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Old 03-09-2009, 03:14 AM
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Valve seals

Couple years back a friend purchased RHS Vortec heads bare. He had the valves, springs, and everything else needed so we took them to my machinist and he assembled them. We installed them and the car smokes like a steam train. I went back to the machinist and asked him what kind of seals did he use, he said he didn`t install any seals on the exhaust valves so needless to say this is why it smokes like crazy. He said he didn`t install them as he thought they were race only heads and they didn`t need them, I thought they needed them regardless of how there being used. It smokes from the very second it`s fired up and doesn`t let up, the heads we had on it prior didn`t smoke at all.
The car has been sitting a while now and were going to install some exhaust valve seals before firing it back up. I`m wanting to know what`s the best type of seals to use? This car sees street use and some strip use.

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Old 03-09-2009, 05:35 AM
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When I bought my Brodix Race Rite heads,it was the same as your buddy's,no exhaust valve seals.And apparently,thats the way they are put together for race useage,as a way to insure the exhaust guides get lots of oil.I installed new Viton seals on mine,I didnt want a "Smoker" for my mostly street car.From what I found out,it seemed like the Viton type were the best way to go.It was fairly easy at the time,the heads werent installed,and I pulled them apart for a thorough cleaning and checked installed heights,open pressure and installed a set of locators in place of the thin shims that came with them.Something like these;

http://store.summitracing.com/partde...5&autoview=sku

Guy
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Old 03-09-2009, 09:38 AM
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Quote:
Originally Posted by DoubleVision
Couple years back a friend purchased RHS Vortec heads bare. He had the valves, springs, and everything else needed so we took them to my machinist and he assembled them. We installed them and the car smokes like a steam train. I went back to the machinist and asked him what kind of seals did he use, he said he didn`t install any seals on the exhaust valves so needless to say this is why it smokes like crazy. He said he didn`t install them as he thought they were race only heads and they didn`t need them, I thought they needed them regardless of how there being used. It smokes from the very second it`s fired up and doesn`t let up, the heads we had on it prior didn`t smoke at all.
The car has been sitting a while now and were going to install some exhaust valve seals before firing it back up. I`m wanting to know what`s the best type of seals to use? This car sees street use and some strip use.

Usually the exhaust doesn't need much in the way of a seal. This is because the exhaust side sees pressure in the port most of the time which tends to blow oil out of the guide to stem clearance space. Compare that with the intake side where the port is under vacuum from a greater (idle/coast) to a lesser (WOT) extent, this tends to pull oil in the guide to stem clearance.

Either of these conditions are also affected by internal engine pressure, that's to say an engine with blow-by will be internally pressurized and this will tend to push oil down the guide/stem clearance. So piston seal can be a contributor to oil consumption down the guides. I bring this up for diagnostic consideration that you will need to consider, since off the bat I don't trust your machinist given what he said and didn't do.

But let's get to basics first; that is valve guide to stem clearance. This needs to be know by you, there are tests for specific engines, they are fairly simple it's a case of measuring side to side movement of the valve when it's positioned in the guide with the stem exposed X number of inches. It typically isn't much movement. A failure to maintain proper clearance is a problem seals can't solve.

For seals there are two schools of thought. One is to reduce the amount of oil that gets on the stem. This uses umbrella seals or simply an O ring and metal shield on the upper part of the spring under the retainer. This system does not seal the stem as such but directs oil away so that it isn't present on the stem in quantities that cause smoking problems. The second way is to use a real seal such as the Perfect Circle, these are made of a hard plastic or rubber. They attach to a machined surface made on the outside of the guide and fit tightly about the stem.

Typically a competition engine uses hard seal on the intake and an umbrella on the exhaust. This is also suitable for a street engine although most OEMs tend to use umbrella or O rings on engines prior to the 1990s. Later models will usually use a positive seal as a method to reduce oil contamination of the catalytic converter.

Guides made of bronze alloys will run with a tighter clearance and less lubrication than older cast iron. But where RPMs are kept under 6000, cast iron is just fine running dryer.

A caution to look for, there is a guide restoration technique called knurling which leaves a spiral groove thru the guide. Guides treated thusly need to have positive seals as this groove will allow a lot of oil thru the guide.

Bogie
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Old 03-09-2009, 10:56 AM
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Smoker

Just a suggestion .... How is the intake sealing up to the heads ? If the heads were milled and the intake wasn`t it could be that it is pulling oil into the intake runners. Yes it will pull oil in without causing an engine miss because its not leaning the cylinders out as would a vacuum leak to the atmosphere. As Bogie said there is relatively no negative pressure (vacuum) on the exhaust side (except during valve overlap ) to pull any significant amount of oil into the cylinder.

Here is a quick check you can use . Back off all your rockers where the valves are all closed . Install your valve covers. Inject compressed air with a pressure regulator set at 3-5 PSI in the PCV hole and listen for leakage around the throttle bores in the carb. If you get some leakage there is an open runner that can pull oil in. This will also show up any external leak points around a rear main seal, valve cover etc.....


Hope this helps ,

Dan Hurst
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Old 03-09-2009, 11:43 AM
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Thanks for the replies. I see what your saying Bogie and it makes sense.
The heads weren`t milled. They are new castings out of the box when bolted on and don`t even have a 50 miles on them. I`m positive there aren`t any intake leaks as this was the first thing I suspected and did all the checks.
When the car is at idle or going down the road it`s boiling smoke.
Since the cylinder heads are the only thing we changed from the old heads which didn`t smoke it points towards something is amiss with the heads so I`ll have to check both the intake and exhaust seals as well as guide wear. If everything checks out okay then I`ll be completely lost as to where the oil is getting in at. The engine is also fresh built, it has a little over 1000 miles on it at the most. Thanks for the help guys.
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Old 03-09-2009, 01:07 PM
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Quote:
Originally Posted by DoubleVision
Thanks for the replies. I see what your saying Bogie and it makes sense.
The heads weren`t milled. They are new castings out of the box when bolted on and don`t even have a 50 miles on them. I`m positive there aren`t any intake leaks as this was the first thing I suspected and did all the checks.
When the car is at idle or going down the road it`s boiling smoke.
Since the cylinder heads are the only thing we changed from the old heads which didn`t smoke it points towards something is amiss with the heads so I`ll have to check both the intake and exhaust seals as well as guide wear. If everything checks out okay then I`ll be completely lost as to where the oil is getting in at. The engine is also fresh built, it has a little over 1000 miles on it at the most. Thanks for the help guys.
Don't forget what Dan Hurst said, what he meant was the intake may not be sealing on the inside, bottom/sides of the ports. This would not be visible nor simply testable from outside the engine. The usual tests for a vacuum leak along the manifold to head only tests for a leak along the top of the manifold.

In this day and age there seems to be plenty of machining errors to go around, it could be the the head or manifold are not meeting at the same angle, or the same alignment along a side or bottom of a port leaving a gap that draws oil out of the valley into the intake. This can be tested by introducing a propane flow into the valley area of the engine when idling, a leak would cause the engine RPMs to come up, but this is sooo dangerous to do as you're essentially making the engine into a cast iron grenade.

Your description of smoking heavily on idle or part throttle certainly points tp oil getting into the intake system. This could also be a faulty PCV or a situation where the oil separator on the rocker cover isn't doing its job.

One also can't discount the rings, an engine that wasn't sealing well with heads that weren't allowing much compression can suddenly start pulling a lot of oil, this doesn't sound like your case, but I'm not there, so I've got to dump what data comes to mind.

Bogie
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Old 03-09-2009, 01:55 PM
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When I built my Vortec engine with close to the same specs, I mistakenly used the stock fel pro gaskets. Needless to say, it didn`t seal and it smoked but not bad. I pulled the carb and oil was everywhere in the plenum. So I replaced the gaskets again same result. It was then I learned use the gaskets edelbrock recommended. On my friends engine we used edelbrock gaskets the first round and after the smoking started we right away pulled the carb and found the plunum dry, no oil anywhere.
We did a compression check and got 190 psi so it seems to be sealing up good, however I don`t have a leak down tester. We also suspected the PCV and disconnected it entirely and that didn`t slow the smoking down any. It has little blow by so it doesn`t seem to be in the rings either. Unless these are just bum heads if the seals and guides don`t pan out I`ve tried everything else I know to try. My friend says if we can`t find anything wrong with the heads we`ll go ahead and pull it back out and check the rings and the bores out closely. I`ll go ahead and list the specs on this engine on the next post as to not make this one too long. Thanks again guys.
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Old 03-09-2009, 02:27 PM
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Specs:
1998 880 Casting Vortec 350. (found in a junk yard in a pile of other engines)
Bored .030 over, honed to piston size specs. Decked .010. Honed for moly rings. Bores scrubbed to be sure no hone grit remained.
PM Rods. Factory windage tray.
Stock 350 cast crank.
Mr. Gasket head gaskets, .028 thickness.
Speed pro Hyper coated skirt 2 valve relief pistons. Mocked up to .016 in the hole. .044 Quench distance.
Speed pro moly rings.
Comp Cams hydraulic Roller cam. .215 duration @.050. .500 lift.
OEM Roller tappets. 1.6 ratio self aligning rocker arms.
Cloyes single roller "Vortec" timing chain set straight up.
RHS Vortec heads. 64cc fast burn chambers. 170cc runners. Manley Street master 1.94 intake 1.50 exhaust valves. Comp cams matching locks retainers and springs.
Edelbrock performer Vortec intake.
Hedman Headers.
HEI Ignition with pertronix internals. Spiral core plug wires.
TH350 tranny. B&M 2400 stall converter.
SMI Quadrajet.

Last edited by DoubleVision; 03-09-2009 at 02:33 PM.
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Old 03-09-2009, 04:38 PM
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Smoke ?

Another possible maybe .... Does the car have a transmission with a vacuum modulator ? If it took a good backfire and popped the diaphragm you could have a trans fluid injection system causing your smoke. Pull the hose off the modulator and see if fluid runs out.

Dan Hurst
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Old 03-09-2009, 06:32 PM
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Yep Dan, I checked that as well. Soon we plan to yank the valve covers and pop some springs to investigate the seals and guides, I`ll let you know what we find out.
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