Redtop pissing me off...

[Boogerlovers]

alright guys here is the situation...i started rebuilding my sr about 6 months ago and i am still having shit ass problems with it. I have pulled and rebuilt this motor four times priort this one. I am rebuilding a 5th time YES 5th time in the last six months!!! I just finished it up today and i gotta say i was pretty damn hyped up...i finished at around six or so, i go to fire her up and no compression on any cylinder what so ever...some of you might be like ugh valves are open or your rings are bad...nope not the case. My teacher showed me a little trick where you pour a tiny bit of oil into each cylinder to help the rings seal. So i did and low and behold cylinder one is a fucking champ...building compression almost instantly. So i move on to two and three and i get nothing. At this point im pretty stumped, for the fuck of it i do cylinder four and again a fucking champ...great compression. so my question is why the hell are only two of my cylinders not building compression...??? any help is more than appreciated...i mean seriously five rebuilds in the last six months...and in case your wondering why so many rebuilds??? Honestly i dont remember...haha, but this last time i bent two exhaust valves and had to replace two valve guids...please help me out... :(

[DTC 360RT]

what did you do 5 times? same head? same valves seats? theres only so many times you can resurface a head and valve seats, honed out cylinder walls? the leak down creates a seal between the rings and cylinder walls...if 1 and 4 build compression, that means valves are closing correctly and youve created a good seal with the oil.....does compression go away after cranking for a while? seems like it would,hypothetically, just cause you had no compression before hand. now if 2 and 3 do nothing, that means compression is going out through the valves. take valve cover off and crank...are valves opening and closing correctly? no binding? im sure you've covered these basics, im just ranting out loud.

try a diff head.

[Boogerlovers]

yeah i did all that...i think i will try a different head...every single time i rebuilt this motor it was from stupid mistakes that i made...on one occasion i put the rings on upside down haha...i fail...but yes one and four hold compression no leaking...i havnt checked where im leaking from...ill check next week....you know anyone selling a head haha...

[blasting_speed]

Craiglist it dude. Get a new running one. Its going to keep giving you trouble. You can also take it to a shop. Its going to cost you but they'll get it running most likely.

[WoolyS14DET]

are you absoultly sure the cam timing is right ????

[Robert]

sounds like bent valves

[WoolyS14DET]

Any update on this ??? :hit:

[Boogerlovers]

actually yes haha...its running like a champ now...i dont know what happend...i sucked all of the oil out from the cylinders using a brakes vacuum bleeder. and then i added just a bit of oil to each cylinder again...and it started to build compression...i dont know why. It built 150psi on each cylinder, and its running great right now, no over heating stuttering or problems of any kind...

[WoolyS14DET]

Nice work !! glad the problem was solved !!!! :thumbup:

[Boogerlovers]

thanx man...and to the ppl who provided suggestions or advice :thumbup:

[WoolyS14DET]

Thats what we are here for !! :mrgreen:

[Robert]

actually yes haha...its running like a champ now...i dont know what happend...i sucked all of the oil out from the cylinders using a brakes vacuum bleeder. and then i added just a bit of oil to each cylinder again...and it started to build compression...i dont know why. It built 150psi on each cylinder, and its running great right now, no over heating stuttering or problems of any kind...

150psi is too low of compression. whats your compression ratio? and how thick is your headgasket. with a 1.2mm head gasket and stock bottom end my sr was @ 165psi exactly across all of the cylinders w/o oil. and about 175psi w oil. try starting your engine. get it up to proper operating temps. turn it off. unplug your fuel pump and cas. test the compression again w/ everything heated up and oiled properly by the engine. when cranking, you need to have the throttle body all of the way open and all of the spark plugs out.

[Boogerlovers]

is it really??? i didnt know that...i have yet to test the compression, since the motor started running, ill do it tommorow, since im going to re-torque the head studs

[Boogerlovers]

according to these ppl and other articles standard compression is 156psi

from a authentic FSM by Nissan :


Compression pressure: kPa (kg/cm2, psi)/rpm
Standard
1,079 (11.0, 156)/300
Minimum
883 (9.0, 128)/300
Difference limit between cylinders
98 (1.0, 14)/300

http://forums2.freshalloy.com/showthread.php?t=56542

and my compression ratio is 8:5:1, cp forged piston, my head gasket is a Cosworth 1.1mm

[Robert]

huh... nevermind then. lol good luck w it

[Boogerlovers]

haha its all good man...i was kind of surprised with your really high compression numbers...