If you have an LT1 block, there is no aftermarket block, and the machine work isnt that much. The balanceing is a little more as allot of places do mallory metal.
The 406 block is a older style block, not as reliable, steam holes between cylinders, and uses a completely different block. It costs more to put a 406 style block in a LT1 than it costs to just do a 396.

 

racerdude isn't talking about the old 400 (4.125 bore) block, he's talking about building an LT1 to those displacements. The cost is about the same, we're just talking about a little more stroke and clearancing. Not recommended, but it has been done.

And the old 400 blocks weren't unreliable when built right.

-Mindgame

 

Okay, when you speak ofa 406 is it most often to referred to as that olde block style, not the LT1, which when talking about over 400 cubes, they are generally a 409. So, maybe we need to be more specific when speaking of Gen 1 or Gen 2 etc engines. The 409 and over sized LT1's are very hard to wrk on as the block work is spendy, as opposed toa 396.

 

406 is done to leave a little more meat in the cyl's to help prevent running hot or caving a cyl.wall. A 409 will take it to max and beyond and shouldn't be bored that far without a sonic check to see if the block in question will go that far.You may go through a dozen blocks and pay for the checking before you find one that will work.
If you were going to the old style aftermarket block I wouldn't stop at 406,I would build a 454 or larger(maybe one of them 502's)$$$$$$$$$

 

A 406 is a 30 over 400 , and a 409 is a 4 inch stroked LT1 motor. The 400 siamesed cylinder blocks of yesteryear had a 4.125 bore, were not recommended to be bored over
30 because of thin cylinder walls. The new "409" stroker motors are motors utilizing the LT1 type blocks, and they have a 4 inch stroke and .030 bore.
Here is a table from JE pistons. Look under the 400 block section,
http://www.jepistons.com/pdf/2002-srp-chevy.pdf
Granted, you can make 406 out of LT1 with a 20 over bore and a 4 inch stroke. But even though it , a 409, is really 408 cubic inches, people in the GM commmunity call it a 409. The 396 LT1 stroker is the same thing, 396 sounds better, even though it is 395.
My point was that there are 2 very different motors here, a siamesed cylinder walled 4.125bore x 3.75 inch stroked 400 cubic inch motor that is of older design, and wouldnt be cost effective to put in a LT1 powered car.
And the LT1 motor has a different block, heads and is in no way compareable to the 400, as the LT1, with the exception of the Opti, is much better designed motor.
The chart should help people see engine combos that are popular and when building a stroker motor, a 383 is very good, and a 396 is a little better sounding and will give alittle edge in HP/TQ. A 400 smallblock of old, bored and stroked is sweet, but overheating her can be costly quick.

 

a 4" stroke and a bore of

4.020 = 405.95
4.030 = 407.97
4.040 = 409.998
4.060 = 414.068

 

THE LT-1 is a thin metal casting and does NOT have the metal in it an earlier 350 has.
I have said nothing about a 400 block. All my CID numbers are an early 2 piece rear seal vs an LT-1.You can take one of these early block to .060 over no problem and without sonic checking. Some can go .080 with checking.A 406 is quite popular in either block.
I am aware of how to build a 406 or larger in a 400 block,try to find a 4 bolt main 400 block-There ain't many that can be had at any reasonable price.
This is why I said after market block in my original post/answer/comment.

Those extra 3CI may not be worth it when the pan is full of water in an LT-1. The stroke and RR puts a lot of extra side load on the bore.

I just happened to be able to race those early engines when they were introduced. Have built and raced from a 265 to a 454 and a Z-11 which most people have never heard of.It was very interesting in those day's. It was not cubic bucks but cubic brain power and mechanical ability that won races and how your work ethic was.

 

Okay , now we seem to be getting really **** and technical. You have raced the ultra rare Z11 409? WOW, you must be real old, in your 50's or your Dad/Uncle had one.
The LT-1, when written like this is a 1970 1/2 Z28/ Corvette/Nove SS type motor (built a few years in various bodies.) The LT1 motor of today is fine bored 60 over and is not considered a thinwall casting.
The bore and stroke numbers can be manuiplulated anyway you can, round up to get a 396 or round down to get a 427, hence the new LS7 motor, which is really a 428.
Anyways, point is this thread was about 396 vs 383. Different strokes, different
budgets. My 396 is sweet, and I like the fact it is all forged, billet splayed caps, etc etc.
A 383 will make less power than a 396 useing same parts, ie compression, heads cam , T Body etc. DOnt argue that one, everyone knows the more cubes the more power.

 

Nothing anil about it.
The Z-11 was a 427.It had valve covers that looked like a 409,but it ended there.
I was part owner and wrench on one and yes I am 59 and holding and been around the block a time or to.
You have to have heads to feed those extra cubes or it won't make as much as a 383,I don't care if ya got 500 inches if it can't breathe it won't run.
Unless you get exotic-SB2,15 or 18* heads and have them fully worked and an intake to match, it won't breathe right and not make it's proper HP.The large 23* heads for an LT-1 are marginal on a 383@7000RPM's and ya have to put a stupid cam in it to get it to breathe and make HP.

Don't try to argue that one.

 

The Z11 was a 409 motor stroked to 3.65 vice 3.6, yes it was 427 cubic inches but it was a 409 block.Well, my point about cubes makeing more power still stands. If you put the same cam, heads etc on a 383 vs a 396 the 396 will make more. Why wouldnt it, it is only 13 cubic inches more, thats 1.625 cu inches per cylinder. Not much, and the heads arent going choke the 396. I have angle milled LT1 castings from a 95 LT1 on my 396, and they make 520fwhp. I am sure they will make a little less with a 383.
Look at the old 396/427/454 High Performance square port heads, open chamber styles. Comparitively the motors had the same heads 2.19 in 1.88 ex. With the same cams, the 454 made more power overall, right. I know there were several different heads and cams etc for these motors, as I had a L78 396 Camaro, and a LS-6 Chevelle (fake one I made).
If 13 cubic inches is such a big difference, then why dont people get super big heads when going from a 350 to a 383, answer because they dont need to.
Now I am talking LT1 motors, not LS1 styles, as there heads are much better than LTx types.

 

Say whatever you want- bigger heads make more power and they ain't available for the LT-1 unless ya go exotic and 5 grand.Soooo you make your HP however ya can and within your budget and I will do it my way.
"O" why do you think an LS-1 will outrun a LT-1 and both are the same inches. Couldn't have a thing to do with the head's,HUH.

 

I just stated that above, didnt you read it. LS1's have better heads, DUH! They are also a better combo period, longer rods, better valves, as they are thinner lighter, and larger.
You old fart, of course heads will be the bigger factor in a motor, whos arguieng that. I stated that a 383 vs a 396 there will be more power from the 396. What is so hard to understand?And to throw a wrench ina fire, If bigger cubes dont make more power with the same heads, then why did GM stroke the 409 to 427, or the 427 to 454, or the 327 to 350 , shall I go on. The heads didnt change, but the HP and torque went up, correct.
Good Lord, why are people like this, Read what you just said. Are you sure you are 59, cause you talk like a 18 year old. Do your homework, or maybe thats just it , you didnt.
PS, you make it your way ? WTF. My goal was a 12 second car, and I have a low 11. My Chevelle with the LS6 ran 11.15 at 125. These are called projects, and projects are cars/motors you build to perform to your goals and aspirations. If I wanted to go make a serious asston of HP I would have gone another route. But , this thread had nothing to do that. he was asking about the 383 vs 396, and with such a little difference in cubic inches, and the little power difference a 396 makes over a 383, because they will probably have the same heads, the 396 is the better. Not the cheaper, just better.

 

Also, where in Alabama are you from? Carroll High school here, Ozark.

 

If you build a 383 and a 396 and keep everything else exactly the same there will be a negligible peak hp difference. The 396 will make a bit more peak torque and it will be at a lower rpm. Depending on gearing and so on this may allow the 396 to be marginally faster. Both 383 and 396 LT1's can be made to run good. The 396 will also have a little more vacuum and be less "cammy". But as has been suggested, the available reverse cool heads are a limiting factor in an all out buildup for either a 383 or a 396 LT1.

Rich

 

i had a buddy back in the day when lt1s were still production that had a MTI h/c package on his M6 car. it went 12.20s@116. with the same heads/cam and the only change being an MTI 396 shortblock the car went 11.40s@123. the extra 2 points of compression helped, but not 7mph worth. the heads flowed mid 250s if i remember correctly.