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Excessive blowby out of breather...

Posted By: SGTFURY62

Excessive blowby out of breather... - 07/03/10 10:14 PM

Well I have the 360 running fairly well in the old truck (1976) but it has alot of blowby coming out of the passenger side valve cover breather. Nothing out of the drivers side pcv just all out of the passengers side. Is not smoking out of exhaust that I can see. Any ideas? I figured worn rings but exhaust is clear.
Posted By: ireland383

Re: Excessive blowby out of breather... - 07/03/10 11:10 PM

Do you have a baffle in the valve cover?
Posted By: Alaskan_TA

Re: Excessive blowby out of breather... - 07/03/10 11:12 PM

Start with a compression check.
Posted By: buildanother

Re: Excessive blowby out of breather... - 07/03/10 11:20 PM

Is the vacuum source to pcv adequate? And have you tried a new pcv valve?
Posted By: topside

Re: Excessive blowby out of breather... - 07/03/10 11:22 PM

Usually starts coming out of the breathers before the exhaust.
Might need valve seals or guides, in which case some smoke out of the tailpipes on deceleration might be noticed. Smoke on acceleration is typically poor ring seal. As noted, do a compression test and a leakdown test, and besides taking the readings, listen for air coming out of the carb (intake valve) or tailpipe (exhaust valve).
Posted By: SGTFURY62

Re: Excessive blowby out of breather... - 07/03/10 11:37 PM

Quote:

Is the vacuum source to pcv adequate? And have you tried a new pcv valve?



No, but going to go and get one asap. Also, will do a compression check as when I pulled pcv out of valve cover that side too was blowing smoke.
Posted By: Crizila

Re: Excessive blowby out of breather... - 07/04/10 12:26 AM

Quote:

Is the vacuum source to pcv adequate? And have you tried a new pcv valve?

Do first. Then comp test. Then pull a valve cover and look for pieces of valve stem seal laying down in the valve spring cup area.
Posted By: dulcich

Re: Excessive blowby out of breather... - 07/04/10 12:37 AM

1. Valve guides won't cause blowby.
2. PCV valve vacuum won't do anything but suck in the blowby.
3. Compression check really won't tell you much.
4. Valve seals won't cause blowby
5. You engine is plum wore out.
6. Schooling is now completed.
-dulcich
Posted By: buildanother

Re: Excessive blowby out of breather... - 07/04/10 12:41 AM

Point #2 Exactly. Because every engine has a little blowby.
Posted By: autoxcuda

Re: Excessive blowby out of breather... - 07/04/10 04:10 AM

Quote:

1. Valve guides won't cause blowby.
2. PCV valve vacuum won't do anything but suck in the blowby.
3. Compression check really won't tell you much.
4. Valve seals won't cause blowby
5. You engine is plum wore out.
6. Schooling is now completed.
-dulcich



I just experianced the eventual fate of #5

I had noticed excessive blowby out of my breather in the Cuda about 6 month ago. Hot cranking would puff smoke before it even fired.

Motor had original 1968 pistons and bore. About 210,000 miles. I did a hone and bearing job in 1993 about 60,000 miles ago. A valve job about 30K mile ago.

Compression was good at 140 psi and even.

Motor was weak. Would not really tune right.

Then #6 rod bearing let go a couple weaks ago.
.
.
.
.
Motor was plum wore out.
Posted By: gamagoat6x6

Re: Excessive blowby out of breather... - 07/04/10 12:20 PM

I have seen the PCV hose blocked solid or collapsed internally and the passage in the carb blocked with crud. Make sure you have not only the correct vacuum reading at the valve but also lots of volume. Your engine should stall if you pull the PCV valve out of the hose. If you replace the hose don`t use fuel line as it will collapse in short order.
Posted By: Crizila

Re: Excessive blowby out of breather... - 07/04/10 05:02 PM

Quote:

I have seen the PCV hose blocked solid or collapsed internally and the passage in the carb blocked with crud. Make sure you have not only the correct vacuum reading at the valve but also lots of volume. Your engine should stall if you pull the PCV valve out of the hose. If you replace the hose don`t use fuel line as it will collapse in short order.

Check first, but dulcich's #5 is probably correct. Just a good idea to verify you don't have another simple to fix problem before you start re-ringing, etc.
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