new piston and rings, head rebuild, ran fine for a bit no compression now...

[IA97GST]

Hi there dsmers , So my night hasnt been so good... Heres the problem.. I just rebuilt my motor and replaced a bad piston. Gave it light hone and put new rings and piston on number 4. Had a head rebuilt. lapped the valves in and new valve seals. So the car ran good for a couple minutes and then died and barely runs. I did a compression check before starting it on number 4 and it had least 90+ now it has absoulutely nothing. number 3 has 90 other 1&2 have 130 or better.. What happened? Any ideas or steps to take next?

 

[Spoolio]

From what i can get from this, you probably didnt seat the rings in that piston properlly. You most likely just dropped the ring or cracked it from improper installation. If i were you, before you do any damage by turning it over anymore, rip it apart, and check all the pistons, and cylinder walls, replace what is damaged and start over again, i hope you coated the walls with that red grease stuff you're suppose to use while rebuilding you're motor. If not ask the local auto part store for it and use it accordingly.

 

[MyÜberFastGSX]

That red stuff is called assembly lube, and you actually not supposed to put it on the cylinder walls, you're just supposed to lube the cylinder walls motor oil.

It sounds like your rings didn't seat in that cylinder. They could've been installed improperly, or just bent or cracked or something.

 

[IA97GST]

Hey guys, Thanks for your replys, I called a few machine shops and they said even if i had broken rings for some reason I would still show somthing for compression. I have absoulutely nothing on that cylinder. The rest seem fine. I was reading on a post that it could be the lash adjusters arent letting the valves close and hang open if they were not bled down properly? Im gonna put air to the cylinder today and see where it comes out at maybe its just valve train.

 

[IA97GST]

I just Put air to the dead number 4 cylinder and the airs coming back out number 3 cylinder. I have the piston top dead center on number 4. I dont understand why my head gasket wouldve popped that easily? It only was running about 5 mins and I torqued everything down to about 85lbs in correct order. Any Ideas guys? Thanks, Larry

 

[JayRolla]

What kind of head gasket did you use? Also before you put the bolts in the head you need to take compressed air and shoot all the material out of the head bolt holes. If there is any water or oil in there(which there usually is), it can give you false readings on your torque wrench. Make sure you clean them out perfect. You can never get a real torque unless the holes are clean.

 

[turbo90gsx]

Theres a good possiblility that your head has server warpage. I blew the head gasket on my old motor, ruined 2 pistions, and warped the head .011" and melted a 1/16th" valley on the head inbetween 3-4. Did you have the head decked/milled in its rebuild?

 

[IA97GST]

Update on the car.. So i had air coming back outta the number 3 cylinder when air is fed into number 4. well after some more research i found that when the piston is top dead center on number 4 the intake valves are open on number threee. so air was being pressed from number 4 back into the intake and coming out number 3 cylinder... makes sense doesnt it... and when the throttle body opened the air comes out of it more so also. so now my question.. how did i float the valves on that cylinder??? as the timing is in mark and all rest are good. i removed the intake cam and still no good.. I have a bent valve.. The only thing i can see is lash adjuster pushed out more then the others and it didnt compress back in and piston hit the valve. I read on forums about not having lash adjusters bled properly... ? any ideas? also do i dare reuse the head gasket after only 5 mins of run time? Thanks for ure replys i appreciate it.. Larry

 

[Spoolio]

Just to be on the safe side, i would just replace the headgasket anytime you remove it, but if you didnt really do much running and the gasket seems in 100% condition, you may get away with reusing it.

 

[phillip]

mmm i would use a new one, better safe then sorry.

 

[My96AWD]

The only time i would re-use a head gasket is when it is copper or mls. Stock are garbage once you torque them down.

 

[IA97GST]

Hey guys, Wow its been a Long day... I pulled the head. there was debris in the cylinders. inbetween the valves. aluminum and porcelan. Reinstalled it and same thing happened again. ran good for three minutes lost everything. so this time i removed it again for third time today... talk about frustrating. this time i pulled the intake off and looked in it. and what i found was all kinds of pieces of aluminum and the porcelan was from the spark plug.. when it chucked the valve on old head it blew pieces of piston and tip of the plug into the intake... weird huh but it did happen i power washed it out and reassembled it.. used the same head gasket. and ran it for about an hour tonight and everything seems to be fine. Thanks for your replys. I learned a few things today.. Happy DSMing...

 

[MyÜberFastGSX]

I'm glad to hear everything worked out for you. I'll be done with my build in about a week. I'm hoping everything goes good for me.

 

[sawnuoff]

It has been a common thing with all makes that when something get dropped, smoked, melted or anything like that and you run it a bit to much it will get into all the cylinders, seen chunks of valves from #1 cylinder end up in 3-4, so as a rule of thumb if any of the above happen be sure to clean the intake out.
I have even gotten the clips from air cleaners out from behind the valve that was holding it open.