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Measuring blow by

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Old Jul 14, 2020 | 09:13 PM
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Default Measuring blow by

How would I go about measuring blow by? More importantly, seeing if I have to much of it?

my car has a -12 AN fitting on each valve cover to a single catch can. At idle you can see some air on chilly night coming out of catch can filter. Other night I was beating on it pretty good with heavy load, 160 in 4th gear, several times and I notice my oil dipstick came up alittle and oil was all over my frame rail. I can only assume it’s from dipstick.

my car falls off power at higher rpm for whatever reason 🤷🏻‍♂️ And was wondering if this is related to that. Look at the sheet, I rev to 6800. If continued the pull on dyno than you would see if shoot power back down pretty good.

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Old Jul 14, 2020 | 11:00 PM
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You use a water manometer to read blow by in inches of water. You need to have a calibrated orfice to run the blow by gases through and the manometer will tell you the blow by. You might be able to find a spec for a stock engine but not for a moded engine. Honestly you don't have an issue with excessive blow by with what you describe. You just need another vent or a larger line. Hell bite the bullet and buy a mighty mouse can they work awesome.
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Old Jul 15, 2020 | 10:44 AM
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Originally Posted by jordoza
You use a water manometer to read blow by in inches of water. You need to have a calibrated orfice to run the blow by gases through and the manometer will tell you the blow by. You might be able to find a spec for a stock engine but not for a moded engine. Honestly you don't have an issue with excessive blow by with what you describe. You just need another vent or a larger line. Hell bite the bullet and buy a mighty mouse can they work awesome.
I’ll look up the Mighty Mouse can. I don’t mind running something larger. Just sick of smoke at lights from little oil residue on heat wrap taking forever to burn off
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Old Jul 15, 2020 | 12:29 PM
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Yep a simple water manometer works excellent
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Old Jul 15, 2020 | 01:17 PM
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How is current catch can vented? 2 -12 should be enough to vent motor. I suspect you have > 3psi in crankcase to blow dipstick out. A basic vacuum/pressure gauge connected to dipstick tube will give you a quick read.

SIde note - based on dyno graph, it appears that peak hp occurs around 5800rpm and projecting to drop 10% by 6400. Am I seeing this right? If so, must feel flat at 6800? Are you using a phone app to monitor acceleration results at different rpm?
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Old Jul 15, 2020 | 04:36 PM
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Originally Posted by tblentrprz
How is current catch can vented? 2 -12 should be enough to vent motor. I suspect you have > 3psi in crankcase to blow dipstick out. A basic vacuum/pressure gauge connected to dipstick tube will give you a quick read.

SIde note - based on dyno graph, it appears that peak hp occurs around 5800rpm and projecting to drop 10% by 6400. Am I seeing this right? If so, must feel flat at 6800? Are you using a phone app to monitor acceleration results at different rpm?





my top of 3rd I always thought felt slower than should but I do know my power falls off decent bit. Also can see the catch can and both lines going to valve covers near firewall.

my 100-115ish before shift slows down for sure. Tech. I shouldn’t have shifted till 122 and slight upward slope but I still have a top end drop of power to figure out. Just wasn’t sure if it’s related to the blow by. I don’t blow out dipstick unless top3rd gear into 4th

Last edited by ricky6991; Jul 15, 2020 at 04:43 PM.
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Old Jul 15, 2020 | 05:43 PM
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