Hi guys, finally getting a chance to build up my 400BB that i have had forever, was foolish and young and listened to the advice of others and tore it down with no budget to rebuild it, now as it sits I have a 400BB , nothing real special just a '78 (date code 10-4-78) block stock bore





stock (to my knowledge) 906 heads

and i was told this is a forged steel 383 crank




the red stuff you see is HD bearing grease to protect the journals



can anyone confirm this is a forged steel crank ?

Also with this crank does my stock 400 rods and pistons have to get balanced as a whole ?

What kind of crank damper do i need to run ? one for internal balance or external ?

got a bone stock '67 727 that i am getting tomorrow from a guy here local, worked when pulled, I will still go through it before i bolt it all up together. What kind of flex plate should i use ? I can't imagine this thing making gobs enough torque to break a stock one in stock form, also does a slant flex plate fit a BB 6 bolt crank ?

I will need a cam for this and i plan on milling the heads to raise compression, is there any way to figure out how much to whack off to bring the CR up ?

I have been hearing good things about a few summit cams,

Summit Racing® Camshafts SUM-6400

Camshaft, 1-Bolt, Hydraulic Flat Tappet, Advertised Duration 288/298, Lift .444/.466,

and Summit Racing® Camshafts SUM-6401

Camshaft, 1-Bolt, Hydraulic Flat Tappet, Advertised Duration 298/303, Lift .466/.488

Any mopar cam recommendations for helping wake the 400 up ?

How much can i mill the heads before i need to worry about adjustable rockers ?

I know alot of questions, but i come from boosted slant land (max'ed at 18lbs of boost before i lost the head gasket all stock engine with a good tune on the carb) and really haven't dabbled to much in big blocks, i will eventually have an all forged as close to stock, (bore/stroke) and run a pair of holset hx-35 turbos, but for now i just need to get it running, so its gonna be bearings, rings and seals, but really looking at cam and head recommendations from those in the know

P.s

First: you're going to want to figure out exactly what the end game is here. Building a stock motor will not yield the same advice as building a twin hair-dryer big block.

Next:
If you don't already have a copy of Don Taylor's "How to Rebuild Big Block Mopars" book. go get one now

Assuming a stock (non-turbo) rebuild:

Yes, that is a forged crank

Yes, you'll want to balance the whole assembly

Stock 383 flex-plate should work and can be found cheaply.

The summit larger cam is generally spoken of as a pretty good stick for a street application.

Compression is what you'll want to focus on to wake up the 400. Milling the heads and / or decking the block will be in order to do that. You'll have to CC the heads in order to find out what they are now and where how far you'll want to cut them. keep in mind that cutting them enough to effect the compression will likely mean you'll have to also cut the intake to fit.

It won't take much work on those heads to get into the price range of a set of Stealth heads. And those would address the compression issue and offer a ton more potential.... just a thought.

BTW: I wouldn't mess with adjustable rockers. Just get new pushrods at the correct length. not too tought to figure out pushrod length, much cheaper and simpler. Adjustable rockers are not designed to make up for milling, and likely wouldn't fit correctly with the standard length pushrods anyway.

Again, if you want to keep playing with the turbo.... NONE OF THE ABOVE APPLIES.

You GOTTA tell us about the slant build first. Waay more interesting.

How much cylinder bore ridge at the top of ring travel is there? That needs to be removed. Also, not a good idea to try and rebuild a block with too much piston to wall clearance from wear. Go by the max bore wear in the factory manual, or very close. KB lists a piston that is hypereutectic (stronger than stock, and lighter) that will fit with your stock rods and give you 8.9 to 9.3 compression depending on head volume of the 906 heads. This is your cheapest route with an overbore. The motor will love the extra full point plus compression, and the pistons show big valve reliefs for all the cam you need. Depending on how much converter stall you will have (assuming automatic here) you can go pretty big on cam if you have a high stall ( 4000 or more) . I have run a 268 at .050 and .540 lift on stock rockers with a mild lobe that lived with the stock valve gear up to 6,000 rpm. Less stall will dictate staying pretty short on duration, go by cam manufacturer recommendations. Stock converters come in low stall or high stall, obviously you want the high stall if you want to go with a stock factory converter. Remanufactured converters can be had for around $120 in high stall. High stall will be somewhere between 2200 to 2600 rpm as a guess. Low stall is listed at 1800, real low end killer.

Hear is a small stroker combo that yields 9.6 to 1 compression at 4.350 bore. 4.375 bore also available with these pistons.
Ross forged pistons, 99907 4.350 bore or
99906 4.375 bore. (max overbore for most 400s.
Chevy big block rods ,aftermarket 6.800 long
Offset grind the crank to 3.525 for a stroke increase of .150
This will produce a light rotating assembly that will make 418 cubes with 4.350 pistons, or 424 cubes at 4.375 bore
This is a cheap stroker combo for a 400 when you consider that you will need to rebuild the old rods, and buy pistons anyway, and possibly regrind the crank.

Before you start this build make sure you know what you want IT to DO before starting it is very easy to get the wrong parts and machine work when you start of wanting to make it run now as easy as possible but know that you want to add more power later, like your suggesting with the turbos Stop, take a breath and think first before starting donwn the path to making this motor run

I have the chuck senatore "BIG BLOCK MOPAR PERFORMANCE" book, its got a lot of good general build tips, but i feel it focuses more on stroker and all out race engines, I will have to check out that book. I would prefer just a piston change if i can help it. For right now this is a "lets get it running" build. so stock cast 4bbl manifold, was going to homeport it, block the heat crossover, 440 source heads would be nice but, not really in the budget now, being military, me and the family are getting ready to move down to keywest, and houses aren't cheap down there, and i prefer not to trailer her all that way.

Now why will the whole thing need to be balanced ? or is that just added insurance ?

what kind of crank damper do i need to run ?

do the SFI fluid damper's not care what crank they are on ?

I understand about the adjustable push rods, but even say i only knock .010 to clean up the heads, can stock pushrods still work effectively on a stock hyd flat tappet set up ?

Is there anyway to measure CC volume of the heads with out one of those fancy kits ? I mean its just a syringe and flat piece of glass with a tiny hole it right ?

I noticed on the rod oiling holes that well, they are not perfectly round, more like jagged holes, can they be rounded and counter sunk to help improve oil to the rods ?

speaking of mains and rods mains measure 2.622" using a brown & sharp 2"-3" micrometer

rods measure 2.344"

all measurements were taken in several spots at each main and rod journal.

which are .30 over(ish) size If i am correct, mains are stock,

I am going to have the oil holes chamfered and a micro polish on the crank, then get bearings after that, which bearing should choose for durability, clevite, dura-bond, etc

I haven't been able to find a domed KB piston, I did find the KB240KTM , they have a bunch of numbers listed below,

Compression Ratios
72-10.6
80-9.8
85-9.3
90-8.9

Is the first number added to the end of the part number to determine size ?
KB Pistons

I found step pistons, would they be as effective ?

again I am just trying to keep machining cost down, that and I really have no way to transport a block.

If i remember right the slant and BB share a few things in common, i wonder if flexplates/flywheels are included in that as well ?

bump

The KB piston you listed is heavy, but if it is the same weight as a stock piston and pin you can skip balancing the motor. If it is not the same weight within a few grams, then balancing is a must to keep the motor from shaking badly. I would use this piston on a cheap rebuild, very mild performance build. The rings are 5/16 which will cost power compared to 1/16 rings used on most newer pistons.
A good quality stock replacement damper will work ok if you are staying under 6,000 rpm or so.
On the stock pushrods, they can work ok provided the rate of lift on the cam and spring rate aren't too high. They are on the weak side, and the stock rockers will not provide advertised lift because they aren't a true 1.5 rocker. There is enough travel in the lifters to handle more than .010 cut on the heads.
To measure head CCs a cheap syringe from a drug store, plastic plate and grease to seal it up and you are in business.

Well i got the bearings and pushrods on order, should be here wednesday, sealed power/felpro gasket kit with blue perma-torques, not digging the cork op and valve cover gaskets, but i will work with what i got.

Thinking about using a summit damper, $100 stock replacement, seems like a good deal.

So how much can be whacked off the heads before the stock (8.55" 3/8 comp ball and ball ) pushrods need shortened ?

which would be better as far as cams go

Summit Racing Part Number:SUM-6400

Cam Style:Hydraulic flat tappet
Basic Operating RPM Range:1,500-5,000
Intake Duration at 050 inch Lift:214
Exhaust Duration at 050 inch Lift:224
Duration at 050 inch Lift:214 int./224 exh.
Advertised Intake Duration:288
Advertised Exhaust Duration:298
Advertised Duration:288 int./298 exh.
Intake Valve Lift with Factory Rocker Arm Ratio:0.446 in.
Exhaust Valve Lift with Factory Rocker Arm Ratio:0.466 in.
Valve Lift with Factory Rocker Arm Ratio:0.444 int./0.466 exh.
Lobe Separation (degrees):112

or

Summit Racing Part Number:SUM-6401

Cam Style:Hydraulic flat tappet
Basic Operating RPM Range:2,000-5,500
Intake Duration at 050 inch Lift:224
Exhaust Duration at 050 inch Lift:234
Duration at 050 inch Lift:224 int./234 exh.
Advertised Intake Duration:298
Advertised Exhaust Duration:303
Advertised Duration:298 int./303 exh.
Intake Valve Lift with Factory Rocker Arm Ratio:0.466 in.
Exhaust Valve Lift with Factory Rocker Arm Ratio:0.488 in.
Valve Lift with Factory Rocker Arm Ratio:0.466 int./0.488 exh.
Lobe Separation (degrees):114

I think the summit 6400 would be a better choice for a mostly stock motor,

-Mike

Lots of good advice. Just a question and comment. To the best of my knowledge, all 400's were made with cast crank. I wonder how it got a forged 383 crank and still stock bore?

Also a comment. The 400 is often compression challenged. With lowish compression and 400 ci, the small Summit cam may make you happier in terms of low/mid range torque.

This is a 400 we have in my boys Dart. We used the forged 383 crank and of course had it all balanced as it uses stock rods and KB pistons. Also use the internal crank balancer. It had Eddy RPM heads that were cut a bit for 10.6 comp. We use the MP .557 solid flat tappet cam and the RPM intake with a 750 DP. It has a 9.5 Dynamic converter and 3.91 gears. At 3550 lbs with him in it he has dipped in the 11.40's @ 117 and it is a driver street car and runs on pump. Course this build wont help you if you are going to go with the turbo. Ron

I think you would be wasting your money to mill the heads to try and gain compression when using stock pistons. The pistons are so far in the hole that the gains will probably not be worth the money spent. Those 400's are good engines...but they are advertised as 8.2:1 compression, but if they are like every BB Mopar I have dealt with, the compression is likely actually much less. I did some quick calcs and assuming the piston is .120 in the hole like a smogger 440 usually is, I get 7.58:1 compression with a .020 shim gasket. I get 8.17:1 compression by milling a typical 906
90cc chamber down to 80cc's.

If I'm wrong on this....someone please correct me though. If your set on using the stock pistons, that is ok...I would just use a stock shim style head gasket and not bother milling for compression. To mill enough to matter you would have to mill the intake side as well and this will all cost money. You could just spend a little more and buy some cheap ($350ish) KB hyper pistons like Greg suggested and get much more gain. But you will have to rebalance because KB's are lighter than stock pistons are.

Or just leave it all stock and live with the compression and use the smaller summit cam listed. It will still have good/ok power.

@AHY I bought the crank from a guy here local thats into BB Dakota swaps, for dirt cheap, got a set of pistons with the deal( still for sale std bore if I remember right)

I have been talking with AllMotorDuster about getting his 2800 stall TCI converter, shes running a 2.94 sure grip rear, eventually getting a 4.10 ford 8.8, I figured a 2800 stall would be a good step in waking her up. I want to keep the compression between 8.0-8.5 to 1. especially when the hair dryers get bolted on.

Anyone know if these are any good dampers ? ebay damper
Talked to the seller they are made by a company called C.A.T Performance, are they any good ?

Now since I am using stock 400 pistons and rods, but a 383 forged crank, will i still need to get everything balanced, or get the crank polished, double/triple check the rod and main diameters and put it together as normal ?


-Mike

There were 383s with cast cranks
There were 383s with forged cranks.
There were 400s with cast cranks.
There were 400s with forged cranks.

Cast to cast, forged to forged, the cranks are the same. For all I know they are the same casting or forging number.

If you're using a forged crank with either 383 or 400 stock crank and rods, and neutral balance converter/harmonic damper, no need to balance.

If you're using a cast crank with either 383 or 400 stock rods and pistons, you will need the cast crank harmonic damper and converter. Then, no need to balance.

Of course, MOPAR balance jobs were the worst of the Big Three, so the stock balance jobs can definitely be improved. BUT, at this stage in your automotive development, you don't need to.

I'd pick the smaller camshaft. 383s and 400s are very easy to overcam.

R.

right on Dogdays, I appreciate the info, got more parts ordered tonight, can't wait to get'em

-Mike

well scored a nice TM-6 with a holley 2bbl on it for $80 locally,, gonna clean up and sell the holley and recoup at least some beer money lol

so got the block spotless, and guess what a few of the cylinders got some deep pitting, its bad enough after running a "dingle-berry" hone to knock off the varnish i could clearly see the pitting. Oh damn now i have to bore it out, So what do you guys recommend for a really good forged piston ?

Also how much HP/TQ can stock 400 rods take ?

I think it would be a good time to upgrade the rods to h-beams, any good brands out there that can take a bunch of abuse ? looking to make around 400+ crank HP, and going either blown or boosted, but i want to build a stout forged bottom end.

Speaking of bottom ends, already drilled out the pick up to 1/npt, suction side of the block, blended and smoothed the OP suction and discharge sides, drilled out the discharge with a 9/16 till about 3/16 from the oring.

I won't know the overbore for a few days, but I want to build this right the first time, and yes I will be keeping the iron heads for now. which i know even with porting and maybe another round of decking (had the shop just machine them enough to clean them up).

While we are at it, I am returning the cardone reman dizzy, thing is a real piece of work, it needs its mag pickup replaced because it is not only almost flush with the tanish rubber insulator, but is angled and is smacking the reluctor, I do have a few slant dizzy's lying about i was gonna take a pick up off of one of them and just install it, but aside from MSD what is a quality dizzy for a low deck, and i already know to avoid that procomp crap,

And i was thinking magnecor wires for it as well,But i am open to suggestions, already have the GM HEI up grade as well,

-Mike

Time to build a simple badazz 451 out of that block. Probably get 500hp even with the stock 906 heads.

Old school and pretty easy. New pistons, 440 crank turned down, 440 rods & a balance.

Will last forever if put together right & good heads with net you 600hp in the future.