leesvet

For guys that have built a 400 and placed it in a C4...
I am looking for the pitfalls BEFORE I get to them...

Mine is going to be forged bottom end, cast crank, flat tops. Looking at a rotating assy "kit" that's balanced and assembled from the mfg. Then we'll bore each hole and match the piston. The short block WILL be solid...

Cam undecided as of now...but it WILL be more of a mid-range. Roller/hyd.

Heads....AFR most likely but may consider something else IF the right deal/style came along...

What, if any problems did you run into with the accessory brackets and the other "stuff" that's bolted to the eng front?
Were there any new holes that had to be drilled, or did things line up as they should>? This will be a street driver capable of running with the new 500hp models...a "sleeper" of sorts...

oh yeah, this will stay EFI. For now the intake will probably be a big mouth base with slp runners all matched to the heads.

I WAS looking at a LT modified intake but after porting a couple, I see those are too thin to get lots of runner vol....and mini's are getting hard to come by. So it might stay TPI style for now.

Any other issues as far as bolt-on items and installation?

also, I forgot to look at my block, but did any of you use the oil temp sensor and where did you put it? I don't think the 400 block has a hole for that...?

This is a virgin, never bored, low miles by the looks of the cyl condition. Its a 515casting, 2 blt, 3 plug.

TIA for any tips/advice on a 400 build.

Kubs

We had a 400 in my dad's '91 camaro a few years ago and all the accessories bolted up fine. Since you won't be using the fuel pump on the side (carb setup), there is a bolt hole that is used to hold the pushrod in place while you mount the pump. I believe it is the highest of the two just to the left of the timing cover. It needs to be plugged or oil will come out of it. Some older blocks have this open, some do not so be sure to check. Also, since they are originally a non-roller block be sure to get a cam button and the proper timing cover for the conversion. It should look like a peace sign on the front of the stamping with a recess for the button to ride in.

rklessdriver

There is nothing really different about a SBC 400 than any other SBC. Accy brackets bolt and line right up no prolem.

When putting one in a C4 Corvette you need to use an aftermarket 7.25" harmonic balancer because the 8" factory balancer hits the crossmember. The Pro Race balancer Summit sells is a decent one. SFI approved and has a removeable counterweight if you need to balance it external or internal.

Of course it's a 2pc rear seal and external balance 400 Flywheels are usually the big 168 tooth... but there are aftermarket 153 tooth availiable both external and internal balance.

The 400 has a tapped oil pressure port right above the oil filter boss for the factory oil temp sendor... usually its plugges with a 3/8 NTP square head plug.

With the 406 inche engine, TPI would not work that well. Even big runners would be severly RPM limited. If you did convert an LT1 intake you can easily get 2.5" crosssectional area out of one... Thats plenty of crosssectional area for a 500hp 400 inch engine at 6000RPM.

When you are ready to buy a cam and bottom end stuff let me know if you want some help. I'll be glad to help you spec out a combo that will do what you want.
Will

bjankuski

Everything will bolt up the same, the only thing you need to be aware of is the oil dipstick will be on the opposite side and you may have to bend it to clear your headers. I am assuming you know that your flexplate or flywheel will be for the older two piece crank seal.

I had no issue with my oil temperature sender, it fit fine.

One side note, it will be hard to get 500 HP out of a TPI style of intake.

T. Wayne Nelson

It is going to bolt right in, no difference from a 350.....easy peezy

leesvet

cool...

that's exactly what I needed to know.

I've got the bottom end pretty well planned. Got a 1st class assembler doing the short block and an established machine shop to do the machine work. The bottom end will be as bullet proof as possible, designed to 'handle' accidental over-speeding past 6000. My goal is to stay together and pull up to/at 6000. Since its a street car there is no need to go beyond that. Street engines are 1/8 mle engines...stop-lite steeple-chase as its called. Not really worried about sustained high rpm.
As previously stated, for the time being it will be TPI style. It'll be ok...the pieces will be fitted and they will all be as opened as possible.
I know that's going to be what limits the output in a 406, but as opportunity and funds come available there are options for other intakes down the road somewhere. As long as I have a solid platform to build on...anything is possible. I'm blowing the budget on the short block. Top ends come and go. Its the short block that's here to stay

rklessdriver...
You're saying the LT intake has enough inside?
I was unsure of what the volume/area was, but I was concerned about the wall thickness after port work and matching...I've done a few and they end up real thin in a couple places if you go for full port matching....IIRC it was the outside runners lower corners that were awful close to other openings or cut-outs...
I mic'd the thin spots and found <4mm of metal in places.
That's after port work and matching, I'm a little worried that the 400 might get hot enough to cause problems with the intake if its too thin.

The one "got-to" is that each piece of the top end MUST be matched to the next...so the 'thin' issue with modified parts has to be considered.. I need to have all the parts together before I can say its acceptable or not...My runner set may end up being useless if they don't mate up well to the heads I buy.. They were cut to fit the 113 heads...so I'll have to see if they will be close to the new head.(probably AFR)

Since I've got the SLP stuff already and sitting on the shelf, I'll probably use that for now. Its no where near what it WAS....you can drop a golf ball in these runners and it will likely roll out the other end. These ARE thin wall ! ( they are now) actually went thru in a couple places and had to weld up and grind again.....they are very light weight design.


************** ***************** ******************
What are all of your thoughts on the pre-balanced rotating assemblies that are available ? getting a set of 8 nice pistons, mounted to nice rods already balanced to a tight spec w/crank is a time saver....IF its the real deal. These 'sets' cost a bit more but that portion of the build is DONE...they can be fitted to a hole right now instead of having to put 'em together and spend a day grinding and weighing each piece. You're going to pay the machine shop to do the work...or the people that made the pieces...6 one way....1/2 doz the udder. I was hoping to hear from someone that had bought and installed pre-balanced assemblies and get some feed back.

Anyway, the big questions were about brackets, senders etc...Those were my main concerns. The answers are appreciated. This will be a couple months project at least, since the body will be getting some needed attention while the engine is out. I'm sure there will be many more questions to come..
Thanks again !

cv67

Defintely have any balance job double checked youll thank yourself first time you start it.

Getting the bigmouth base to work with a 195 head shouldnt be a problem. The LT1 will be a HUGE step up that 400 will eat it up. Dont be afraid of epoxy, Ive done heads where the pinch point is half epoxy and hold up just fine.

Avoid billet cam gears make sure your cam endplay is in spec. Basic assy stuff

rklessdriver

Yes plenty of meat in an LT1 intake to port it to an AFR 195. It get's a little thin in some places but nothing I would worry about. The 400's I have built don't run any hotter than any other SBC.

Pre balanced rotators are kind of a PITA for me. I honestly hate going thru other peoples balance work, espc mass produced stuff..... I end up spending more time stopping and re-positioning bob weights when re-checking their stuff.... Sometimes it's honestly more work than just working up a bob weight and balancing a crank from scratch.

When parts are within 2 grams out of the box it's not a lot of work usually to get them down to .5 gram which is far closer than a pre balanced assembly is going to come. Takes about 2 hours and I know it's a good as anybody could ever get it.... Just one of those deals where I prefer to do it my way on engines I build.

Not to say the mass produced pre balanced assemblies don't work. At 500HP they do fine for 99% of the people who use them.

The other thing is your limited to the parts they offer pre balanced.... I'm personally not keen on having my internal parts selection limited by budget, availibility and what ever joe schmo decided to offer as a balance rotating assembly....
Will

383vett

Hey Lee, I was wondering what you meant by this statement. A forged bottom end means a forged crank. If you're going to run a cast crank, and are overbudget, I would also recommend running hypereutectic pistons. They will be less expensive, have closer tolerances than forged pistons and will hold up fine to 6000. Your motor will be fine with this setup for what you are doing. When I was running a 383, I was running a cast, nitrided crank and hypereutectic pistons and spun to 6000. The motor lasted for years, took me into the low 11's and is still alive today in a C3. Willie

WVZR-1

I noticed the same thing when I first read the OP's post but thought I'd give it some time to see what comments it might generate. He mentioned the 2 bolt block and the cast crank so I had no idea what he had in mind. Your piston construction I would say makes sense but I haven't shopped 400 SBC stuff for a couple decades so I've no idea what's available. Perhaps the OP might offer up some of the packages he mentions finding. There are certainly some packages that leave a lot to be desired.

T. Wayne Nelson

make sure you file the rear main seals to fit. A 400 is a two piece seal and needs to be fit to your crank. Just file the ends until they fit perfectly.

Churchkey

The 400 cu in 5.565 rod length might create problems @ 6K, to much rod angularity.
In 4 bolt main blocks I ran 3.48 arms with either 5.7 or 6" rods & custom pistons, .030 over bore = 377 inches. It will live past 7000rpm if a good crank is used but you will never see that rpm with the planned intake & cam.

Suggest reconsidering the "cast" crank.

2 piece rear main seal motor will require an 84 pan or a canton pan. Suggest a canton pan or run an extra quart of oil in a stock pan. Maybe add some "wings on a stock pan for more capacity. A 4qt pan can be sucked dry @ 6k.

Good luck.

leesvet

Yeah, regarding the statement "forged bottom end"...

I was being very general. I'm looking at forged pistons (JIC of bottle blowing at some point) w/ rods and probably a top shelf cast crank. Several good mfgs out there.
Then the whole mess balanced.

As I suspected, the feedback on the pre-balanced 'kits' is not a raving revue. I'm a little leery of just opening a box and sticking parts together....I'd pay the extra cash for the balanced stuff and then have it double checked anyway...so whats the point?

from rkless...
When parts are within 2 grams out of the box it's not a lot of work usually to get them down to .5 gram which is far closer than a pre balanced assembly is going to come. Takes about 2 hours and I know it's a good as anybody could ever get it.... Just one of those deals where I prefer to do it my way on engines I build.

That was to be my next question....whats the spec? .5gm is good? I wish I had asked when they did my current motor....its longevity and reliability must be the direct result of the precision assembly and balancing. I'm a believer....After all, it couldn't be the Pro-Long that's always been in the oil.....since I cannot prove one way or the other...I'll continue to do both.

My builder/consultant has a billet main cap he wants to sell...$150.
do I NEED a billet rear main cap ? its not going to be a race engine...just capable of performing like one if necessary.

The intake...???
still kicking that around....I know the LT is a bunch more breathing friendly with its short, fat runners, and a fair size plenum....but the big mouth and other baseplates have some huge ports as well and the SLP runners are practically open all the way down after grinding away 50% of the metal...all I need do there is mate it to the base. I'll do some more research on flow.. I like the simplicity of the LT. I have to consider the SLP & base TPI style since I've got that sitting here...and like I said, I'm planning on blowing the budget on the short block so any money saved is welcomed. I can't pick a cam until I decide on the intake...don;t want to starve it with too much cam on the tpi that won't feed well...but I DO want as much of a cam as it will handle.

Lots of good info here from you guys and its all appreciated. great food for thought. Lots of decisions to be made in the next few weeks.
Lots to think about.

When this is all said and done...there will be a new thread a week later titled:

700R4 builders... how do you get one to stay together behind a hi-hp motor?

cv67

Not that the TPI wont work it will but even ported the LTx manifold will still outperform it
If it were me the 2 bolt caps would stay. Maybe some studs or good bolts at most get a good line bore etc &put it together

rklessdriver

2 grams is "good"... as thats is what most parts are balanced to by the mfgr.... Keep in mind this could mean as large as 4 grams of error if the assembler wrongly matched up a heavy piston with a heavy rod or light piston with a light rod....

.5 gram is is as absolute perfect as you get. Thats the accuracy limit of most scales.

You do not need billet caps and do not want straight 4 bolt caps installed on a GM factory 400 block. The main web is very thin under the outside bolts and they will crack eventually. Not to mention the cost involved is not worth it on a GM 400 block. So got a good deal on $150 for caps but you still got alot of money to spend.

$200 to line bore install the caps on the block....
$200 for bore and hone the cyls
$300 to deck
$100 to clean and install cam brgs/core plugs....

You just put $950 in stock GM block (not counting whatever you paid for the core) and because it's a stock GM block, it'll never be worth anything.

A new DART SHP block is only $1500.

If you have a good stock 400 block my advice is build accordingly and enjoy it for what it can be. The days of us making them into 430+ inch 600+HP time bombs is over and theres no reason to spend that money on one today...
Will

cv67

Thats what steered me away from doing on myself
Seen too many times after sinking all the money into parts machining....torquing down the head bolts then hearing it pop...nice crack to the cyl wall.

If it were me id do a "driveway rebuild" +/heads cam and cross those fingers

It could last many thousands of miles or, god forbid if the block choked youre not really out much of anything

T. Wayne Nelson

I have a built 406, all the right stuff, and I mean the right stuff, easy $12,000 in the motor. I built it to be about 400 at the rear wheels, and that's what I got. Car runs really good, and is fast. But, if I had it all to do over again, I would drop in an LS motor in a new york second, and never look back...

DHobbs

Check out pro-filer heads

leesvet

yes, I'm well aware of the risk involved with the GM 400.....that's why they don't make a 400 sb anymore. It was at the design limit with the stock GM components.
Adding "up-grades" chisels away at the reliability pretty quick...

This one will stay 2 bolt. The 2 bolt caps are meatier than the 4's and the splaying looks like it enters the danger zone, although talk of splayed caps is good, I see the potential weakness.

the cast crank is JIC it ever see's a bottle and because GOOD cast cranks are just about as reliable. Its not going to "live" at redline....

The forged rods/pistons are for reliability and JIC it ever gets on the bottle...(hate the thought but its possible) besides, I've shattered hypertheuretic (sp???) pistons before. Not fun. I keep a couple (pieces) on the shelf as a reminder.

However, that being said and understood, I am a firm believer in a PLAN and doing homework. I believe that IF it is assembled correctly, and the block IS completely gone thru and machined, it will survive the performance parts installed and occasional romps to 6000 rpm. Its NOT going to see that kind of stress everyday...not even every MONTH,...only when some jackass in a ford or a dodge or even some foreign made 'sports car' looks down on my ancient Corvette...

Maybe its remembering when our BlackBird T/A got SMOKED by a 4 door chevy impala with a 400 back in the 70's...many years ago.....That humbled us for weeks.

If I wanted to build a motor to race and abuse, I would have done the shortcut to a Dart block and expected it to do MORE because its designed to DO MORE.

But, this is just a street-able healthy stump puller for a C4. It will ruin tires. It will keep ford products in the mirror and it will get on the freeway ramp with the new cars
(vettes, chargers, etc) that seem to look down at "classics" around here. I want to remind them that their wallet is not nearly as big as my ambition...and my current motor has done that job quite well for many years. Its getting up in age and a little loose, so its time for a new one. Why not go for a step UP? stroking a 350 has limits, ends up being just as fragile and there ain't much else to be done with it. And, everybody's got one. Again, with the correct assembly, and I MEAN precise, holes bored/honed to fit specific pistons, balancing, calculated quench, the whole enchilada, I believe the horror stories will be someone else's problem...not mine. I've built too many high performing bike engines to screw up something like this.
Precision is the key. (actually its CASH,but being exact helps)

My attitude is this....
..any A$$hole can BUY a fast car. All that takes is MONEY. It takes someone that LOVES cars and Corvettes to BUILD one that does the same tricks. Everyone here is proof of that.

The input and experiences of the members here is part of the homework assignment. The block is bought, already cleaned, shot-peened and checked out. It will get decked, line bored, then bored to fit the pistons marked for that hole. Precisely spec'd each cylinder. I've already requested torque plates to be used as well.
Then balanced. Getting a good GM 400 for under $600 that was stock bore was a deal....most were used and abused, bored to the limit and ready for the scrapers...
yeah, it'll be easy to get $750+ in machine work by the est I've got around here...maybe more, but it will be right and that is priceless. Good 'nuff is not acceptable.
Rotating assy...up to $2000. $1000 in heads, another $500 to $1000 in incidentals, misc stuff that's thought of as needed, and the mystery amount that will be spent on the chassis and eng bay while the motor is out....harness repair, clean-up, etc.

THEN....
we go to paint. Total stripping, disassembly and repaint. Lets spend that much AGAIN.

This is therapeutic. Its necessary to my survival...I'm writing the project off as healthcare this next year. When you get old and tired, you need dreams like this to be motivated to get dressed some mornings. This should be good for at least the next year....

BTW...

that $150 cap...
was ONE cap. Not a set. Just a single billet steel rear main. Probably NOT absolutely necessary.

383vett

I've been running a World Products 400 block. for the past number of years. It has priority oiling and all the good stuff. I would choose an aftermarket block before a used GM block.