Compression test numbers stock 76' l28e?

[hooahh3]

Hello all

 

I was wondering if anyone had the bone stock Nissan facotry l28e compression test numbers?

 

Cant find anything on what there supposed to be stock. Every thread is my engine is this or mine runs that. Google isn't helping me out at all for stock numbers.

 

Im now at going thru a quart of oil every 150-200 miles (oil psi drops to nothing at idle by this point from lack of volume) so I know something is off. Plugs look like crap even after new and 150~ miles. Thinking its the rings since it does smoke a little bit. lol 13.7 mpg average and powers down from when I originally bought it for sure.

 

compression test numbers are

 

1-130

2-125

3-125

4-125

5-120

6-122

 

engine was warm after drive and cylinders seemed pretty wet just from the normal driving already.

 

Any help is appreciated.

[NewZed]

The procedure is described in the Nissan Factory Service Manual.  It's the difference between cylinders that matters most (that's also mentioned in almost every single compression check thread).  Actual numbers will vary with the gauge and adapters used.  Bad valve seals will also cause high oil consumption.  Worn oil scraper rings won't show up on a cylinder pressure check.  They work in the opposite direction.

[hooahh3]

Yea ive looked at a lot of threads on this. It all starts out with this is what I got for mine, then people go to well my engine has this, but ive got this work and that work done to it. Seems nobody has just a stocker l28 anymore. lol and it varyies from 160-220 some people say. and that's just to big of a range to nail down and use as the base line.

 

Im hoping its just the valve seals, be a lot easier then pulling the pistons. Gonna pull the valve cover tomorrow and see what its looking like in there.

 

The one thing I noticed in all my digging, no body's numbers were as low as mine, basically 130 across the board.

[NewZed]

Engine Tuneup chapter.

 

 

[malibud]

New zed is right. I ran with those numbers for a while. As long is it not smoking or fouling plugs your fine. I even got close to that with a broken ring and ringland but smoking like a freight train, Leak down test showed it was #5 . Most all engines should fall in the 10-15% of one another  

[hooahh3]

You got down close to the numbers Im showing with the broken ring and land?

 

And Its fouling the hell out of the plugs. brand new plugs are already burnt up and fouled after only 200 miles. Plus the 1 quart of oil its burned since then. #1,5 & 6 seem to be the big culprits. Those were the worst plugs. They latterly had a caked on oily crude that I couldn't even get off with a wire brush, I tired to clean them up so see if I could get an idea of just how bad they were. Slightly fouled or way way gone for a long time....they were wayyyyyy gone. So that tells me I got a big problem with those 3 at least.

 

I was thinking it could be the valve seals, but could they be that bad to go thru 1 quart or more in 200 miles? with the low performance I was thinking more towards it being the rings and a loss of CR in the cylinders along with the fouling and "2 cycling" of the engine.

[NewZed]

You haven't said much about how long you've had it, what condition it was in when you got it, and how you drive it,  Or how well tuned the EFI system is.   Could be fuel-fouling.  Other things, like a clogged PCV system can also lead to high oil burning.  Need details to make good guesses.

 

I had an old head with worn valve seals that would burn a lot of oil if I used it hard, but not much if I just cruised around.  It ran great though, just tended to get a lumpy idle if it wasn't abused

[hooahh3]

Its a all stock, numbers matching everything, short of radio and new alternator, 3 new injectors. AC compressor and bumpers removed (weighs in at 2560 with out me). 1976 280z 4 speed. owned it for 16 months. im 3rd owner.

Tore it apart and only found rust on and around the door hinges, couldn't find anything else where, I looked hard being a 40yr old car and the typical rust these have.

 

She is my daily driver. Never do any racing as I need to do the suspension work first. Engine trouble has taken priority though.

I do occasionally romp on her when im feeling antys. usually a 6k 1st and 2nd shift. When I first got her she would chirp the tires dry in first and pulled a lot harder. can defiantly tell she is down on power.

I don't even romp on it anymore with the oil and oil pressure issue related to that. just normal driving around town will burn up 1-2 quarts in 200 miles. I don't doubt she isn't running rich also, but the plugs I pulled were defiantly oil coated not fuel. Had the thick oily carbon build up. Smelled more like oil then fuel also, probably cause they couldn't have been fireing worth a shit at that rate. also had oil pooled on the threads of the plug ports when I pulled them.

 

Replaced them at the store and drove home 6 miles, pulled them right after getting out the car and they were already back to burnt and kinda oily. put 180 miles on in since then and its used another quart and still getting the same MPG.

[malibud]

A leak down test will tell a lot more . I think you could probably get one at HB. on a stock engine rings should be good for many miles.  My turbo car had numbers in the 120s. one cylinder with a broken ring was down to 100 . I would be checking other things before tearing into the engine esp. if it is your daily  

[hooahh3]

Found it!

 

In the 280z service manual, on ET-5 in calls for numbers from 164-178psi.

 

In another location I cant remember it says if numbers below 164 theres basically a big problem and you got bad rings. A table actually calls for a rebuild, just cant remember what page I read that on

[malibud]

below 164?rebuild  umm rings usually last a long time. 10% within one another ...  

[steve260z]

Is the throttle body open when testing?

[Tony D]

Lower Limit is around 100 psi... "Around" -- meaning as said above if it's not objectionable in oil consumption or smoking it is usually better off with what is in there from Nissan than whatever you put in now.

They start having issues starting once they drop below 90 psi.

Valve Seals can suck oil like you wouldn't believe. My 76 runs 185 psi (on my gauge) and that was at 225,000 miles. It could take 3,000 miles to suck down a quart, or it could go in a day at the Auto-X... When I drove the car cross country on interstates, it didn't use a quart (just above  "low" from "full" on dipstick) from LA  to Detroit. In the next two weeks driving two-lanes in Canada  having to be on and  off the throttle  passing logging trucks, etc I was down TWO quarts in under 900 miles! Engine would smoke on startup, if you were behind it you could smell oil burning but not see smoke continually.

With the compression, I've left it that way and added another 100,000 miles on that engine. 

The economics of a rebuild are  RARELY justified by oil consumption. BRILLIANT marketing and parts sales job on the part of the OEM's! BRILLIANT!
You look at the cost of your oil: a quart every 1000 miles is 100 quarts in 100K, it's 200 quarts in 100K, even at a quart every 250 miles it's what? 400 quarts in 100K miles? If you are daily driving it and put 10Kmiles on it annually....even at a quart every 250 miles you are looking at a cost of a quart of oil X 40 per YEAR to just run what you have!

In my case, with 185 psi (on my gauge), and spinning 147 HP to the rear wheels bone stock, there is hardly any reason to mess with what is in there!

It SOUNDS bad. It may LOOK bad... But when you actually start thinking about it.... If you drive more like most people here (infrequently, or weekends) you are talking maybe 400 miles on a weekend, around 2~3,000 miles a year your oil costs are 1/3 what they are as a normal commuter...

 

Against a $3,500 overhaul... (And I mean GOOD PARTS DONE RIGHT OVERHAUL)

Just something to think about. That additional 100K I've put on my 76 has cost me $200 in additional oil costs over around 10 years... $20 A YEAR.

If  you have valve seals, doing those on  the car by yourself may be about the only thing justified!

My 74 260Z is similarly compressioned, I don't know because of rings or L28 N47 head on it... but it runs great and I was commuting in it daily. Similar consumption on highway <qt in 3K miles, and if I go to the AutoX maybe 1/4 qt in a 500 mile AutoX Weekend. A lot less oil consumption, but "low compression"---by all accounts something that 'should be attended to" as shop owners might say...

But as a bone stock L26 it's spinning 126 to the rear wheels, has 125 psi on the cylinders (changed head gasket 100K ago because exhaust valves were leaking and had 100/100 on cyl 3 & 4... Never checked after the gasket change and valve relap... All I know is I've driven it that 100K without a hitch and the "low compression" has my stock L26 running a dyno just as good as many stock L28's I see...

Like I said, OEM Marketing has brainwashed a whole industry to do things they really don't think about... and when you do the engineering analysis, the loss of performance or additional oil costs just don't cut it.

Note recently when Porsche went to Mobil-1 Synthetic from the START (no more 'break in oil') they just said "from an engineering standpoint we can not justify the additional wear imparted  on the engine internals which means less lifetime. It is a performance engine, just accept it will consume 1.5L per 5000 km."

It's a performance engine, just accept it will consume 1.5 L per 5,000 km.

 

They decided the extra 30,000 miles scraped off the cylinder walls was  not worth the performance increase seen.
Similarly BMW surveys showed the engines  continually gaining power up to 30,000 miles... due to seating of the rings very gradually. The realization that they WILL indeed seat opened people's eyes that the rush break in they get really just shortens engine life. With the cost of repairs, they have to make the engines run longer between overhauls---and much of this honestly is driven by emissions warranties now going out to 100K 10 years. It now makes sense that they seat gradually now that oils have no catalyst-poisoning components in the additive packages.

 

The rush to seat rings is a holdover from domestic machining properties, cheap repair costs and the desire to move parts in the aftermarket...along with non-catalyst engine operation with high zinc and phosphorous oils...

"RUN IT!"

[Tony D]

^^^^In the above ramble, you note I say "on my gauge"... don't discount the fact that your gauge may be significantly off. That old gauge is about the only intact 'cheap compression gauge' I still owned at the time.

Nowadays I buy Harbor Freight compression testing sets and throw the gauges away. I replace them with liquid filled High-Accuracy gauges which oftentimes give SIGNIFICANTLY different readings than the gauges that came with the set.

While any cheap gauge can give you accurate differential, I would not trust them as far as I could throw them insofar as reading ultimate cylinder pressure. 
I have linked in the past to Dwyer Instruments Electronic Test Gauge... It's about $60 which is more than most guys spend on their compression tester, if you are interested in ACCURATE numbers, buy one of them and fit it to whatever SCREW-IN compression tester bits you have on-hand. A great second choice is a 0-250 psi 4" Gauge Liquid Filled Ashcroft. I like the Dwyer since it's accurate within 0.1% of scale chosen, has a huge range, and you can select your units: PSI, kPa, KgC, Bar.... It's  also rubber armored for minimal bumping around.

Buying a REAL calibrated, large diameter calibrated gauge is the best thing you can do to get good compression testing readings from any compression tester, even a cheap Harbor Freight one you bought on sale for $9.99 the accessories  are what you're buying---the gauge is where the real costs  lie!

Because the leakdown tester is a relative measurement, the quality of the gauges is almost irrelevant. Harbor Freight sells them as well.  For the cost of the Dwyer Gauge, an HF Compression Tester, and the HF Cylinder Leakdown Tester you can have a very accurate diagnostic set. Most importantly, one whose ultimate readings  you can  trust.

[Tony D]

Found it!

 

In the 280z service manual, on ET-5 in calls for numbers from 164-178psi.

 

In another location I cant remember it says if numbers below 164 theres basically a big problem and you got bad rings. A table actually calls for a rebuild, just cant remember what page I read that on

They're blowing smoke. See above 'lower limit' general  rule of thumb.

If you want to read something, read  things about the relationship between compression  ratio and ultimate torque  or horsepower produced.

 

A key thing to know is  you don't lose as much as you would think from low compression. If you have tuned the engine properly the falloff will be very, very little even if extreme.

[hooahh3]

well ive also figured out the rear main is leaking. cleaned engine off and took a spin. engine was clean( gasket location wise) and had oil dripping out from the bell housing hole on the bottom. Was enough to drip on to the concrete. No other explanation there but a rear main seal right?

 

The more you convince me of it, I think ill just limp it along till I swap the 5.3 in. 3-4000$ can get me a good setup and 300+ hp since I already have a running eng/trans setup sitting in my shed waiting for me.

 

Ill keep the original powertrain since you don't seem very many numbers matching all original s30's anymore. Most are v8, ET swaps, Turbo conversions, or just built for such HP that they've lost there "originalness" ya know. hell its a factory air, kinda rare for a 76'. didn't really become standard till 77 from what ive seen and herd (am I wrong there?)

 

Thanks for the convinceing. lol was sitting on the fence and just need the push in the right direction.

[Tony D]

Each drip is (more useless knowledge) approximately 2cc's.

You can account for your losses there  almost entirely I'd bet (especially if you don't see smoke on startup or after decel/flogging it...)

[hooahh3]

She will smoke a little on start up. Nothing bad if you didn't know the car to know it wasn't right. never looked after flogging it, usually looking for cops or other idiots on the road. lol

 

And with it being the rear main, I can imagine how much the clutch has on it, and its probably glazed over the flywheel and pressure plate pretty good to at this point. Probably loosing 5-10% extra drive train HP right there from sliping.

Edited October 17, 2016 by hooahh3