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Old 08-26-2010, 02:27 PM
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383 smoking-running out of ideas??? Need Help!

I need some help as I'm running out of ideas on what could be causing my 383 to smoke. Here are the specs:

Factory GM 010 block bored. .060
Eagle cast crank, I-beam rods and Keith Black Hyperutectics pistons with Hastings moly rings
Factory smog heads-valve job
RPM Intake and Holley 670 Avenger
Lunati Voodoo 268 cam and lifter kit
Advertised Duration : 268 /276
Duration @ .050 IN/EX : 227 /233
Gross Valve lift IN/EX .489''/.504''
LSA and ICL 110/106
RPM Range: 1800-6200

Engine has around 500 miles on it. Has been using oil around 1-1 1/2 quarts in 300 miles. Does not burn oil at startup or when revving in neutral. When driving and I step into it, I can see a trail of smoke behind me. Also if cruising on interstate and let off gas, I can see a trail or puff of smoke.

About 100 miles ago I replaced the intake gaskets (with Felpro) and that did take care of smoking for a short period of time but it has returned. The engine plugs are showing a tan/dark tan burn color but the threads have oil on them.

Unfortunately after I purchased the engine kit my machinist said the KB Hyperutectic pistons have been known to butt the rings together and pop the top of the piston off. So they said to add about .010 gap to the piston rings when filing them, which I did.

The engine pulls hard and seems to have plenty of power. I'm just stumped on what is causing this oil burn/consumption. My machinist wants me to do a leak down test to rule out blowby but he is leaning more towards another bad intake leak. I looked inside radiator cap and there is a small amount of brown crud on the inside of cap but the antifreeze looks clean.

Any ideas ??

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Old 08-26-2010, 02:54 PM
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The larger required top ring end gap on a KB piston WILL NOT CAUSE OIL CONSUMPTION OR LOSS OF CYLINDER PRESSURE.
You cannot make the top piston ring end gap too big.

A small ring end gap will result in ring butting/scuffing or busted ring lands which will make it use oil.

The oil is probabily from a faulty PCV valve, lack of PCV valve baffling or a leaky intake gasket or leaky intake valve guides. or you are crushing the valve oil seals at full lift. If you did not shorten the smog heads guide bosses this is very likely.

Start with the PCV valve/baffling. If the mufflers are full of oil it will take time purge that out.
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Old 08-26-2010, 02:59 PM
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Do all the plugs show the same characteristics ie: oil on threads same color etc?

It could be a good possibility that the block was bored to big or the pistons are to small.

I would also look toward the valve guides.
Pop a valve cover off and grab a hold of the top of the valve springs that the rocker arms are loose on. If you can wiggle or move them side to side then the guides are bad. The type of valve seals don't really matter unless you are building a real high performance engine. Stock valve seals are fine.

Now there is another thing to look at and that is the crank case ventilation system. Does the valve cover have a baffle in it and are you using a pcv valve. Find out more about this and let us know. I had a fellow that said he replaced the valve covers on his engine with custom ones and he blocked of all of the vent hoses. I had a hard time explaining to him why the engine needed to be ventilated but when his truck started smoking he asked for my help in hooking up the pcv system. Result: engine quit smoking.

The little bit of brown crud that you spoke of is normal in the radiator on a fresh rebuild.

It could still be the intake gasket but this shouldn't be a problem granted they are on correctly and unless you milled some off the heads.

If the intake gasket was leaking it would idle rough. Im gonna tell you about a quick check but for god sakes be careful! While the engine is idling spray some starting fluid along the top of the intake where it meets the head, do one side at a time and remember this stuff is extremely flammable. If the engine idles up then you have a leak. How ever this quick test will not tell you if it is leaking from underneath.

I think that the first thing I would check would be the PCV system.
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Old 08-26-2010, 03:14 PM
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Thanks for the quick replys!! When I first started the engine i was not running a PCV valve: Just a breather element (K&N style) breather on each side. I had purchased new GM Performance valve covers but they were non baffled and was shooting oil out both breathers and leaking down on the headers. All the plugs are showing the same tan/dark tan coloring and oil on the threads. I was running Accell short header style plugs and they actually had carbon buildup on them, a dark oily appearance after running just a week. I then switched back to AC/Delco R45's and they are the plugs I currently run.

I then put a PCV valve in left a breather on the drivers side-but the PCV valve would pop out of the valve cover from pressure that was building up inside. What I found out was the PCV was filling with oil and could not take the pressure build.

I then bought a new pair of Edelbrock baffled valve covers and installed them with the PCV valve on the passenger side, running it to the carb by a hose. The drivers side still has a breather element. And the oil spray is gone.

My top ring gap is set at .026 and the second ring set at .016. I have not changed the PCV valve but it does rattle when I shake it. The engine does have a small rough idle but I cannot tell if that is from a leaking intake or the cam itself. It sure sounds like the cam to me. The block was zero decked but the heads were not milled. I will check the guides with the instructions given above though tonight.

My machinist also wanted me to pull the vacuum line from the tranny modulator (TH400) and see if there is oil in it, which I need to do tonight. He also questioned the carb (Holley Avenger 670) and was wondering if it was running to rich and fuel washing the rings? Not sure about that ....I did run the jet sizes up a little on the carb but that did not change the smoking situation. The tailpipes are very sooty and it's almost a tacky feeling soot-if that makes sense

How should I test the PCV system other than shaking the PCV and see if I hear the rattle?

Last edited by Blownchevelle68; 08-26-2010 at 03:22 PM.
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Old 08-26-2010, 03:22 PM
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If you are getting enough pressure to actualy push the PCV valve out, you did something wrong. The rings may not be seated.
Hard WOT running (without detonation) will seat the rings.
If you baby it, the rings will not seat. But fix the oil migration first.

.026" top ring end gap is a the absolute minimum for this motor.
.032" is not too much at all especially if you will be standing on it hard.
Many people find this hard to accept and tend to want to run small tight ring end gaps reguardless of the clear KB directions.

Motors with KB pistons rarely need more than 34deg timing for max perf.
Recurve the distributor for 24deg base at idle and 34deg at max advance
and limited 10deg vacuum advance at hiway cruise speed.
Try some Champion RV8c plugs in the smog heads.

The carb is small for max performance. A 750 holley would not hurt this combo.

Yep all the pretty looking aftermarket valve covers have no or crappy oil baffling and the breather/pcv hole is usually mis located.
They are made to look pretty not functional. its up to you to create a functional PCV/breather/oil separator system.
Usually the uglier the creativity the better the functionallity when it comes to PCV/breather oil management.

Last edited by F-BIRD'88; 08-26-2010 at 03:34 PM.
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Old 08-26-2010, 03:23 PM
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Quote:
Originally Posted by F-BIRD'88
If you are getting enough pressure to actualy push the PCV valve out, you did something wrong. The rings may not be seated.
Hard WOT running (without detonation) will seat the rings.
If you baby it, the rings will not seat. But fix the oil migration first.

Motors with KB pistons rarely need more than 34deg timing for max perf.

After I put the valve covers on with baffles it no longer pushes the PCV out....That only happened when I was running non-baffled covers. So far so good with the new valve covers-I have no leaks.

Currently running 14 deg initial timing with total of 36.
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Old 08-26-2010, 04:06 PM
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Change your oil and put in some good stuff. When I built my 350 it was building too much crank case pressure cause the pcv wasnt working. After switching it to positive vaccume the oil blowing out quit. Who put your motor together. Maybe you have a broken ring or your scraper ring is upside down. Check see if your oil smells fuely. Your carb is not flooding is it. Good luck hope you get it figured out.
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Old 08-26-2010, 04:13 PM
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What FBird said..

Quote:
Originally Posted by F-BIRD'88
The larger required top ring end gap on a KB piston WILL NOT CAUSE OIL CONSUMPTION OR LOSS OF CYLINDER PRESSURE.
You cannot make the top piston ring end gap too big.
A small ring end gap will result in ring butting/scuffing or busted ring lands which will make it use oil.
.
What FBird said.. except no one mentioned that .010" is tight. Should be .017" ish... I'm thinking........Duntov
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Old 08-26-2010, 04:21 PM
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Quote:
Originally Posted by juniors revenge
Change your oil and put in some good stuff. When I built my 350 it was building too much crank case pressure cause the pcv wasnt working. After switching it to positive vaccume the oil blowing out quit. Who put your motor together. Maybe you have a broken ring or your scraper ring is upside down. Check see if your oil smells fuely. Your carb is not flooding is it. Good luck hope you get it figured out.

Thanks for the reply. I broke the engine in with Royal Purple break in oil along with Comp Cams break in additive. I have since changed the oil 4 times and have been using Valvoline VR1 oil each time. The oil doesn't smell like it's getting any fuel in it....

Is there any way for me to test the PCV ??
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Old 08-26-2010, 07:31 PM
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Took the valve covers off and tried moving the spring assembly around to see if the guide was loose as suggested-does not move around-only thing that moves a little is the spring itself.

Pulled all plugs and all but 2 of them are a little oily and all of them have a small amount of oil on the threads. All cylinders had 175 psi when checking compression (engine cold) with 76cc heads.

The pcv valve rattles freely although it appears there is a little oil residue inside the valve and also a small amount in the hose going to carb. I believe this is leftover from the old valve covers that had no baffles and pcv was getting plugged with oil. I'll replace the pcv valve tomorrow.

Still looking for suggestions....at least all cylinders are showing good pressure.
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Old 08-26-2010, 07:41 PM
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What you think is oil on the plug threads is likely not oil, it is unburned fuel minus the light hydrocarbons, leaving the heavy hydrocarbons and carbon black behind, pushed up the threads of the plugs, as the sealing surface is the taper or gasket above the threads. Smell it and/or taste it to verify. I suspect you have a either a rich condition, poor ignition spark strength, or excessive reversion going on.

What color is the smoke you are seeing on acceleration?? more blueish tint, or more black/dark?
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Old 08-26-2010, 07:52 PM
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You said your problem was solved for a short period with new intake gaskets? Sounds like you're not venting vacuum properly or something. Are you sure your new gaskets were installed correctly?

If you're sure the problem went away when you installed new gaskets I would forget about ring gaps- its pretty clearly no the problem.

K
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Old 08-26-2010, 08:10 PM
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Quote:
Originally Posted by ericnova72
What you think is oil on the plug threads is likely not oil, it is unburned fuel minus the light hydrocarbons, leaving the heavy hydrocarbons and carbon black behind, pushed up the threads of the plugs, as the sealing surface is the taper or gasket above the threads. Smell it and/or taste it to verify. I suspect you have a either a rich condition, poor ignition spark strength, or excessive reversion going on.

What color is the smoke you are seeing on acceleration?? more blueish tint, or more black/dark?
Hmmm ok, I guess I just assumed it was oil as it looked like it. I did smell it, does kinda smell like oil and gas mix.

The smoke appears to be a blueish tint, not black or dark. Tailpipes have alot of black soot in them.

It has a new Summit brand mechanical distributor with their CD ignition box and coil. Carb is a 670 Avenger, I did put bigger primary and secondary Jets in it.

Last edited by Blownchevelle68; 08-26-2010 at 08:25 PM.
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Old 08-26-2010, 08:17 PM
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Quote:
Originally Posted by killerformula
You said your problem was solved for a short period with new intake gaskets? Sounds like you're not venting vacuum properly or something. Are you sure your new gaskets were installed correctly?

If you're sure the problem went away when you installed new gaskets I would forget about ring gaps- its pretty clearly no the problem.

K
Im starting to wonder if I didnt mess up another set of intake gaskets. After I put the new ones on, it seemed to run a little better and I did not notice the smoking. But it has since come back....

Another poster mentioned spraying around the intake with starting fluid and seeing if the engine idle increases, to rule out a intake gasket problem. Not really sure if I want to do that, what other methods are there for checking other than taking off the intake.

Also another problem I noted is when I have been tuning the carb with a vacuum gauge, that the needle jumps around and is not steady at all....Is this a indication of something wrong or normal? It jumps around 2-3 points on the gauge back and forth....Never could get a steady reading.
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Old 08-26-2010, 08:40 PM
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Have you measured your vacuum.
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