alik

iTrader: (3)

I burns oil.

I lose maybe 2-3 quarts per 3k.

The builder, C.A.T.'s performance in Flagstaff, tells me that he doesn't know why the engine smokes.
It's been over 3k since the install.

Builder says that the walls have been scuffed for the rings to get seated. Rings have been cryogened.

My SpecMiata builder says it's rings and/or valve guide seals.

Question to those who know.

How do I tell which one it is?

And, how impossible is it for DYI to tackle it?

I'm not that bad when it comes to working on my car. I've done timing belt, swapped clutches, tranny, rear end, suspension swaps, but I don't usually work on the engine.

Thanks in advance.

Braineack

iTrader: (62)

leakdown test.

ArtieParty

iTrader: (1)

+1

alik

iTrader: (3)

Will do tomorrow.

Thanks!

mrtonyg

iTrader: (1)

What is it with people recommending a compression test or a leak down test if they are burning oil?

A leak down test or compression test reveals the cylinder's ability to hold or seal air...it does nothing in regards to oil control!

As far as determining if you have a valve seal or a piston oil ring issue...the most common is if it smokes on start up or on deceleration it is usually valve seals. If it smokes all the time most likely it is rings.

Good luck.

Braineack

iTrader: (62)

obviously is oil is burning, it's leaking somewhere, so a leakdown test can pinpoint it.

if compression is lost through intake, intake valves.

if compression is lost through exhaust, exhaust valves.

if compression is lost through radiator, head gasket.

if compression is lost through oil filler cap, rings.

mrtonyg

iTrader: (1)

Braineack, we are talking oil burning not a cylinder misfire or other such thing.

Sorry, but no.

If anything, oil seeping into the combustion chamber will increase the sealing ability of the cylinder, thus increasing the compression test readings.

There is no test you can perform that will tell you if it's valve seals or an oil control ring problem.

paul

iTrader: (21)

If you have bad rings you'd get pressure loss into the crank case which would pressurize the valve cover area so you'd have pressure out the oil cap and dipstick, right?

Now if you have bad valve seals wouldn't that pressurize the valve cover too and give you pressure out the oil cap too and dipstick too if cap is on?

sbrian2

iTrader: (12)

Wrong!

I was getting 2% leakdown on my motor that had a freshly built head and was loosing a qt. every 500 miles. It also had great compression #s. The problem was the oil control rings were stuck from the motor sitting for too long (junkyard pull). If this is a new motor with new rings though, then that is not your problem. I just wanted to point out that a leakdown test will not necessarily pinpoint the problem. I replaced the rings on mine 3K miles ago and have had zero oil consumption since then.

Braineack

iTrader: (62)

keep talking back to me...i dare you all!

mrtonyg

iTrader: (1)

Paul, the first part of your statement is true.

However, faulty valve seals would not pressurize the crankcase. The valve seals are there to keep oil from seeping down the valve stem and into the combustion chamber. This is especially true when a cylinder is in the intake stroke and causing a partial vacuum. The valve seals are not holding down any pressure.

paul

iTrader: (21)

I'm confused. You have oil on one side(under the valve cover) and combustion chamber on the other side of this seal.

Ah, I got it. The valve is seated during combustion so the valve seal doesn't see the pressure. Unless a valve isn't seat properly but then the pressure would just escape though the open port. I guess I didn't think it through to thoroughly.

Thanks

96rdstr

iTrader: (4)

Smoke at start up= bad valve seals
Constant burning= bad rings

My 90 Celica GTS had bad valve seals. It burned oil that seeped into the chamber as the car sat overnight. It stopped once the engine warmed and the seals expanded. The dealer replaced all the valve seals and that stopped the consumption.

mrtonyg

iTrader: (1)

You got it!

gman3

So can valve seals be done correctly with head still installed?

mrtonyg

iTrader: (1)

Yes, no need to remove head...but it is a PITA.

Some specialized tools are needed to:

1-pressurize cylinders
2-remove valve keepers
3-remove valve seals and reinstall
3-install springs and keepers

Not recommended as a DIY unless you have prior experience working on engines.

supra441979

iTrader: (10)

That's just wrong...

alik

iTrader: (3)

This is interesting.
My builder tells me that the engine sat for 3 months before he sold it to me.

I didn't get the leakdown test.

The head honcho told me that his 30 years of experience (and, this opinion was seconded by his engine builder) tell him by the way the car smokes under acceleration that the rings are bad.
Oil rings, as the car pulls like a beast.
It's a built 1.6L.

My problem is that I've somewhat outgrown the stock power, and my turbo kit is just dying to be installed.
I don't want to, however, install the turbo on the engine that's pissing oil.

My only advice came as "bore out the block, put in larger pistons".
Don't feel like pulling the engine, after all, the builder put in a ton of work into it.

I can get a block on fleabay, and work on that, and then swap the blocks, keeping the head.
Or, drive the car to SpecMiata builder, and have him replace the rings....

Decisions, decisions.

mrtonyg

iTrader: (1)

Different situation...his engine was used....yours was recently rebuilt.

Used engines develop carbon deposits and if the engine sits for a long time, the rings could seize in the piston ring lands.

There is no reason for your engine to have stuck or frozen rings...unless it was due to a build issue.