Blow by Question
Thread Starter
Drifting
Joined: Dec 2020
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From: Central Florida
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So I moved the vac hose to the out port on the can. Capped off the top port and connected the pcv hose to the in port on the can since that port has a screen built into it. I’ll test drive after work tonight. Also put the breather back in on the other valve cover. Thanks for all the help on this. After I drive it I’ll check the dipstick again to make sure it’s staying out.
Le Mans Master
Joined: Apr 2011
Posts: 6,284
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From: Hermosa
So I moved the vac hose to the out port on the can. Capped off the top port and connected the pcv hose to the in port on the can since that port has a screen built into it. I’ll test drive after work tonight. Also put the breather back in on the other valve cover. Thanks for all the help on this. After I drive it I’ll check the dipstick again to make sure it’s staying out.
Safety Car
Joined: Jan 2009
Posts: 4,000
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From: New York
I am one of the few on this forum who push venting the crank case. Its a big deal because it prevents gasket failures and keeps the oil clean. One of the easiest and old school ways was by using the exhaust. Using a kit like this one. And the best way is to use a vac pump. Which adds up to 20 plus hp.
https://www.summitracing.com/parts/s...QaAgZ2EALw_wcB
https://www.summitracing.com/parts/s...QaAgZ2EALw_wcB
Thread Starter
Drifting
Joined: Dec 2020
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From: Central Florida
2024 Corvette of the Year Winner - Modified
2023 C3 of the Year Winner - Modified
2021 C3 of the Year Finalist - Modified
So I took it out for a spirited drive with the changes described on my prior post. Now the dipstick pops out again like a quarter inch. It’s like it helps to have both valve covers connected to vacuum? Any thought? I don’t want to not have the breather in one for wot conditions. Should I connect it back but put a breather filter at the top of the can instead of blocking it off? Or maybe back off the block off cap a little to have a let out for wot conditions?
Le Mans Master
Joined: Apr 2011
Posts: 6,284
Likes: 1,171
From: Hermosa
The cap you are using for a vent only has a small 1/2" hole or so as a vent correct?
What if you used something like this;
Or maybe even more free flowing like this
With all vacuum and no vent and your dipstick did not pop up I would conclude that you are pulling a fair amount of vacuum at WOT? Only explanation I can think of for the engine not popping that dipstick out in that configuration.
Just to clarify, when you say "spirited" driving does this mean WOT operation? Or is it just aggressive driving?
I don't see that vent on the catch can providing much venting given it's coming though a 3/8" line to get there.
What if you used something like this;
Or maybe even more free flowing like this
With all vacuum and no vent and your dipstick did not pop up I would conclude that you are pulling a fair amount of vacuum at WOT? Only explanation I can think of for the engine not popping that dipstick out in that configuration.
Just to clarify, when you say "spirited" driving does this mean WOT operation? Or is it just aggressive driving?
I don't see that vent on the catch can providing much venting given it's coming though a 3/8" line to get there.
Thread Starter
Drifting
Joined: Dec 2020
Posts: 1,586
Likes: 956
From: Central Florida
2024 Corvette of the Year Winner - Modified
2023 C3 of the Year Winner - Modified
2021 C3 of the Year Finalist - Modified
The cap you are using for a vent only has a small 1/2" hole or so as a vent correct?
What if you used something like this;
https://www.amazon.com/Edelbrock-440...68098744&psc=1
Or maybe even more free flowing like this
https://www.amazon.com/Spectre-Perfo...a-569070190009
With all vacuum and no vent and your dipstick did not pop up I would conclude that you are pulling a fair amount of vacuum at WOT? Only explanation I can think of for the engine not popping that dipstick out in that configuration.
When you say "spirited" driving does this mean WOT operation? Or is it just aggressive driving?
What if you used something like this;
https://www.amazon.com/Edelbrock-440...68098744&psc=1
Or maybe even more free flowing like this
https://www.amazon.com/Spectre-Perfo...a-569070190009
With all vacuum and no vent and your dipstick did not pop up I would conclude that you are pulling a fair amount of vacuum at WOT? Only explanation I can think of for the engine not popping that dipstick out in that configuration.
When you say "spirited" driving does this mean WOT operation? Or is it just aggressive driving?
Thread Starter
Drifting
Joined: Dec 2020
Posts: 1,586
Likes: 956
From: Central Florida
2024 Corvette of the Year Winner - Modified
2023 C3 of the Year Winner - Modified
2021 C3 of the Year Finalist - Modified
The cap you are using for a vent only has a small 1/2" hole or so as a vent correct?
What if you used something like this;
https://www.amazon.com/Edelbrock-440...68098744&psc=1
Or maybe even more free flowing like this
https://www.amazon.com/Spectre-Perfo...a-569070190009
With all vacuum and no vent and your dipstick did not pop up I would conclude that you are pulling a fair amount of vacuum at WOT? Only explanation I can think of for the engine not popping that dipstick out in that configuration.
Just to clarify, when you say "spirited" driving does this mean WOT operation? Or is it just aggressive driving?
I don't see that vent on the catch can providing much venting given it's coming though a 3/8" line to get there.
What if you used something like this;
https://www.amazon.com/Edelbrock-440...68098744&psc=1
Or maybe even more free flowing like this
https://www.amazon.com/Spectre-Perfo...a-569070190009
With all vacuum and no vent and your dipstick did not pop up I would conclude that you are pulling a fair amount of vacuum at WOT? Only explanation I can think of for the engine not popping that dipstick out in that configuration.
Just to clarify, when you say "spirited" driving does this mean WOT operation? Or is it just aggressive driving?
I don't see that vent on the catch can providing much venting given it's coming though a 3/8" line to get there.
Le Mans Master
Joined: Apr 2011
Posts: 6,284
Likes: 1,171
From: Hermosa
You could take your current vent and drill it full of holes to see how that works. All along the bottom like you see on this one.
This would make a mess but what if you just put a piece of hose in that vent hole in the valve cover for testing and see if the dipstick pops up then? Maybe stuff a bit of that steel pot scrubber in the hose to keep the oil venting down. The idea is to test to see if that side is allowed a nice free flow of air if the dipstick still pops out. If it doesn't then go buy a good free flowing vent for it.
Notice on the Spectre vent that the bottom hole is large. Maybe 3/4" or so. Something like that. Many of the vents I've seen have a built in grommet and the hole in that grommet is very small. Defeats the purpose of a good vent. You may even need to mod something up to get adequate flow.
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Thread Starter
Drifting
Joined: Dec 2020
Posts: 1,586
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From: Central Florida
2024 Corvette of the Year Winner - Modified
2023 C3 of the Year Winner - Modified
2021 C3 of the Year Finalist - Modified
Ok, that explains why your all vacuum to both sides worked. You still have manifold vacuum @ 4500. But apparently plenty of blowby too. You can try a different vent, I would go with as free flowing as possible for that motor. Or you can go back to all vacuum if you want, as long as you never really go WOT operation. But that does not seem like a very good permanent solution IMO.
You could take your current vent and drill it full of holes to see how that works. All along the bottom like you see on this one.
https://www.amazon.com/Edelbrock-440...68098744&psc=1
This would make a mess but what if you just put a piece of hose in that vent hole in the valve cover for testing and see if the dipstick pops up then? Maybe stuff a bit of that steel pot scrubber in the hose to keep the oil venting down. The idea is to test to see if that side is allowed a nice free flow of air if the dipstick still pops out. If it doesn't then go buy a good free flowing vent for it.
Notice on the Spectre vent that the bottom hole is large. Maybe 3/4" or so. Something like that. Many of the vents I've seen have a built in grommet and the hole in that grommet is very small. Defeats the purpose of a good vent. You may even need to mod something up to get adequate flow.
You could take your current vent and drill it full of holes to see how that works. All along the bottom like you see on this one.
https://www.amazon.com/Edelbrock-440...68098744&psc=1
This would make a mess but what if you just put a piece of hose in that vent hole in the valve cover for testing and see if the dipstick pops up then? Maybe stuff a bit of that steel pot scrubber in the hose to keep the oil venting down. The idea is to test to see if that side is allowed a nice free flow of air if the dipstick still pops out. If it doesn't then go buy a good free flowing vent for it.
Notice on the Spectre vent that the bottom hole is large. Maybe 3/4" or so. Something like that. Many of the vents I've seen have a built in grommet and the hole in that grommet is very small. Defeats the purpose of a good vent. You may even need to mod something up to get adequate flow.
Le Mans Master
Joined: Apr 2011
Posts: 6,284
Likes: 1,171
From: Hermosa
Thanks. We think a lot alike. I was thinking of leaving it unplugged but your suggestion would make it cleaner with a hose and filter for a test drive. I don’t want to have wot issues later so that’s not an option for me. The breather you posted is the exact one I have. It’s the larger diameter although I can’t remember the holes size. I’ll check later but I think it’s the largest one I can use.
In either case drill the holes or if it has holes make them larger perhaps.
Thread Starter
Drifting
Joined: Dec 2020
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From: Central Florida
2024 Corvette of the Year Winner - Modified
2023 C3 of the Year Winner - Modified
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I thought the one I saw in the pics looked like this
https://www.amazon.com/Edelbrock-441...00CN52TY&psc=1
In either case drill the holes or if it has holes make them larger perhaps.
https://www.amazon.com/Edelbrock-441...00CN52TY&psc=1
In either case drill the holes or if it has holes make them larger perhaps.
Thread Starter
Drifting
Joined: Dec 2020
Posts: 1,586
Likes: 956
From: Central Florida
2024 Corvette of the Year Winner - Modified
2023 C3 of the Year Winner - Modified
2021 C3 of the Year Finalist - Modified
I thought the one I saw in the pics looked like this
https://www.amazon.com/Edelbrock-441...00CN52TY&psc=1
In either case drill the holes or if it has holes make them larger perhaps.
https://www.amazon.com/Edelbrock-441...00CN52TY&psc=1
In either case drill the holes or if it has holes make them larger perhaps.
Thread Starter
Drifting
Joined: Dec 2020
Posts: 1,586
Likes: 956
From: Central Florida
2024 Corvette of the Year Winner - Modified
2023 C3 of the Year Winner - Modified
2021 C3 of the Year Finalist - Modified
Le Mans Master
Joined: Apr 2011
Posts: 6,284
Likes: 1,171
From: Hermosa
What PCV are you using currently? If it's not appropriate for the engine (most are not unless stock motor) it's not going to be drawing a vacuum as it should through the power range.
when you had full vacuum to the engine it did not pop up the dipstick and you were not even full throttle. so that seems to indicate that the PCV in there now is not appropriate for the engine perhaps as it is not adequately evacuating blowby.
Yes, as pointed out it's only a 3/8" line but it's under vacuum, 21" or better for any motor much above idle. 30" is equivalent to 14.7 psi. So if you want to look at it that way then the PCV provides a good 10 psi of vacuum above idle.
Venting is a passive method of controlling blowby. So it's going to take a much larger hole to passively vent and engine (the crankcase has to blow the vapor out) vs sucking out the blowby pressure. Not to mention, we are venting through the oil drain back holes in the heads, then out the valve cover, so those drainback holes provide a restriction to venting as well.
You may want to look into that Wagner one I linked earlier if you want better evacuation below WOT.
Edit: forgot about the whole lifter Valley and past the pushrod holes to the valve cover, lol. So no, the drain back holes are not a restriction.
when you had full vacuum to the engine it did not pop up the dipstick and you were not even full throttle. so that seems to indicate that the PCV in there now is not appropriate for the engine perhaps as it is not adequately evacuating blowby.
Yes, as pointed out it's only a 3/8" line but it's under vacuum, 21" or better for any motor much above idle. 30" is equivalent to 14.7 psi. So if you want to look at it that way then the PCV provides a good 10 psi of vacuum above idle.
Venting is a passive method of controlling blowby. So it's going to take a much larger hole to passively vent and engine (the crankcase has to blow the vapor out) vs sucking out the blowby pressure. Not to mention, we are venting through the oil drain back holes in the heads, then out the valve cover, so those drainback holes provide a restriction to venting as well.
You may want to look into that Wagner one I linked earlier if you want better evacuation below WOT.
Edit: forgot about the whole lifter Valley and past the pushrod holes to the valve cover, lol. So no, the drain back holes are not a restriction.
Last edited by REELAV8R; Jan 5, 2022 at 04:32 PM.
Racer
Joined: Mar 2021
Posts: 278
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From: Kansas
Dumb question but at the angle it looks like any engine movement or hose movement would cause a hose to touch the dipstick top, is it doing that and then breaking the seal so to speak and the path of least resistance pushing the dipstick out?
Also a leak down test would be beneficial and point you in the right direction
Also a leak down test would be beneficial and point you in the right direction
Le Mans Master
Joined: Apr 2011
Posts: 6,284
Likes: 1,171
From: Hermosa
This is a relatively new engine, correct? When you ran two breathers you didn't have the dip stick popping up. Was there a lot of oil misting under the hood on the valve covers and exhaust manifolds prompting the change to venting?
Thread Starter
Drifting
Joined: Dec 2020
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From: Central Florida
2024 Corvette of the Year Winner - Modified
2023 C3 of the Year Winner - Modified
2021 C3 of the Year Finalist - Modified
Dumb question but at the angle it looks like any engine movement or hose movement would cause a hose to touch the dipstick top, is it doing that and then breaking the seal so to speak and the path of least resistance pushing the dipstick out?
Also a leak down test would be beneficial and point you in the right direction
Also a leak down test would be beneficial and point you in the right direction
Not likely as it was pushing out the stick before this et up too.
Thread Starter
Drifting
Joined: Dec 2020
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From: Central Florida
2024 Corvette of the Year Winner - Modified
2023 C3 of the Year Winner - Modified
2021 C3 of the Year Finalist - Modified
Yes. New crate 383 with less than 2k miles. Probably much less than that actually. No oil misting when I had the 2 breathers. Baffles in the covers worked well. I could always go back to that but I like the idea of pulling the blow by out as it seems like the engine would get better aspiration and maybe better performance. Again, I’m not an expert here, just a guy that loves doing this stuff as a hobby.
Le Mans Master
Joined: Apr 2011
Posts: 6,284
Likes: 1,171
From: Hermosa
Yes. New crate 383 with less than 2k miles. Probably much less than that actually. No oil misting when I had the 2 breathers. Baffles in the covers worked well. I could always go back to that but I like the idea of pulling the blow by out as it seems like the engine would get better aspiration and maybe better performance. Again, I’m not an expert here, just a guy that loves doing this stuff as a hobby.
The lack of excess oil misting leads me to believe that you do not have a serious mechanical issue. Just a bit of extra blowby to manage.