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Discussion Starter · #1 ·
We recently purchased a 1974 Manta with the 1900 engine, Weber carb, and automatic transmission. It blows lots of oil up into the air cleaner from the valve cover. I confirmed that the small hose from the valve cover to the intake orifice ("PCV") is not blocked at either end. The oil blows up the larger hose from the valve cover to the air cleaner. Through the hole in the valve cover I can see the sheet metal deflector but no "mist screen".

I took it to a local mechanic and had a compression check and the cylinders are 125/120/125/120. What should they be? Is this compression acceptable enough to eliminate the rings?

I am assuming at this point that the valve guides and/or seals are leaking and a valve job is in order.
 

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The compression sounds fine. I would try something before I looked at the head seals. What I have done in the past was put a small bit of medical gauze in the end of that tube. I also put a piece of heavy screen on either side to be sure it didn't go anywhere. Also make sure that your tubing rises coming out of the valve cover. What this does is let the oil collect and return instead of being pushed into the carb.
 

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Let me ask this, can you feel or see any pressure from the PVC tubes? You might have some blockage in the oil drain holes from the valve train area. What was your mech's opinion?
 

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Andy's 74 said:
.... Through the hole in the valve cover I can see the sheet metal deflector but no "mist screen".
If that mesh screen is missing oil mist could be pulled directly into the air cleaner. There's a post in here about using a stainless steel wool pad as a replacement. If I remember correctly, you should not use regular steel wool.
 

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Discussion Starter · #5 ·
Thanks for the ideas. After we bought it and drove it a little while we discovered that the air cleaner was saturated with oil. That's what I mean by MAJOR oil in the air cleaner. It's seems to be alot more than what a screen would prevent.

As "nobody" suggested it could have been a droopy tube. To eliminate future air cleaner problems I installed a small air breather right at the valve cover (see picture). But in just ten miles I could smell oil. Inspection showed that the filter was wet (it used to be blue not grey) and oil was dripping a puddle on the top of the valve cover.

As "Old Hippie" suggested I wondered about the drain holes being slow to drain and too much oil stayed on top. I'm not sure that he did a differential type of check to test the block as well as the cylinders. The receipt suggested valve guides but was vauge. I need to call him. Something has gotta be blowing it out. It can't be sucking it to the air cleaner 'cause I removed that hose.

I'm still open to more ideas before I pick up a wrench. Thanks.
 

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Looking at your picture and is that a pcv valve between the cover and the breather? Is this a manta or wagon? On a GT it has a filter element in the cover itself. I am not sure what is in that steel cover but with no pcv valve that is your problem. On one of my GT's the PO had removed the filter element and had put a similar breather on it. It smoked like it was on fire and the motor was like new. Before it gets to that breather or the other line there needs to be a filter type of element that catches the oil and allows it to drain back down. Some of you guys with experience on those steel covers might have an idea what is missing. Or do this for a trick, loop your lines up and in a circle before the air filter.

I just looked in mine and what it has are baffles before it gets to the holes. Inside the baffles are scouring pads, like for dishes or at least thats what it looks like. It is stock and it is steel. Magnet proves that. Something is missing in that valve cover of yours.
 

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welded

The stock Opel valve covers have an internal "chamber," if you will, in the top of the valve cover. This chamber has a couple of mesh filters that are little more than scrubbing pads to trap the oil and let it drain back into the motor. Unfortunatly, unlike the GT aluminum valve cover, the steel valve cover has the chamber welded in to the top of the valve cover so it is very hard to take apart.

That said, if the wire mesh is missing you probably would be best served finding a different valve cover.

Unfortunatly, it doesn't end there, though. your compression readings would be great on an American V-8, but on an Opel they are on the very low side. Fire the motor up with the oil filler cap removed and place your hand over the hole. There should be very little pressure in the motor, especially at idle. I'll bet if you compare the breeze coming out to the one coming out the tail pipe you'll find them uncomfortably similar. If the pressure in the crankcase is signifigant, there is no good option other than rebuilding the motor.

As a stop-gap measure you could hook a hose to the breather long enough to run to a catch can of some sorts, but you would need to remember to checkthe oil level fairly often.
 

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Re: compression check

Andy's 74 said:
We recently purchased a 1974 Manta with the 1900 engine, . . .

I took it to a local mechanic and had a compression check and the cylinders are 125/120/125/120. What should they be? Is this compression acceptable enough to eliminate the rings?

. . . .
That's about right for your "low compression" (dished pistons) engine and indicates that the rings and valves/seats are in good shape. :)
 

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Discussion Starter · #9 ·
Thanks again for the info guys. I went out and removed the oil filler cap and checked the pressure at idle. Bummer. It's blowing thru the valve cover oil filler hole like my tailpipe. With that much pressure it may very well be the rings and not the valve guides and seals.

I'm disappointed in myself for not catching this before we bought the car. Pulling the head is not the end of the world but I really did not want to pull out and rebuild the motor. I bought this car for my teen age son. It looks like he's going to learn about car repairs quicker than he thought. Either that or it's time to bail out. This car is the 29 year one-owner Manta from California that Bret Brummitt bought back in the summer of 2003 and had it shipped to the Dallas/Ft. Worth area. We are not emotionally attached to the car yet if anybody is interested......
 

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time for a little more R&D

Before you give up on the car, how about some more simple tests to further isolate the problem? Nothing too difficult or expensive here, and all well worth learning to do to any used car you might buy in the future. The following are the things I like to check when I invest in a used car:

1- Blow-by: pretty self-explanitory, and free. Remove the oil filler cap while the motor is running to check crankcase pressure. My cutoff point is less breeze out the cap than the amount of air you would get across your hand in front of your face from a sigh out your nose.

2- Compression: again, pretty self explanitory. Sears sells a nice compression tester for @$25 that includes various attachments that screw in in place of the spark plug that the guage then hooks on to with an air hose type of fitting. It is very easy to use, and a solid investment. In a reasonably stock motor, <90# is bad, 90-110# or so is not so good, 110-125# might be OK, 125-140# is good, >140# is super. There are a lot of variables here, though, and those are ust my #'s. Also, the values should be 5-10% of each other.

3- Compression "super test": This is taking the compression test to the next level, and needs a little explaination.
-First step- regular compression test, repeated at least twice with both sets of #'s recorded for consistancy.
-Second step- repeat compression test, but with 1 tbs of oil added to each cylinder before the test through the spark plug hole, and at least one full engine revolution to spread the oil around before the compression checker is hooked back up. This small ammount of oil on top of the rings will temporarily help them seal and will affect a change in the #'s most if the low compression was due to ring leakage. I have seen a cylinder go from 15# to 145# on this step.
-Third step- run the motor to burn off that oil and get you back to initial baseline conditions.
-Fourth step- leak-down test. A real leak-down tester can be rather expensive, but if you got the recommended compression tester you can build your own for $25 or so at your local hardware store. You need to go buy a matching air hose-type female fitting to go onto the compression tester screw-in adapters, a pressure guage (0-150#, or so), another male and female air hose fitting, and a tee fitting. The female fitting for the screw-in adapter, the guage, and the other female fitting all need to screw into the tee fitting. the remaining male fitting needs to get connected to an air compressor, or even a good bike pump if that's all you've got. Put the cylinder at TDC, or if that's too hard to find you can loosen the rocker arms for the same effect. The valves both need to be shut, though, for the next part. The adapter gets screwed in to the spark plug hole, the new rig you made gets connected to it, the air pressure source hooked-up, and pressure in the cylinder raised to 125-175#. Uncouple the air pressure source, and record the reading on the guage. Walk away for a while, 15 min or so, and record the guage reading. If everything were perfect, it would hold pressure almost forever, but in real life 75% after couple of hours would probably be OK. If it goes away quickly, time for step 5.
-Fifth step- isolation of that lost compression. Now you will need an air compressor, and that rig you just built, but this time you are going to leave the compressor hooked up to the cylinder. There are only 3 places the air in the cylinder can go, right? Intake, exhaust, and past the piston. Is the air you're pumping in coming out the top of the carb, the tail pipe, or the oil filler cap? In a running engine exhaust could also be getting past the valve stem and into the crankcase, so that *could* be the issue too, but not when the valves are supposed to be shut.

By now you should be able to tell for sure where your blowby is coming from, and have a pretty good feel for the overall condition of the motor. If it's a valve issue, not a huge deal, but rings might make the project get a lot more difficult pretty quick. At least you'll know what's going on.
 

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Re: Compression check - flat top piston vs. dished

oldopelguy said:
Before you give up on the car, how about some . . . things I like to check when I invest in a used car:

1- . . . .

2- Compression: . . . . In a reasonably stock motor, <90# is bad, 90-110# or so is not so good, 110-125# might be OK, 125-140# is good, >140# is super. There are a lot of variables here, though, and those are ust my #'s. Also, the values should be 5-10% of each other.

3- . . . .
Your scale is pretty accurate for a pretty stock HC (flat top pistons) engine, but you're only going to see a maximum of about 125# on a freshly rebuilt LC (dished pistons) engine, like the one we're talking about here. Otherwise there wouldn't be any point to raising the CR of an engine.

;)
 

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I'm with Otto on this, as I've never seen any higher than 125, and most Low compression late model motors I've tested were always between 112-120+ range.

Dick and Andy,
If you have time, drop it back by. I want to yank the valve cover off and see it and watch it. I feel pretty dumb not noticing the oil in the air cleaner and wondering why it was running a little rougher after a highway drive.
Plus worst case scenario, I've got all the gaskets here if we need to dig in further.

And if you get too fed up with it, I kinda need a second car again, so I'll take it back.

Bret
 

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Discussion Starter · #13 ·
Thank you Bret. That is very generous to offer to take the car back. I was not looking for that when I mentioned your name and where the car came from. I was more like fishing for public interest in the car if we decided to sell. I won't give up on the car just yet. I have already purchased the gasket kit for the head job.

Thank you Stephen. This is what I expected from the mechanic but since I asked for a compression test I did not get the "super test" portion. I think that I did not communicate to him very well. A guy at work recently explained this same process to me and called it a differential test . I got a new Craftsman catalog in the mail last week. I could have bought a compression test tool for what I paid for the trip to the mechanic. I usually consider that to justify the purchase of a tool vs. letting someone else do the work. But, I was also looking for a different set of eyes.

It's time for a trip to Sears and the hardware store. Thank you all very much for the explanation and the motivation. I'll let you know what I find out but be aware that it may be a week or more. I've got a lot on my plate right now.
 

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bret brummitt said:
I'm with Otto on this, as I've never seen any higher than 125, and most Low compression late model motors I've tested were always between 112-120+ range.

Dick and Andy,
If you have time, drop it back by. I want to yank the valve cover off and see it and watch it. I feel pretty dumb not noticing the oil in the air cleaner and wondering why it was running a little rougher after a highway drive.
Plus worst case scenario, I've got all the gaskets here if we need to dig in further.

And if you get too fed up with it, I kinda need a second car again, so I'll take it back.

Bret
First, is the car still stock with Solex and points?

Especially if you still have the Solex, THAT may be due to the oil being sucked down the carb throat and clogging those tiny air correction holes in the copper seals at the top of the emulsifier tube passages.

If you still have points and get over-enthusiastic oiling the distributor cam, it may sling off excess oil onto the points causing misfires and rough running. Check it in any case.

:(
 

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dist

High crankcase pressures can also push oil vapor out along the distributor shaft, where it gets inside the cap and gets carbonized by the sparking in there. It also tends to force oil past the seal at the base of the fuel pump, which is one of the classic first leak spots for most of our motors.

Sorry guys if my #'s were off, I haven't owned a Manta in over 8 years, since my now ex-wife made me sell all my Opels 'cause she didn't want to pay for the registrations. I should have known then that if you have to choose between your wife and your Opel remember that the car can't write it's own checks.
 

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Stuck Rings

If the car is lower milage and has been sitting a while before you got it then 10 to 1 the oil rings are gummed up and full of nasty white stuff (aluminium corrosion). Get some upper cylinder lube into the cylinders ( "Redex" if available or even penetrating oil)

Give the car a good hot run and change the oil and filter after you get back to remove any contaminants.

It is sometimes amazing how well cars that have been off the road for a while respond to a bit of hard driving and a flush out.

Years of experience resurrecting old flathead V8s and Studebakers from under hedges:D
 

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Actually its not that I'm offering since you mentioned me, My finances are a little better now and I want the car back.

You need to check with me as I have several head sets and other gaskets over here in a box that I keep for my Gt which are the same for the manta as I randomly pick up Beck-Arnley discontinued Opel lots. That way you can dig in and not have to worry about waiting on shipping since you're close-by.
 

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Discussion Starter · #18 ·
I pulled the valve cover for inspection and cleaning. I ran the motor breifly with the valve cover off and I could feel pressure coming up from the block past the timing chain but it did not feel excessive. The pressure with the valve cover on and through the oil filler hole may feel excessive because the mist screens are satuarated with oil and not letting air get through. I soaked and cleaned up the mist screen that is embedded in to the top/inside of the valve cover to ensure ventilation.

The top of the head looked good without any build up of gunk.
I found an interesting home made looking rolled up sheet metal "tube" in the drain hole. I talked email to Bret and he talked about a cast iron insert that's available for a "bath type" cam. Attached is a picture of the head drain hole.


Does the Manta 1900 engine need or require this type of insert? I am hoping that the extra oil being retained on the head is causing the oil to get blown out the top through the ventilation system.

Any more comments and ideas out there before I button it up (without the tube) and try it again?
 

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I Think You Have it...

I recall a thread some time ago when this was discussed. The drain hole outlet was raised to hold oil in the cam chamber, and it was to aid in valve train oiling. I believe RallyBob (aka Bob Legere) suggested this modification, but you would have to ask Brett if that is the case. I think that Brett (like most folks on this site, and even around the Opel World), hangs on most of what Bob says. Perhaps the outlet tube is too tall, and you are getting excessive oil spray when the cam beats the oil like an egg beater. RallyBob sometimes lurks around here (and I will send him a note if he doesn't see this particular thread), so if I can, I will get his input. I was having trouble figuring out from your photo where the tube was, so I took a photo from a different angle. Here it is (to the right of the head bolt hole):
 

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