breaking in... (rebuilt engine)
Can somebody tell me what will happen if you crank it with the igniton unplugged? Coz my mechanic unpluged the coil packs and the crank it he said to build oil pressure. then when he connected the coil packs he tried to start it...the we heard clank sound then we found out that was the valve hitting the piston! He said he checked all the timing and everything was good. but how did we bent valves and broke pistons? what went wrong?

I just need advise so this wont happen again. Please help me breaking in.

my car is almost done maybe this weekend and im still scared to see him starting my car!

buschur's:
The 4g63 is not a small block Chevy. You do NOT crank it with the fuel disconnected or the ignition unplugged to prime the oiling system.If you truly wanted to try and prime the oiling system before starting a new engine you would need to leave the timing belt off and crank the oil pump seperately. Same thing if you DID have a small block Chevy, you'd spin the oil pump through the distributor hole.
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My advice would be to change mechanics.

 

can't do that now... they covered everything.

 

sounds like something was not timed correctly the 4g63 is a zero clearance motor meaning if your timing is off you bend a valve

 

^^^ What he said.

 

could be timing...did you scope the cylinders or take the head off yet? if you did and you have valves bent and having touched pistons in every cylinder or two cylinders that fire together its going to be a timing problem. do you have aftermarket cam gears? the fidanzas can be a real problem when it comes to timing after re-assembeling a motor.

did you have any head work done? specifically valve oversizing?

my bad i didnt actually read everything you wrote...well advice would be to check and re-check everything...ensure your cam timing is zero-ed have they used the same head and just had it decked? what about the block? was the block decked? (and honed...) were the cams magnafluxed? did you cycle cheap oil through your system to clean it out just in case also?

 

Buschur's advise is solid - to prime an Evo you spin the oil pump with the timing belt off. After it's primed you will need to realign the balance shafts & oil pump correctly before reinstalling the timing belt. Do not just line up the TDC marks & go, the balance shafts could still be out of whack.

If you had pistons hitting valves, then there's a good chance until the head comes of and the vales are replaced then the car will never run at 100%. Valves contacting pistons means the cam timing (timing belt and/or adjustable cam gears) had to have been installed way off - usually more than 1 belt tooth.

 

the best way is to crank the pump like buschur said, otherwise you can crank like you did but something was definitely wrong with the timing or your pistons wouldnt have hit the valves

 

I remember he crank it(for 5 seconds for 3 times) with the coil packs unplugged to build oil pressure....
my question is why it didnt break or bent the piston when he first crank it???? It only hit the valves after he connected the coil packs. Until now he really keep saying that he double check the timing and everything was good. He said the oil pump got seized up. Is this true also?

 

Was the motor out of the car when the timing belt was being done?

Wouldn't it be wise to turn the motor over by hand once the belt is on to confirm whether anything is out of wack?

 

Coil packs have nothing to do with mechanical movement of the pistons and valves. If the oil pump seized, your timing belt may have slipped changing the timing completely and THEN you had piston to valve contact.

 

how could the timing belt slip? is this possible to slip?

 

if it was slacked at all it could have jumped some teeth maybe...

 

Basically the situation you describe doesn't make sense mechanically. If the oil pump was "locked up" (or the balance shaft also connected to it) the engine shouldn't have spun freely for the priming. Also if there was a timing belt issue then you also should have heard that contact when he spun the engine to prime it.

The following is pure speculation without verifying facts:
About the only way I can imagine just re-connecting the coil packs could cause a problem is if they were installed to fire the wrong cylinders, and I'm not sure that's even possible. If that did happen, then it's possible he sparked off a cylinder on a compression cycle and that probably would force the timing belt to skip teeth possibly forcing the pistons & valves into contact. Again, all of this is pure speculation - I haven't looked at the details to see if this is really possible.

What does seem to come out of this is that you may not have the whole story. If your oil pump locked up it would be a very unusual failure. I would first look into how the engine was assembled and the steps taken to ensure the assembly was correct. Unfortunately without being able to do the work yourself you are dependent on someone else to do the tear down and failure analysis. If the mechanic who build the engine has already done a tear-down then any evidence of mistakes he may have made will be gone.