400 help

[Silverray76]

Hey guys so i found a 400 sb for sale its just the block, no internals. I plan to build it form the ground up and i would like some tips from a more experienced builder. I would like this motor to but out at least 475-550 or anywhere between that. The person who im buying it off of said it original and has never been resurfaced which means Im going to have the block resurfaced. Now Im going to go some kind of racing pistons also it there a specific bore size i have to go to? and would be great parts for the motor. Opinions would be helpful or recommendations.

[gchemist]

Measure the bores with a caliper. Drill some steam holes. By resurfaced, do you mean bored out? Resurfaced is a term mostly for head milling/surfacing. The deck should be flat to mount the head. Are you going to use aluminum heads? Even good Vortec heads will have trouble at the 475 HP range. You need to plan out your parts carefully, or buy a kit with everything. Post/move this post over the engine forum.

[Hazieview]

I have just recently finished building my own sb400. It was my first time to ever build an engine.

In order to give you more feedback I'd have to know more along the lines of what your budget is.

If I had I choice to build mine over again I would get a totally balanced and forged bottom end! These engines make a lot of torque in a very narrow rpm range.

Also dont expect to get too much HP out of an sb400. They are torque monsters!

DO NOT GET A HUGE CAMSHAFT!!!
From the research I have done the gains of a sb400 after 5500 rpm is very minimal. So you want to get as much power out of one as you can from 0-5500. That is where you need to spend your money.

With a stock bottom end, cast heads, air gap intake, 650cfm carb, I was told I should be making around 580lbs of torque. Not sure how accurate this is but I'll be putting it on the dyno as soon as I get the rest of my truck bolted up.

I would not rebuild a sb400 unless it was a two bolt main. (The 4 bolt main sb400s are not usually strong enough to handle near as much power. Just my opinion.)

DRILLING STEAM HOLES IS A MUST AS STATED ABOVE!!!

I would not bore a sb400 more than 60 over. If you ever bang out a sb400 that is bored 60 over you might as well start looking for a block and throw yours in the scrap metal bin. I went 30 over just in hopes that if I do make a mistake somewhere I still have a chance to go 60 over with it.

Now I'm not a professional racer, engine builder, or anything like that. I'm a guy that likes cold beer and nice chevys. However I've taken a lot of good advice from very knowledgible people. A lot of them you will find on this board.

Every man has different theories as to how one should build an engine. Which theory you choose to believe is your own.

Good luck man! Take care!

(just my 2 cents dont take this crap for gospel)

[Silverray76]

Originally Posted by Hazieview

I have just recently finished building my own sb400. It was my first time to ever build an engine.

In order to give you more feedback I'd have to know more along the lines of what your budget is.

If I had I choice to build mine over again I would get a totally balanced and forged bottom end! These engines make a lot of torque in a very narrow rpm range.

Also dont expect to get too much HP out of an sb400. They are torque monsters!

DO NOT GET A HUGE CAMSHAFT!!!
From the research I have done the gains of a sb400 after 5500 rpm is very minimal. So you want to get as much power out of one as you can from 0-5500. That is where you need to spend your money.

With a stock bottom end, cast heads, air gap intake, 650cfm carb, I was told I should be making around 580lbs of torque. Not sure how accurate this is but I'll be putting it on the dyno as soon as I get the rest of my truck bolted up.

I would not rebuild a sb400 unless it was a two bolt main. (The 4 bolt main sb400s are not usually strong enough to handle near as much power. Just my opinion.)

DRILLING STEAM HOLES IS A MUST AS STATED ABOVE!!!

I would not bore a sb400 more than 60 over. If you ever bang out a sb400 that is bored 60 over you might as well start looking for a block and throw yours in the scrap metal bin. I went 30 over just in hopes that if I do make a mistake somewhere I still have a chance to go 60 over with it.

Now I'm not a professional racer, engine builder, or anything like that. I'm a guy that likes cold beer and nice chevys. However I've taken a lot of good advice from very knowledgible people. A lot of them you will find on this board.

Every man has different theories as to how one should build an engine. Which theory you choose to believe is your own.

Good luck man! Take care!

(just my 2 cents dont take this crap for gospel)

My budget is a bi weekly paycheck. I make about 1800 a month. The block is a 2bolt main. Now my bottom end wont be stock I plan to buy a new crank and race piston,cam rods ect. Now you say drop my money into the 0-5500 range.. Now do you mean the low end? Now i was planning to bore about 40 over bad or good? what parts would you rec? I was going to go comp thumper cam and a entire comp lifters,rockers,ect.

[Hazieview]

I'm a little confused man. Sorry...

If you are wanting to go with a different crank, rods, and 'racing' pistons I would recommend a full scat rottating assembly.

$1,852.95
Scat Engine Rotating Assemblies(this kit is for an sb400 bored 40 over)

40 over is good. However I would recommend 30 over because it's just more common.

I would not get a thumper cam. It sounds good but you kind find other cams that will produce power way more effeciently.

When I say 0-5500 there are parts out there that are designed with this particular range in mind. Look up various intake manifolds, camshafts, etc. Most of the time it shows you their power range. My engine is actually designed to make its power from 1500-6500 rpm. However I have a 2200 stall converter so it works well with my application.

I would also recommend using your stock bottom end if nothing is wrong with it. That's what I did. I got new pistons and used my original crank and rods. I then spent more money on the top end.

For what you are saying you want it is going to end up costing you around $10,000 or so. I highly recomend creating a budget so you can come up with the total amount you want to spend on your engine.

My total was $3,000 tops... I ended up spending $6,000 and still have a stock bottom end...

If you want to play you have to pay!

[Silverray76]

Originally Posted by gchemist

Measure the bores with a caliper. Drill some steam holes. By resurfaced, do you mean bored out? Resurfaced is a term mostly for head milling/surfacing. The deck should be flat to mount the head. Are you going to use aluminum heads? Even good Vortec heads will have trouble at the 475 HP range. You need to plan out your parts carefully, or buy a kit with everything. Post/move this post over the engine forum.

Its a original block from what im told so i guess it has a stock bore. Drilling steam holes? Ive never heard of it yet im willing to learn. Im not to sure what heads im going to use yet i might go aluminum. This is the part where i go to experienced builders to give me advice

[Hazieview]

What's your budget? I got over $6000 in mine just to give you an idea. That's with my stock bottom end and cast heads.

[gchemist]

Buget an issue? DESTROKE IT!!

[INSIDIOUS '86]

Originally Posted by gchemist

Buget an issue? DESTROKE IT!!

i would leave it stock stroke, although there is nothing wrong with a 377 ( i have one) a 406 is better suited to our flying barns,

for 420-450 hp use some flat top pistons with about a 9.2:1-95:1 compression ratio so pump gas is an option. get some aftermarket iron heads( dart/world) or scoggin dickey modified vortechs. a comp cams magnum series cam, with matching valvesprings, and roller rockers, scat rotating assembly (dont need forged yet) with SCAT i beam rods NOT STOCK RODS! have your engine magnafluxed tanked and bored .30 over and TORQUE PLATE HONE! throw on your 4bbrl of choice in an single plain high rise or victor jr dual plane airgap msd street fire distributor

500-550 hp, use the same top end, but change heads to edelbrock perf rpm or afrs aluminum and raise the compression to 10.5:1-11:1 still use the .30 overbore and honing/ magnaflux, add deck milling and a line hone as good options for thouroughness, get a scat FORGED crank, FORGED pistons of choice of your brand ( I Like ross) and MAYBE I beam rods from scat or h beams if you want to beat the **** out of that engine, get a nice spendy crank dampner and then finish with a hamburgers oil pan (#1088) melling HV oil pump, msd billet series hei. msd 6al (for rev limeter, your going to need it) full roller rockers of your choosing. (pst... harland sharps) and the cam should be a SOLID flat TAPPET or roller that is big, (530-545 lift) also add a windage tray

as always i recommend you call comp cams for the camshaft selection as they will set you up with a good choice cam from the getgo

thats how i build my engines, bullet proof them! anybody agree or disagree with parts above?

[Hazieview]

Why would u not reuse the stock crank and rods if they are still in good shape?
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[85Bowtie]

You never bore an engine anymore than you need to clean up the cylinders. The steam holes somebody mentioned I believe you drill because the 400 is a siamese bore if I remember correctly.

I'm not sure what parts will get you 550HP the "easiest" on a "budget"....but I will tell you 550HP is a PITA for a vehicle you plan on driving often, especially in a place like LA. I make trips to Edwards AFB often, and I would never drive anything like that on the 405...

[INSIDIOUS '86]

Originally Posted by 85Bowtie

You never bore an engine anymore than you need to clean up the cylinders. The steam holes somebody mentioned I believe you drill because the 400 is a siamese bore if I remember correctly.

I'm not sure what parts will get you 550HP the "easiest" on a "budget"....but I will tell you 550HP is a PITA for a vehicle you plan on driving often, especially in a place like LA. I make trips to Edwards AFB often, and I would never drive anything like that on the 405...

400 is a siamese bore and i wouldnt even bore a 400 over .30 overbore since the walls get to thin for high hp.

and getting 500 hp is just a pita in general cause its a whole fiffrent ball game, alot has to change to make it rather reliable, and its even more pita to make it streetable at those levels

and to answer why i wouldnt reuse the stock crank and rods is that i just dont trust stockers past 400 hp to be reliable and a cast crank from scat is as cheap as refurbishing a used one just about, plus its lighter and you may as well get a matched and balanced rotating assembly instead of mix and match, just how i like to do things anyway, but for a 450 hp stock rotators and hyperutectic pistons do the job just fine

[406 Q-ship]

Ok this thread needs alot of clean up. I have a 406 SBC in my 71 Monte Carlo that puts 425 hp / 480 ft lbs with GM iron heads.

The block already has the steam holes that everyone speaks of, it is the heads that will need the steam holes drilled (unless you use heads off the 400). The stock crank is fine for up to 500 hp but edgy at that (450 better), the rods in a stock 400 are shorter than all the other SBC which is harder on the bores. If you choose to use the stock cast crank you will have to use external balanced flywheel/flexplate and harmonic balancer. DO NOT go over .030 over bore either, cylinder walls in a 400 are thin enough.

How do you want to use this engine, will it be a weekend warrior down at the local strip, will it be in a 4x4 that gets to go rockcrawling, or is going to take you back and forth to work everyday and must run on street gas?

I would not go above 10.00 on the compression if your going on a street gas engine, and at that high it will need good aluminum heads (9.0 with iron heads), on a race engine that may see the street go up to 11.0 compression. Cast bottom end is OK for a street driver that see track time but do NOT try to put a big cam in it, or try spining the engine to the moon. Use the 400's torque to your advantage, ignore all the Horsepower talk. Horsepower is a formula on a piece of paper, if you build it for torque, horsepower will take care of itself.

Here is the question to ask yourself:

1. What do I want to do with this engine in the truck? Daily Driver, weekend warrior, show truck?

2. Will it run on pump gas?

3. 2wd or 4x4?

4. Automatic or manual trans? If auto what converter and how much stall speed to live with?

5. What gear ratio?

[Tony@AirRideTech]

yup.... if it were mine....

350 crank.... good heads.... descent cam around a 510 lift with a standard trans and let her eat Also... personally I wouldnt go more than 30 over with the bore.

[406 Q-ship]

Originally Posted by Tony@AirRideTech

yup.... if it were mine....

350 crank.... good heads.... descent cam around a 510 lift with a standard trans and let her eat Also... personally I wouldnt go more than 30 over with the bore.

I actually agree with the 3.48 storke and spacer bearing in the 400 block, or get a 3.48 stroke crank in 400 main bearing sizes. With .030 overbore you get a 377, it has torque like a 350 but with a RPM range like a 327....oh my GOD what fun a 377 is! I have a fitting 400 block that I plan on making into a 372 (stardard bore 400) but I will not use it in my truck but in a nice road racer.

[3r!c84]

you dont need all that to go fast. i mean how fast do you want to go? just a weekend toy to take to the strip? this is what i got in mine..


400 small block. two eyebrow flat top pistons standerd bore 9:5to1compression . elgin cam split lift .503 .510 and split duration. stock truck heads.with bigger valves 1.5/1.9inch, 1:6roller rockers. edelbrock eps intake. holley 750 carb. msd ignition box. billet hei. stock th350 with a trans go shift kit. stock stall converter. 10bolt with 3:42 gears and airborne race posi. 235/75/15 tires.





and the video tells the rest..

84 c10 pbir - YouTube

[87Bob]

If I had a solid 400 block I'd build it. But these days if you want great power with out having to build a motor the LS series motors make great power. With more and more winding up in junk yards you can get a iron block for several hundred and not have to build it. One of the shows on the Spike Power Block did a transplant. Just get a low mileage one. It will have much more potential the the old small blocks. There are lots of performance parts available. Better fuel economy as well. True story: A friend of mine has a 92 Corvette LT1 with a blower from Lingenfelter, I have a 99 Corvette with a bone stock LS1 We are equal from a rolling 35 mph start. His blower cost 5,000 extra. Good luck with your build remember you have options.

[BigBlocksRule]

Use a stock crank, they're nodular iron (just like big block cast cranks) and are generally good for more power than the stock block can take.
No real reason to destroke one, you're costing yourself power. Torque comes from displacement, more cubes = more power.
Find some Vortec heads, drill 'em for steam holes, get some pistons that'll put you at no more than 9.75:1 and build it. You'll have big block torque and small block economy.

[bmchevy1979]

I actually agree with the above about using a stock crank I have this exact decision to make right now I have a 400sb out of my blazer that has a shot crank and a good 350 crank and rods that I could put in with some spacers and new pistons or buy a used crank and hope it is not in the same shape as my current one or even buy a whole new crank I am still undecided but if you can I would go with the stock stroke crank

[406 Q-ship]

No matter what you choose to do, use the longer rods from the 350 Chevy. The 5.7"(the lenght of the rod not the engine size) from a 350 will reduce friction in the engine along with more power the engine will last longer. The rods from any 1969 and later 307/305/350 are forged (except the really late 305/350 that had powdered metal ones) and more good for a hard running 406 SBC. My 406 has regular old GM 5.70" SBC rods. They will require a bit of clearancing if the base circle on the cam gets too big (mine has had this done).

[jrcaprai]

1st thing to do, is make sure you get the block Sonic Checked to make sure you have enough cylinder wall to Bore...

Remember this, by the time you get your Crank And Rods Refurbed, you will be close in cost as a new Crank And Rods

Mine is a 408... .40 over.. I bought a Scat Forged Kit, 4340 Crank, Flat top Pistons, And 6.0 Inch Forged I beam Rods... It is Internally Balanced...

DON"T Destroke it... you will lose about 30-40 Ft-LBS of Torque and Horsepower...

The Heads, and Valve train are what limits your RPM's Not your Stroke.... Mine goes to 7000 RPM

You Want Big Power, #1 Priority is Good Heads... then Valvetrain... But make sure you have a solid Bottome end to support it.

I have 11.6 to 1 Compression, use Pump Gas and Drive on the Street...

My Cam is a Comp Roller 242/248 Dur @.50 and 576/600 Lift...

I have a 3000 RPM Converter, and it is very street-able...

Don't let these guys scare you into a torqey engine that falls off at 5000 RPM...
theres nothing like having a truck that screams to 7000 RPM before it falls off, and has just as much if not more torque than the 5000 RPM motor

Unless you're only going to Tow or Haul stuff with it

[406 Q-ship]

Originally Posted by jrcaprai

1st thing to do, is make sure you get the block Sonic Checked to make sure you have enough cylinder wall to Bore...

Remember this, by the time you get your Crank And Rods Refurbed, you will be close in cost as a new Crank And Rods

Mine is a 408... .40 over.. I bought a Scat Forged Kit, 4340 Crank, Flat top Pistons, And 6.0 Inch Forged I beam Rods... It is Internally Balanced...

DON"T Destroke it... you will lose about 30-40 Ft-LBS of Torque and Horsepower...

The Heads, and Valve train are what limits your RPM's Not your Stroke.... Mine goes to 7000 RPM

You Want Big Power, #1 Priority is Good Heads... then Valvetrain... But make sure you have a solid Bottome end to support it.

I have 11.6 to 1 Compression, use Pump Gas and Drive on the Street...

My Cam is a Comp Roller 242/248 Dur @.50 and 576/600 Lift...

I have a 3000 RPM Converter, and it is very street-able...

Don't let these guys scare you into a torqey engine that falls off at 5000 RPM...
theres nothing like having a truck that screams to 7000 RPM before it falls off, and has just as much if not more torque than the 5000 RPM motor

Unless you're only going to Tow or Haul stuff with it

Mostly true but understand this too, a high RPM engine wears itself out faster, is more expensive to build because it requires better valvetrain and bottom end componants to stay together with the heavier 3.75 stroke To get the RPM to 7000 with a 3.75 stroke will require a cam that does not come on till at least 3000 RPM, and at that your throwing away alot of the reason for 400 SBC in the first place. That big of a cam will require a bigger stall converter, deeper gears, and low engine vacuum (think no boost on the power brakes), all of these things will get you a real gas using engine that is not fun on a daily driver, I am not trying to offend just give all the realitys. Do yourself and your wallet a favor, keep the RPM down to 6000 and under. My 406 pulls right up to 5500 and is the most fun you can have with your clothes on. Besides I run a stock L88 torque converter (2200 stall) and 3.31 gears and it runs down the highway without turning 3500 to go 65 mph.

[jrcaprai]

[QUOTE=406 Q-ship;4851763 a high RPM engine wears itself out faster, is more expensive to build because it requires better valvetrain and bottom end componants to stay together with the heavier 3.75 stroke To get the RPM to 7000 with a 3.75 stroke will require a cam that does not come on till at least 3000 RPM, That big of a cam will require a bigger stall converter, deeper gears, and low engine vacuum (think no boost on the power brakes), all of these things will get you a real gas using engine that is not fun on a daily driver, I am not trying to offend just give all the realitys. Do yourself and your wallet a favor, keep the RPM down to 6000 and under. My 406 pulls right up to 5500 and is the most fun you can have with your clothes on. Besides I run a stock L88 torque converter (2200 stall) and 3.31 gears and it runs down the highway without turning 3500 to go 65 mph.[/QUOTE]



You don't have to run to 7000 RPM all the time... I don't... But when I do.

that old saying goes, How fast do you want to go? how much money do you want to Spend?

What do you mean with the "heavier" 3.75 Stroke???? 3.75 Stroke is Stock...

The RPM's come on sooo Quick that 3000 RPM is a Blink of an eye... Mine I'm Sure has as much or more torque than most at 3000... there is no Lag time..Whatsoever.

I'll give you the Brakes and Gas Mileage... I had to add a vacuum Reservoir
and I get about 8 MPG

I have 3.73 Gears and a 3000 RPM Converter, and it runs about 3800 RPM at 65, which does suck, but that's what Overdrive Transmissions are for...

Do your self a favor and get a Hydraulic Roller Cam... most Big engine builders are pushing their customers away from Flat tappets, due to the high rate of failure, due to the lack of ZDDP in today's oils...

[406 Q-ship]

Originally Posted by jrcaprai

You don't have to run to 7000 RPM all the time... I don't... But when I do. Don't you think that 5800 to 6000 is fun too? The OP sounds like he might be on a tighter budget than you were, so keeping the RPM down will make the build much more economical

that old saying goes, How fast do you want to go? how much money do you want to Spend? If you have the cash and want to spend it.

What do you mean with the "heavier" 3.75 Stroke???? 3.75 Stroke is Stock... The longer the stroke then the heavier the counter weight on the crank, so it is harder on a 400 crank than a 350 crank to spin it to 7000. As the rpm and the weight rises the forces on the crank goes up exponentually. In other words if you double the weight of the crank the forces go up by a factor of four.

The RPM's come on sooo Quick that 3000 RPM is a Blink of an eye... Mine I'm Sure has as much or more torque than most at 3000... there is no Lag time..Whatsoever. That is your 3000 stall converter doing its job and your cam comes in at right around 3000. Mine starts pulling at 1500 with a big long flat torque curve that makes for a fun driver, without all the issues. I don't need deep gears, high stall, and mine has gotten 17 MPH (TH400) in a 4000 lbs car that will run 12.90's all day long. I am not knocking your build, just not the engine I would do in a full size truck.

I'll give you the Brakes and Gas Mileage... I had to add a vacuum Reservoir
and I get about 8 MPG

I have 3.73 Gears and a 3000 RPM Converter, and it runs about 3800 RPM at 65, which does suck, but that's what Overdrive Transmissions are for...

Do your self a favor and get a Hydraulic Roller Cam... most Big engine builders are pushing their customers away from Flat tappets, due to the high rate of failure, due to the lack of ZDDP in today's oils...I totally agree on the Hydraulic Roller cam but will raise another issue with high RPM. HYD Roller cams have heavy lifters and it does nasty things when you get spining them real hard. Keep the RPM 6000 and under or you will see bad valvetrain harmonics (read valve float), unless you invest in a rev kit.

Whatever way the OP descides to build it, the 400 is a barrel of fun engine!

[85Bowtie]

Originally Posted by jrcaprai

Do your self a favor and get a Hydraulic Roller Cam... most Big engine builders are pushing their customers away from Flat tappets, due to the high rate of failure, due to the lack of ZDDP in today's oils...

Roller cams are good ideas...but the whole "high rate of failure" thing is blown way out of proportion.

A flat tappet cam is fine. Break it in correctly and run a good oil with a bottle of zinc additive and you shouldn't have any problems. You use to be able to just run Rotella Shell 15w-40 diesel oil in them but now they have something like 1400ppm zddp. I usually just pick up a bottle of Comp Cams break in lube and throw it in with an oil change, but I change the oil in my cars maybe once a year. I do however run Rotella Shell and a bottle of STP Oil Treatment in my old Diplomat with a flat tappet and it runs great...haven't wiped a lobe yet after 50,000 miles.