Would like to here from some of you guys, that have put a relativly stock 400 in your third gen....What kind of performance did you get out of it....What mods did you do??? Would you do it again??? If so why???? and if not why not??What would you do different, if anything???..Thanks for any replys....Tom

 

Define "relatively stock". A completely stock 400 will perform pretty miserably.

 

well just your free breather...... intake, maybe exhaust...You got me on a technacality...lol.....No major motor work, just simple bolt ons........Thanks....

 

180HP stock or so. A stock L69 with new plugs will run circles around it.

Bolt ons? maybe up to 210HP or so. Heads and cam are what's going to put you in the high 300HP number.

 

are you serious? I have the chance to buy a l98 with trans and tpi for 850 or a 74 400 two bolt, for 700 with a th350..

I read that in 74 it was rated at 240..

while theese are low performing numbers, but a budget build up will get you over 400, and i know on nasty z28 theirs a guy runing a 413 vortec heads in a 3760 pound car, 12.15.. so theese motors can perform..just need some help

 

Of course, any motor can perform with some help. The huge amount of cubes help that. vortec heads are great, on big cubes like a 400, and a respectable cam, that will do just awesome.
ok, *maybe* in '74 it was rated at 240HP. I do know that... I think the '76 or something was around 180HP. Say in a 2500 truck.
BOAT ANCHOR. Until you cam it, and throw on some heads.

 

the 74 numbers he gave me
sound about right?

 

The 509 is probably the most common 400 block. Nothing special there. All stock heads that came on the 400s were garbage, and are possibly even worse than having no heads at all.

 

I guess it's post '72 or whatever, so it's not "gross" HP. None the less, I still think it's exaggerated.
Anyway, you're jacking this guys thread, so...

 

Every stock 400 2 or 4 bbl, from 1972 up with the NET rating was under 200 Net HP. Most commonly, I see them sitting at 175 Net FWHP @ 3,600/290 Net FWTQ @ 2,800. I can tell you that a good running stock 1978 K5 Blazer with a 400 will get waxed by a newer 87 K5 Blazer with a 350 TBI (210 Net FWHP @ 4,000/300 Net FWTQ @ 2,800). I saw the same result about 10 times the same night. Funny though, they BOTH got owned by a 305 powered Van.

 

I if I recall correctly the 400 SBC has limited performance potential because the cylinder walls are siamesed together preventing ample coolant flow between the cylinders.

 

The 400 sbc was never built as a performance engine by GM. It was always built as a cheaper alternative to a big block, like a 396 or 402. It was only used in trucks and the really big cars - early Monte Carlos, Impalas - stuff like that. They were meant to haul grandma and her 5000lb tank to the grocery store on Saturday and to church on Sunday. They were never built by GM as 'street/strip' engines like the 327, 350, 396 engines were.

That said - the 400 small block has alot of potential. Its got the biggest bore of any factory SBC engine at 4.125", and its also got the longest stroke of any factory small block at 3.75". Its also got larger main journals than the "large journal" 302/327/350 engines had. The biggest problem that the factory 400s had with their bottom end assemblies were the one-off connecting rods. They were the shortest ones Chevy used in any of their V8s at 5.565". All other small blocks used a 5.7" rod.

Now, if you are going to rebuild the shortblock, you can buy off the shelf pistons to use a 5.7" rod with the 400 crankshaft, which is something I would recommend doing for a performance build. I would also suggest using a set of flat top pistons, and using larger chamber heads to get the compression ratio you want.

There aren't really any factory heads that can do a very good job of feeding a high performance 400. The factory stuff, whether its double hump castings, Vortecs, whatever, work fine on the smaller motors, but just don't feed the big 400 very well. I would suggest using a set of high-performance aftermarket aluminum heads with a 400 - at least 195cc ports. AFR has heads what work great with 400s, as do others like TrickFlow, Dart, Brodix, etc.

The cam is the other important factor with building a 400. Anything that would work well with a 350, you'll want a cam about 5-10% larger for use in a 400. Those 400 cubic inches can take what would be a wild cam in a 350 and turn it into a tame truck cam fairly easy. I have an XE274 (230*/236* 110 LSA) in my 350, and its a pretty hot cam with this engine, but a friend of mine has a cam only a tiny little bit bigger in his 406 (236*/242* 108 LSA) and it runs ALOT tamer than what I have. Keep this in mind when picking out a cam for a 400. What would be a hot cam in a 350, would be tamed down alot with a 400.

 

Or you can build a 383, kits to do this are getting pretty reasonable and you don't have to have steam holes drilled in your heads, plus you can punch it out and rebuild it again when it's worn down. I personally don't see a big advantage to doing a 400 swap unless you find a very good condition block and have heads for it already. By the time you buy the longer rods and pistons you're approaching the price of a 383 build.

 

stroke it to a 406 and spray the **** outta it. 115+mph traps

 

A 406 is just a .030" overbored 400, no stroking necessary.
ah, didn't think i'd be pointing that out to "Lo-tec", different user here.

 

ha my mistake. was typing at a furious pace!

 

Air Adam
Thank you very much for your post...You seem to really know your stuff...I agree with you on most all of it, and I think I am leaning towards the 400..I beleive with the right heads, and cam, it could be a strong peformer.....Bound to make lots of tourqe if done right...I DO NOT WANT GRANDMA LATE FOR CHURCH...............................

 

Build the 400 with around 10:1 CR, some nice aluminum heads around 195-200cc, Edelbrock RPM and a 750cfm carb (Holley, Qjet, whatever) and a cam around 240*/246* and I think you'll be very happy with it. It would be a very fast combo, but also a very steetable combo as well.

 

Yes, must be streetable as it is my daily driver.......In my last Thirdgen, i went with all the Edelbrock Performer Parts...Cam, Intake, Exhaust..It was a really good low RPM motor, never broke nothing, and ran the hell out of it...Might try the RPM stuff this time...Thanks, Tom

 

Well, one of my buddies has a 72 Chevy with a 6 inch lift and 34 inch Swampers. It has a 408 with 10.5:1 flat top pistons, 750cfm Demon carb, and I forgo the specs on the cam but according to the sheets, it has about 485 hp, and redlines around 8grand. When he mud races it, he shifts at 7k and never had a problem with it, until he accidentally took it past 8 grand and stretched a rod he thinks. Still haven't took it apart yet to find out.

 

just do it like mine or buy mine whatever.
400 bored .030
stock crank
stock rods
speed pro hyper pistons 10.1 comp with 64 cc heads
cast iron bowtie heads (phase 2 castings)
.480/.480 lunati bmII cam and lifter set
edelbrock air gap intake

 

had a .040 over 400 flat top with decent heads and a small cam, it ran 12.65 @115 with a 780 holley 700r4 and 3.23`s , tried it with the tpi but it wouldn`t run past 4,500...with the holley 7,000 no problem. you`ll love the torque and horse...I went to a bigblock from the 408 and I was sorta sorry for leaving the big inch small blocks.....at first

 

greezemonkey......................WOW.......................................

 

thats kind of a sad number, ive heard 12.2 in a 412 ci smallblock with vortec heads, and it was a 3800 pound second gen...

 

11.70's from a 406, 195 AFRs, 236/242 108LSA cam, RPM Air Gap and 750dp carb - open headers. Not mine though. 3600lbs car.

 

No, 12's are very respectable, just what I want....Easy 12's are great....Thanks everyone for the replys.....Tom..

 

I think im going to step into the barely "streetable" category with mine...

brodix track 1 heads 221cc
solid lifter 252/ 260, Lift .540/ .558
850 holley dp
10.5:1 compression
6" rods.
Arp Studs throughout

 

This is what I am looking at. I bought a 1972 GM 400 4-bolt main smallblock for $400 bucks. I am planing on throwing this in my 92 camaro, probably attaching AFR 210's, and undecided cam, a T56 trans, an undecided fuel injection(already have a TPI but not sure if it will work), and a Procharger P1SC blower. I already have a Ford 9" rear end built by Moser modified to fit my camaro, and I definitely want everything to be streetable. After reading this thread I am a little worried about the strength and "buildability" of the 400. Am I putting together a good mustang killing streetcar, or should I be heading a different direction? What kind of HP numbers should I expect from this setup? I know I left a lot of questions unanswered, but when I fianlly get the $$ to build this, I am going to do it right. I appreciate the help and advice.
Cole

 

400s are quite capable of good performance.. the cooling is sometimes marginal (don't bore any larger than 0.030 if possible) and dont forget to drill steam holes in the heads if using aftermarket ones , TPI would not be a good choice for a 400 , and if you use a stick trans finding a flywheel may be a problem as they are externaly balanced , otherwise the engines respond the same as any other sbc , even in stock form a 400 is an upgrade from a stock 305 or TPI 350 .. the torque is where it's at with the stock 400 they pull like crazy to 5000, even with a stock cam and intake will out run most stock 3rd gen engine combos I had a stock 71, 400 that was originally a 2bbl (170 HP) put a stock 4bbl Q-jet intake and hedders on it and ran 12.2s in a car with 3.23 gears no other mods ... and it lived for five years (had over 150.000 miles on it)...

 

Well if I dont use the TPI., what will be the best fuel injection that I can get for my setup that will accept a Procharger blower?

 

400's are easy to get power out of. And, contrary to belief, you don't need steam holes, the guys that built mine, used 350 head gaskets.

But, I would really reccomend at least 5.7" rods and good pistons. Heads, with bigger cubes, get at least 190cc runners. I would take a 400 up to a 412 and not be scared to run it daily. Anything over that, forget it. If you can find a nice 509 casting, still new at .030 or virgin bore, get it...they are getting harder, and harder to find.

 

Im actually rebuilding a 74 sbc 400 casting 509 for my '89 Bird . Planning on a .030 overbore , ported heads (stock 882's) , cam , intake and carb . If you still interested i'll post you some news in two months when it'll run ...

 

sounds like a good build, but if you had any budget, get rid of the 882's, ported or not, that will kill your performance.....if you could find some used Vortec's even, 100% improvement

 

definitely true on the heads. I would look for either vortec's or aluminum vette D port heads. can find them both fairly cheap.

 

Chevy High Performance did a Vortec head 400. Here is the link.

 

let the block set out in the weather for 5 years or so the cyl. will rust but it will also cause them to harden...i did this inadvertatly and when i had it bored the machine shop said it was the hardest bore he had ever done and they have been doing race motors for over 20 years

 

True for the heads , but it seems I aint got no budget ... at least it's still better than a 305 .

 

Whether or not thats true (about the weather hardening the block) I can't really say, I'm no metalurgist, but I do know that hardness = brittleness. Not such a good quality in an engine block IMO.