A leak down test is your best best for looking at ri g sealing issues.
Do each cylinder at TDC and 10 degrees after TDC for you best look at what's going on there.

Intake sealing, crank case venting and valve guides are often over looked common places where oil can be sucked into the combustion processes.

What's the story on this engine?

 

Thank u for your response. I have a leak down tester coming via ebay in a week or so. The engine was rebuilt by a friend. It was a low dollar affair. Everything is perfect minus the oil consumption.
I might add all spark pugs look identical. not really wet but black. I thought about possibly disconnecting the pcv valve to rule that out but I didnt know if that would create other problems.

 

 

Th leak down test is definitely going to tell you condition of the ring sealing to the bores and valve to valve seat sealing. And there is a chance that you need to run it a little farther - repeat chance.

Questions, was it bored and was it plate honed? If no, then how was it honed?
How was cleaned after honing?
Are the rings installed correctly - correct side up?
What was done to the heads?
Is it smoking? The assumption is yes, so when is it smoking (accel, decel, initial startup. etc.?)
How was it broken in?
What are you using for oil?

1 qt per 100 miles is ALOT for a fresh rebuild. If I were in your shoes, then I'd be proceeding as you are with the leakdown test 1st. HOPEFULLY, your leakdown numbers are decent - 10-20% and consistent (keep in mind that numbers near 30% won't use the amount of oil you're using.) If this is the case, then I'd be pulling the intake to see if there is oil entering the intake ports. Again, hopefully that is the case and you can resolve this with a better sealing/correct intake gasket. If the the leakdown numbers are good and you don't find oil entering the intake ports via bad intake gasket seal, then either you need valve seals and/or guides.

If the leakdown numbers are bad, then you need to listen for where the air is escaping - carb, exhaust or dipstick. Keep the valve covers on when doing the test because it will make it easier to identify where the air is going. The hardest leak to determine is the exhaust valves because the manifolds are installed. The dipstick tube is easier if you can access it with your finger or via piece of hose on it.

You're about to find out if your freind's low dollar affair was worth it.

Keep us posted - Jim

 

Either a failure of ring seal, or broken or improperly sized or installed rings, incorrect pistons insufficient cylinder walls prep. What did the low dollar rebuild include?

A leak down test actually you don't need that much rocket science just hooking an air compressor up to the spark plug holes and listening will tell a lot. Unfortunately, a non running engine leaks a lot of pressure, much goodness is because of the extremely short running cycle time doesn't allow for much leakage and the operating pressure are very high which is a major part of getting rings to seal so just sitting there with compressed air in it there will be a lot of leakage so it isn't as easy a diagnostic and it sounds to be in theory.

Bogie

 

My race engines leak down 2 percent when new and they don't hiss air either so I cannot agree to that bogie.

If the rings cant hold 100psi shop air than how would you expect to them to hold 3000psi combustion gasses?

 

Because the compression and combustion pressure pushes the top ring against the cylinder wall. I.E. the whole purpose behind those vent holes drilled in the piston crown intersecting the ring groove behind the top ring. This lets you get away with lower tension rings which greatly reduce ring to wall friction during 3 of the 4 cycles. That puts more power on the crankshaft and less into ring and cylinder wall wear. For a street engine this pressure has a more circuitous route of having to pass over the edge of the piston, flow between the ring and the top land and finally apply radial pressure to the backside of the ring thus making the seal.

The ring also has to make a seal with its land, tough job when the motion dynamic forces to switch from making that seal on the top land in one direction and the bottom in the other.

Bogie

 

Not all pistons used in racing are gas ported and still leakdown is expected to be less than 5 percent if the cylinder is plate honed with the right surface finish.

 

That would be true in which case the high pressure has to work its way into the ring land and pass to the back side to force the ring outward. This has the disadvantage of opening the ring gap which is the reason for so called gapless rings.

Keep in mind the subject here is not a racing engine it is a rebuild done on the cheap. What ever that exactly means?

The leak down test simply puts some measurable criteria to the leak rate. But I figure that if he can hook on a compressed air source he can listen for leakage. Like adding oil when doing a compression test seals up the rings the leak test on a dry whether quantified by measure or qualified by simply listening will show a higher degree of leakage than it would in a warm, oiled cylinder if not a running cylinder.

Frankly, though sight unseen by myself if he has the cylinder to cylinder consistency oil consumption he reports is there, I'd strongly suspect the rings were not installed correctly. Or one I saw once was standard pistons with 30 over rings in a 30 over bore. It would scream but clattered something horrible. When it came to me and I pulled it apart finding 7 out of 8 skirts were already cracked. That thing was essentially a bomb going someplace to detonate.

Bogie

 

FWIW, I built a 454 for myself and used low tension oil rings. I thought it would be OK since it was for limited street use. After about 3,000 miles, it was using a quart in 100 miles, too. Sealed up fine and had minimal leakdown, but the low tesnion racing rings just would not do the job on the street.

 

I once seen an engine that ran great but used oil and around 5500rpm and higher would start huffing blue smoke like a freight train. Turned out the shop had managed to put to put standard rings on a .030 over piston in a .030 over bore.

 

Shortest answer to a common problem that happens alot.

Guy's do the "rering" and install new bearings on a decent crank and rods (no reconditioning). Send the heads out to a decent shop for a "valve job" and they come back decent. Assemble the thing correctly, no leaks, get it running somewhat decent but usually adjusted too rich and timing is not optimized.
Sound familiar guy's??
Then they come to find that the engine uses oil but can't see it burning it.
Sound familiar guy's??

Everytime I have run across this it has been caused by a few simple details lacking or a poor judgement on techniques and small important details.

Mostly.....

Poor techniques of cyl. wall deglazing and cross hatching.
Poor tune and rich carb, resulting in washing the cyl's.
Break a ring unknowingly.

This is all assuming that they have assembled the engine correctly, including valve adj., t-chain, and distributor if equipped.

Most of the time a leak down will not catch these kinds of problems, (some yes.....some no)

The best way to find and correct the problem is to....be absolutely sure it is not a washing down of the cyl's with a bad tune to the fuel system, if your convinced it is not? ..... then teardown, inspect, address the problem with honest answers and correct them.

Seen it happen many times. The answer to all was found to be one of the above.

 

The above has another assumption.....the assumption that who ever did the work has good knowledge, experience rebuilding and has used the correct parts of decent quality.

It comes down to just not paying attention to what you are doing and what it takes to at least get done correctly to meet an ends.

 

Gentleman, thank you for all your input. I am waiting on the leakdown tester to arrive before I move on to any further steps
The engine was built by a friend and diesel mechanic that builds his own gasoline engines that he drags with at the track. Of course, mistakes happen, but he is competent in my opinion. I have lost contact with him as he has moved.
More facts worth noting is, the engine is running rich and the timing is set at 12 degrees and 32 max.
I broke in the engine myself with lucas break in additive. I than ran the engine a few hundred miles before I took it to a dyno to get everything dialed in.
I may have made a mistake but I wanted to make sure the engine was running perfect before I spent about 400-500 dollars on the dyno pulls and tune.

So, maybe this is my fault, ill own up to it. But, I am trying to diagnose the problem before I send it out for new rings and a hone job.
The pcv was sucking oil so I am thinking of removing the pcv valve and replacing it with a breather filter and then run the car some more miles.
I will try to take additional better pictures of the spark plugs and post them here.
The engine was a low dollar affair as the long block with performer intake cost me $400. It was an engine he no longer needed and re-freshened himself. I cant say what rings or how well the hone job was but, he is an honest guy and I pretty much trust his work.
Again, thanks you all for your time and input. Ill keep you all posted. Thanks.

 

I was having a similar issue on my 350, the PO installed unbaffled valve covers and my PCV was sucking a lot of oil into the intake. I was getting a lot of blueish smoke out exhaust, especially wit higher RPM then deceleration. I installed baffled valve covers and it drastically reduced oil consumption to less than 1/2 qt per 1000 miles. I also have no smoke coming out exhaust anymore. My plugs looked just like your did, carbon built up with oil.

Do you have baffled valve covers?

 

 

Gentleman, I did the leak down test today and see you can see, this was pretty much the norm on all 8 cylinders. The pictures are of 3 different cylinders. None really exceeding 10% and no leaking sounds out of the carburetor, exhaust, or breather filter on the valve covers. The test was done with the engine cold. Should I try with the engine warm? Will that be necessary? Thanks again.

 

You need to check all 8 cylinders. If they all come out in the same range then that's great news. To answer your question - reread post 6 and no it doesn't need to be done withthe engine hot, you can and the numbers will be minorly different.

 

You need to make sure the valve seals are installed correctly. Those plugs look like it is suckin' oil pretty good on a couple of cyl's.
While you have the leak down checker, pressurize the worse looking plugs cyl. and remove the springs on that cyl. Check the seals on those valves.

 

Also, you said the PCV was suckin' oil. Why? Is there a baffle installed in the valve cover under the PCV.

 

leak down test % don't look too bad. shouldn't be using a qt. every 100 miles with those #'s.
how old are these heads????
you may have worn intake valve guides and valve seals, causing oil to be pulled thur intake guides.
changing seals now, is what I'd try 1st.

 

Compression seal and oil control are separate issues, the compression ring can seal fine and the oil rings be hosed. If its sucking oil past the intake valve guide seal, the intake valve will be oily, usually crusty.

 

I believe that type of tool is designed to operate at 100psi. 85psi shop air at 15% leakage is not 15% leakage. At 100 psi the leakage is likely 25% percent.

Regardless, 25% isn't that bad for a shade tree reringed street engine however it should be done hot for the best results.

 

bet the 2nd ring was installed upside down !
dave

 

Some sparkplugs looking great and some totally crudded over like that usually means you are sucking oil past the intake to head gasket in some spots... try snugging all those bolts up a little each at a time to a total of ~20-25 lb.-ft. and see if that helps... if not, may need a new gasket... if the engine has ever gotten low on coolant and overheated, it can shrink that gasket... re-torquing the head bolts first is also a good idea (some are under the valve covers)...
Sucking oil past some rocker arm studs threads can also do that... some of those stud holes may go into intake ports...
If pull the gasket, check that intake manifold surface and head surface are exactly parallel... milling heads and/or manifold can create an uneven gap top to bottom for the gasket to try and seal up...

 

Gentlemen, I apologize for the delay. I've been working on the car when work allows. I appreciate everyone's help and patience.
The reason the pcv was sucking in oil was due to some baffles that where not very effective. See pictures below.




So, I swapped out the valve covers for stock baffled covers. As well I removed the pcv entirely and plugged the port at the carb. I installed new spark plugs and then drove the car this way for about 30 miles or so.
Here is where things get interesting.






The pictures above are from the same spark plug.

All 8 plugs look very similar. Before pulling out the spark plugs, I indexed and marked the plug with a marker to show where the plug sat pointing straight up in the head. And it seems as the oil is coming from the valve side of the head and not from the piston side of the chamber. Can this point to the heads? Or does this have nothing to do with anything? All plugs again identical with reference to the index marks on the spark plugs and oil stains.

 

Looks like bad valve seals since on all 8...

 

Thanks to everyone that responded. Well, I pulled off the intake and took a look at the valves and the were dripping in oil. The seals and guides were done.
I tossed the heads and am installing a set of vortec heads. The cylinder bores look very good. Again, thanks to everyone that helped with advice :thumbup:

 

Thanks for the feedback SS