Ventilating engine on a 54 Merc

5

54Merc

Junior Member
Wanting to replace the vent tube with a better vent system.
It leaks on the floor, and not sure if I have a problem with it since I am blowing oil out the rear main (1 qt every 150 miles), and I’ve noticed vapor coming out of the oil fill pipe when pulling off the cap. The car has 1500 miles since the overhaul.

I have no ports on the valve covers, oil filler cap, or the air cleaner. The manifold port is taken up with the double action fuel pump.

How should I get started?

Thank you in advance for taking the time to help!

Jim from Iowa
 
54Merc said:
Wanting to replace the vent tube with a better vent system.
It leaks on the floor, and not sure if I have a problem with it since I am blowing oil out the rear main (1 qt every 150 miles), and I’ve noticed vapor coming out of the oil fill pipe when pulling off the cap. The car has 1500 miles since the overhaul.

I have no ports on the valve covers, oil filler cap, or the air cleaner. The manifold port is taken up with the double action fuel pump./QUOTE]

Have you checked the filter element in the road draft tube? How about the oil fill cap? Booth must be open or crankcase presssure will build up and push oil out the rear main seal (and other seals and gaskets).
Was the engine completely rebuilt-rebored, new pistons, rings, bearings, seals, gaskets, etc? Or was it just overhauled-new rings on old pistons, a valve job, some bearings and new gaskets?
Is the rear main seal the old style rope seal? These are tricky to install, especially if done in the car.
You could fabricate a homemade PCV system or find a factory system from a '63 or'64 pickup with a 292 and bolt it on. This will eliminate the oil vapors.
However, I suspect a bad rear main seal (or badly installed seal) is the cause of the leak.
Click to expand...
 
^^^^^. Both the lower breather canister and the oil fill cap are often ignored. The caps easy, the canister is a PITA. But that’s the place to start.

There’s numerous articles on open and closed PCV systems here and at yblocksforever. Done with the valley pan and the oil breather. That’s the best long run solution, but the intake usually has to come off the remove and modify the valley pan.

If you get into the rear seal, check out Ted Eaton’s article on that at

https://www.eatonbalancing.com/2008/09/10/neoprene-rear-seal-installation-for-the-y-and-others/
 
Wanting to replace the vent tube with a better vent system.
It leaks on the floor, and not sure if I have a problem with it since I am blowing oil out the rear main (1 qt every 150 miles), and I’ve noticed vapor coming out of the oil fill pipe when pulling off the cap. The car has 1500 miles since the overhaul.

I have no ports on the valve covers, oil filler cap, or the air cleaner. The manifold port is taken up with the double action fuel pump.
Click to expand...

There are several ways out of this.

It is a 54 MERC 256CI 4V?

Firstly, as mentioned, was the actual breather filter serviced when the engine was rebuilt? The oil filler cap is also the air intake filter. Has that been cleaned/replaced?

If the CCV (crankcase ventilation) has excess pressure, it will not only make it's mark while sitting but will blow back on the engine and appear as an oil pump or rear main oil leak as it moves down the road.

You can add a PCV SYSTEM fairly inconspicuously (college word) and it will be hard to be noticed if you want the original look.

If she's blowing smoke, either the CCV SYSTEM is inoperative or the rings did not seal after rebuild.
 
Kind of a last thought. If the engine was rebuilt with the original rings (as opposed to modern improvements) they take some time to seat. At 1500 miles, they should be, the normal range was about 500. But that kind of assumes it got some real miles. When I bought my bird it had 1600 miles over a 6 year period. It hadn’t gone enough miles to get really warm and seat the rings. A couple weeks with me driving it (30 mile trips each way, on the freeway, varying speed) the oil consumption went done to a quart in 6-700. Had it been broken in and better stored, it should have been a 1000 miles even with me driving.

I don’t think this is your problem, but a quart in 150 is pretty high if the rebuild was good at all. So checking the draft system is a start.
 
I believe you guys are right on! I think if I clean the filters, that might be most of my problem. It didn’t seem to be leaking when I had it in the shop a long time during the body restoration. Probably all the short trips gummed it up. I’ll come back on after I do this. I might have some questions on improving the ventilation.
Thanks guys for your help!

Jim from Iowa
 
After cleaning the filters on the breather cap and the vent tube, I looked under the car after I had drove 20 miles or so. The vent pipe was dripping oil. I started it back up to see if the dripping would change. After it ran about a couple minutes, the drip got a little faster - a drip every couple of seconds. I also noticed a drip on the concrete drive every 4” or so as I approached the garage.
 
The only time I had a drip every 4” was when a screw on filter adaptor failed. That’s a lot of oil imo. I guess the first question would be is the road draft/vent properly assembled and not damaged. I’m not real familiar with them as the Thunderbird set ups are different. It’s almost like it’s an opening to the crankcase without the separator (? I’m not sure that’s the right word) function working.

It might also be time to run a compression check. I’m getting a little nervous about a new leaking rear main and a lot of blowby on a new rebuild. Take a look at the plugs when you do the compression check, specs for oil.
 
Now this is going to sound stupid, but ...

If you put a vacuum gauge on the dipstick tube and rev the engine while holding the gauge (or even driving with the gauge taped to the windshield) and it shows little or no vacuum reading on the gauge (may show pressure), the crankcase is pressurized. whether caused by an inoperative CCV SYSTEM (ROAD DRAFT in your situation) or blow-by from say not properly seated piston rings.

This system is not/was not very effective. One reason for PCV INTRO.

There is a drain tube within the canister that is designed to return excess oil from the filtering element to the crankcase. It may be plugged.

SPARK PLUG READINGS will indicate if it is burning/consuming oil.

Is the car original or a dedicated restoration? You can perform an PCV CONVERSION without it's being noticeable.
 

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It seems to me there was/is a California conversion where you used a oil filler cap with a hose nipple on it and an air cleaner with another hose nipple on it. This was supposed to take he fumes from the engine (oil filler cap) into the air cleaner which in turn went down the carb.
 
^^^^. Looks just like the oem fill cap, but the bottom perimeter is sealed and there’s a 3/8” or so hose tube. Got one on my roadster. The 69 Camaro also used a sealed tube with a threaded bung. Those are available in chrome or plain. It’s what I used on the finned valley cover on the bird. In both cases, I took them to the air cleaner and ran a valley pan PCV valve to a modern carb that had that fitting.

I’m not sure this is the right one, but it’s what they look like. You’ll have to measure the fill tube diameter

https://www.amazon.com/Stant-10070-Oil-Filler-Cap/dp/B000C8223I/?tag=atomicindus08-20

I didn’t know there was an internal drain tube like K references. That could be the culprit.
 
Last edited:
To answer 40 Deluxe,
New pistons, .06 bore, crankshaft ground, valve job, break in oil 30 wt non-det.

Engine overhauled 2014. Not driven until body work done and painted in 2019. Had a repaint and some body work due to winds in 2020. Started driving late 2021 after interior done. Probably 1000 miles plus on break in oil. Changed oil to 10w30 valvoline. Now have about 1500 miles on this oil.
 
54Merc said:
To answer 40 Deluxe,

New pistons, .06 bore, crankshaft ground, valve job, break in oil 30 wt non-det.

Engine overhauled 2014. Not driven until body work done and painted in 2019. Had a repaint and some body work due to winds in 2020. Started driving late 2021 after interior done. Probably 1000 miles plus on break in oil. Changed oil to 10w30 valvoline. Now have about 1500 miles on this oil.
Click to expand...

Was the engine 'RUN-IN'? That may be the big problem, rings not seated and gummed up. Was the engine rebuilt by who?

The oil filler cap is open/filtered to intake fresh outside air. If using a closed type, the engine cannot breathe. Original caps (open) had hog hair for the filtering element. It had to be serviced/changed on a schedule. Later caps went to a wire mesh. Some have a plastic filtering element. Stay away.

If you direct fresh air intake through the ACL with a closed style cap, you will foul the ACL if the engine has extreme blow-by.
 

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The filter shown is the one I dug out of the extra parts bin, cleaned up and put on. This was the original the engine. I had a new one on it prior to this and it had a foam filter. I suspected that it didn’t breathe enough.maybe the new one that has been on the engine for 2000 miles plus has the engine all gummed up. Maybe it’s going to take some more miles on it to either seat the rings and/or to ‘clean’ the engine out. Does anyone think I should put a break in oil back in it for a while?
Thanks for helping.
 
I have driven a few hundred miles since using the original type oil breather cap and it is venting better and minimal dripping coming out of the draft tube.
 
KULTULZ said:
KULTULZ, I think you're looking at your Powerglide problem all backwards! What is really happening is, that PG is starting in 2nd and then shifting to 3rd! It really works like an early Fordomatic except there's no manual LO position. The cure is to trade that old Chevy in on a Ford.

PS Wanna buy a bridge in Brooklyn?
Click to expand...
 
KULTULZ said:
!!! YO !!!​



...uh ... THE POWERGLIDE (slip and slide) is a 2-speed transmission, as is the F/M/2.

The reference is to most believing the SINGLE-RANGE F/M is a 2-speed whereas it is actually a 3-speed.

You need to setup a little better as they are flying over you head and the only reason I would buy a bridge in NY METRO is to ensure I have a way out of there.
Click to expand...

I guess humor is wasted on the humorless. Apparently everything must now be properly labelled in triplicate!
 
40 Deluxe said:
I guess humor is wasted on the humorless. Apparently everything must now be properly labelled in triplicate!
Click to expand...

:confused:​

40 Deluxe said:
KULTULZ, I think you're looking at your Powerglide problem all backwards!

What is really happening is, that PG is starting in 2nd and then shifting to 3rd! It really works like an early Fordomatic except there's no manual LO position. The cure is to trade that old Chevy in on a Ford.

PS Wanna buy a bridge in Brooklyn?
Click to expand...

OK, I see what you are saying now.

My apologies, am retaining water this week (reading comprehension is not all that good either) ... :o
 
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