400 big block

-
Status
Not open for further replies.
mopar7172

mopar7172

Banned
Joined
May 20, 2009
Messages
550
Reaction score
20
Location
las vegas,nv
are 400 big block engines any good?i have 73 400 big block.how can i boost the compression up? & get a little more horsepower?
 
without going into the block and spending alot of money, i would pull the heads, and mill them around .050 and do a mild port and valve grind and put it back together with a steel head gasket. this should boost compressio by 4/10ths of a point.
 
The 400 is a great engine for a lot of reasons.

Big bore helps not to shroud the valves.
Very strong engine blocks.
In fact they are the strongest stock block ever made outside the hemi.
Low deck is easy to live with in a tight a body.
Great rod ratio.
For example:
A 318 and 340 have a 6.123 rod and a 3.31 stroke.
By dividing 6.123 by 3.31 you get a rod ratio of 1.84.
The 400 has a 6.358 rod and a 3.38 stroke.
By dividing 6.358 by 3.38 you get a rod ratio of 1.88.
What this all comes down to is piston speed.
A better rod ratio lets the piston move at a slower speed, due to the rod staying closer to the center of the bore when moving with the crank.
How much slower???

Well, a 512 stroker has a piston speed of 5250 ft/min at 7000 rpms.

A 400 can be twisted up all the way to 9000 rpms and still only have a piston speed of 5070 ft/min.

At 7000 rpms it's 3943 ft/min.
It really is a big block screamer.
Give it compression and a good cam and it will work great.

I just bought one in the fall---- built to stock specs(1973)low comp.8.1
This man and his son built it over ten years ago with all the machine work done by napa.
They threw it on a brand new engine stand and never used it.
It came out of a 1973 charger from what i was told.
I guess the charger hit a pole side ways and was toasted.
Anyways......They spent a little over two grand.
I got the hole engine and stand,plus a 727 transmission, plus a 650 holley all for $300 bucks.
I do everything on a budget and it's nice to get lucky once in a while.
It will take some time to get all the parts i need.
I just bought the new victor single plain intake and it's a nice piece.

I think the 400 is a great engine.
The 400 engine i got is stamped with a hp.
From what i read ,it has a premium cast crank in it.
It's suppose to have a different part # then a standard cast crank.
Is it any better???We will see when i crack it open.
It should with porting the heads and the right cam and compression be near the high 475 to 500 horse mark.
The only thing is if i go to aluminum heads down the road will i exceed the cast cranks strength?
500 horse seems to be the max on a cast crank according to a few sources.
Well i could always flip it over and install a steel forged crank right???
I will be lucky to be able to buy a set of good headers and a radiator without loosing my mind.

Sometimes i respond to stuff here and get a little crazy with the keys.
good luck :thumbup: mopar7172.

PS If the engine runs good and you can't swing a rebuild, run a small performance cam in it with some new valve springs and seals installed on the heads.
 
Stroke it to 452 (440 crank with cut down mains), several companies make the kits, go's and rev's like stink.
 
The biggest draw back to a stock 400 is the low comprsion pistons. And the price to upgrade to a high performance slug. There valves are to small for serious performance but there fine for "General Purpose/hi performance" useage. You can get going quick with them, just not blazin the road fast.

There like a big whoppin overboared 383.
the make great strokers
the fit into A bodies easier
Indy "E-Z" heads are made for this big block swap and help greatly with header fitment.
 
That is not what I have read elsewhere. Maybe you could go into some detail?

People don't talk much around here for some reason. . .
 
056 kid said:
That is not what I have read elsewhere. Maybe you could go into some detail?

People don't talk much around here for some reason. . .
Click to expand...

Back up the boat there 056 kid. First off exactly what have you "read elsewhere" concerning the 400, leave out the riddles please and secondly we talk plenty especially when posters want to listen. Try reading the forum on BB's, there's plenty of info on stroking 400's and 440's. Thirdly, do it all in your own thread and quit hyjacking this one.
 
056 kid said:
That is not what I have read elsewhere. Maybe you could go into some detail?

People don't talk much around here for some reason. . .
Click to expand...

Pot calling the kettle black.
 
The 400 is a great platform to build big strokers out of, but you can still make some power in its stock form as well.
As stated you want some more compression. One way to do this would be to find a set of closed chamber heads. 915's would be prefered but the 516's will work too. Have a good valve job done with some oversize valves possibly some bowl work and you'll make some decent power on the cheap. A mild cam and a dual plane intake would round out the package nicely.

Ted
 
I have a 72 400 and I have a 73 Steel crank 440 I plan on building a 452, I have had these motors stashed for a long time, I read in Mopar Muscle magazine about 10 years ago that the early 400 blocks the 72 and 73 are what you want, they have a thicker main webbing and make a stronger block! I saw a 400 Stroked 452 incher in a Duster years ago and man,
the 400 is NO SLOUCH!!! when built correctly!!! It is the esscence of MOPAR POWER!
 
There were what was called "cold weather blocks" that had some extra meat, but they are pretty rare. The basic 400 block is much beefier than all the other B & RB blocks so you can build a pretty stout engine out any of them as long as you do the basic checks, sonic & magnaflux ect. I'm currently collecting parts to build a 499" stroker from a '74 block.

Ted
 
I am building a 451 also,possibly a 470 depending on the condition of the crank. I now have a set of KB280 pistons/pins. Very lite,weight 520 grams or so. Combine it with the excellent 440 crank/rods and you have the ultimate budget 451 with the reliabilty of a 440!

I see 451 engined mopars on pinks all the time. Many of them make it to the final 8.

It' makes an awesome bracket motor in a lightweight car.Im hoping to get my Darts weight under 3000.


I wonder about that cold weather block.A good chance many canadian and northern states cars came with one.
 
DusTed74 said:
The 400 is a great platform to build big strokers out of, but you can still make some power in its stock form as well.
As stated you want some more compression. One way to do this would be to find a set of closed chamber heads. 915's would be prefered but the 516's will work too. Have a good valve job done with some oversize valves possibly some bowl work and you'll make some decent power on the cheap. A mild cam and a dual plane intake would round out the package nicely.

Ted
Click to expand...
how much more compression&horsepower?
 
OK, I did some "REALLY ROUGH MATH" and switching to a set of closed chamber heads and if you used a .020" head gasket you would bump your static compression up approximately one point. This is based on if your heads are 83 cc's now and the replacement heads are 73 cc's.
We dont know where your piston is @ TDC. By that I mean is it at zero deck or is it way down in the hole. If for some reason it's close to the top of the deck then you will gain some power from the quench area of the head.
Basicly what I'm saying is that its really hard to say what you would gain from doing these mods but you have a good platform to begin with. The 400 has the largest cylinder bore of all the big block engines so it responds well to things such as oversize intake and exhaust valves.
Also keep in mind that you dont want to get too caught up in the big compression game. Yes a bump in compression will usually make more power but keep in mind that you live in the desert and tuning and cooling will be a big factor.

Ted
 
DusTed74 said:
OK, I did some "REALLY ROUGH MATH" and switching to a set of closed chamber heads and if you used a .020" head gasket you would bump your static compression up approximately one point. This is based on if your heads are 83 cc's now and the replacement heads are 73 cc's.
We dont know where your piston is @ TDC. By that I mean is it at zero deck or is it way down in the hole. If for some reason it's close to the top of the deck then you will gain some power from the quench area of the head.
Basicly what I'm saying is that its really hard to say what you would gain from doing these mods but you have a good platform to begin with. The 400 has the largest cylinder bore of all the big block engines so it responds well to things such as oversize intake and exhaust valves.
Also keep in mind that you dont want to get too caught up in the big compression game. Yes a bump in compression will usually make more power but keep in mind that you live in the desert and tuning and cooling will be a big factor.

Ted
Click to expand...
ok thanks for the advice.
 
400 std. bore = 440 + .020"; 400 +.010" = 440 + .030", etc.
426 bore & stroke includes "street wedge", Max Wedge (Ramcharger) & 426" hemi.
 
If you really want to be impressed, look in the big block tech section for MRL's build on a stock stroke 400 two barrel build. It was built for a restricted race class that only allows two barrells. That's Mike Liston the owner. We have him, Brian from IMM engines (ou812) and a host of others here with a LOT of knowledge and the thing is, they SHARE! There are some AWESOME people here that will help you if you'll listen. This is the best damn automotive site on the net, bar none.
 
StrokerScamp said:
If you really want to be impressed, look in the big block tech section for MRL's build on a stock stroke 400 two barrel build. It was built for a restricted race class that only allows two barrells. That's Mike Liston the owner. We have him, Brian from IMM engines (ou812) and a host of others here with a LOT of knowledge and the thing is, they SHARE! There are some AWESOME people here that will help you if you'll listen. This is the best damn automotive site on the net, bar none.
Click to expand...

LOL same page again
 
Status
Not open for further replies.
-

Back
Top