Magnum blocks, grade of the cast iron?

The title pretty much says it. I got into an argument, sort of, over what they are made of. I quaoted Shepards comments in How to hop up Magnum motors. Shepard says they are made of the same high nickel material as the Hemi blocks?

The same guy who wrote all that horsecaca about thinwall blocks?

The same guy who told us we were too stupid to understand how to pick a camshaft based on duration at 50 lift so DC and MP would only tell us lift numbers?

Yeah, I am still carrying that grudge.

The only way to tell for sure is to do hardness testing on the block, then send a sample off to be analyzed.

These engines seem to have very hard cylinder walls and some here think the Mag blocks are way better than the LA blocks regarding material strength. So it would make sense.

R.

every magnum motor i tore apart had much better bores then older blocks.could be rings,fuel injection,or hardness of block idk

These have a higher nickle content than blocks of
years ago... now days all blocks have the high content

You can definatly tell when you hit em with a grinder back to back. I have built a few strokers that need clearance and the magnums are certainly tougher.

I can't say for sure, but I would bet big bucks that there is NO WAY two blocks cast 25 years apart have the same metallurgy.

Technology just moves too fast... Granted we're talking now in 2017, but for comparison sake we're not even using the same plastic resins we were 2-3 years ago at Chrysler, let alone 25 years later.

I do agree the magnum stuff is much better. Not sure if it's quality control of the castings, material, or designs... but they seem to be able to hold better power then the early stuff.

They also have at least thinner decks and are more prone to crack form the head bolt holes when producing power

I just picked up my 73 360 block and the first thing the machinist said, dam that block is hard as hell.

I asked if it was harder then a magnum block and he said it made the diamond hone sing like the industrial blocks do and pulled the motor just as hard.

So he said in his opinion my block was harder then any mag block hes bored/honed.

So... But really I dont care either way, im going to use what I can/have.

But I do have a couple mag blocks this makes me think about.

Do this then if you have both, take a carbide grinder go grind on an un important part on both and see for yourself witch one is harder. I wrote a big post pointing out all the differences in the two but no one seems to care to read it they just keep swearing the early 360 block is the best because their grandpa said so years before the magnum block ever came out. The magnum bock also had more meat in the pan rails and main sadles anchoring the mains, probably a good idea for the guys insisting on running 4 bolt mains.

Dave ive read and watched most of your stuff concerning the mags, even to the point of running out the the shop and looking at a 318 mag pan rail when you mentioned it vs others.

I dont doubt it a bit, it is hard for me to accept "newer" is better, esp in the mag. world when costs are so important to the company.

I will do that after bit just for kicks.

Ive never ported or ground on magnum heads, are they harder as well?

I am open to anything, my 318 mag is ready to build and is a per mag roller and ive a 360 pre mag builder.

Hmmm does this apply since they are pre mag blocks?

Magnum blocks get a bad rep they are very tough, I jknow this from my own racing

Has anyone tested the Brinell hardness on any of
these blocks.. I know they did at Chrysler but I
dont know the numbers for any one year.. I always
thought they were in the 150 range.. or do a
rockwell C on them

150 Brinell sounds kind of soft to me. I assume that they use an SAE grade of cast iron. This would be a G1800, around 20ksi tensile strength. My Hemi block (older MP block) is 185 Brinell.

https://en.wikipedia.org/wiki/Gray_iron

Although I didnt have time for both I cleaned up my 73 block today and although the machinist thought it was a really hard block my cutter worked better then it should have.

I will hit the mag block tonight.

Don't see the bonus in having a hard block, we all know that hard stuff cracks. Id prefer a soft Aluminium block. Could someone school me on this ?

In most ferrous metals, the harder it is the higher the tensile strength, and also the more brittle it becomes. There is a trade off to be made. For the hardness of cast irons, the link above gives a ratio of tensile strength to hardness.

"In the automotive industry, the SAE International (SAE) standard SAE J431 is used to designate grades instead of classes. These grades are a measure of the tensile strength-to-Brinell hardness ratio.[2] The variation of the tensile modulus of elasticity of the various grades is a reflection of the percentage of graphite in the material as such material has neither strength nor stiffness and the space occupied by graphite acts like a void, thereby creating a spongy material."

You really don't care about harness at all if you want to get 'engineer' about it.

Material that fractures shortly after its yield point has a very small plastic region. This type of material, we often think of as being hard or brittle when we use common terms. Like ceramic or glass. Material that you can continue to stress beyond its yield point before it fractures has a large plastic region, and we often think of these materials as soft or malleable.

But the bottom line is both materials were stressed beyond their yield point and have received some sort of permanent damage that will never go away. Either a crack, or the material has deformed. Both are bad for an engine.

True but you want it strong/stiff enough so it
doesnt distort and stay/yield.. it has to have
enough nickel for strength
Like everything.. there is a balance to all this
stuff.. even for making iron
EDIT
Look back 70 years.. a iron block was LUCKY to
last 70K.. now days they go 250K on miles and still
dont have a ridge

OOOk Getting all speedtalk.com on us here. But really great info.

All I know is my race blocks take more effort to massage then does my oem blocks. I dont doubt the mag blocks are "different" in possibly a better way then the la blocks.

Ive never had my hands on the so called "magnum race blocks" ive heard about but would like to one day.

I went from 4.04 to 4.05 just now on my 360 block and was running hellfire rings for a while at the 4.04, they seem to wear on a bore very quickly.

I also read Dave's stuff on the Magnum blocks and my next sm blk build will probably be based on a Mag block.

Yes, and while I'm sure the metallurgy has improved, I'm sure a lot of the gains in block wear can also be attributed to thinner rings, and EFI to more precisely control fuel delivery so the rings never get washed with fuel

For sure on the above, along with some major lube improvements. I also believe a lot has to do with the quality of the castings - mainly core shift. I have been running a 1979 E58 block for some time now - pushing around 650 HP through it. All the walls sonic tested over .2 on this block. So far, so good. I would guess that the block casting procedure's / tolerance's have improved over the years also.

So what would one need to do really, cut an ear off each type block and send it in and have it checked by the pros and if so what results would we be looking at?


Does it even matter knowing what we already know?


I cant find it but I know Dave had sonic test info iirc.

Right now there is a pre mag 360 roller block builder, running, complete for $150 near me and I might just go snag it.

The memory goes with age clearly, because I forgot I had taken a 360 mag block and made room for the common comp la style roller lifters with the link bar.

I did have to cut into the tops of the lifter boss on a few so the lifter would stay on the camshaft. (linkbar hit)

I dont recall if I used a cutter or sand rolls, but id think id almost of had to of used a carbide cutter the maybe sand rolled it.


But I do recall it didnt take more then a day of putzing around to get it done.

Why did you grind the block for LA lifters?Solids maybe? The Magnum lifters are inexpensive and you have the bolt bosses for the spider guide plate with your block so no need for any tie bars.Just curious as to why all the seemingly extra work done to your block.~RT

Would be interested in cylinder wall sonic check sheets from some magnum blocks? I have found the late la and magnum machine work is MUCH more accurate and have sonic tested older blocks,just not many mag blocks.

Why did you grind the block for LA lifters?Solids maybe? The Magnum lifters are inexpensive and you have the bolt bosses for the spider guide plate with your block so no need for any tie bars.Just curious as to why all the seemingly extra work done to your block.~RT

I had run mopar solid flat tappet lifters in that block maybe 15 years ago, its a pre mag roller and used 5/16 pushrods and with X heads outwardly looking in things were at odd angles but all worked properly.

As for the rollers, the block was clearanced for solid mech lifters,I forget the part number but they were the most common comp rollers that didnt need to be bushed and were more or less drop in but the link bar on some would hold the roller tip off the cam. 828-16 iirc.

Back then there were no cheap lifters, even the oem units I dont think were that cheap and a hydro roller cam at the time, say a good crane with the fuel pump eccentric was nearly $400 so I went and ran a comp mech roller, Id have to look at that cam card but it was one of comps smaller "street" mech roller cams.

Mechanical cam and years ago,got it EV2.Thanks for the answer,
RT