Compression ratings

[Pharaohabq]

What is the stock compression rating supposed to be in an L28 NA engine? I don't want to have to tear mine apart unless I have to, though I know I probably should considering the car is at 119K miles and it's been sitting for 8 years...

phar

[evildky]

at 119K that L28 si just getting broke in, my 183k junkyard motor which detonated 5 cylinders still had crosshatch in the cylinderwalls, the standard reading is somethign like 160 psi? any fsm or even haynes manual will have ti published, the important thing si that they are consistent readings across the cylinders, they should be within 10 psi of one another

[Pharaohabq]

okay I took my readings last night. I've got: #1 = ~100 PSI,#2 = ~120 PSI#3 = ~120 PSI#4 = ~120 PSI#5 = ~120 PSI#6 = ~110 PSI

They're all about the same cept for #1. I couldn't find the block#, but the head is an N47. I adjusted the timing, and properly gapped the plugs, I need to replace a lot of things like the plug wires and better plugs, but with all that I was able to get the car started and after sitting for between 5 and 8 years it smoked a little. but that got better as it ran, now I think it's only smoking from the valve seals, though if I pull the head I might also pull the Pan and still go for the full rebuild. But right now I'm happy it runs!

Phar

[evildky]

might want to check those numbers by a service manual, and the block casting is just forward of and below the drivers engine mount, the N47 bhead came on 77-80 N42 blocks, low compression dished pistons, if you want to do a build try finding an 81-83 F54 flat top block, this with an N42 head will get you about 9.5:1 and is a very popular setup, plenty of these around on the cheap definitely worth picking them up, if you want to go thogh the trouble of a build spend a couple hundred more and start with better parts

[Pharaohabq]

ooh very good advice. I'll keep that in mind if I decide to do a build. I haven't yet decided on wether to keep it a stock restore, or go for the S130 turbo upgrade. I guess it kinda depends on what I can find around here for Donor Car.. I got picts I'll post on another thread. Pharaoh

[JSpecGC8]

Glad someone asked this question, makes me feel real good about the Z I bought.

The cylinders were all between 150~155!

[Pharaohabq]

yeah, I need to retest mine now that the car has been running for a couple weeks, do both the dry and then wet compression test and see how it comes out, my ~120psi readings were all dry. I'm going to be pulling the engine anyway, and maybe if I'm lucky I'll get a good deal on a L28ET... rather than rebuild mine... What car did you find? Phar

[Bleach]

What year is your 280ZX? 1979-80 had lower compression stock than the 1982-83 models.

That compression ok for the earlier years but pretty bad if your engine started out at around 170psi for 1982.

I had 168-170psi at 199,000 miles on a 1982 280zx non-turbo. It was still running at 232,000 when I swapped it out for an L28 turbo.

1975-80 8.3:1 compression1981-83 8.8:1 compression