When I got my '85 with a swapped 3.4L pr engine it had an oil leak. I replaced the distributor O-Ring seal and reseated the unbolted dipstick tube. I thought I had fixed the oil leak. I've been working on it for a while now without driving it and today I drove it quite a bit.

There is a severe lack of power and high oil pressure. I watched my oil fill plug shoot up 10 feet in the air while I was accelerating, and the distributor is leaking again. I double checked the distributor o-ring seal and it is still in good shape.

I have a set of chrome Edelbrock valve covers that do not use the stock oil cap, but a rubber based push-in type plug. That is why it was able to shoot up in the air.

What would cause so much pressure to be built up like that?

Also, I have replaced my PCV valve with a vented oil catch can.

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Club Redline - Northern Minnesota Sport and Modified

Never heard of that happening, but I would remove the oil filter and see if its plugged, but for teh most part to see what it trapped in it (large metal shavings) Other than that I have no idea what could have caused such a spike in pressure.

PCV valve needs to be hooked to vacume if not it wont open and take any blow by out of the engine then prsure builds and there go's somthing poping

The PCV valve is gone and replaced with an oil catch can sort of like this one:


The vent tube goes in and then through the can, and into the air intake pipe. I don't think there's much vacuum on it like if it was off the manifold, but if there is any pressure, it should be vented just fine.

with a catch can, which is unrestricted venting (mostly) to blow the filler off, you have to have a case fo extreme blow by. (rings/piston clearance issue) you need to first do a comp test and leak down test. then I would rig a vac guage to the fill fitting, a rubber stopper with a tube thru it to the guage. most vac guages will show low pressure. blip the throttle, if you see any pressure build up, or it pins the guage, you most definately have a problem with at least one cylinder ring seal.
sometimes you can isolate the cylinder by removing the plug wire and watching the guage pulse. the ignition stroke and firing is what usually blasts the pressuer into the crankcase.
typical causes are cracked rings, carbonized and frozen rings. worst cast is a small hole/crack in the piston (detonation can blow a small hole thru)
good luck!

I had the rubber plug on a Chevy 4wd Blazer blow out once on a long steep grade in low-low. All I could see was hood at the time so didn’t know what happened at first. Walked back down the road to look for debris (from the loud bang) and found the rubber plug. Never had it happen again, even traveling the same road many times.

Other than the oil fill, does that side have a vent too? I am guessing the front valve cover has the catch can and the back valve cover has the oil fill.

that is correct. There is no vent on the oil fill side. That is the way it was when I got it and it was never a problem before.

[This message has been edited by Oslo (edited 10-29-2007).]

Did the car pick up any power when the oil cap blew off?

Or even a hole in a piston.. but that wont casue high oil pressure... what kinda of oil filter are you using... if its a fram... THROW it away... get a a/c delco or wix.. ive had two frams collapse internally.. how much oil are you putting in it? too much will cause a drag on the crank aka loss of power..what weight oil also??

quote Originally posted by Hudini: Did the car pick up any power when the oil cap blew off?

No. But it was smoking a little bit out of the oil fill hole.

i thought we couldn put synthetic in our fieros............something about the crank an cam needing the zinc or lead or something like that in regular oil to prevent/ lessen wear on the camshaft lobes n stuff
something bout it filling in microscopic wear spots or some crap idk i dont quite remember the thread i read it on

A clogged filter will not blow a filler cap off, it will just bypass. clogged head return valleys might, but it would also suck all the oil out of the pan and you would see the loss of pressure.
as long as the returns are clear, it will never blow it off anyway as there will never be enough oil in there. even if they are blocked, it will be ble to leak back down thru the pushrod holes long before it would build up any pressure.
the crankcase is pressurized for some reason, and that is almost always blowby.
tho there is the vague chance the oil is full of coolant, overflowing the top of the engine,but that would be noticable, cause it would have spurted out along with the cap.

The purpose of the PCV valve is two-fold. Most importantly, it's a check valve so that any backfire out the intake is prevented from traveling back into the crankcase and igniting the oil vapors there, causing an engine explosion. The second function is as a calibrated vacuum leak, since air is always going through it the orifice size is important since it controls that air flow.

The full PVC circuit is as follows: Intake full vacuum draws air out of one valve cover. That air comes from the other valve cover via the crankcase. Clean air enters the other valve cover via some filtered source, such as the air intake snorkel, the air filter housing, or a separate dedicated air filter.

It looks like your engine is trying to vent through tiny hoses that restrict air flow, and normal (or slightly abnormal) blowby is therefor pressurizing your crankcase. You need to use engine vacuum to pull the air through your engine, that's why it's called Positive Crankcase Ventilation.

JazzMan

I'm going to try and re-route the oil catch can to a vacuum line on the intake manifold instead of the air intake pipe.

Ok, I capped off the hose on the intake pipe, and re-routed the crank case vent to an intake manifold vacuum source.

Also,
I did a compression test tonight and this is what I came up with:

Dry Test:
cyl 1: 185 lbs
2: 180
3. 180
4. 170
5. 165
6. 150

So, they are not within the 10% rule, but I think that it should still run pretty good even with those numbers.

May still try a wet compression test though. We'll see.

The engine was reportedly pulled out of a '95 Camaro with 50K miles on the clock and it has gone through about 15K or so miles since then.


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Club Redline - Northern Minnesota Sport and Modified

[This message has been edited by Oslo (edited 11-04-2007).]

Smoke coming out of the filler hole with a cap having been blown off along with a noticeable power loss is almost certainly an issue with excessive blow-by although some smoke is to be expected on a hot engine, the compression test will not simulate the extent that will be present under an actual combustion load on the cylinder, I believe that's where the leak down portion of the compression test comes into play to give some idea.

Those numbers might be tell-tell given the relatively low mileage on the engine. If it were a fresh rebuild it could be attributed to ring seating being still under way. Coincidently the lowest compression is in the two cylinders that GM has had the most trouble with in the fwd engines in which those two pistons #5 & 6 came with anti-friction patches in some of the motors and the first addition of oil squirters on the 60 degree V6 is on those two cylinders. I've never heard of it being a problem with the 3.4L and I believe it is partly the result of the coolant flow difference between the F body motor and the FWD motor however, considering the intake manifold is turned 180 deg in the fiero the same as in the fwd engines it may have introduced the suspected lean condition for those two cylinders that have been alluded to as part of the piston problem in that area on the FWD engines. I posted a picture of the rapidly disentagrating #6 piston from a 3100 in the 3900 swap thread that had a problem when it was acquired before install.

Every engine I had a problem with something being blown off the valve cover such as a PCV hose or considerable smoke coming out of the valve cover was bad news, chipped pistons or burnt rings or both.

If I did a wet compression test, would that tell us anything more about the condition of the rings?

I do not have the equipment to do a leak down test, however if I really need to I'm sure I could locate it.

I believe the wet test is just a diagnostic aid, however I never read up on how to interpret it. I know it will or should bring your compression numbers up in which case I would suppose a drastic increase in pressure would confirm a ring seal problem as opposed to leaking valves.