150 Miles per Quart???
Race Director
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From: SW Florida.
i assume these are not tired old heads somebody threw seals in. it ain't the valve guides. unless one valve is so loose you can wiggle it spring and all cuz something in the casting let go. smokes more on the right. pull the 4 right plugs. the nasty one is where you will find the manifold gasket vacuum leak.
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Melting Slicks
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From: SUFFIELD CT USA 2023 C8 CORVETTE UN-MODIFIED FINALIST
2023 C8 of the Year Finalist - Unmodified
i assume these are not tired old heads somebody threw seals in. it ain't the valve guides. unless one valve is so loose you can wiggle it spring and all cuz something in the casting let go. smokes more on the right. pull the 4 right plugs. the nasty one is where you will find the manifold gasket vacuum leak.
Le Mans Master
Joined: Sep 2001
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From: Unreconstructed, South Carolina
Dart heads ... even cheaper ones ... Doubt Dart uses O-ring stem seals ... Likely all guide-mounted, Posi-stop seals ,,,
... but maybe seals're damaged ... or Not seated ... or weren't installed.
also, doubt ATK buys assembled Dart ... Likely buys bare & installs seals, valves etc.
... but maybe seals're damaged ... or Not seated ... or weren't installed.
also, doubt ATK buys assembled Dart ... Likely buys bare & installs seals, valves etc.
Last edited by jackson; May 25, 2020 at 08:27 PM.
Le Mans Master
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From: Cool Northern Michigan
When you think about the main job of a Valve Stem Seal, its purpose is to keep the oily mist, under the valve cover, from getting sucked into the combustion chamber.
For example, blueish exhaust smoke at start-up? Stem seals. Where did this oily mist come from? Pushrods / rockers.
But lately, the posts are saying the stem seal job is to keep oil from entering the area under the valve cover? How can that be? The valve stem seals are under negative pressure most of the time, such as the Intake stroke = suction. Not spraying oil out the grommets.
If there were no piston rings what-so-ever, Then yes, it would blow oil past the stem seals.
Like d.d. said, its not the stem seals.
For example, blueish exhaust smoke at start-up? Stem seals. Where did this oily mist come from? Pushrods / rockers.
But lately, the posts are saying the stem seal job is to keep oil from entering the area under the valve cover? How can that be? The valve stem seals are under negative pressure most of the time, such as the Intake stroke = suction. Not spraying oil out the grommets.
If there were no piston rings what-so-ever, Then yes, it would blow oil past the stem seals.
Like d.d. said, its not the stem seals.
Le Mans Master
Joined: Sep 2001
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From: Unreconstructed, South Carolina
for the resident pseudo-physicist ... VSS don't only control valve-guide lube ... but also blow-by .. and some VSS do so better than others.
https://www.engineerlive.com/content...r-pressure-lip
https://www.engineerlive.com/content...r-pressure-lip
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From: SW Florida.
ok. engine is a reputable build as is the installer. did the engine come intake and all? or was it a block-heads and the local shop put the intake on? the intake has to come back off. if the shop who installed engine received the engine with the intake already installed, it could end up being 2 different entities saying "i ain't paying for it!" if YOU pull the intake, the shop could say warranty No Mas! so pull the right bank plugs to see which one or two is oiliest. ask the shop to do a manifold vacuum test then change the intake gasket looking for sealing issues at the port(s) corresponding to the dirtiest plug(s).
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Melting Slicks
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From: SUFFIELD CT USA 2023 C8 CORVETTE UN-MODIFIED FINALIST
2023 C8 of the Year Finalist - Unmodified
ok. engine is a reputable build as is the installer. did the engine come intake and all? or was it a block-heads and the local shop put the intake on? the intake has to come back off. if the shop who installed engine received the engine with the intake already installed, it could end up being 2 different entities saying "i ain't paying for it!" if YOU pull the intake, the shop could say warranty No Mas! so pull the right bank plugs to see which one or two is oiliest. ask the shop to do a manifold vacuum test then change the intake gasket looking for sealing issues at the port(s) corresponding to the dirtiest plug(s).
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Melting Slicks
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From: SUFFIELD CT USA 2023 C8 CORVETTE UN-MODIFIED FINALIST
2023 C8 of the Year Finalist - Unmodified
I just dropped the car off at the install shop. Counted 11 Vettes outside and there are usually 5 or 6 inside ! They would not commit to a time frame. They had 3 come in on a flat bed and one more on its way. When I know something I will post. I am not one to start a thread and then just disappear !
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Melting Slicks
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From: SUFFIELD CT USA 2023 C8 CORVETTE UN-MODIFIED FINALIST
2023 C8 of the Year Finalist - Unmodified
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Melting Slicks
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From: SUFFIELD CT USA 2023 C8 CORVETTE UN-MODIFIED FINALIST
2023 C8 of the Year Finalist - Unmodified
Kossuth may be right. The shop called me and asked if those were the original valve covers that came with the new 383. I bought them from Summit because the ones that came with the long block were just cheap stamping. I gave the very expensive new valve covers to the shop still in the box. So apparently there are PCV valve covers and non PCV ?
The plan is to replace back to the original ATK covers and then for me to put a couple hundred miles on the car. There was oil everywhere when they pulled the covers. All plugs were black and oily ! I hope it is just the valve covers and that they are also my idling problem!
Edit: I checked the paperwork on the valve covers and it says " SBC Tall valve covers 1958-1986 Roller Rockers with Baffles" The shop says there are no Baffles in there?
The plan is to replace back to the original ATK covers and then for me to put a couple hundred miles on the car. There was oil everywhere when they pulled the covers. All plugs were black and oily ! I hope it is just the valve covers and that they are also my idling problem!
Edit: I checked the paperwork on the valve covers and it says " SBC Tall valve covers 1958-1986 Roller Rockers with Baffles" The shop says there are no Baffles in there?
Last edited by BPHORSEGUY; Jun 1, 2020 at 09:15 PM.
Le Mans Master
Joined: Sep 2001
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From: Unreconstructed, South Carolina
FWIW, last iteration of SBC ... GM L30 & L31 vortec ... no more O-rings on stem below keys ...instead, guide mounted posi seals that both work & last Very well.
Race Director
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From: South Western Ontario
I've seen a grommet like this called a baffle and that seems like a stretch to me.
https://www.moroso.com/breather-grom...-package68775/
Maybe they came with something like that instead of actual baffles around the breather holes???
https://www.moroso.com/breather-grom...-package68775/
Maybe they came with something like that instead of actual baffles around the breather holes???
Le Mans Master
Joined: Sep 2001
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From: Unreconstructed, South Carolina
OP BP
? Exactly which ATK engine part number did you order/receive ?
? Did the VC that came on your ATK motor use centerbolts or perimeter bolts ?
? Did you have to acquire a Vortec-style intake manifold? Or did conventional intake fit those Dart heads ?
Regardless of what leaking/oiling issue is, your mild street motor Should have an operable PCV system that Breathes. PCV system that flows air Into one VC then Through the motor, then Out the other VC via PCV Valve then Into carburetor base/intake Plenum. Hundreds of Millions of vehicles came so-equipped, including your C3; engineers were right again.
Repeat: top of my list of oil burning culprits is How the intake was installed.
? Exactly which ATK engine part number did you order/receive ?
? Did the VC that came on your ATK motor use centerbolts or perimeter bolts ?
? Did you have to acquire a Vortec-style intake manifold? Or did conventional intake fit those Dart heads ?
Regardless of what leaking/oiling issue is, your mild street motor Should have an operable PCV system that Breathes. PCV system that flows air Into one VC then Through the motor, then Out the other VC via PCV Valve then Into carburetor base/intake Plenum. Hundreds of Millions of vehicles came so-equipped, including your C3; engineers were right again.
Repeat: top of my list of oil burning culprits is How the intake was installed.
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Melting Slicks
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From: SUFFIELD CT USA 2023 C8 CORVETTE UN-MODIFIED FINALIST
2023 C8 of the Year Finalist - Unmodified
HP 94, perimeter bolts, Conventional Weiand Intake I believe. I slid the orignal ATK VC under the shop's fence last nite, so hopefully they are working on it today.
I will double check the spec sheet for the intake
Edit: It is a Weiand Street Warrior.
I will double check the spec sheet for the intake
Edit: It is a Weiand Street Warrior.
Last edited by BPHORSEGUY; Jun 2, 2020 at 12:15 PM.
Le Mans Master
Joined: Sep 2001
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From: Unreconstructed, South Carolina
https://www.high-performance-engines...5hp-p/hp94.htm
Funny, ATK pic shows Pro-Filer heads while description lists DART SHP.
Pic shows chrome steel VC ... one w/ both grommet & fill cap; the other w/ grommet only
֎ Again, me thinks you need a real PCV system w/ baffled grommet holes ... cannot beat OE PCV system.
֎ Again, me thinks culprit's install of intake ... who knows if installer will divulge.
Funny, ATK pic shows Pro-Filer heads while description lists DART SHP.
Pic shows chrome steel VC ... one w/ both grommet & fill cap; the other w/ grommet only
֎ Again, me thinks you need a real PCV system w/ baffled grommet holes ... cannot beat OE PCV system.
֎ Again, me thinks culprit's install of intake ... who knows if installer will divulge.
Le Mans Master
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From: Hermosa
I’ve been following this thread and I think these guys are spot on as far as the potential causes for your oil consumption. I do have some experience with the Dart SHP heads however.
In my experience the install height for the valves on those darts is way too high. The seats are cut at various heights so spring pressure varies quite a bit from valve to valve despite shimming.The height causes spring surge during use. I had problems with the spring dislodging the valve stem seals and then it would start smoking pretty good during high vacuum situations.
ultimately the bad install height IMO contributed to excessive guide wear and/ or the guides were pretty loose straight from Dart. Unfortunately I did not check them when I received them, I didn’t have a good way to do that at the time, so I can’t say for sure . They were pre assembled when I received the heads.
I can say that the install height led to many issues, from loss of spring control and valve float to unseating the stem guides seals. My opinion of those heads is not very high.
In my experience the install height for the valves on those darts is way too high. The seats are cut at various heights so spring pressure varies quite a bit from valve to valve despite shimming.The height causes spring surge during use. I had problems with the spring dislodging the valve stem seals and then it would start smoking pretty good during high vacuum situations.
ultimately the bad install height IMO contributed to excessive guide wear and/ or the guides were pretty loose straight from Dart. Unfortunately I did not check them when I received them, I didn’t have a good way to do that at the time, so I can’t say for sure . They were pre assembled when I received the heads.
I can say that the install height led to many issues, from loss of spring control and valve float to unseating the stem guides seals. My opinion of those heads is not very high.
Last edited by REELAV8R; Jun 2, 2020 at 10:21 PM.