need some advise(cylinder #4 is dead)

[dsc4130]

just rebuilt the motor and the 4th cylinder is dead. .could it be a valve stuck open? anyone know how much a good short blow would be?
Modified by dsc4130 at 5:22 PM 7/10/2007

[themadscientist]

could you be a little more specific, dead?

[dsc4130]

sry, 1,2,and 3 have about 145psi compression and 4 has nothing,has a new oem hg and the head was decked but i dont know if the stem seals were replaced

[themadscientist]

Stem seals wouldn't net a complete loss of compression like that. Can you give me a quick narrative on exactly what went on after you dropped the motor in, how you tried to start it the first time? I can't see how you could bend just one cylinder's valves but it looks like a distinct possibility.

[float_6969]

The only way you would have no compression is bent valves, or to a lesser extent, a screwed up piston or a HG problem.

Is it possible that the cams were off and smacked the piston?

Could the HG be installed improperly?

Did the pistons get checked at all?

[dsc4130]

the pistons were checked. they were all fine, he hg is oem nissan from japan, the more i think about it, it had alot of valve noise in the rear of the motor when it started and then went away.

mad- i dropped the motor in, hooked everything up, made sure everything on the out side looked right, then struggled witht the wiring for a day. finally got it to crank so i primed the oil pump, then turned it over. and now it idles very hard cause #4 has no compression. im kinda starting to think that i bent a valve stupid question but if this happened could it have cracked my piston?

[themadscientist]

Valves normally lose on a meeting with a piston. Most pistons survive. Pull the valve covers and rotate the engine by hand so the cams on on the base circle on the "4 lobes. I hope I am wrong but if you bent a valve the lifter would most likely be slack on the affected valve.

[float_6969]

The pistons are usually OK. But I'll bet you bent a valve.

[r34 gtr]

you arent going to bend a valve turning the engine by hand. the valves wont make contact with the pistons unless the engine is running SO unless you bent one when cranking it, i would suspect the gasket or rings or something. your machine shop should have noticed if a valve was bent. mine replaced an exhaust valve that i would have never noticed was bent until they showed me. pull the head off and make sure you put the gasket on the right way. not trying to call your skillz into question, but it just doesnt sound right for this to happen when you havnt even gotten on it.

[dsc4130]

not trying to call your skillz into question, but it just doesnt sound right for this to happen when you havnt even gotten on it.

dont worry i question skills all the time thats why im on here asking the mods that know what there doing. cause im a 19 year old idiot thats not scared to try, the head gasket only goes on one way and the motor has started and ran. just not #4 and like my other posts said there was alot of valve train noise in the rear of the motor when it started

[sideways danny]

sounds like a lifter has over inflated to me