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Old 08-17-2010, 09:58 AM
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New motor smoking - Don't know why!

I rebuilt an '88 GM 350 about 2 years ago. This year I installed it in my project street rod and it is smoking. Can you give me some ideas where to look?

Motor rebuild included: 0.060 overbore, stock flat tappet cam, new hydraulic flat cam lifters, stock valve springs, push rods and rocker arms. New pistons, rings, gaskets, oil pump, etc. Edelbrock #2104 intake manifold used w/ stock cast iron heads. The heads were reconditioned with the stock valves reused. All valve seals were replaced. I used intake manifold gaskets that came with the gasket pack.

Assuming all the valve seals are fine, is it possible the intake gaskets could be differant for the Edelbrock intake manifold compared to the stock GM manifold? Of course, I do not have all the smog equipment on the motor any more. Would that be a possible source of oil getting into the cylinders?

I have ruled out the oil rings for the present time because I cannot bear the thought of pulling the motor and tearing it down again right now. If I cannot find the problem on the top of the motor, then I will reconsider pulling it.

Any advice or suggestions would be helpful.

Is it possible the intake manifold could be cracked and is sucking oil into one or more cylinders? I'm really reaching now.

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Old 08-17-2010, 11:02 AM
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Intake gaskets meant for aluminum intakes are different composition than what is used for iron intakes, due to the higher heat expansion rate of aluminum. Use of gaskets for iron intakes(like those in most all gasket kits)often results in a leak into the lifter valley area, or to outside air. The iron intake gaskets don't have as much compressability or rebound ability. The aluminum intake heats up, expands more, crushes the gasket more, then leaks after it cools and the gasket can't rebound back with it. Once the gasket has leaked and oil tracked, it will always leak, no retorqueing will fix it. Time to get the right gasket.

Don't feel bad, many people don't know this, the question comes up on a fairly regular basis.

Edelbrock sells a line of gaskets for their manifolds, Fel-Pro has their Print-o-Seal line(do not confuse with the Permatorque Blue for iron), Mr.Gasket has theirs like the Print-o-Seal.

Were the valve guides in the head replaced, or in good shape?? Worn guides won't seal well even with new seals.
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Old 08-17-2010, 11:45 AM
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Valve guides

If you are confident the rings are installed correctly with the right cylinder wall finish, and the gaskets are not leaking oil into the intake ports, the valve guides are probably the culprit, especially with a high overlap camshaft.

You should have installed new K-line valve guide liners with new Ferrea stainless steel valves. Any good automotive machine shop should have suggested that as a routine operation when preparing the heads.

Machine the valve guide bosses to .531" OD and install K-line manganese-bronze guide liners with a smooth wall finish. Install 0.530" ID teflon positive stop valve seals. Some people prefer viton seals but I prefer teflon because virtually no oil gets past teflon seals. That is why you must use the phosphor-bronze "self-lubricating" guide liners. The valve stem clearances should be 0.0015" - 0.002" I and 0.002" - 0.003" E. Tight clearances permits accurate valve seating.
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Old 08-17-2010, 11:53 AM
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FWIW, when GM used aluminum intake on the GENI engines, they used the same gasket as the steel intakes. Make sure the intake blots are tight, 30ftlbs.

When does it smoke? better or worse under load? Only when hot? or cold?

Does it have a vacuum pressure modulator for the trans hooked to manifold vacuum?

Is it smoke or is it steam?
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Old 08-17-2010, 12:00 PM
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If you added the thick STP (or similar) "oil treatment" to the engine oil from the very beginning before the rings were broken in, the rings will not seat. As in, NEVER.
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Old 08-17-2010, 12:25 PM
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We installed a rebuilt in a chev pickup (work truck) that was built using the chrome rings and it smoked bad at first..well it was needed for work so it was just driven..at about 5000 miles the rings finally seated and it runs strong now..

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Old 08-17-2010, 01:08 PM
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Thanks guys! I was not aware that I should use a differant gasket. I'll confirm with Edelbrock what gasket I should order.

I am using Mobile 1 Racing oil for break-in. The only additional additive has been 4 oz. of ZDDP additive.

It smokes bad on initial start up and a small amount of smoke on continuous running. I was suspicious of the intake manifold.

I do not have a vacuum pressure modulator between the manifold and the brake booster. Should I? What does it look like? How big is it? Are there different sizes? Does it require an electric connection?

New valve guides were installed and sized to the old valves. It was less expensive than all new valves and the mechinist told me it would be a very reliable set up.
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Old 08-17-2010, 01:17 PM
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Quote:
Originally Posted by jpd37
It smokes bad on initial start up and a small amount of smoke on continuous running. I was suspicious of the intake manifold.
This sounds more like a valve stem sealing issue than anything- the heavy smoke at start up would be the give away for that.

Quote:
I do not have a vacuum pressure modulator between the manifold and the brake booster. Should I? What does it look like? How big is it? Are there different sizes? Does it require an electric connection?
The vacuum modulator is located on the tranny if you have a TH 350/400, etc. It can leak fluid into the vacuum line and will then enter the intake tract, causing smoke.

Quote:
New valve guides were installed and sized to the old valves. It was less expensive than all new valves and the mechinist told me it would be a very reliable set up.
The problem w/doing this, is the worn portion of the stems will be what "sets" the oil clearance. The guides have to be large enough to pass the unworn portion of the stem up near the tips of the valves.
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Old 08-17-2010, 02:36 PM
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If it was chrome rings, it may take a few thousand miles to fully seat, but once they do they last practically "forever",
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Old 08-17-2010, 04:50 PM
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Size new guides to old valves?

Valve stems do not wear staright, therefore in most cases new valve guides cannot be sized to fit worn valve stems. That is because valve stems are worn by the thrust of the rocker arms, meaning that the valve stems wear on the side opposite the rocker arm at the top of the guide and on the other side at the bottom of the guide. Valve stems are chrome plated and for that reason most engine builders do not attempt to resize valves stems. Some production engine builders use new valves with oversize stems and hone the existing valve guides to fit. It is cheaper to buy new valves with new standard size chrome stems and tighten the guide clearance using K-Line Bronze Bullet valve guide liners. If your machinist used umbrella type valve seals, that is part of the problem. Those type valve seals are junk. However, even positive stop teflon seals will not solve a oil consumption problem due to poor fitting valve stems.

Many GM heads do not have the valve guide bosses machined for teflon positive stop seals and for that reason many machinists don't use them, especially on a economy rebuild. Even the exhaust valve guides should be machined for positive stop teflon seals. That is because the exiting exhaust flow will create a vacuum on the exhaust guides and will pull oil from the valve cover area and into the exhaust port. The oil will then burn in the exhaust system, and if yoiur car is equipped with a catalytic converter, it will cause that device to run hot and fail.

I am not saying that your valves needed to be replaced due to excessively worn stems, but IMO, if they had more than 100,000 miles on them when the face angles were re-ground and used with new valve guides, the valves should have been replaced.

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Old 08-17-2010, 06:45 PM
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I would not sweat the valve/guide issue too much. GM only used o-rings for valve stem seals for decades without much oil consumption. Many late model heads have little to zero valve guide and valve stem wear, especially compared to pre-1978 engines.

Yes, a positive type seal is better especially for engines needing to meet emissions.

Continuous smoking is usually either rings or intake.

Is the crankcase properly vented, as in valve cover breathers and a PCV?
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Old 08-18-2010, 08:17 AM
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Is the oil synthetic? If so, it won`t break in on synthetic oil. I`ve already been down that road by experience in the mid 90`s on a friend of mine`s ride. He had racked up countless miles and the car still smoked, I told him to switch back to mineral oil and by the 3000 mile mark it was broke in and running strong with no smoke. Now for the can of worms. In the past when this is mentioned, I get about 10 guys that tell me you can break in a new engine just fine on synthetic because the factory does it. According to red line oils and other synthetic brands they all recommend a new engine be broken in on mineral oil. The factorys now have hone techniques where the engine is already broken in before it`s even put together so it can be filled with synthetic before it hits the door.
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Old 08-18-2010, 08:31 AM
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I don't know why 30W oil isn't used more for break in. I use it exclusively and have had no oil-related break in failures of any kind, knock on wood.

From the Mobil 1 FAQ page, on their 0W-50 racing oil:

Q. Do we need to run break-in oil before using Mobil 1 Racing 0W-50?

A. There is no need to run a special break-in oil if using Mobil 1. Mobil 1 has a robust additive system which helps provides protection during break-in as well as normal operation.

HERE is a PDF showing the zinc and phosphorus levels of the various Mobil 1 oils as well as various manufacturers approvals.
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Old 08-18-2010, 08:42 AM
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Cobalt, no disrespect intended. From my prospective, it doesn`t mention which type of break in, be it cam, or engine in general. Since it mentions a additive package, It seems to me it`s referring to the cam as I`ve never heard of a additive package to aide in ring break in before.
I could be wrong, so don`t quote me on that.
Even so oil companies I`m sure use different formulas for there oils, however, the intention is the same. This is red line`s view:
: Can I break-in my engine on Red Line motor oil?
For peformance engines, we recommend using conventional 10w30 motor oil to ensure proper piston ring seating. We recommend using this oil in combonation with our Engine Oil Break In Additive, which features the antiwear chemicals necessary to protect valve train components like camshafts, rollers, and tappets. Though most conventional oils are missing the important antiwear components that you find in Red Line's synthetic motor oils, the conventional oil is not as slick as Red Line and will allow the piston rings to seat more quickly. If you allow 1500 to 2000 miles in a street engine or 20 to 30 minutes on the dyno at low rpm, the rings will have had sufficient time to seat and the high initial break-in wear will have occurred. For new road cars, always follow the manufacturer recommendations and initial oil change recommendations for break-in.
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Old 08-18-2010, 08:47 AM
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I'm with Doublevision, I would NOT try to break in on synthetic, especially with chrome rings.
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