n1kki6

In my recent 383 lt1 build it looks like I am burning oil to the tune of about a quart every 500 - 600 miles. The engine now has about 5k on it and as slowly became worse it seems. It only smokes at wide open throttle, I would think burning this much I would be seeing more smoke. In a previous thread about my coolant it was mentioned that it is probably rings or seals. I pull the compression number last night and here is how I am sitting.


#1 - 225
#2 - 225
#3 - 235
#4 - 240
#5 - 240
#6 - 200 - 220 (This one I checked a couple times, the first time it was about 219, then the second time it dropped to about 200, then I tested again and it was back up around 210, then 220)
#7 - 235
#8 - 240 - 245

There looked to be a bit of build up on the plug for cylinder 6, but the plugs were dry, I will post pics of the plugs tonight.

Oil pressure is fantastic and the car is running strong. I have been running 10w-30

Do those numbers look ok?

I am also getting some knocking it sounds at start up but it goes away once the oil gets a bit warmer, someone mentioned it probably just piston slap since it goes away. It also is not all that constant its noticeable off an on at idle, sometimes, reving sometimes when the revs drop. Its almost like a knock sounding rattle.

I can't get a hold of the builder(long story), but could it need rings or do the compression numbers show that its probably not the problem, low tentsion oli rings was also mentioned, possibly seals. With a search I found people changing there pcv valve with no luck.

Could it be some sort of valve adjustment I could make? I am a bit green to everything so far.

Can I just keep dumping oil into it until I have time to really tear it down?

jmgtp

Perhaps blowby under the load of full throttle?

I had a very similar issue with another car. Under full throttle it would smoke a bit out the pipes. I had recently installed fresh set of valves and valve seals so I knew it wasn't a valve guide issue and more likely a ring problem. This developed after some pretty serious mods, including ported heads, and the motor was making significant more power than the stock setup - I concluded blowby was my problem.

I ended up converting an electric smog pump (AIR pump) from an f-body to pull vacuum from a valve cover under full throttle. I then routed the output from the pump to evac tubes located in the tailpipes (yes a lot of tubing from front to back). It worked, it pulls about 2-3" of vacuum at full throttle which is enough to negate the pressure from the blowby in the crankcase and keep the oil from sneaking past the control rings and burning up and out the exhaust. You could check to see that the pcv and breather are working normally too, though when there is no vacuum - such as full throttle situation - the pcv system isn't doing much to pull blowby from the crankcase.

There are also some really good high end vacuum pumps available that are belt driven. The increase ring seal is supposedly good for some hp too.

BrianCunningham

stock PVC setup?

n1kki6

Yep, stock.

n1kki6

I was thinking blowby as well. I was just thinking 1 qt every 500 was a bit much though, could this be in the norm?

0Paul Ruggeri

Start the engine and pull the pcv valve out of the valve cover. If you see little puffs of smoke coming out, you have blow by. From what you're discribing, I say you have a piston problem in #6 cyl.

n1kki6

I should no better than this, but after some searching on here, i have read abotu some people having luck with engine restorer http://www.restoreusa.com/Engine_Restorer.html for engine burning oil. These are mostly higher mileage cars. Would trying it on a newer build engine cause any problems, its only 10 bucks if it does nothing.

Could that much oil consumption be from a pcv?

Should I maybe roll with a 20w-50 oil for a while incase things didn't seat properly?

I am guessing if low tension oil rings were used this is just something I will have to deal with.

n1kki6

That was also a concern of mine. I don't feel like pulling all the plugs just to test one cylinder again, if i only pull the one plug could i get an accurate reading. Cylinder 6 is also a pain to get the compression tester on and the hose was kind of jammed down there so I don't know if that could have been an issue as well.

devildog

Mike,

Do a leak down test (cylinder on TDC pump in compressed air watch gauge). Somewhere on internet you can get procedure and how the simple test device functions.

Compression test are OK, but a leak down give you better data for evaluating rings.

Joe

htrdbmr

I have the same issues with my 383, oil consumption and piston slap. The plugs are all the same, visually perfect. I built my motor with 6" rods, and KB 164 pistons (1.125 compression height) so the pin does intrude somewhat into the oil ring land. I'm guessing this is the cause for my oil consumption.

rklessdriver

Both Paul and devildog have given you some very good advice.

1. See if there is any positive crankcase pressure comming out the rocker cover by removing the PCV from the rocker cover or removing the oil cap when the engine is running. Do this when it's cold (start up) and omce it gets hot (operating temp). It should get worse as the engine gets hotter. It will be a noticeable mist and if its really bad you will be able to feel the air pressure/pulse comming out the hole on your hand.

2. Run a leak down test and if its over 10% listen to hear where the air is going. If it's the valves, you'll hear it comming out the tail pipe or TB. If it's the rings, you hear it comming out the crankcase (rocker cover oil cap or PCV).

Now if you don't have any positive crank case pressure and the leak down test checks out... it could still be low tension oil rings but one other thing it could be it the valve stem seals so pull you rocker covers and see if the valve stem seals have been damaged. IMO that is doubtful - as it's using a lot of oil for the valve stem seals.

Will

BrianCunningham

forged or cast pistons?

forged takes a little longer to warm up, and generally have a looser clearance.

I know race engines are set up loose so there less drag.

383vett

At this point, put in a can of STP to see if it helps. It certainly won't hurt anything and the increased viscosity might help some. I think it's only $6.00 for a can.

blkzr1

hi, i also had problems with my 383 using some oil but not that much. i just happened to look in the throttle body one day to check to see if the blades were opening fully and noticed alot of oil "shine" in the intake. i removed the intake and found that the bottom side of the intake port gaskets where the gasket was supposed to seal was not sealing. i replaced the intake gaskets carefully and checked the valve seals and found 5 of them bad. replaced them also and now have no problems. i also have what i think is piston slap but mine will not go away after warm up. i run mine at 5700 rpm for extended periods of time and have never had a problem yet. see ya

n1kki6

Forged Pistons. Seriously the car flies, so if some oil is the price to pay i am fine with it, but I am just trying to find out what is the norm, if I need to fix something, etc...?

Thanks for all the input, I will try to tackle some of the advice this weekend. Still on the learning curve with the car, bout the car when I was 19, 27 now and always learning still. Thanks again. I will check back.

n1kki6

The noise I have goes away after a couple minutes and then I only notice it at 2k rmp's if i press the gas or let off it goes away. I think it might be a dual mass flywheel problem , they spun it against my what I said. I will be going to a single mass and new clutch this fall, I don't care about the added noise.

I can pull the intake and valve covers fast enough. Do i need to pull the heads to check the valve seals?

steve40th

I think it is very simple. Low tension oil rings. Your plugs will look fine, compression test is fine etc.
I went through this with my 396LT1 with SRP pistons, which are a little tighter than there other pistons, JE. But the low tension rings was/is a oil consumption problem. It gives a little more power, but uses much more oil. My 2 top rings were 1/16 "at .018 and oil rings were 3/16 at .018. Pretty darn tight, and pistons were 30 over with .003 clearance.
Search my name, steve40th, and there are many threads on this, on many forums.
I just changed my rings, with about 5000 miles on them, to standard tension rings, and now I am around 1200-1500 miles per quart, which is better than the less than 750 a quart before.
Thats my 2 cents.
Ask your builder what rings he used.

BrianCunningham

Make sure the car is warmed up before you "get on it" otherwise you could induce wear.

Which might have already happened

cv67

Bet your problem may be as blkzr1 suggested, happens more often than youd think. Pull the intake and see what you got.

n1kki6

lol, could be......