desirable. I am still using the stock rods/crank in my 400 but wish I waited another month this past summer when I put it together to save and buy new rods instead. As long as the 400 block is in good shape there's really no reason to not use it, and instead go with a 383. Especially if this motor is going to see any street time. Even destroking the 400 block down to 377 would only make sense if racing and rules didn't allow larger. All the power you can make with a 377 or 383 can be made easier and at a lower rpm with the full 400 cubic inches.

Have you decided on the rest of your setup or what the use of it will be?

Originally posted by Zman:
I did a search, but only came up with limited info...
I was given a complete '71 400 small block, 4 bolt main engine, with flywheel, and harmonic balancer, less intake, and carb.
With all the talk about "stroker" motors, I'm not sure which way to go. :confused:
Why don't more people build 400s? (other than they're a little harder to find)
Is there any great advantage to a 383, or a 377 over the 400?
I would think the more CID the better....
I also recall something about Steam holes in the 400 heads. Can a guy use "normal" heads on a 400 block?
it will end up in a 68 Camaro.
Any other pros, or cons?

Thanks in advance graemlins/beers.gif Do a search on username 68chevelle533. He has a really nice, mild 400 running low, low 12's in his Chevelle.

Rod

Build the 400 if you wish but you'll want good cylinder heads and a compatable cam obviously.I can tell you if I wanted to build an efficient very powerful smallblock it would be a destroked 400 with heads with a reduced valve angle, something of the order of 4.155 bore and 3.250 stroke and at least 18 degree heads. If you run the basic 400 at least run a longer rod if you can and of course you'll need the special pistons that go with it.......the difference between a 400 and 377?.....I'd go with the 377.....all this is assuming the stock block is used and BTW the short rods make me nervous :D :cool:

Thanks for all the replies guys!
Actually, the motor will be going in a friend's 68 Camaro.
I've been doing some research, and talking with others, and I think we'll go with a 406, with after market Crank, rods, and heads.
The car will be mostly street driven, with an occasional trip to the track just for fun.
Thanks again for the infos.

bore it 20 over if it will clear so you can save the block as long as posible .since your going with after market rods and piston i asume your going with 5.7 rods witch is fine but it will not run any faster than the 5.56 rods.the only weak link in the rods is the bolts as with the stock 5.7 rods.the lighter the piston is the faster she will rev.you will have to clearance the rods if you use 5.7 rods or use a small base circle cam so dont just stick it together with out checking as you build it.the right heads and cam ,gears and converter 11s are easy to obtain

This is what I have-

407 3.75 Scat 4340x 4.155 bore
6" Scat rod, SRP Flat top, 10.3 comp.,
XE274 Comp Cam, 1.6 Crane rockers,
AFR 195cc Heads, RPM Air-gap, 770 Holley.

I clearanced for the rods, but had no problem with the cam clearance.

Runs FANTASTIC! TOO much bottom end. Idles well, no overheating, not enough vacuum for power brakes.

Don't use stock rods,they don't work in a stock application, let alone a performance one.

My 2cents,
Doug