so i rebuilt my b16 and during the process "someone" turned the intake cam 180 degrees and then back again with number 1 cylinder TDC, before the timing belt was on... long story short, its burning oil now, not much but enough. could i have a bent valve or is there maybe something else going on? the car seems to run good other than the smoking. all i can think is bent valve but was hoping for some insight..

 

bent valves wouldnt cause you to burn oil, try doing a compression check. i

 

burning oil could be the valve seals or the oil control rings now thats only if its blue smoke. you'd notice it on aceleration and slowing down.

Did you replace and install the valve seals correctly?

If you put new pistons in did you install the oil control rings the right way?

I take it the cylinders were bored and honded, im not sure on what im going to say if this is possible, but if they were a little out of round oil could be seeping by and geting burnt off. How much oil do you burn off in lets say a months time?

 

its been about 3 mos since the rebuild, so i was thinking the valve seal could be wearing out. ive never done a comp test, would the valve not seal properly if bent? thx im a total noob at this, my friend and i just took it apart and learned as we went.

 

maybe a quart in a month, including a slight leak at the exhaust cam seal. i had a machine shop do a pnp and replace 2 burnt valves and all the seals. i did the pistons myself, following a haynes manual, im pretty sure they were right, and the block was perfect.. no boring

 

Did they replace your worn valve guides in the process of changing your valves?

 

oh man... i have no idea, are the guides different from valve seals? i took them a bag of 16 little round rubber pieces, so if thats not it then im sure they didnt.

 

Yes very different from your valve seals. I would definitely look into it if I were you cause this can lead to a list of things that can go wrong and also premature failure of those shinny new valves you had just installed.

 

Did you replace the rings and/or hone the cylinders?

 

yep, replaced pistons and rings, and all the gaskets, bearings and seals from top to bottom. ive put 143k mi on this car, and the cylinders had no ring groove, measured perfect, and you could still see the cross hatch. i ran a glaze break through it very lightly and rechecked the new rings in the cylinders. im pretty certain the bottom end is bulletproof.

 

What do you mean by "glaze break"?

I would see about doing a leakdown test (not a compression test) to see how well your cylinders are sealing. A bad leakdown test would likely point to the rings not sealing very well.

Or you could take the intake manifold off and see if there is any oil in the intake ports. If there are, that'll indicate valve guides/seals or even PCV issues.

Good luck.

 

Exhaust cam seal is leaking but it is also smoking? If I had to guess I'd say it is your engine hone/rings not being properly seated. Bent valves are NOT your problem, they dont cause smoking and they would cause the car to run like crap. Could be a few other things, but 70% confidence on the rings not sealing up due to not having the block freshly honed.

 

glaze break is what country boys call a three bar hone...the cross hatching was spot on. occasionally when i start it after its sat for a couple of days itll idle really rough for about 10-15 seconds and then smooth right out. im totally confused cause it runs great, just uses way more oil than a fresh motor should. oh yea, the machinist says the valve guides were replaced as part of the valve job. is a leakdown test something i can diy?

 

Neither a leakdown or compression test will tell you anything about an oil consumption problem unless your engine is running like crap. And if that's the case your primary complaint wouldn't be about oil consumption.

 

Ehhhhh, I don't know about that. If there is excessive air leaking past the rings during a leakdown, there would likely be an oil issue as well. Usually if the compression ring isn't doing it's job, neither are the oil rings.

For example, a friend of mine bought an engine from a guy off of the internet. He started the engine up and it ran great, but it would smoke. It wasn't even a lot of smoke, but it was enough to indicate a oil control problem. He took a cylinder head off, and not only was a good chunk of the top ring land missing, the cylinder sleeve was cracked as well. Even though a leakdown test was not performed, it should be obvious that that cylinder would have failed miserably, yet the engine still ran just fine.

 

I highly doubt the engine ran well if it had a cracked cylinder and part of the ring land was missing, that's just impossible. Did he have this engine in the car running under load or was it just idling on a stand?

Here is a cut-and-paste from my response to a post a few months ago:

Doing a compression test to check oil consumption is a myth that keeps spreading. The oil control rings on the piston control oil, not the compression rings. The compression rings only seal compression, they do not control oil. You could take the oil control rings off the piston and run a compression check and it would be higher than originally due to the oil entering the cylinder. Valve guide seals don't seal anything but oil anyway plus they are outside of the cylinder so they don't show up either.

If your PCV system is OK then there really is only two ways to get oil into the cylinder to be burned. Either the valve guides are not sealing due to excessive valve guide clearance or faulty seals or the oil control rings are faulty or stuck in their ring land due to carbon/varnish build up.

The valve guide seals themselves can get dried out and brittle and not seal but more commonly on a higher mileage engine that has been beat on the valve guide to valve stem clearance is excessive which wipes out the seal as the valve stem rocks around in the guide. Putting new seals on valve guides that are excessively worn is only a temporary repair and the new seals will be destroyed in short order.

Generally you can diagnose your oil consumption problem with a simple test. The problem with this test is if you have a catalytic converter it may mask the problem and you will have no smoke out the exhaust. If you have a cat it is better to do this test when the engine is dead cold so the cat hasn't had time to heat up. If you can install a test pipe in place of the cat that is even better. Get on a road where you can do full throttle blasts in 2nd or 3rd gear up to redline. Get the car moving and put it in 3rd gear and at about 2000 rpm put the accelerator all the way to the floor up until redline. If the engine smokes while you are accelerating you have faulty or stuck oil control rings. Then, after you have gotten to redline let your foot off the gas but leave it in gear so you are engine braking. If it smokes while decelerating then you are getting oil past your valve guides due to wear or faulty seals.

The reason accelerating causing the rings to pass oil is something called 'pumping' when there is excess oil on the cylinder walls because the oil control rings are not doing their job. As the engine is under load, the gas pressure (when you are decelerating there isn't much pressure in the cylinder) and motion of the piston physically pumps oil from below the rings to above the rings and into the cylinder. There are holes or slots on the piston behind the oil control ring land where oil can drain through and back to the crankcase. These holes or slots are not present on the compression ring lands. The thin oil control rings physically scrapes the oil off the cylinder wall and out these holes or slots.

Oil is consumed through the valve guides on deceleration because you have the throttle slammed shut and the engine rpm is high. This cause very low pressure (high vacuum) in the intake port at the outlet of the valve guide. the oil is 'sucked' through the valve guide due to the higher pressure in the crankcase. Oil doesn't go through the valve guides during acceleration because the pressure in the intake port and the crankcase are approximately equal at WOT.

 

The guy who sold it to him claims the engine ran very well, and was only replaced for a bigger engine. When my buddy ran it, he ran it on a test stand he built himself in his garage and posted the video online. It ran fine at idle and when the throttle was cracked open, response was crisp. The only sign that there were mechanical problems was the smoke coming out of the exhaust.

I didn't say compression test, I said a leakdown test. A leakdown is not the same as a compression test, which is what I alluded to in my post. This is a fresh build with only 3 months on it. If a leakdown test reveals that the compression ring is not sealing the chamber, it's very likely that the oil rings are failing to seal as well. The same reason causing the compression ring to fail would likely cause the oil rings to fail as well.

I didn't say a leakdown would point to guide issues either. What I said was that oil in the intake manifold would, or a PCV issue, since both-like you said-are outside of the chamber.

You can if you have a tester and access to an air compressor. What a leakdown test does is the pressurize the chamber with air, and measure how much is leaking out. For a freshly rebuilt engine, 3-5% is good, 5-15% is ok, and any more probably deserves some attention.