Open/Semi-Closed/Closed Deck Engine Blocks

[Batmobile_Engage]

Here's a few questions for our experienced engine builders, that may benefit those
of us looking to complete a built motor...

What are the main differences between...

*Open Deck
*Semi-Closed Deck
*Closed-Deck

I understand that there is more metal in the closed (and semi-closed) deck blocks
than in the open deck blocks. I believe, all factory blocks are open deck, though
there might be a factory semi-closed.

Semi & closed deck blocks can handle more heat, and for a longer duration.

Besides these listed above (which I may not even be totally correct on) what else
can you guys add to this?

Also, when building a motor, either starting with a used block or a new one, at what
point does acquiring a different block or modifying an existing block be warranted?
Lastly, what is the cost difference between these options?

Thanks in advance for your input!

EDIT: I don't think this has been addressed before. IF it has, and it's in another
thread that I haven't found yet, let me know and I'll move the thread/post.

 

[HolyCrapItsFast]

Good Question...

The deck of the block refers to the surface of the block that mates with the head. When someone refers to a block as closed deck, the water jackets are closed and only holes are visible that allow water to pass through to the heads (see pics below). This design is typical of older EJ22 blocks. Many would argue that this design is the most robust for race applications because there is significantly less cylinder flexing to occur and I tend to agree. Though there are reports of cooling issues and head gasket sealing issues, this seems like the better block.

When referring to open deck, this design leaves the deck fully open to the head and there are either no connections from the cylinder walls to the block or there may be one connection at either end of the block as shown below. This design is typical of the EJ20. It is argued that this design is the weakest and offers the most cylinder flex. I am on the fence with this argument because the cylinder wall itself is much thicker than the EJ25 and there is less flex in the inherent design.

The semi closed deck adds connections at the top and bottom of the cylinders for a total of three connections per cylinder and one in between the cylinders. This adds stability to the cylinder for turbo applications with a thinner wall. This design is typical of the EJ25.

Many people will sleeve the block to strengthen the cylinders and prevent flex and ballooning under heavy boost or when spraying NOS. Sleeving is only recommended for racing applications and it does not make for a reliable street or daily driven machine. There are other alternatives like pinning. Pinning adds four more connection points to the cylinders and you can see an example of an engine I recently built employing this concept. I have seen this done many other times and with great success.

 

[Batmobile_Engage]

Wow. Great post. This will become a sticky!

 

[IGOTASTi]

Great question, and great answer!

 

[Batmobile_Engage]

Hopefully we can go over cost, availability with engine builders, necessity, options and so forth. For example, I understand that some people have "had their semi-closed deck, closed" by an engine shop. How do they go about that? Is it basically just pinning? Is it expensive, cost effective, etc.

I hope this thread becomes the great resource I envisioned.

Thanks again Holy!

 

[HolyCrapItsFast]

Making a closed deck is more process intense than just pinning so if cost is an issue then pinning would suffice in most cases. I would recommend closing the deck if you are sleeving the block to prevent it from moving under high HP applications.

I'm not really sure of the process behind making an open deck block into a closed deck block, but I would imagine it involves some melting and pouring in of new material and a bunch of machine work.

 

[Jnorth85]

Hey guys!
I am Justin the owner of Off the line performance, we are distributors for the outfront closed deck.
If you have any questions about the process, the strength or the reliability of the block feel free to hit me up!
or Ill be happy to answer any questions in this thread

 

[Batmobile_Engage]

Do (factory) cylinder heads require any rework to mate up properly with a closed deck block?

 

[Jnorth85]

Do (factory) cylinder heads require any rework to mate up properly with a closed deck block?

None at all, we do recommend the use of JE pro seal 1mm head gaskets for proper deck height.

If you chose the 1/2" head stud option the heads do have to be modified for the studs but on a standard head stud closed deck block no modifications are necessary.