Compression & Leakdown results

[Samio]

 

Hey folks, 

 

I have a 280zx 2+2 , 5 sp Turbo production of Aug 1982 so it has the Hyd lifters.  Car has 45k Orig miles.  was modified by previous owner so it has an intercooler, wolf chip, 300 zx ecu, Performance Fly wheel & clutch, i believe an upgraded turbo & injectors.  Car is a beast...

 

it starts with the tiniest flick of the switch, and it idles beautifully.  I do see & feel the extra vibration or imbalance as i sit in the car.  

 

when i first got it, i noticed some white smoke near the turbo.  then few days later i notices white smoke out of tail pipe.  

i did dry & wet compression, #s are almost identical.  led me to believe there is no ring issue

 

** compression results show issues on p1 & p5 
P1 ~ 6
40, 132, 132, 131, 80, 132

** leak down tests were
P1 ~ 6
%80 loss Red , Green , Green, Green, Red %80 loss, Green

 

air is only escaping from oil fill.  there is no bubbling in the radiator or the reservoir.  oil looks clean

 

the borescope arrived today.  Sadly piston 1 is extremely shiny & clean  i can read the p90 on there. 

Piston 5 ironically wasn't shiny, it looked just like the other good pistons.  

i rotated the crank and watched the valves on P1 move up and down. 

I have not had the need to add any antifreeze, not sure why that piston looks shiny

 

i used STP pro formula 10w-30. should it be on synthetic?

 

much appreciate your feed back

 

 

[Brad-ManQ45]

Shiney = lean...

[Samio]

interesting. 

 

most of my research suggests coolant getting in there.  how can i relate the %80 loss in compression to what ever is causing a lean operation? 

 

are you suggesting a sticky valve is allowing some leakage?

 

im lost here  

[NewZed]

Not an expert but it seems like you'll need to remove the head to find the cause.  The "wet" test might not fix broken rings.  As for head gasket, you could use the chemical test to check for combustion gases in the coolant if you wanted to be more sure.  Turbo engines are susceptible to detonation when they're pushed.  Detonation can cause drastic damage.

 

Worrying about oil type now seems pointless.  Good luck. 

 

https://www.oreillyauto.com/detail/c/evertough/rental-tools-evertough-combustion-leak-tester/ren1/67094

 

 

[Samio]

Much appreciated NewZed,

 

yup, it looks like the head needs to come off.

 

Couple of useful tips that might help someone one day

 

1) the Borescope light was too strong leading me to believe piston is shiny.  once i raised it to TDC it was apparent that piston is not shiny and looked just like other pistons.  all other pistons looked shiny when not in TDC.

 

2) was given a hint by Saturn engineer.  there was a defect in oil drain design that caused carbon build up to lock up rings.  so they use seafoam directly in spark plug hole after they warm up engine.  let car sit for couple of days if you can afford it.  crank car once a day & add seafoam accordingly during these days to help release locked ring

 

will update you guys in few days, i hope this works, i hope it helps someone

 

BTW, any idea where i can find the PCV hose? or a suitable replacement?

 

tnx!

[zboi]

Ooof 40 and 80 are really bad. Bad results wet would point to broken/pinched ring, but if your really lucky a sooted up ring. I used something called b12 chemtool in my cylinders when I got the motor. It had been sitting outside at the previous owner's place and got some water in the intake. To my surprise it cleaned up perfectly and had 135-140 compression on all cylinders. Valve sticking would be very obvious to spot with the valve cover off, you would see a valve noticeably lower than the rest, unlikely to be the issue though.