Blow by in a '62 390

[Bob Hannon]

I have a '62 Cadillac with a 390 and 58,000 original miles. It runs as new, but has serious blow by from the breather tube by the oil pan. There is never any smoke what so ever from the tailpipe. The breather cap is perfectly clean. Is there anything I can do short of an engine rebuild to fix this problem? Thank you. Bob Hannon, member ID# 20195.

[Otto Skorzeny]

What makes you think you have a serious blow by problem? It's normal for gases to blow out of the tube, that's what it's for. It's more noticable at stop lights etc.

Keep the oil changed at 3K or sooner if you want.

Make sure your draft tube is perfectly clean and not gunked up. Oil and crud in there will make it smoke more.

You could also convert it to a PCV system.

[Dave Shepherd]

A cylinder leak down test will tell you if in fact excess pressure is geting into the crankcase, which of course is caused by worn rings/cylinder bores. As Otto says it may be normal, no way to tell from here.

[cadman59]

Before its rebuild the engine of my '59 also suffered from a badly smoking draft tube when idling (i.e. for a traffic light). It was so bad, sometimes you even got the feeling there had to be something in fire under the hood....
After the rebuild the only thing that smokes a little bit is the breather (oil filler) cap, but only after shutting off a hot engine.

Feiko

[The Tassie Devil(le)]

Excessive Blow By is caused by badly seating Compression Rings.

Draught Tubes were okay, and acceptable on dirt roads, but not these days of sealed roads.

Bruce.

[brian faull clc#25881]

If your motor is carboned up you can use a top engine cleaner to soak the cylinders to loosen up the rings. You can also run a quart of tranny fluid in your oil and the detergent will begin to clean all the built up gunk inside the motors. Alot of those older motor oils espescially quaker state which was prevelant on the east coast would leave waxy deposits inside the motor. I had the same problem with my 62. The valve covers and rocker arms were packed with a waxy oil build up. Also make sure the oil you use in the car has zinc as most companies removed the zinc additive from oil to prevent damage to the catalytic converter. However if you have an old car they require the zinc or you can start losing bearings. Good luck with that smoking locomotive. Brian.

[Guidematic]

Zinc (ZDDP) has not been eliminated, but it has been reduced.

Also, a word of caution about loosening up that gunk in your engine if indeed it is heavy. They can be released in oil passages which can actually plug them up and lead to oil starvation.

Mike

[sirjimi]

I have a 1961 Deville and have a few questions related to this posting.

1) Regarding PCV conversion - what would a ballpark cost be to pay someone to convert to PCV?  This would reduce a lot of the air that comes out of the breather cap, right?

2)re cadman59 response: My recently purchased 61 oil cap also has a little smoke wafting out of the breather (oil filler) cap - only visible after turning off a fully warmed up engine (e.g. 15 minutes of idling).  It sounds like this is perfectly normal.

On another note, my engine compartment is very clean (cleaned before it was sold), but I did noticed a slight film on the air cleaner cover - the vent of the breather cap was facing the air cleaner, so that must be the culprit.  I wiped it off with a paper towel and it was a brownish color.  Again, this is *normal*, right?  Should I expect a film in the engine compartment after normal driving over time?  I know it is probably a dumb question, but it is my first classic car so want to check with the experts.  I've never had experience with breather caps.  :-)

BTW - I did a test and wrapped a white paper towel loosely around the breather cap vent and left it on there for about 10 minutes while the car was idling (I also revved it a few times).  After the test, I didn't see anything noticeable (albiet a few specks of dirt that may have flown loose when I revver it up).  Again, this is perfectly normal, correct?

Thanks,
Jim (26013)

[Otto Skorzeny]

Hi Jim,

1. The conversion is fairly straightforward. I would not trust someone to make it up as he went along, though. What you and I might regard as a common sense approach to this conversion might not be so to someone else. Post this question on the modified forum. A regular user there recently converted his 390 and could probably post some pics and tell you what valve he used, etc.

2. It is normal for a little smoke to vent from the breather cap but make sure it's cleaned with kerosene and then lightly oiled. Also turn the cap upside down and look at it. There is a land that fits in a cast groove in the oil filler neck. A lot of people shove these on backwards. When put on correctly, it should just slip right on and off without any application of force. Make sure your draft tube is also nice and clean and not gunked up.

[sirjimi.]

Thanks for the reply Otto.  The oil cap is now on correctly.  Once I aligned the groove, the cap "vent" now points toward the radiator.  I also looked under and it appears relatively clean.  Perhaps this weekend I'll give it a cleaning per your recommendation.

Regarding the oily residue/film I noted in my engine compartment in the general area around the breather cap (not really noticeable until I wiped with a paper towel): is this to be expected over time as well?  If fumes *normally* blow through a breather cap, and those fumes are coming from a crank case full of hot oil, then it seems logical that the engine compartment will get slightly oily over time (along with all the road grime that will accumulate).  I'm just a little unsure (maybe a little paranoid  ), given that the last time I worked on an old car was a few decades ago in my high school power mechanics class - I'm quickly trying to re-learn what is normal for an old car and what things I should be concerned with.  

Thanks!
Jim

[Otto Skorzeny]

With the breather cap now facing the right way, you will probably get better crankcase ventilation. Air flows into the cap, through the engine, and out the road draft tube. When shut off, it's normal for hot air inside the engine to rise and come out the breather. Normally this won't be a lot. It shouldn't look like it's on fire or anything.

Park the car on ramps and run a bottle brush up the draft tube to see how dirty or clean it is. If it's really filthy with caked on thick grime, take it off and clean it. It's held by two bolts on the right rear of the engine.