Manifold drains

[Richard]

Just noticed that the intake side of the 360's have a hole in the cylinder! That's where that excess fuel comes from. Wait a minute. That sucker is open to the world! Does air suck up into the intake from those lines? If so, why didn't they put a one way valve on the thing so you don't get nice unfiltered air into your engine? In automotive this would be considered an intake leak that causes rough idle. Maybe I'm mixed up. We didn't see any one way valves on the thing.


Richard

[GMAs]

Ahhhh... someone looked into the intake hole... yep indeed they are open...have to be to get rid of the excess fuel that you pump in when you boost the engines too long... and keeps you from haveing a hydralic locking problem breaking the rings...

No as to the air getting in... naw.. not that much.. see you have this long pipe attached to it that runs all the way from here down to their.. and with the small inside dia... not much air is going to be flowing in thru it... besides you don't have that much pressure differental once your up and flying.... to pull anything in with... as the throttle valve is wide open.. thus the pressure goes to zero at that point.. only the valve in the head and the piston on the other side are pulling air thru....

Now your right at idle you are pulling a little air thru.. but, the injector is setting right over the top of it... so that any air coming in is mixed with fuel.... and thus enriched.... again because of the small hole in the tube and its length... no valve is needed because of the natural restriction of the fittings and tubing...

Most of the dirt is flushed out of the end of the tube when you go to start up the engine... and this amounts to anyting that may have made it up a small way... however when you shut the engine down after idleing in... you will find some traces of oil coming out of them... its natural for this to happen...

Here is why

When you look at the head assembly.. you will see that the intake valve has two area that have access to the stem... one is up in the rocker arm cover area... the other in the intake area of the intake pocket... where this hole is... located on the bottom and the injector on the top... looking right at the intake valve backside...

So what happens... well when you are flying the pressure inside the crankcase and the intake pocket area... is pretty much the same.. just a little difference... and as such the oil that is being pumped up to the rocker arm... is splashed around on the intake valve stem under the return spring... this oil is being sucked into the guide along the shaft so it can lube the thing...

But, when you pull the throttle back.. the intake MP goes down... and here is where we really see the overboard vent line actually fighting the air that is trying to come in vs. the oil that is trying to get out... why... well because when you pulled the throttle back.. and the MP went down you changed the pressures.. the crankcase/rocker arm pocket area.. now has atmo... the other side of the intake valve guide is seeing about 1/2 to 1/5 of the pressure... so it starts to suck oil thru the guide and into the intake pocket area in the head...

Now what are we going to do with all this excess oil... by the way it is the major leading cause of oil consumption in the engine... and as the engine gets older.. the consumption goes up because the intake valve guide is wearing out larger and larger... Well it falls down to the bottom of the intake pocket.. where the vent hole is located... now if you have oil trying to get out.. and air trying to get in... which one do you think is heaver.... and has its way.... Hmmmmm you have 10 seconds to weight the problem.... times up... if you said the oil going out.. your right... thus it really seals the air trying to get in out while your on the ground...

How much oil... well we have taken engines intake manafolds appart... after they came in the shop.. and poured...yep poured oil of of the pipes... so that oil that is what you thought going past the rings... well not so... its being sucked into the engine at idle and burnt... but.....

It doesn't happen in flight... because their is not as much differental pressure....and the oil stays where it should and the air stays where it should because we are moving so much more thru the intake manafold when we are flying... at a high MP pressure... so no harm is done...

Ahhhh but, Dave over their said.. ya but..... what about the new cyc... ahhhhhh yes .. well several years ago.. we had a gent who on landing would kill his engines with oil.. when he slamed the throttles back... real rough kinda guy... yep they would foul out the plugs... it was a high time engien with real worn intake guides... and he couldn't get them started again... he would suck in about a quart of oil... on landing... we brought this to cont attention... and they went to work on the problem... and helped us out by cutting the intake guide under the valve spring... and putting a intake guide seal on it... they also went back to the bronze guides.. which while they wear out quicker... still gave a good service life over the steel ones... Ahhh here oil consumption went to almost a quart in 25 hrs... no more oil fouled spark plugs and life was good again under the cowling... but, the TBO life of the engine went back down to 1400-1600 hrs... so you gave some to get something back... low oil consumption... no fouled spark plugs... and a engine that idled much better.... or did it... well that became the next topic.. and some fuel injector system changes had to be changed... in the older systems... no more idle mix screws... and a richer mixture on the bottom side... with leaner on the top of the curve... minor things...

Anyway...now you see what the little hole in the bottom of the intake pocket was for...

Oh.. and yes the new cyc come with the intake guide seals standard... see they did improve them over the years...

Question" can my old engines have the seals put in... if I don't have them...

Answer... yes it can be done right on the engine without taking it out... they make a tool that they will rent/loan you.. it goes in a drill... you have to be careful that you don't drop the valve all the way into the engine.. but,you can remove the valve rotator and springs... and carefully pushing the valve into the cyc with the piston down... part way... get engough room to put the cutter bushing into the guide... and make the cut.... then when you finish you put the new seal on the guide... by the way.. they are the same ones that fit the ford pinto... intake valve ... smile... hey it was convient.. and they were cheep... did I tell you we have a pinto wagon ... yep it was the loaner... and not too many people really used it when we had it... smile.. wonder why...

Well hope that this lecture helps you understand the hole at the bottom thing.... smile..

by the way if you want to learn more... besides asking me... here is a good manual by one of the experts in the field... John is a great engine man... and has written a few books on the subject... they used to be one of the biggest shops for repairs in the valley here... their address is... check it out

http://www.avweb.com/sponsors/skyranch/engintoc.html


OH AND DON'T START READING THIS BOOK AT BED TIME... ELSE YOU WON'T BE GETTING A GOOD NIGHTS SLEEP... AND WILL HAVE NIGHTMARES... ABOUT YOUR ENGINE PROBLEMS THAT COULD OCCUR..... SMILE...
GMAs

[Richard]

Once again some wonderful information. I'm learning alot about things just reading. Love it.

Even though I do fly and love it. I still am frightened by flying. I'm working on the problem. Part of it is learning as much as possible about the power plants so that it all makes sence. I'm working with the AP and IA that are working on my plane. I probably drive them nuts. I respect the AP's out there alot more by doing so.

GMAs, you have been a wonderful contributor to this and other sites. Thanks again. If you need anything in the computer world, I'm your man.

[Richard]

Ordered the books. Thanks for the link.