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post #16 of 35 (permalink) Old Jun 3rd, 18, 10:31 AM Thread Starter
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Re: What is normal Blow By

Changed Pcv valve and breather. Will put some more miles on it and recheck.

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post #17 of 35 (permalink) Old Jun 3rd, 18, 11:38 AM
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Re: What is normal Blow By

Do large ring gaps contribute significantly to blow-by?

Some sort of crankcase-evac setup can help to reduce front/back seal leaks. Also, applying some Right Stuff the right way (cleaning up the surface good first) can buy some time before leaking again.

I've always thought the PCV is also a big contributor. It has to work for your combo and not all replacements work the same.
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post #18 of 35 (permalink) Old Jun 3rd, 18, 1:58 PM
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Re: What is normal Blow By

If you got low tension oil rings it will have blow by and use oil. Check the number for your rings and see if that is the problem.
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post #19 of 35 (permalink) Old Jun 3rd, 18, 3:17 PM
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Re: What is normal Blow By

1. Beware of using leakdown percentage. The indicated leakdown in percent is as dependent on the leakdown tester as it is on the actual leakage. A leakdown tester with a small orifice will show high percentage numbers, a leakdown tester with a large orifice will show smaller numbers on the same engine.

2. While not as useful for WFO problems, my standard for blowby is to run the engine at fast idle--1200--1500 rpm. Stick my thumb in the vent side of the engine--opposite to the PCV valve, and hold for ten or fifteen seconds. When I pull my thumb off the vent, the crankcase should have vacuum, not pressure. The vent will suck air into the engine, not blow smoke out.

Do you have a WORKING PCV valve? Is it the right one for the engine?

Finding the "right" PCV valve is trial-and-error, since there's no listing of orifice sizes, spring tensions or any other specs that would help to compare two PCV valves. You can't even go by part numbers like you used to be able to do with spark plugs.

I know there was a thread many years ago about leaking front seals; the cause was...shiitty front seals made in India combined with front covers that mis-located the seals so they ran off-center on the damper hub.

A quality seal, combined with assuring the seal is concentric to the hub (and the hub doesn't have a groove cut in it from the previous seal) might go a long way toward fixing your leakage.

The 454 in my boat uses a front cover that is not drilled for the alignment dowels. Aligning the seal requires installing the damper hub through the seal while the front cover is still not fully bolted down. Once the damper aligns the seal, I finish tightening the cover bolts.

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post #20 of 35 (permalink) Old Jun 3rd, 18, 4:45 PM Thread Starter
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Re: What is normal Blow By

Quote:
Originally Posted by Schurkey View Post
1. Beware of using leakdown percentage. The indicated leakdown in percent is as dependent on the leakdown tester as it is on the actual leakage. A leakdown tester with a small orifice will show high percentage numbers, a leakdown tester with a large orifice will show smaller numbers on the same engine.

2. While not as useful for WFO problems, my standard for blowby is to run the engine at fast idle--1200--1500 rpm. Stick my thumb in the vent side of the engine--opposite to the PCV valve, and hold for ten or fifteen seconds. When I pull my thumb off the vent, the crankcase should have vacuum, not pressure. The vent will suck air into the engine, not blow smoke out.

Do you have a WORKING PCV valve? Is it the right one for the engine?

Finding the "right" PCV valve is trial-and-error, since there's no listing of orifice sizes, spring tensions or any other specs that would help to compare two PCV valves. You can't even go by part numbers like you used to be able to do with spark plugs.

I know there was a thread many years ago about leaking front seals; the cause was...shiitty front seals made in India combined with front covers that mis-located the seals so they ran off-center on the damper hub.

A quality seal, combined with assuring the seal is concentric to the hub (and the hub doesn't have a groove cut in it from the previous seal) might go a long way toward fixing your leakage.

The 454 in my boat uses a front cover that is not drilled for the alignment dowels. Aligning the seal requires installing the damper hub through the seal while the front cover is still not fully bolted down. Once the damper aligns the seal, I finish tightening the cover bolts.

Thank you. This is what I done so imo its not a issue. When I hold my finger over the breather hole I do get vacuum after a while. No pressure. Even with the PCV off I have no pressure. This just is one of those things that is in the back of your mind. When you do a detailed build you just expect better. Oil leak is fixed.

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post #21 of 35 (permalink) Old Jun 4th, 18, 1:54 PM
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Re: What is normal Blow By

I agree with a previous poster in saying that anything puffing out of the valve cover is not a good sign. Do a regular compression test and see what you get. Blow-by is loss of compression.
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post #22 of 35 (permalink) Old Jun 6th, 18, 10:45 AM
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Re: What is normal Blow By

Put a PCV valve or run the breathers to the headers. No more vapor. Any engine with just breathers will have oil dripping out of the breathers over time.
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post #23 of 35 (permalink) Old Jun 6th, 18, 12:08 PM
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Re: What is normal Blow By

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Originally Posted by Schurkey View Post
1.

Finding the "right" PCV valve is trial-and-error, since there's no listing of orifice sizes, spring tensions or any other specs that would help to compare two PCV valves. You can't even go by part numbers like you used to be able to do with spark plugs.

I know there was a thread many years ago about leaking front seals; the cause was...shiitty front seals made in India combined with front covers that mis-located the seals so they ran off-center on the damper hub.

A quality seal, combined with assuring the seal is concentric to the hub (and the hub doesn't have a groove cut in it from the previous seal) might go a long way toward fixing your leakage.
.
I posted about this about 10 years ago.... exactly as stated, ID of seal that came in gasket set was too large and opened a small gap on one side of balancer when installed. Finally figured it out and bought several different front seals. Was surprised at the difference from various manufactures. Think i ended up using a Detroit seal. It had the smallest static ID of all.

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post #24 of 35 (permalink) Old Jun 6th, 18, 7:02 PM Thread Starter
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Re: What is normal Blow By

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Originally Posted by Jeff65SS View Post
I posted about this about 10 years ago.... exactly as stated, ID of seal that came in gasket set was too large and opened a small gap on one side of balancer when installed. Finally figured it out and bought several different front seals. Was surprised at the difference from various manufactures. Think i ended up using a Detroit seal. It had the smallest static ID of all.

Jeff it wasnt the front seal. After pulling the balancer it was the front of the pan gasket walked in. 1 piece Felpro blue pan gasket. I forget where I got it. But my gut tells me its a china clone in a felpro looking box. So I loosened the pan fished the front seal out and sprayed it with trim cement slide it back in then just snugged it up. After the glue dried I tighened it the rest of the way. Once tight I filled the groove in the front of the pan with black RTV and let dry. No leaks. Just hope that keeps it in place.
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post #25 of 35 (permalink) Old Jun 6th, 18, 7:04 PM Thread Starter
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Re: What is normal Blow By

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Originally Posted by bracketchev1221 View Post
Put a PCV valve or run the breathers to the headers. No more vapor. Any engine with just breathers will have oil dripping out of the breathers over time.

I hate pcv valves. So I was always told running both breathers down to the headers is too much for the street. But how about one down to the header evac and 1 normal breather. Pcv really does nothing at WOT.

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post #26 of 35 (permalink) Old Jun 7th, 18, 12:42 AM
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Re: What is normal Blow By

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Originally Posted by 67 SuperSport View Post
I agree with a previous poster in saying that anything puffing out of the valve cover is not a good sign. Do a regular compression test and see what you get. Blow-by is loss of compression.
I disagree with this. The 496 in my Nova uses no oil and runs excellent. It doesn't have a PCV and on a hot day it will puff a little spoke/vapors out of both breathers at stop lights. Never any drips or oil soaked breathers though.

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post #27 of 35 (permalink) Old Jun 7th, 18, 2:48 AM
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Re: What is normal Blow By

Cylinder leakage measurements with a leakdown tester can definitely help diagnose sealing problems but its a static test. The only way to know how much blowby you have is with a blowby meter on a running engine. Usually a hot street car shouldn't have much over 10 cfm
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post #28 of 35 (permalink) Old Jun 7th, 18, 7:48 AM Thread Starter
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Re: What is normal Blow By

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Originally Posted by 496blaze View Post
I disagree with this. The 496 in my Nova uses no oil and runs excellent. It doesn't have a PCV and on a hot day it will puff a little spoke/vapors out of both breathers at stop lights. Never any drips or oil soaked breathers though.

This is the same way mine is. Only hot. My small block was the same as well. No pressure just a little vapor.
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post #29 of 35 (permalink) Old Jun 7th, 18, 7:59 AM
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Re: What is normal Blow By

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Originally Posted by StevenS View Post
I hate pcv valves. So I was always told running both breathers down to the headers is too much for the street. But how about one down to the header evac and 1 normal breather. Pcv really does nothing at WOT.
Its not that it is too much for the street. It was that the exhaust velocity was not high enough to pull any appreciable vacuum on the crankcase.
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post #30 of 35 (permalink) Old Jun 10th, 18, 6:45 PM Thread Starter
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Re: What is normal Blow By

Ran the car for another 75 miles. Ran the leakdown test again hot. All cyls just about even under 10 percent. I got 5 to 9 percent. I just dont get it. Hitting the cyls with 90 psi is a chore at tdc. Spins that motor over real fast. LOL. Could not hear no real air leakage. All plugs look dam good. I used Plasma rings. I really have to wonder if this was plate honed. I have not used any oil or water. But at least I know its not self destructing.

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