04/30/2026
So, lets have science class today concerning blocks, shims, and liners.....
This isn't meant to be exhaustive discussion of metallurgy, just some generalized information to consider when deciding what's important to you when repairing counterbores on engine blocks.
I prefer Rockwell C as my measuring stick for hardness just because i have a better practical understanding of that rating system. But during research, lots of the materials don't have that listed, so I chose Brinell because that was a consistent measurement across what I could find.
Lets first establish some of what a google search has offered concerning materials involved.
1) Grey cast iron, what engine blocks are more than likely made of.
SAE Grade G2500 – Minimum Tensile Strength: 25,000 psi (173 MPa) – Brinell Hardness
Rating: 170 to 229
SAE Grade G3000 – Minimum Tensile Strength: 30,000 psi (207 MPa) – Brinell Hardness
Rating: 187 to 241
SAE Grade G3500 – Minimum Tensile Strength: 35,000 psi (241 MPa) – Brinell Hardness
Rating: 207 to 255; 124,000 to 145,000 PSI compression strength
SAE Grade G4000 – Minimum Tensile Strength: 40,000 psi (276 MPa) – Brinell Hardness
Rating: 217 to 269; 120,000 to 160,000 PSI compression strength
We aren't sure which one engine blocks are for sure, my best guess is the G3500, but it is a guess, if its really premium, its G4000.
2) The cast product I use for sleeves is rated 160-220 Brinell and approximately
429,000 PSI compression, and min 65,000 tensile strength. More on this later...
3) Grade 304 Stainless Steel- compressive strength 30,000-45,000 PSI, Brinell hardness
150-185; its ductile which
means it will permanently deform under high compression
rather than fail completely.
Cold worked or full hard can be higher due to work hardening. It can get harder, as it deforms (strain hardening).
4) Grade 316 Stainless- compressive strength 24,650 to 45,000 PSI;
Brinell hardness 150-217; Also cold working can make it harder,
also after deformation.
5) Alloy steel- The alloy steel I use for shims: Brinell hardness 250-320
(would be towards the higher end of that due to the metallurgy report I
receive with my steel when I purchase, they don't give me Brinell, they
say 32-36 Rockwell C);
Typical compressive strength of 110,000-160,000 PSI.
Now, why all these specifications......
Well, its meant to draw a picture of everything working together as a system and show the how and why I chose to use what I use for shims and sleeves. Lots of companies state stainless steel is what they are using for shims, I used the above examples as a reference, because they are widely available, not because I know that's the alloys they are using. Solid bar materials are easier to source in varieties, but.....take longer to machine (a lot longer) and more of it goes in the scrap bin, so doesn't seem to be the best choice to use financially. It equates to more weight shipping, more machine time, higher labor costs, and more tooling costs. Stainless is however, a good buzzword, it sounds cool. It does offer more corrosion resistance than alloy steel, But, at a cost of durability in my opinion. While corrosion resistance is nice, lets look at the inside of the engine block, there is air and oil on one side, and coolant on the other. Oily metal doesn't corrode for the most part. Assuming the coolant is in any kind of decent shape, the ferrous metals don't present horrible corrosion. If the coolant is poorly maintained, then who cares? All the ferrous metals are going to have failure routes. Think rotten coolant holes on the decks, rotten liner registers, etc. The overhaul you spend so much money and time on goes down the tubes with poor maintenance no matter what. So, in my opinion, the materials we use, offer a nice blend of upgrade over competitors and OEM materials. Our products are generally a little harder, have higher compressive strengths, less elongation and deformation when it does compress, and the only down side is a possibility of corrosion.
Its gonna rot at the same time the rest of the head and block does in bad coolant situations. Probably less because of the actual surface area exposed, a few thousands of exposure at the perimeter, if the air and coolant makes it to the sealing surfaces, well, there is already a leak, so its a moot point.
The sleeve material we use, well, its similar in hardness to the premium possibility in block material and a way higher compression strength. I don't know what the other guys use, I just chose it because I didn't consider just one property. I chose it because it has a good hardness, superior toughness, easy to machine in the field, and nearly identical thermal stability. Why care about thermal stability? Because it will maintain same/similar expansion as the parent material its pressed into and not loose its press fit during heating and cooling cycles.
Now comes the flames LOL.........
shims, , , ,
