USMC RCT

Hey guys,
First off a local mechanic told me that 400s are really only good for torque, Said most of em were made for trucks. I was figureing more cubes more horsepower, am i wrong here? He said it would be a better idea to just build a 350. But i dont want to do that. Is the 400 aftermarket stuff really that much more money, because i would much rather build the 400. Everyone has a 350 it seems. So i guess my question is the 400 a waste of time and money or am i gonna love it? im lookin for 425-450 horses. Sould i just build the damn 350? thanks guys,
Joe

five7kid

iTrader: (14)

The heads, cam, rods, intake, carb, and exhaust that came on small block 400's was the stuff of low RPM torque.

Get rid of all that, and you've got yourself a barn burner.

Start with a Motown shortblock, you've got the stuff capable of real power.

Parrydise7

iTrader: (1)

Do a search. There is a lot of information available on this subject.

RB83L69

Sounds to me like your "mechanic" thinks you have one, and is trying to talk you into gifting it to him for some kind of a sweet deal.

He's right in part; in factory trim, they sucked. The factory set them up for low-RPM grunt.

But that has nothing to do with what you can get out of one in a performance application. Put a set of heads on one that breathe, and a cam that does more than just crack the valves open for a few degrees, it's amazing what they'll do.

Parts cost is pretty muich the same as for an otherwise equivalent 350. In fact, alot of the parts ARE the same as for a 350.

If you can find one, build it.

MrDude_1

your mechanic is obviously ill-informed to performance motors.

find a diffrent mechanic before you start building your motor.


almost every bolt on part, from intake to heads to cam works with the 400.. the only diffs are:
heads and head gaskets need "steam holes" you can add these with a hand drill or pay a machine shop $30 to do this.

the balancer and flywheel/flexplate are external balance. you need 400 specific ones.


other then that, its just a small block chevy, and everything works on it. its not "special". parts dont cost more (except for 400->T56 flywheels.. ouch.) people just spout their ignorance when they dont know the answer, but they feel they must tell you somthing because they're a mechanic.

Air_Adam

In factory trim, yes, they were torque motors. They were designed to pull tree stumps or 5 kids and their junk on vacation, not to run 12's.

But its a big bore and big stroke. Get some preformance heads, intake, pistons, etc... in there and watch it start skinning every 350 on the street.

USMC RCT

thanks guys you just made my day, oh and hes not my mechanic hes just some shmuck who sells old chevys and parts for them and fixes late models on the side. I was looking at the holley systemax II system for a 350 build up but how would that perform on a 400? It says its for a 350 so if that setup wont work for me do you guys have any suggestions? This is my first engine build up so as of right now im clueless.

http://www.jegs.com/cgi-bin/ncommerc...50&prmenbr=361

Thanks, Joe

RB83L69

Yes it will work.

Keep in mind that a 400 is about 15% larger than a 350 (duh); so everything in the system — EVERYTHING — needs to flow 15% more at the same RPM. Or, turn that around backwards, and consider that if something maxes out at 6000 RPM on a 350, it will max out at around 5000 RPM on a 400. Think BIG.

TP355Z

Just a side-note - is your block a 4 or 2 bolt main? If you're going for real big hp numbers (over 550ish) and lots of RPM, you're safer with a 2 bolt with a good set of studs. Just a note.

Ty

4BoltMain

As far as I know all 400's were 2 bolt mains....

Oh and one other thing

Horsepower is what sells cars, TORQUE is what moves them.

CaptPicardsZ28

Actually that is false. All 400's were not 2 bolt mains. The 4 bolt mains were weaker than the 2 bolt. Like everyone said, get the right combo of stuff and your good to go. You will be very happy with a 400. They are in high demand and getting harder to find. I had mine bored .030 over. My next one will be .060 over.

Riley's35089rs+

My 406 Stomps all over my 94 Z-28 YEEE HAAAA!!!

89firebird400

most 400's are 2 bolts cause the only 4 bolt ones were only made from 1970-73. From 1973-1980 they were 2 bolts. I have a whole casting number list here if you would like to know what yours is. I believe that most if not all of the 4 bolts had the casting number 3951511. hope this helps

Parrydise7

iTrader: (1)

The good capt (Picard) is right. There are some four-bolt main 400s, but they are less desirable. IIRC the four-bolt mains actually weaken the block. Again, IIRC, Chevrolet introduced splayed four-bolt mains to correct the problem.

Air_Adam

Nope, not on a production-car/truck block. Race block maybe, but not a regular production block.

Riley's35089rs+

Thats right! I had a 327 one time that came with 4 bolt Mains..now we all know there are no 4-bolt 327's. Someone had enterd splayed caps along the way.

Air_Adam

Or it was a LJ 327 block... which was also a 350/302 block, and could have 4-bolt mains.

Riley's35089rs+

Mine was for sure SJ. But thats a good point

wesilva

iTrader: (35)

Although the four bolt mains webs are weaker, I would not pass them up if you find a good deal. You can simply use main studs instead of bolts. Studs pull evenly between the main cap and the web where bolts put most of the stress on the web. I have a four bolt motor living a very happy life with no worries. If you are going .060 over, it is almost mandatory to have the block sonic checked. 400's have fairly thin cylinder walls. Mine needed to go .060" and I had it sonic checked then filled it some with Hard Blok water jacket filler.

Confuzed1

iTrader: (4)

And there's something wrong with a lot of torque?? I just don't see it myself. You want a strip only car, or a street/strip car?

Strip only, I'd build for HP in the upper rpm range. For a street/strip type build, I'd bring everything down to a more useable rpm for the street.

As mentioned above, it all depends on the combination of parts you put on it.

Oh BTW - If I were building a strip only car, I'd go with a 2 bolt, or better yet -splayed main caps. For a street engine, either a factory 2 bolt or 4 bolt should hold up to 6 grand I would think....

Just my .02

OOOHRAHHH!!!!

CamaroRS385hp

true, but you'll probably spend over half of your engine-building budget on the block alone. for those with the money, it doesn't get much better than a motown block, but for most people, money vs. power wise, they're MUCH better off getting a 400 block from a junkyard and having it cleaned up