Блок оказался успешным.

Оказался means turned out (to be) or proved to be.

So Блок оказался успешным is literally something like:

• The block turned out to be successful
• The block proved successful

This verb often suggests that the result became clear only afterward.

The dictionary form is оказаться.

In this sentence, оказался is:

• past tense
• masculine singular
• perfective

So the breakdown is:

• оказаться = to turn out, to prove to be
• оказался = turned out / proved to be (for a masculine singular subject)

If the subject were feminine, you would get оказалась.

Because Russian often uses оказаться when it means to turn out to be rather than simply to be.

Compare:

• Блок был успешным = The block was successful
  → a neutral statement

• Блок оказался успешным = The block turned out to be successful
  → emphasizes the discovered result

So оказаться adds the idea of an outcome becoming known.

Because after verbs like быть, стать, оказаться, являться, Russian often uses the predicate noun/adjective in the instrumental case.

Here:

• успешный = successful
• успешным = instrumental singular masculine/neuter

So:

• Блок оказался успешным
  literally = The block turned out [as] successful

This instrumental predicate is very common in Russian.

Because успешный is the nominative singular masculine form, but this sentence needs the instrumental after оказаться.

So:

• успешный = successful (dictionary form)
• успешным = successful (instrumental form)

That is why the sentence is:

• Блок оказался успешным, not Блок оказался успешный

Блок is in the nominative case because it is the subject of the sentence.

So the structure is:

• Блок = subject, nominative
• оказался = verb
• успешным = predicate adjective, instrumental

In the past tense, Russian verbs agree with the subject in gender and number.

The subject here is блок, which is:

• masculine
• singular

So the verb must also be masculine singular:

• оказался

Compare:

• Система оказалась успешной = The system turned out to be successful
• Проекты оказались успешными = The projects turned out to be successful

Оказаться is perfective.

That matters because the sentence refers to a completed outcome or a result that became clear:

• it turned out
• it proved to be

A rough imperfective partner is оказываться, which would be used for repeated, habitual, or more process-oriented contexts.

For example:

• Он часто оказывался прав. = He often turned out to be right.

But in your sentence, there is one completed result, so оказался is natural.

Yes. In English you say turned out to be successful, but Russian does not need a separate word for to be here.

The idea of to be is built into the construction:

• оказаться + instrumental

So оказался успешным already means turned out to be successful.

Yes. Russian word order is flexible, though the neutral order here is:

• Блок оказался успешным.

You could also say:

• Успешным оказался блок.

That version gives more emphasis to успешным or sounds more stylistically marked. For a learner, the original order is the safest and most neutral.

The stresses are:

• блок
• оказа́лся
• успе́шным

So the sentence is pronounced approximately:

• Блок оказа́лся успе́шным.

The stress is important because Russian stress is not always predictable.