wavy

I just installed a new motor in my 85 8v and after running for less than 3 seconds the motor has locked up. Does not turn over at all even with spark plugs removed. The timing belt is fine and the engine has oil. The engine used to turn by hand before it seized. Any ideas on what could've caused it to seize? Do I probably need a new motor?

Rich_Jenkins

Welcome! What is the model/year of your Porsche?

Edit: Is it a 1985 928?

GregBBRD

3 seconds?
That's an incredibly short period of time!
It takes more than 3 seconds for oil to reach the heads, but regardless of that, an engine will run for more than 3 seconds, without any oil!

More details needed.
What is the history of the engine?
Why did you replace the original engine?

Mark Anderson

sounds like a small object was in the cylinder when it was cranked

drkekar

That is what happened to me when I bought one. Cylinder 7 I could not even knock out the piston trying both ways.
Hence I had one rebuilt.

GT6ixer

Manual? Verify it's not in gear and clutch is disengaged.

Kevin in Atlanta

Did the engine spin before you put it in?

GerritD

Always first try to spin the engine by hand to see whether there are no obstructions. Afterwards you can do a real start.
I did this with my engine (16v 4.7 300hp) to make sure timing and belt is properly set.

ealoken

Questions:

When you built the engine, what did you change?

Pistons?
Piston ring gap?
Did you prime oil before you started?
Can you spin it backwards? ( slow by hand )

3 sec sounds like a shim or object inside the engine.

GregBBRD

The OP seems to have posted and then just disappeared.

Another 928 destined to be parted out?
Another 928 mysteriously catches on fire?
Suicide Help Line intervened with a 5150 hold?

SteveG

Well if it has only one valve per cylinder, I think you have found the problem.

DeWolf

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