Acceptable compression on new car?

[andrewwr32]

Guys,

I just a had car I'm lookg at buying comp tested at 138 - across all cylinders. This seems a bit low to me...

Thoughts?

Andrew

[97Sky]

As long as there all around the same number it should be fine.

[andrewwr32]

As long as there all around the same number it should be fine.

Thx for the reply.

Yeh that's what my mechanic said. The ODO says ~61000, with a Tomei speedo, but even the dealer agreed that's probably unlikely the real KMs (I've been very happy with the honesty of these guys, it's really worked for me and brought me on board).

Mechanic they are all the same, 138, that that indicated probably up to 100 thou kms, but nice treatment and no abuse. The car's condition is excellent.

And MAN is it FAAASSSSTTT! :crazy: :crazy:

[gun32gtr]

yeh when i bought my gtr i got the dude to get it comp tested b4 i bought?145 across all six?why would they be different?less kms maybe

[andrewwr32]

yeh when i bought my gtr i got the dude to get it comp tested b4 i bought?145 across all six?why would they be different?less kms maybe

Yeh quite simply engine wear will reduce compression. If there is variance between cylinders, that shows abuse or ill-health, so I am told from decent sources. Compression will just reduce over time - over KMs.

I am aware motors that have been sitting for some time will show lower compression when first started - I saw this with an SR20DET of mine. It increased by 10 after a week or two.

However, I've flogged this thing enough myself - so I don't see that being the case. I will however, as my mechanic suggested (best mate) check it in a few weeks of driving. He old man, who runs the shop, reckoned it won't change since I've already flogged it. We'll see who's right

They're always arguing... lol :chairshot

[andrewwr32]

Mechanic they are all the same, 138, that that indicated probably up to 100 thou kms, but nice treatment and no abuse.

I'm starting to miss a lot of words when I'm typing posts. I think that drinking on the weekend might've actually damaged my frontal lobe or something...

:bonk:

[gun32gtr]

haha i think ur right it happens though..thanks

[gtr fan]

Hi Andrew, That compression is a bit low and your right in the fact well at leasts its the same over all 6, but the reading does tend to indicate that the motor is now old (obviously) but is probably whats the word 'rattlier' / not so tight anymore. A fresh gtr engine comes in at around 180. Mine is an aussie delivered one and when i bought it had 108k on the clock and comp tested in the 160 accross all six.

My suggestion try to find a tighter one, sure it may go hard.... for now.

[andrewwr32]

Hi Andrew, That compression is a bit low and your right in the fact well at leasts its the same over all 6, but the reading does tend to indicate that the motor is now old (obviously) but is probably whats the word 'rattlier' / not so tight anymore. A fresh gtr engine comes in at around 180. Mine is an aussie delivered one and when i bought it had 108k on the clock and comp tested in the 160 accross all six.  

My suggestion try to find a tighter one, sure it may go hard.... for now.

But I love everything else about the car! It's my only concern... :goddam:

I could just take it, and expect to replace rings, bearings and gaskets in a year or so. I'm guessing 3-4k for that. Whaddya think?

[Duncan]

6-10k unless you can do all the labour yourself.....

[andrewwr32]

6-10k unless you can do all the labour yourself.....

Well my best mate is a mechanic. I would get cheap labour, but not REAL cheap (they still have a business to run, and he has a partner, and he don't work outta hours, much like me).

Not speaking off full rebuild, just the rings and necessary bits like bearings gaskets and stuff...

Less than 6k you think Duncan?

I hope so !!!

[Duncan]

Pistons and rings 1300

head reco 500

bottom end clean, hone 300

crank and rods test and check, balance all 300

gasket kit 500

water pump 200

n1 oil pump 500

rod bolts 100

head bolts 50

thats 4k to get started.

then labour for engine in and out say 10 hours

+ actual build time

[gtr fan]

If you really like the car and you feel you are getting a good price and have factored in the engine condition go for it.

How long have you been looking for a GTR? Can I ask how much this one is (don't reply if question not appropriate) There are lots of really good ones out there its just a matter of finding one. It took me about 3-4 months.

[andrewwr32]

If you really like the car and you feel you are getting a good price and have factored in the engine condition go for it.

How long have you been looking for a GTR? Can I ask how much this one is (don't reply if question not appropriate) There are lots of really good ones out there its just a matter of finding one. It took me about 3-4 months.

The car was up for $27990. I'm trading two silvias, fairly hammered in terms of paint & interior, one Q, one K with mods (GT-SS, Apex Hybrid, 2450lb clutch, 3" mild steel, z32 brakes, etc). So the two silvys + 16,100. I could do better with a private sale on the silvys, but it so much hassle and with their nick and people test driving and stuff - I really can't be arsed.

I've been looking just a few weeks; I'm probably impatient to my own detriment, but I don't see myself finding much any better, without flying to Japan. (?)

Thing is I'm looking for something virginal. I don't want a modded, hammered car - it's condition is fantastic. Color is great. Brembos (big deal for me), great interior. Spotless engine back (the slave cyl has leaked at some point and stripped a little paint but it's well rusted on that little patch (surface) and hasn't seeped even with me really CLAMPING on the anchors, so I believe that's history.

Here's my spiel on the car I posted, with some (nokia) pics....

http://www.skylinesaustralia.com/forums/sh...ead.php?t=77434

Seriously, tell me like it is. I want feedback

[gtr fan]

You say the plenum hasn't lost much paint so thats always a good sign.

My honest opinion - the comp ratio would worry me. I realise you are able to trade in your current cars and the appeal of Brembo brakes is always tempting (however this can always be done later, some people say they are over rated, never experienced brembos - another thread.lol)

I would be surprised though if a perfectly standard car returned that comp ratio, gut feeling thinks it may not have been so standard with its previous owner.

Personal choice I would skip it.

End of the day anything is fixable if you really like the rest of the car which sounds pretty good.

[andrewwr32]

Pistons and rings 1300

head reco 500

bottom end clean, hone 300

crank and rods test and check, balance all 300

gasket kit 500

water pump 200

n1 oil pump 500

rod bolts 100

head bolts 50

thats 4k to get started.

then labour for engine in and out say 10 hours  

+ actual build time

Scuse ignorance, but couldn't you change rings, bearings and gaskets without doing a lot of this stuff? I mean pumps, head reco, bottom end clean, balancing? I understand once the engine is down you might as well do it all, and I would, but just a Q from curiousity...

Still, when compression is gone I guess valves n stuff (head reco) has to be done - cos that could be the issue. Then, that could no doubt be tested.

I guess the answer is no, that'd be silly

[Duncan]

yeah thats how I looked at it....the parts are about 1/3 to half your rebuild price so there is no point in skimping....its the hours of labour that are the killer

[gun32gtr]

i actually looked at the comp test i had again and said all 150 so i gather thats ok for a 15year old car

[andrewwr32]

i actually looked at the comp test i had again and said all 150 so i gather thats ok for a 15year old car

Yes, that's really quite good I would say! No rebuild at any point? What KMs?

I wish mine was 150. I've done a lot of posting to old sites (S13 related, etc) to knowledgeable people who've done lots tuning etc. The consensus is the motor will be fine, but if I boost the shit out of it I'm in trouble. Boosting isn't my primary goal, I've owned turbo jap cars long enough to understand it's all about flow - not rising boost. Sure, if I wanna race or whatever, I'll up it. But as I learnt with the Silvia, you can change turbos and intake/exhaust etc and get more power at less boost, thereby giving your engine a longer life. This is my intention with the GT-R. If and/or when I want to go high boost, I'll be prepared to tear the motor down.

There is no variance in the cylinders, so it's just age. There is also the vague possibilty that my mechanic's gauge is not spot on.

He also did not release fuel pressure, as the manual states. I would imagine though that if anything that would give a higher reading (fuel pressure added to the cyl compression). He didn't seem to think it mattered (the fuel pressure being there).

[lang]

well you mentioned the manual so youve probabaly allready read this but anyway

Standard is 171psi at 300rpm

Limit value is 128psi at 300rpm

maximum variance limit between cylinders is 14psi

so 138 is still above that, but not a huge amount