87_TA

Well Im getting tired of building the same 355's and have decided to go bigger.
Right now I currently have a 350 and 400 block lying around which is better? I personally believe in the theory"there is no sub for cubic inches" but hear so many good stories of 383's.

This motor will have my canfield heads ,11ish c/r and be topped of with either my mini ram of a converted victor jr,and my 230/230
560/560 cam.
Street fighter 3000,373's

onebadwagon

i dont like strokers, but i also dont like short rod motors, now a 6 inch rod 406 would be sweet.

thats just me, either way, it should run well.

adam

B4Ctom1

I have a P1SC and I am afraid it just wont be enough blow for the big motor even though the D1-D1SC's, P1SC's and P600's have the same housing dimensions but different volute impellers. My decision is to destroke my 400 block with a 327 crank.

87_TA

This isnt for the Blower car,Its for my T/A.
Thanks for the info-keep it flying.

Thats one of my options also,Ive really been considering that one.
Im kinda leaning to the 406 for Cubes and help with my extremly large 2.08 intake valves.

86irocL98

i would do a 377.....

87_TA

Care to elaborate?

383backinblack

a 377 is a 400 block with a 350 crank, basically its the opposite of a 383 stroker

87_TA

I know what it is LOL,
I meant why would he build that as opposed.
I also know it would be a high revver.

383backinblack

they are different, and they rev good.

87_TA

Well 307's are also different, but im looking to make the most HP
or avg. HP for my money.
Being that it still a street car I dont think a 377 would be a good choice for me to make lots of usable torque and HP ,maybe i said that wrong,make the most HP.

Air_Adam

302? (350 block, 283 crank)

You want a motor that can rev, a 302 is as good as it gets

And how often do you see a 3rdgen with a 302?

B4Ctom1

I would run a stock crank 400 with 5.7" rods, use the dished forged TRW/speed pro LW2606. this will allow reasonable compression for street with your heads.

94-6spd

I'd go with a 406 with 5.7 or 6.0 rods. I like cubic inches. The more the better.

aziroc

i went the 6" rod 406 route.. look where it got me

:lala: :lala: :lala: :lala:

87_TA

Well Im pretty sure im gonna start this buildup within a few weeks ,
Looking like its gonna be the 406.
just need to hurry up and figure out which rod to use,I would guess the 6" would yield greater torque and 5.7 more willing to rev.
6" harder on crank,5.7" harder on pistons... Hmmmmm.

383backinblack

youd actually be surprised at the minimal differences that you will see with the 6 inch rod.

dont get me wrong i love them, my 383 has 6"ers in it. but the actual torque gain isnt as substantial as people have thought, there have been recent dyno tests that showed little differences.

however, they do improve the angle on the crank and are probably more efficient

aziroc

id go with 6" rods personally cause 400 blocks werent really ment to be rev'ed past 6000'ish rpms.

87_TA

Well bought a scat crank from e-bay yesterday,getting a little worried though.
I have a good 400 block (not bored yet), After talking to my machinest he thinks I should square deck the block. Im worried after square decking it may take more than .030 to bore,and there is no way to tell till after its been decked.
But I may just skip the square deck and go with a regular decking and bore job,Lots of people don't blueprint their engines.

aziroc

i would balance/blueprint the block, specially if u are going to make this engine have some power in it. *why be cheap now?
plus if u have to bore more then .030 yu not try for a 422 or 427 SBC granted it will cost more to do.. but the looks on peoples faced when u tell them u have a422 or 427 SBC will be worth it **** i wish i went that route.

87_TA

Well cheap was the catalyst for this build,I have 2 good running 355's but figured I would try a budget build.
But the blueprinting has nothing to do with price,Its only $50 more than a standard deck/bore but I was scared of having to go more than .030 due heating problems.

aziroc

everyone says heating problems with 400 blocks. i live in AZ.. yes.. the 120* in the summer time AZ... and with my engine i have yet to hit 165*(even while bracket racing.. well when i turn the car off and let it sit, and check back in 5 mins its in the 200-210 range). granted the griffan nascar radiator may have something to do with it($500).. but thats a small price to pay to not have to worry about heating issues.

383backinblack

you can get the new bowtie blocks for 1800 bucks from scoggins dickey.....dont have to worry about heating issues on those bad boys....i think the max bore is like 4.250

onebadwagon

i wouldnt hesitate to go to .040 over for a street motor, just make sure your cooling system is in good shape.

6 inch rods would be the only way id build a 400, i dont like pushing the cylinder walls all sorts of different ways, and longer rods help.

adam

Breadfan

If you square the deck that has nothing to do with the cylinder wall thickness , or the need to over bore . All you are doing when you square the deck is making sure that the deck surface is level with the crank center line . this will insure that each cylinder will have the same deck height .

87_TA

.NOT TRUE,
My machine shops bore machine squares itself off the deck surface,therefore if the deck angle changes than the bore angle
will change also.
Ive done my research on this and its almost never that much,but my machinest had just done a 400 block that would not clean with 030. so the owner junked it.
But ive heard from more than a few that 040 will be fine also,so im not gonna sweat it

Breadfan

all the bore machinces that i have seen , and used square off the cylinder . How would you know where the bore center line was if you went off deck surface . Yeah you level the boring bar off the deck but the center the machine up i don't see that . Now did your machine give the option of reloacting the bore center line to to insure the thickness would be greater ? If i was you i would check out a different machine shop or at the very least get another opinion from one .

B4Ctom1

this is all fine and dandy if there is no core shift. 400's were notorious for core shift due to the design and the period of production. sonic testing is the only sure way to know...

Breadfan

I think i indirectly said that all ready " Now did your machine give the option of reloacting the bore center line to to insure the thickness would be greater " because the only way to know where to move the bore center line would be by doing a sonic test

B4Ctom1

I apologise, more reading and less speeding on my part would have cought that.

Breadfan

no problem

paul_huryk

There are two main advantages to the 406;

First, it is 23 cubic inches larger - which will give you more torque (all things being equal).

Second, it is a larger bore - which will allow the valves to breathe a little better (or you can use a larger valve 2.08 instead of a 2.02).

The one good thing about a 350 based motor is the fact that they have been making them in one form or another for 30+ years, the 400 was only made for a few years (if we talk about factory blocks). Aftermarket is a different story - there are 4" and 4.125" bore blocks in iron and aluminum from many different manufacturers (including GM).

Another good thing about the 400 block is the fact that you can stroke it even more - 3.875" to 4.125" (some aftermarket blocks), which can give you 440+ cubic inches out of a small block package (if you have the $). Don't forget that a 406 can use a 6" rod, but anything larger than a 383 with a 350 block will need shorter rods (unless it is an aftermarket block with increased deck height).

I guess it really depends on your budget and how much power you want. FYI - a really strong 406/420/434 with a power adder will put you in the power range that a built 700R4 will start to fail - so keep that in mind when you decide.

87_TA

Well thx for all the info Paul,But not sure if you saw I have already started the 406 build W/6" rods was the route I am taking. I could not help but notice you running 121 mph 12.1,
With that MPH you should be near low 11's ,what kind of build did you do for that? or is that not naturaly asperated?

aziroc

he has the same problem i have... no traction...

83 Crossfire TA

iTrader: (2)

OK, what am I missing here? Both will have the same deck height and there is no reason that changing the bore would change the acceptable compression height for the pistons, so there should be no difference what rod length you can use assuming that you're using the same stroke in both blocks...

paul_huryk

The extra bore allows you to get more cubic inches out of the "bigger block" than stroking the 350. The extra .125" bore with the same stroke is worth about 23 cubic inches (406 vs 383). If you go with a 396 (3.875" stroke 350), you must decrease the connecting rod length - but a 406 can use a 6" rod.

My car ran 121+ on NOS a couple of years ago. I tuned and tweaked it last year and it should run about 112-114 on the motor and another 12-14mph more on NOS (124-128mph). Traction problems will be fixed this year - Global west TQ arm and drag radials. I hope to run 11.3 or better in street trim.

83 Crossfire TA

iTrader: (2)

OK, but both deck heights are the same, so with the same stroke you can get away with the same rod/compression height combination. I thought that you were implying otherwize.

BTW, I've seen a 6" rod 396, but personally I don't think that I'd even use a 6" rod on a 383 unless it was an all out effort and long term durablility is not an issue. The minimal power increase is just not worth the tighter ring packs, more piston rock and less stable rings...

87_TA

A 6" rod makes the motor more durable by bringing the pivot poing closer to the ring pack as opposed to down in the skirt (the weak part of a piston) the only time you run into a problem is if you have to get a piston with a oil ring support. And you get less piston rock due to lesser side loads on the piston

aziroc

if u r going to do a 400 or 406.. y be cheap with the rods...

B4Ctom1

I believe in the K.I.S.S. rule, a 406 is not as much of a violation of that rule if a 5.7 rod is used because; the pistons associated with the 5.7 rod version of this engine are more affordable, the rings used are larger (therefore stronger) because the pin placement does not tresspass into the area usually reserved for the rings by design, and if required could be built with either an aftermarket or stock rod.

87_TA

Who is being cheap? Where did that come from?

B4Ctom1

I guess Im being cheap because my 412 (.060 overbore 406) has 5.7" rods with the "X" mark on them. they have been inspected and ARP'd, but thats it.

aziroc

sorry.. didnt mean cheap.. i should have said, y not jsut go with the 6" 's?

383backinblack

with 6" rods like i have in my 383 you need to order pistons with the correct compression height. for a 406 they would be the same compression height as my pistons actually.....but with regular 5.7" rods you can just use off the shelf pistons. the torque gains with the 6" rod are really not as significant as people claim they are.

build the 406....its not gonna cost that much more money to build. also, my next motor is 400ci or larger, and 406 just sounds cooler....who doesnt want 400cubes?

B4Ctom1

One of the car mags did a camparo and to every ones surprise the stock 400 rod 406 built identically to the 5.7 rod engine actually made more torque. Now Im not suggesting that anyone build a 400 rod 406 unless of course they are really broke. But the longer rod does help angularity problems that try to "tilt" the piston in its bore eventually resulting in a ring seal problem, but remember 400s ran with thier own rods for years when they were built originally.

383backinblack

ya the longer rod is supposed to position the piston better and reduce rocking......

do you mean the engine with 6" rods made more power?

and as far as ring seal goes......i have 6" rods and im currently in the midst of a ring seal nightmare....im gonna have to pull the heads and get out the micrometers

83 Crossfire TA

iTrader: (2)

Some of you out there really need to pull out your high school trig books and do some math, there is nowhere near the gain to be found by going with longer rods. To be honest, I’ve come to the conclusion that people noticed that engine builders building engines optimized for specific situations were messing with rod length, and the someone had luck with longer rods (not necessarly made more power, I mean, how many of us really have the means build 2 identical engines with one change to see which works better for our street car, I mean that it didn’t blow up) and now everyone is copying based on their results.

Let me throw some #’s at you… going from a 5.7 to 6” rod you only gain .7% less angular displacement at the maximum point. That translates to roughly .1% difference in side load and power transfer to the crank. You will see a bigger difference in power by modifying your cam timing to work best with your rod length then you will with changing your rod length. BTW, there are some people out there running cars in classes that limit camshaft lift (assorted stock classes) that run sorter rods (typically something along the lines of the mid 5” range in a 350) because a short rod engine is less likely to experience reversion and that allows them to run a little more duration to make more power. From what I’ve seen, most of the parts makers that make the parts that allow you to run longer rods recommend against it stating that it’s probably a waste of time and money unless it’s a max effort engine with cam, intake and exhaust specifically designed for the longer rods. I believe that Isky used to have a tech article about it that just came up in another board or list….

Second, piston rock is mostly up to piston design (ring location, skirt length/shape, and pin offset). This assumes that the pin is in the correct vertical location in the piston. If you want max power you can offset the pins to the thrust side which will have a bigger effect on the angle that the rod makes to the crank then rod length will. Of course, you’ll end up with at least half the pistons being noisy when cold and a shorter lived engine. The cheap way to do this is to get some offset pin pistons (designed that way to prevent piston noise when cold) and install them backwards (common trick in old ford v8’s which were more likely to have offset piston pins, but it’s been up in production Honda engines lately showing (offset the other way, to make more power)). Either way, a shorter, correctly designed piston will never have less rock then a longer, correctly designed piston.

If you’re in the situation that you can have both a long rod and a tall compression height (sort stroke engine with a tall deck, think 302, 327, some Pontiac combinations…), great. If not, for an engine that’s not going to be torn down regularly, that’s going to see some miles, choose whatever is cheapest and/or gives you the best piston design. If you’re going max effort, race only… then choose a piston/rod length that matches the rest of your design and rules restrictions, for that matter, if you’re building a max effort engine, something that the small percentage difference will matter, what the hell are you doing here?

383backinblack

.1% sideloading difference, take that value and multiply it over the strokes a piston makes in a normal street engine over its life time....from an engineering standpoint .1% difference in a load over a life cycle is extremely significant. thats alot of reduced wear.

ctandc

Maybe I'm missing something here...but the whole "dump the short rod" badwagon is pure crap for anything less than a 550-600 HP monster.

The 400's advantage is TORQUE. More cubes = more power from an engine with less strain ( RPM ).

The "theory" is all well and good...but I've seen too many BASIC 400,406,408 combo's use the factory short rods w/ good bolts and go DEEP into the 11's and faster with attention to detail and the right parts selection.

Now if you want to rev the **** out of it, sure go for it...but why start with a 400 in that case anyway?

But I think the 400 gets a bad rap...first the cooling problems...I've NEVER had a cooling problem in a 400...okay..I did once...turns out the previous owner had swapped heads and didnt' drill steam holes.

Next the "short rod" motors can't rev...

I shifted my last short rod 400 at 6800 RPM all day long....and granted the cam in that thing was too big for the street ( it was a freebie, I'm cheap )....after a good 100 1/4 mile runs and driving the thing damn near everyday ( put 24k miles on it in 16 months ) I never had a problem related to the "short rods"....

It was a BUDGET motor...heck it was stock bore, just broke the glaze off the cylinders, ringed it, bearings, and double and triple checked all clearances...I did add ARP bolts to the rods...

And if you're worried about core shift, and it's a strip motor, why not just use some block fill? This will all but eliminate any problems the factory block could cause in higher HP apps....


Hey, if it's your car, build it however you want...

My personal opinion is that $ for $, for more power, I'd spend the money elsewhere.

I once saw a dyno run between two identical 406 motors.....

The ONLY difference was one had the short 5.565" rods, one had 5.7" rods..and of course the pistons...both were right at the same compression ratio...same heads, same headers ( dyno headers ) etc...

There was less than a 10 HP difference across the board....and the long rod motor actually gave up some torque to the short rod motor ( again very little ) in the low range.

Now, if the short rods in the 400 you're building need refurb, I can SEE the common sense of going with the 5.7" rods since they are dirt cheap and end up cheaper to buy ready to go than resizing the short rods, new bolts etc..

Just My opinion...

87_TA

Well actually I dont even have rods,Just have a block.
I have bought a scat crank and it says for 6" and longer..
I could not imaging the difference but thats what the add says,which is all fine because thats what I planned on doing anyway.
I am probably going to use scat or eagle rods w/arp bolts,Hyperutectics high 10 low 11 ish compression.
My heads currently have 2.08 valves which is probably hurting me
now but will help the 400 I hope.
This is not just a strip car either, its my other driver just looking to get some more HP with what I have . current 355 has a few scratches due to a bonehead machinest who did not put spring cups under springs when he assembled heads for me,digging in the aluminum and throughout motor.
I tore it done,honed cylinders ,polished crank and replaced bearing but never did a leakdown and I dont trust it.
And its also been spitting out oil at WOT but seems to be improving-had less than 3000 miles before teardown and rings did not seat,now they are worse.

383backinblack

everyone knows that using longer rods isnt going to turn a mild motor into a monster.....its just an option you have. its not really a big deal.