Dynoday ended with enginevomit...

[falcor]

Took my 914 (2.0) to the dyno today to get the EFI system tuned.
We let it warm up and did a few soft pulls up to 3000 rpm ish to le the guy ding the tuning get a feel for it.
Then he did a couple of pulls up to around 5000 rpm and on the last one there was a nasty mechincal noise and just after that I noticed that it was dripping oil from the righthand side of the engine. We shut it down and that was the end of my dynoday, put it back on the trailer and drove the 3 hours home.

Once home I started it up and it didnt leak a drop, and no noises. I just put it into the garage and put it up on jackstands. From what I can see it seems like the cylinder 3-4 valve cover puked the oil. I was using the upgrades hi temp silicone seals from 914 rubber but I think i'll go back to the regular cork gaskets.

What could cause the valve cover to puke oil like that, pressure buildup in the rocker area? My heads has the vent tubes but they're capped off.

Gratefull for any ideas that can get me towards a solution.

[Piledriver]

New engine, rings not seated yet can have a lot of blowby.
You can vent the 1/2 side, it won't fill up with oil like 3/4 side will at cruise RPM due to windage.
Windage assists oil return from 1/2 side.

Its also possible that valve cover wasn't initially quite seated, and its just residual oil.
It can also have a leak at the top, so its only apparent under high load/RPM due to case pressure.

AMC heads usually require a little... massaging of the valve covers lip or the OD of the rocker box seal surface so it can seat fully.
(may take repeated attempts, prussian blue (machinists bluing) can help to see if its fully seated)

I severely doubt blowby in ~any volume will cause "a nasty mechanical noise" unless it was just case pressure unseating the valve cover, but that would just sound like a pressure release, not anything mechanical.
Further investigation absolutely required.

The silicone valve cover seals are not even a potential problem... unless they got sucked in.
They have to be prepped just right then glued in.
They may have had residual mold release, and didn't stick under pressure.

[falcor]

Engine wasnt newly rebuilt but I'd never driven it hard before so I dont know the full history of it.

Nah, was a bit more that residual oil, was a puddle about 12 inches big.

You can hear the noise and see the start of the leakage in this videoclip:

https://www.dropbox.com/s/5y7zk76e135g0 ... 2.m2t?dl=0

Let me know if it doesnt work.

[Marc]

Sound's not very good on my notebook, but I think I'm hearing the onset of valve float. Valve springs may be too weak...did you get a printout on that run showing what the RPM was when power fell off?

It's natural for rockerbox pressures to build at high RPM due to the volume of crankcase gases pumping back & forth as the piston pairs go in & out - a significant part of that exchange takes place via the pushrod tubes and the resultant pressure pulses tax the VC gasket and bale's ability to keep the oil in. As Piledriver points out, crankcase windage tends to push more oil up on the 3/4 side than can drain down against the rush of "air" pulsing through the tubes so there's more oil to leak there than on the 1/2 side. In everyday driving you seldom hold the RPM that high for long so it may not be an issue, but I'd put a breather box on it if I was going to drive it with enthusiasm. Even just cross-connecting the heads with no opening to atmosphere should help some too (that's standard practice on circle-track V8s for similar reasons).

[Steve Arndt]

Check that all your valves and retainers are level across the board. Check for a broken valve spring.

[falcor]

Thanks for the ideas guys. The engine was rebuilt in 2001 way before I bought the car but hasnt been driven much since. At least not acccording to the odometer. I did a valve adjustment just last weekend as preparation for the dyno so everything should be ok. But I'll recheck all the valves and springs again.

I dont have the printout of the last pull but i'll try to get it. It did make 85 whp at about 4700 rpm if I remember right.

[Marc]

Typically at the onset of spring surge the power curve will get "jumpy", following a generally level or decreasing slope, and the A/F ratio will suddenly go rich. All springs have harmonic points, certain RPMs where they lose strength; dual springs are more desirable than singles in this regard because the harmonic points of the inners & outers come at different RPM, allowing one to "cover" for the other enough to make it past a harmonic point. Inners, being made of smaller wire as a rule, are more prone to breakage and once they go and you're left with only the outer in play, float will be more likely to occur. Another clue is the wear pattern on the end of the valve, because when the springs start surging they also rotate more - you may be able to see asterisk-like wear on the tip.

While you're looking at things also see if there's any discernible difference in the amount of valve stem projecting past the keepers. That could just be the result of trimming the tips to even out the installed lengths after the valve job was done, but it could also indicate that the keeper grooves are getting worn wider - that could eventually result in them failing completely and a dropped valve.

[Piledriver]

Valve float definitely makes funny mechanical noises, esp in a shop, with walls bouncing the noise around..
What ^^^they said...

The "plug 3/4 vent' prevents the rocker box from filling up with oil at highway cruse RPM, which is also where you will run it RPM wise in lower gears if you are even mildly in a hurry..
As opposed to a T1, a T4 has enough oil to ignore that, but it just sits in the head and cooks to no gain.
Better off in the sump, the ex valve stem leakage pressure will push it back down.
(There are other methods)

The valve springs and keepers should be replaced with CrMo keepers (ground a bit so they clamp/don't touch on both sides of the stem) CrMo retainers as the facotry units totally suck and have been know to pull through on stockers
This can be done in place with a air compressor>spark plug adapter (like for leak down testing) and a common spring compressor you can probably rent.
On a 914 it MIGHT be easier to drop the motor/trans a few inches for better access, doesn't need to be much, you may get away w/o disconnecting everything, shift linkage at a minimum.

Carefully eyeball all the linkage bushings, while at it, my LE was parked by the PO 20+ years earlier due to a "bad trans" diagnosis from a known unethical shop that was probably going to silently install $20 worth of bushings (at the time) and probably fake the rebuild of the perfectly good transmission at Porsche rates If lucky.

...Physically inspect. Pull the rockers for a good look at stuff...
You should be able to stick a metal rule across the valve tips with almost zero daylight between them on a fresh or very low mile build, at least if the head guy was worth the title.

This checks for multiple issues... Bent valves, stretched valves, sunken seats...
(Note that all of which Hydraulic lifters will "hide" until you suck an exhaust valve, which is ~universally fatal to the engine)
Over time the exhausts stems stretch. Period.

They should be replaced at intervals depending on usage, maybe 50-75K pushing a bay bus, a 914 can go a lot longer if driven by Grandma on Sundays, as long as she doesn't run AX for a hobby.
You are usually better off with a valve job freshen up at ~50-75K anyway, plus new crank seals etc.
(OE//Dealer part is best for those, and sometimes cheaper)

Compression check, Also to check for bent valves and a baseline if you don't have it...
Plugs all out, injector fuse pulled, TB wired at WOT if needed.
you should be able to "rent" a tester at any FLAPS.

[falcor]

Pulled the plugs and they look ok to me.

https://www.dropbox.com/s/bu05qkitwwhod ... 0.jpg?dl=0
Cylinder 1 to the left and 4 to the right.

Did a compression test and got some varying results: 8,5/10/8/10,5.
Average value of 9,25 +/- 10% on that would give the range 8,3-10,2 so slightly outside of a 10% variation.

[Piledriver]

Pulled the plugs and they look ok to me.

https://www.dropbox.com/s/bu05qkitwwhod ... 0.jpg?dl=0
Cylinder 1 to the left and 4 to the right.

Did a compression test and got some varying results: 8,5/10/8/10,5.
Average value of 9,25 +/- 10% on that would give the range 8,3-10,2 so slightly outside of a 10% variation.

Unfortunately you cannot tell anything from new plugs, and with modern fuel blends reading plugs... You might as well tune via reading tea leaves vs. reading plugs these days.
A WBO2 setup is the only sane way.

10 bar (145 PSI) is excellent.
(if really stock you might consider curing that serious suck issue, it cooks heads on anything but a 1.7)

If it has been sitting a long time there will likely be at least that range of imbalance even if all new.
We're mostly looking for a >30% or such low hole. (i.e. bent or burnt valve)

You probably just need new valve springs etc, the PO may have used 40 year old 400K mile stockers.

You might also consider popping off the heads and giving them a stern eyeball RSN, if not RFN.
If one side is low that head may be flycut different... Imbalanced compression sucks.

[falcor]

Thanks Pile, I'm just trying to offer as much info as possible now so you guys with more experience may catch on something that I havn't noticed that might explain the problem.

[raygreenwood]

You note that this is a 2.0.....and that its injected?

What EFI system?

Also...do you have the original rocker box tubes hooked up with the stock D-jet PCV system? If not...hook it back up. There is virtually nothing out there that beats it for PCV and oil baffleing ...you should have "0" pressure build up in the case with the stock PCV system.

Also....check your pushrods for straightness and flatness...and check the pushrod retainer wires. And most important....check your valve covers for marks from the adjusting screws.

What I saw and heard in the video....is the exact symptom of what happens when a pushrod nearly falls out of the rocker arm cup....or when a pushrod is almost arrested early in its stroke due to an adjusting screw hammering on the valve cover. This can also cause the cover to leak if it hits hard enough....
....a short, sharp, "clank/pop"...hard to explain. If its the pushrod trying to pop out of the cup....it does not always bend the pushrod a noticeable amount...but usually happens as others have noted.....with either valve float and is exacerbated by excessive geometry issues, aftermarket pushrods whose ball end and shoulder is not quite right for the cup....etc.

It can also happen from stiffer than stock springs and using pushrods that are not stiff enough. You can get an oh so subtle flex as the pushrod loads up and at just the right angle it slips 50% out of the cup. the positioning of the pushrod safety wires is critical. They cannot touch but should be very close....if they are to work in a situation like this. Look for telltale marks from the wires on the pushrods.

I wasted an engine in Dallas with pushrods that were too flexible. Ray

[falcor]

The efi is a Maxxecu, like MS but with a few more bells and whistles amd in a neater package (no relay board)
I've got nothing Djet left on the engine. Dont have the parts left either.

Retainer wires are all in place, no marks on the valvecovers, valve adjustment within spec.
I'll pull the valve covers again to take a few pictures and post up.

[raygreenwood]

The efi is a Maxxecu, like MS but with a few more bells and whistles amd in a neater package (no relay board)
I've got nothing Djet left on the engine. Dont have the parts left either.

Retainer wires are all in place, no marks on the valvecovers, valve adjustment within spec.
I'll pull the valve covers again to take a few pictures and post up.

OK...so what is your current method of crankcase venting?

Unless there was something mechanical that displaced a valve cover...rocker hitting it etc...then the ONLY reasonable suspect is internal case pressure....either blow by ...or oil. Though windage can push oil into the rocker boxes I have NEVER seen it happen with enough pressure to displace a valve cover.

As I noted...the stock PCV system that 411, 412 and 914 cars with D-jet came with....I have not seen an equal to except with exhaust vacuum scavenging systems. 99% of all type 4 owners do not study or understand the stock system ...and remove it because they assume its JUST a smog device cluttering up their engine bay.

The stock PCV system does not actually vent the rocker boxes at all.
It vents INTO the rocker boxes....with clean filtered, cool air...and PULLS that fresh air through the rocker boxes, through the pushrod tubes (pushing oil out of the rocker boxes), through the engine case...taking gasses with it....using manifold vacuum,,,through a fairly excellently designed oil baffle under the oil chimney...through an orifice ...into direct manifold vacuum.

I would reinstall the stock PCV system. If your head has the tubes....it should be about 2 hours work...and plumbs straight into the balance pipe (if you have ITB's) with a 2-3mm restriction in the hose....or straight into the plenum if you have a plenum. Ray

[falcor]

At the time of the incident I only had a single line from the port on the oil filler box to the drivers side air filter.
I had read somewhere that Jake Raby and someone else had done tests and found the vents on the rockers wasnt needed so I simply plugged them up. Obviously this wasnt a good choice so I'll hook some sort of system up again.
With that I'm hoping the leakage should be solved. Right now I'm chasing the source of the sound.