Best 440 block ? • The Dodge Challenger Message Board

by **Lars-Göran Sundblad (Lars** » 22 Mar 2002 13:19

I'm planning to build a "new" street engine for my -70 Challenger R/T 440 727. How many different types of 440 blocks exists? I have heard of three. Two with thicker walls (whith and whthout stiffening ribs) and a thin wall design. Are there more types around? Which type is best (most durable) as starting material for a high torque (stroke) street engine? How to idenify diffrent types? Things to look at when purchasing an old block? Thanks!

by **Dave-R (Roppa440)** » 22 Mar 2002 13:49

I can look in some of my engine books when I get home (late) tonight but does it have to be a 440?

The 400 block is a better starting point as this is the strongest block. It is also smaller and lighter than the 440 and has a bigger bore as standard. It will take a modified 440 or stroker crank (or you can modify the block) to give you 450-500 inches easily.

Hughes Engines ( http://www.hughesengines.com/ ) are developing a welded crank right now with a 4.25" stroke that will give 511 cubic inches with a 4.375" bore. And the good news is it will cost only about $400.

$4000 will get you a complete short block in just about any size you want.

by **Hans (72challenger)** » 22 Mar 2002 15:37

Lars, did you already read the "440 over bore" subsection on this board? It gives some info about the different 440 blocks. The best 440 to use for real high performance goals is the thick wall with the stiffening ribs. They can also be overbored further, but If you overbore it I shouldn't go to the max. If so and something bad happens you can't overbore it again so rebuild it.

Dave, you're right about the stroking a 400 thing, but although the hughes crank isn't that expensive I do think it's cheaper to build a HP 440 instead of a stroked 400. It just depends on how much hp Lars wants and how many $ he is willing to pay for these hp's...

by **Dave-R (Roppa440)** » 22 Mar 2002 16:05

Just tempting him Hans! BTW looks like we could be getting a lot of Dutch Mopar owners over for the Mopar EuroNats in July.

by **Hans (72challenger)** » 22 Mar 2002 19:21

Let's hope Dave, I recently heard that it would cost about 75 sterling to come by boat with the challenger! If so, I will come to the Nats...
But then would it be a nice idea if you come to the dutch Mopar meeting Dave

by **Dave-R (Roppa440)** » 23 Mar 2002 9:49

I have been thinking about it Hans!

by **Christer (Christer)** » 23 Mar 2002 17:33

How thick are the walls in a 400-block compared to a 440-block?
What is the max recommended overbore on a 400-block?

by **Hans (72challenger)** » 23 Mar 2002 18:57

All right Dave, hope to see you June 1st and 2nd...

by **Dave-R (Roppa440)** » 23 Mar 2002 20:43

Is that the dates? Sorry can't make it. Clashes with my local show organised by my friends. trying to organise a few Mopars to meet up at that one. If the show is not a success this year (bad weather three years running!) the club will not be able to run another show again and will be in finacial trouble so I have to support it.

by **Dave-R (Roppa440)** » 23 Mar 2002 21:06

Right.

Big blocks.
all of Chryslers 'B' and 'RB' blocks are very strong and if this is a street/strip car you should not worry about any of them because there is no way on Gods earth you are going to stress the block enough to damage anything.

Also don't bother with align boring the main bearing bores as unless you have bought an ex-race engine it will most likely be fine. The bottom end of Mopar blocks is very strong compared to other makes because of all the heavy casting and deep skirt to the bottom of the block.

The 383 has a bore of 4.25" and the 400 is 4.34".

The 440 has a bore of 4.32 so a 400 engine can be built with a much wider bore than a 440.

All may be bored up to 40thou oversize no problem. They also both may be bored 60thou over but you have to start checking the cylinder wall thickness which should be at least 0.080" thick. Thicker than that is better and the thicker the cylinder wall is the stronger your engine will be.

Just don't use anything cast after 1976 as these are much thinner and can only be overbored by 20thou.

by **David Robson (Admin)** » 23 Mar 2002 21:09

by **Ted S (Teds)** » 24 Mar 2002 1:03

the thin wall casting stuff is b/s, i have seen 77-78 blocks that have thicker walls than some 68-70 blocks.

by **Lars-Göran Sundblad (Lars** » 25 Mar 2002 7:29

OK, thanks for all info. Some confusion still though:
1.Ted, do you have more info on which "after -76 blocks" that are thick wall design?
2.Last question first message "Things to look at when purchasing an old block?" Are there for instance any crack sensitive parts of the blocks? Are potentiall damages obvious to the naked eye or are there risks for hidden damages?
3.Were are the stiffening ribs located? And what casting number (numbers?) are they related to?
Sorry for my ignorance but I thought that the casting number related to one unique design, but by looking at the casting numbers above (thanks Dave!) there is only one number for 440 before -73 (2536430). So are thoose blocks with or without stiffening ribs? Or have I got everthing wrong so that with and without ribs can have the same casting number?
4.Yes Dave you are temting me with the 400 suggestion! Anyone with practical experience in line with Dave's suggestions?
5.Last stupid question: What does "B" and "RB" stand for?

by **Dave-R (Roppa440)** » 25 Mar 2002 13:39

I would have to research the stiffening question.

Any block can have casting faults. It is very, very rare though.

Chrysler used to have two main blocks. The 'A' block and the 'B' block. The 'A' later became the 'LA' (Light-A) and the 'B' later became the 'RB' (Raised Block - because of the taller deck height)

Talk to the lads at Hughes Engines. They have been building and racing these B and RB blocks since 1968 so they know a think or two more than me about it!

by **Christer (Christer)** » 25 Mar 2002 20:41

In Mopar Action, April 2001, they have sonic checked 20 (randomly chosen) B- and RB-blocks with a sonic tester. They tested no fewer than 160 holes. The results are rather surprising. Turns out, while there are plenty of “thinwall” cylinder blocks, their appearence is random, not year or casting number-based!

Here are some highlights from the article:

Low deck vs. RB motor:
Another variable that should be touched on briefly is the length of the cylinder wall. Any mechanical part is going to be weaker as it gets longer. A simple test with a yard stick versus a ruler will show you the dramatic difference in deflection as the unsupported length increases. By sliding a rule down into the water jacket of a block and you’ll see that the unsupported section of a B-block cylinder wall is about 5.25” long, while a RB cylinder is about 6.0” long. This means that the unsupported length of a RB motor is about 14% longer than on a B motor. A 14 % increase in unsupported length doesn’t sound like much, but when you crunch the numbers, it turns out to result in a significant increase in deflection for the same load.

Hardness:
The softer the material, the further the ball is pressed into it. The hardness value is then read directly from the scale. The numbers for the big blocks was interesting. All of the material samples tested at 200 or more on the Brinell hardness scale until we got to the 1976 and later blocks, then the values dropped more than 10%. This would indicate that the material strength was reduced in 1976 by about 10%. So maybe the folklore does have some basis in fact!

Conclusions:
Now we know that the factory information on big blocks doesn’t tell the whole story. While the blocks cast after 1976 do not appear to be “thinwall” castings, they do appear to be cast from material which is inferior to the earlier castings. It could have been this knowledge that led the MP engineers to caution racers against using the later blocks.
If at all possible, have a few block available to choose from. If there’s any core shift, try to select a block with the unevenness in the desirable direction - towards the major thrust side. If you don’t have access to a sonic checker you might just rely on block weight to help you decide. While a heavy block isn’t guaranteed to have the material in the correct place, at least it is a step in the right direction. For a high horsepower application, a heads up engine builder should consider having the blocks hardness tested as well as sonic tested.
It isn’t completely clear as to the value of the later blocks versus the earlier blocks. While the later blocks appear to be just as thick or thicker, they are also conducted of material which is marginally softer. I suppose it comes down to individual testing of various blocks for all of these properties and then picking the one that is the best available choice. Obviously, no one should pass on a 440 or 400 motor just because it has a casting date that is 1976 or later.
Straight, round, strong cylinder walls are what make power - by keeping the pressures from combustion in the cylinder and combustion chamber, not leaking past the rings. So we just offer these words of gospel as a friendly remainder: never bore an engine any more that you must!

by **Dave-R (Roppa440)** » 25 Mar 2002 21:10

There you go. I whole hartedly agree with that last sentance too.

Plus it looks to me like they all had the stiffening ribs you were asking about Lars.