OK - so here is the scoop on the '74 AZ car that has me about to learn new things.

This is the car that has the 2.0l case with 1.8 heads. Runs strong, good pulling power, no bad noises, and has good oil pressure. Came to me with a recently put together engine with no guarantees but believed to be redone heads and fresh bottom end. Price was right on everything so I bought it, no regrets.

The issue I am seeing is that the engine has too much blow-by. After a short time (under 30 miles) it started smoking very noticeably from the breather and blew out the oil seal on the breather tower.

Since then I've changed the oil and done more heat cycling and it's smoking significantly less (barely noticable now) but I still have too much blow-by. I don't think I have much to loose by driving it some more and seeing if the rings seat better but I am working on the expectation that isn't going to work.

Assuming the most likely case, which is that the rings don't seat any better, I believe I would need to pull the heads and pistons off and start again. Yes/no?

Should I be thinking of just replacing the jugs and pistons with a new set from AA or do these clean up (in general). I believe replacement is the usual approach these days.

I think I would plan to send the heads out for servicing as a precaution so I know I have good ones with good oil control going back on.

Assembly from this point should be pretty straight forward I'd think?

Thanks, appreciate the continuing education here.

Does the fill tower have a hose nipple on it? Where are the vapors being drawn off to?

@rhodyguy - hope you are well.

It does have a nipple on it and it vents to the carb (single Weber currently).

Well, many possibilities for too much blowby. Could be past the rings - worn, improperly seated, "clocked" incorrectly (i.e. All ring gaps line up with each other), etc. Compression and leak down test results are what?

And, since you say you have 1.8 heads and other mix and match parts (2 liter case)...do the heads have the EGR holes? If so, where did you route them? (Could block them). If done wrong, this could make a tremendous blowby problem...

Best wishes with the fix!

@tejon007 - thank you for the response. I didn’t build this engine so I don’t know if any of the internal stuff was done improperly, but I will check to see what they did with the EGR openings. I haven’t done a week down or compression test yet because I was thinking, perhaps incorrectly, that if the blow by doesn’t go away I was going to have to open everything up anyway and at that point it doesn’t really matter. I would imagine that a leak down/compression test would tell me which hole had a problem but it’s gonna have to be opened up to fix it anyway-right?

Couple thoughts:
Since you don't have history on the engine there are too many unknown variables but it might still be seating in the rings and improve with milage. It can easily take a couple thousand miles to fully break in an engine.

You say it has a single Weber carb and runs well, so the engine has much more potential since the single carb on a flat four works poorly in general, meaning with better induction it could run really well.
The long flat intake runners with the single carb promotes air fuel seperation between the carb and the heads and fuel falls out of suspension. Warm climate help keep fuel in suspension but is not enough. Commonly the single carb is set up overly rich so there is still enough fuel in suspension for the engine to run on.
One of the potential issues you maybe dealing with is too much raw fuel getting to the cylinders from an overly rich mixture to make the carb seem to work. The concern here is with the excess fuel washing oil off your cylinder walls leading to rapid piston, ring and cylinder wear.

Test, don't guess.
Do compression test AND leak down and see what is going on.
If you tear down latter you will still want to know what the compression and leak down were before you took it apart.
Nothing like guessing about issues before you reassemble.

Jim

Note: No 1.8l 914 engines have EGR ports in the heads. Late 2.0l heads have Air Injection ports but that is just the 75/76 2.0l engines.

The single Weber carb thing is never something you actually WANT on one of these cars.

Just sayin'

Not true...I had a '72 with EGR heads (from a bus). Ok, so it's not normally an issue, but he said there was an unusually large amount of blowby. Shouldn't have even mentioned it...

Mixed and matched parts from unknown motors...could have heads with EGR ports as one possibility. If so, what was done? It's anyone's guess. Inspect and as we both said, perform compression and leak down testing...

So, whatever...less guessing and more testing.

My Best

Good morning. It came like this and is not ideal but kind of a second-tier issue at this point. I have a spare set of Weber’s ear marked for when the time comes.

Thanks!

Breather set up - you can see where it blew out the cork seal. 2nd one it did that to.

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Sounds like the only "magic pill" is at minimum, a top end. Heads & rings, if you're lucky P & C kit more than likely, so add rod bearings and getting the rods rebushed.

you need to do a leak down test or otherwise this is just pissing into the wind.

Interested to find out the solution...so, please share the testing results when you have them.

It's weird that you blew out that gasket (twice) especially with the breather hose connected (and even if you're running with no vents in the heads or valve covers).

Is the breather housing restricted or plugged maybe??

Hi guys-should be able to get gauges on this car over the weekend.

@tejon007 - that is weird isn’t it, it was allowing airflow into the carb because you could see smoke coming out of the carb although that has significantly diminished the last couple times I ran it. There is still pretty good puffing coming from the oil filler cap when you remove it, it might be interesting to run it for a bit with the cap off ( with the car being stationary and making sure nothing gets into the engine via the cat being removed ) to see if that happens again.

Oil smoke from the carpet?

@rhodyguy - oops! That was supposed to say “carb”, Siri switched the word out and I didn’t catch it. Sorry!

Just had a quick chat with a well regarded engine builder, the shop who did my 2002 Tii engine, but also builds a lot of air cooled engines, and he said it almost certainly needs to come apart and it’s likely one or more broken rings. Until you open it up you never know but I’m inclined to agree with him.

@IronHillRestorations
@tejon007
@jcd914
@rhodyguy

First of all, good morning and happy Friday gentlemen.

I drove this car quite a bit yesterday and heat cycled the engine, did lots of rolling full throttle acceleration pulls and no change in the blow-by. I didn’t really expect it to suddenly improve but not much to lose by giving it another go.

Going to pull the plugs today and see if I can find out which cylinder is problematic, but the thing that has me scratching my head is that it actually runs well and has quite good power and doesn’t smoke out the tailpipe Even taking into account that this car is somewhat stripped , and is thus a bit lighter, the engine feels really healthy and strong even with the single Weber.

So with all that in mind here is the question that I was hoping to get some thoughts on-I think it’s one that’s relevant to the knowledge base here in general which is also why am asking - how can this thing be making good power if the problem is with the rings? I would have thought that if the rings are letting this much blow by happen that it would also be impacting compression to a point where the engine would be off song.

For education purposes other than rings, what internal to the engine would cause excessive crank case pressure?

The biggest concern IMHO would be a broken ring, which could score a cylinder.

Me, I'd probably try and put a couple thousand miles on it and carefully note oil consumption. If you're using more than a quart every 600 miles it's rebuild time. I have seen older engines that had been non-op for a long time improve a little over the first thousand miles or so, but not every time.

Nothing wrong with running a single Weber progressive carb...if setup correctly, they work - - ran one for about 15 years that came on the car when I bought it, ran one on a bus too. Not the problem. (But, yes fuel can wash the cylinders...)

As a poor high school/college kid many years ago, I drove a 2 liter Capri with a progressive Weber (almost identical to yours). It had a badly burnt valve for maybe 2+ yrs. Made good power ☺! When I tore it down, more than a third or close to half the valve was gone.

We don't know if it's the rings...please test the compression and perform the leak down test. This will tell you which, if any cylinder is bad...then you can figure out if the problem is the rings, valves, or something else.

Test, test, test please...it's not that much time investment and the tools required are cheap

What can cause excess pressure in the crankcase??

Worn, scored cylinders, excess cylinder to piston clearance
Rings, badly seated, excess gap, gaps lined up, broken, etc.
Pistons, bad or worn/broken ring lands
PCV system (some also advocate not venting from the cylinder heads or valve covers)
Plugged breather
The wrong type of oil or overfilling can create excess vapor in the crankcase from Windage

I had this problem recently. My car wasn't down on power either.
While the car is running remove the oil filler cap and if there's pressure there you have a cracked ring or piston. (Most likely)
I have a video of mine with is pretty dramatic. I'll try to upload it today.

https://youtu.be/AP65Q-l-jiM

Wow - that is way worse than what I’ve got. Bet that was an eye-opener the first time you did it.

Did you do a full rebuild or just the top end?

Thanks for the post in the video.

It was pretty awesome. I was behind a GTI on the track that was smoking bad. Once I passed him i first couldn't figure out why my car was still full of oil smoke. It took me to the next corner to figure out what was happening.
I'm just glad I didn't damage my Hoffmann Heads.

The pistons were about 10 years old and when I put a higher lift cam in we machined the top for valve relief. I knew i was on borrowed time.
She's great now.

Shane, Good video. I've never seen that before.

If you duct that blow by into your air cleaners, it would be like turbo charging your 914. But we all know, you can't.....

Good morning gentlemen, happy Sunday to everyone. It’s been a little bit so I thought I would update this thread.

I’ve started to dig into the bodywork on this and that has meant getting it to the workshop with the professional welding equipment. I drove it over there to save the money from trailering it and also to see if running it at highway speed‘s would help, and it appears to have done just that. I still have too much blowby but it’s definitely decreased. At this point it’s probably only got 100 miles, or even worse, on it so I’ll just keep cleaning it up and make sure it’s got good oil in it and see how it goes.

As a sidenote this 2.0 L case with 1.8 heads makes quite good power, I’d not hesitate to do a build with this set up because it feels strong even though this engine is obviously a bit off song. YMMV.

Now that the front suspension is sorted and most of the welding complete I need to figure out the oil blow by.

Compression test: cold and dry (sounds like a good adult beverage)

#1 - 128
#2 - 150
#3 - 128
#4 - 135

Cold oil pressure looks decent to me at idle and at 2,000 rpm
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get rid of the valve thing , its not venting enough...a 2.0 with that vents through the heads..
https://members.rennlist.com/pbanders/PCV.htm

Thanks for the reply. This, correct?

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Compression is a bit uneven from what most like to see but that's from a cold engine,tune it and reset the valves and then go out and give it a good hard drive,retest compression after that run,please report back if the car can be driven otherwise do another test after a full stationary warm up.

I think you need to back up and look at the external bits before you dig into the engine itself. A few things you mentioned stand out to me.

1. You mentioned you are running 1.8 heads. You didn't specify but I assume given your situation that they don't have the head vent port by the left side intake manifold stud?

2. You appear to have an earlier 1.7/2.0 oil tower and PCV valve that is vented to atmospheric pressure (air cleaner)

The crankcase vent system changed somewhat significantly between the early and late cars, and it sounds like your whole crankcase venting system is mismatched in addition to having a PCV valve that requires manifold vacuum and head vents to operate properly.

So it sounds like you essentially have very minimal crank case venting capacity, which is most likely why the engine keeps venting itself by way of the oil tower seal.



Ill give a little more background info to illustrate what i am talking about

1.7, and pre 75 2.0s use an oil tower with a small port (13mm hose) with a PCV valve (whose internal passage is closer to 8mm + restrictions from the square valve) that connects to manifold vacuum. These cars ALSO have 13mm vents in both heads that route to the flashback valve and into the air cleaner. You can read about the PCV operation here https://members.rennlist.com/pbanders/PCV.htm but the main take away of consequence here is that under high load the crankcase pressure exceeds the capacity of the PCV with the excess pressure venting via the heads (which i am assuming dont exist on your motor).

The 1.8 engines eliminated the head vents, and use a different oil tower with NO PCV valve and a MUCH larger ~22mm vent hose that routes to the air cleaner with all crankcase pressure venting unregulated through the MUCH larger oil tower vent.

So I may be wrong, but I suspect your issue is probably related to the inability to vent what pressure you do have more so than something mechanical causing to much pressure to be generated.

Swap out the oil tower for one from a 1.8 or 75+ 2.0 and see what happens.

Fix vent issues, all numbers will improve....Ferrari tune up....will seat and clean up improve compression....Short and sweet...

Either one of these is what you are looking for

1.8
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Late 2.0
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@JamesM - thanks for the follow-up. I think I have the later style, will have to double check.

This looks like the right heather setup (putting aside if the PCV is blocked shut for a second), yes?
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Tube from the breather goes to the carburetor now. I checked the PCV valve by seeing if I could get air movement from the breather tube and I can. In other words the PCV allows air flow up from the breather and out.

Do I just need to route the breather exit tube to a EMPI breather box or oil catch can and drive it for a while and see what happens?

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Plug #3 was oily, think I found the culprit.

So - unless someone has more clever ideas (likely, since I am a bit of a dolt) I can;

#1) connected a breather box/oil catch can and run it as-is and see if it gets better

or

#2) drop the engine and take the top end apart looking at the pistons/jugs/rings to see what when wrong.

Seems like #1 is very likely kicking the can down the road. Given that the oil pressure looks good it seems like I've got a good bottom end (insert jokes here:________) to work with and should just plan on new cylinders/pistons/rings. Not that hard to do based on what I learned from taking apart the 2.7L engine build.

Sound right?

Thanks!

No, thats the wrong (early) setup. The port on either of the ones you will need is about 4x that size area wise. Removing the PCV valve and replacing it with just a barb might help a little, but there was a reason VW/Porsche massively increased the oil tower vent size when they removed the head vents.

I have spares of both out in the garage, ill see if i can get a direct shot of the ports side by side to illustrate.

Ah - thanks, didn’t see the size difference. Thanks for the dope slap.

Picture for size comparison.

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Good morning @JamesM , that makes it clear. That is a very significant difference in size.

I’ve got oil fouling on a plug so I think this engine has to come out in the top and get inspected and likely replaced.

I will make sure to track down a correct larger size breather.

Thank you for your responses and coaching.

Good morning gentlemen. Picked up a proper 2.0 L breather, it’s on the car and I’m gonna run it tomorrow but given that I’ve got one cylinder that clearly indicates that I’m burning oil (but only one) at some point the top and needs to be redone.

For planning purposes if I’ve got good cold and hot oil pressure and the bottom end appears healthy I believe standard practices to just leave the bottom end as it is in overall the Pistons/drugs/heads. I believe that’s conventional wisdom on the bottom as being pretty tough, but just wanted to triple check.

Thanks and happy Saturday morning.

Leakdown Gauge.

You have to see if its valves or rings .......or just buy new pistons and cylinders and heads from Len at HAM

Leakdown test.

I had this happen on a car before. If I recall correctly, it is not smoking when it is cold but when it gets hot. That leads me to believe the leak down test is going to point to faulty valve guides or a bad guide somewhere. It is the most overlooked piece and if the wrong guide was used, or they skipped it during the "rebuild" then that is a likely cause.

Thanks gentlemen