!964 Avanti R1 engine back pressure

[jpiatchek]

I have a 64 Avanti R1 engine in a Lark that is leaking oil thru the distrbutor. It is an electronic Thibeault unit. Pulled the distributor today and it has a good gasket, but it looks as if the oil is coming up thru the distrutor shaft and out the bottom of the drain holes in the bottom of the distributor. Also, when I run it hard, oil comes thru the oil filler caps and runs down the side of the valve covers. THe car was rebuilt with all quality parts 10 years ago by Studebaker Heaven in California but only 10,000 miles. It runs strong, starts good, and doesn't seem to smoke out the tailpipes. The plugs have a go0d color and everything seems good except what seems to be excessive back pressure. Any ideas on what the cause might be? Thanks for any help.

[sbca96]

It sounds like what you are experiencing is not "back pressure" but a
"blow by" issue. Its a buildup of pressure inside the crankcase. If
the engine has low compression (less then say 125 psi in each cyl) it
could cause this. A more realistic cause with only 10,000 miles is
an improperly installed PCV valve. Flow of the "Positive Crankcase
Ventilation Valve" should be TOWARD the carb, in other words, if you
blow through the valve, the air should go into the base, but not back
into the valley cover. Studebaker used a screw-in PCV valve on the
engines other then the R1, to be honest I havent looked at mine to
see if its the same valve. Though after 40 years, who knows whats on
the engine now. Many people replace them with in-line valves, which
would require a hose nipple screwed into the valley cover. I've also
seen screw in PCV valves that have the OPPOSITE flow of Studebaker! If
the person putting one on doesnt check this, and only goes by someones
"find" at a local parts store .. a "blocked" vent could result.

EDIT : "Back pressure" is usually in reference to the exhaust system.

Tom

'63 Avanti, zinc plated drilled & slotted 03 Mustang Cobra 13" front disc/98 GT rear brakes, 03 Cobra 17" wheels, GM alt, 97 Z28 leather seats, soon: 97 Z28 T-56 6-spd, Ported heads w/SST full flow valves, 'R3' 276 cam, Edelbrock AFB Carb, GM HEI distributor, 8.8mm plug wires

[jpiatchek]

TOM--Thanks. My Avanti R1 engine has a pipe that bolts into the side of the oil pan. From that pipe there is a large hose and a smaller diameter hose.The large diameter hose goes to the side of the air filter and the other smaller hose to a port in the back of the carburator(an Edelbrock aftermarket). I just put a vaxuum gauge on the car and it reads a steady 17 or so. The neddle seems to respond properly when you gas it and let off. There doesn't seem to be another PC value located anywhere else, but I haven't examined that closely. Should the large hose going into the air cleaner or the small hose going into the back of the carb be sucking vacuum? Should there be a vauum pull form the port at the back of the carb that the small hose is plugged into? any help would be appreciated. The car runs extremely strong and starts and idles perfect, so I would be surprise if it was low compression. Thanks for help. John

[1956 Hawk]

I am not familiar with an R1, but on an R2 the small hose goes to a pcv valve that screws into the back of the carb, and the large hose to the air box is so that excess crankcase pressure will be sucked into the intake when the car is under boost.
From what you say I would check the pcv valve in the carb. Take it out and make sure you can blow through it from the hose side (so air goes into the carb). I had a pcv valve get pluged on my 259 Lark, and it would blow the breather cap off when I drove on the freeway.
Also Edelbrock suggests that the pcv goes to the front of the carb, not the back.
David

[Dan White]

You should check and make sure you have a PCV on screwed in the base of the carb! When I got mine it was plugged off!!!! I blew off the valve cover breather one time and wondered what the heck! Make sure the PCV valve is working and in the right direction as Tom notes. You can get the correct PCV from NAPA, Dave Thibeault, or Myers Studebaker. A small hose should connect from the PCV to the small pipe that Y's off the larger pipe coming from the oil pan.

Dan White
64 R1 GT
64 R2 GT

[jpiatchek]

I checked the car tonight and there is a PCV in the back of the carb and it is working and going in the right direction. With the car running at idle there is vacuum at the back of the carb and then the vacuum gets milder are goes away as I give it throttle. Everything seems to be working as it should. Any other ideas? Thanks for any help you can give. John

[sbca96]

You might try a compression test .. just as a base reference. You
can get a compression tester from Sears for about 40 bucks, I prefer
the one that screws in with a hose, and has a standard air hose bibb
on the other end that the gauge attaches too. The hose can be used
(with the schrader valve removed) with an air compressor to charge a
cylinder with air while you remove valve springs for new valve seals.

Tom

[jpiatchek]

Tom--The fellow I purchased the car from said he just had the valves adjusted. They are a timy bit noisy. Could one or two or them be adjusted wrong and be causing the blow by? Thanks John

[jpiatchek]

Thanks--Will pull the hose from the PCV and see if that helps. Will do a compression test in the next few days and see what happens there. The oil has just been changed a few hundred miles ago and my mechanic said it looks good and doesn't smell like oil. If they tightened one or two of the valves on the adjustment too much, could that cause the problem. You guys are great. John

[John Kirchhoff]

If the PCV valve is ok and such, you might do as Tom suggested and check compression. There could be a broken compression ring and the pressure on that cylinder should read as less than the others. Warm the engine up first so that the pistons have expanded and oil has been circulated around. Have all the plugs removed and the throttle completely open when you check to get accurate readings. While the maximum readings are important, don't have a heart attack if they all read lower than what the manual says. A tired starter, dry bearings in the starter, corroded battery terminals and such can all result in the engine cranking slower than normal. Do observe the differences between cylinders. 10% is nothing to worry about but if a couple are considerabaly less than the rest, there might be something going on. Squirt maybe a teaspoon of light oil in the cylinder with something like a syringe and then check. If the compression reading goes up significantly, it's rings leaking, if it's still low, it's probably a valve leaking. If you really want to go whole hog, spend $75 at Harbor Freight and get one of those Chinese leak down gauges. It will give you an idea of each cylinder's leakage. I don't have one but I seem to remember that 8-12% leakage is normal but if you're building a souped up drag racer or such, 4% is the max. If over 25%, she's getting a little tired. Those figures could be wrong because I'm recalling something I read 25 years ago and you know how a person's memory is. But, squirting oil in the cylinder will pretty much tell you the same thing the high dollar gauge set will, just not as accurately. By the way, oil will raise the compression on even a good cylinder, just not nearly as much. It may raise a good cylinder 10 pounds whereas one with bad rings will go up 40 pounds.

If you're wondering about the crankcase venting, just disconnect the vent hose from the PCV valve, leave it open to the air and plug the vacuum side of the hose and see what happens then. You might try this first.

I know this sounds pretty obvious, but have you checked the oil level in the crankcase? If it's too high the crank is going to be whipping the oil up like a Hamilton Beech blender. If for some reason there's more oil in the crankcase now than what you put in, drain it out to make sure there's no anti-freeze in it. If it hasn't been run for a while, you can always drain just a bit out because the anti-freeze will be at the bottom. If you find coolant or the oil is emulsified into something that looks like a chocolate shake, don't run the engine! This means you most likely have a head gasket or cracked head leaking coolant and anti-freeze will glue an engine so tight, you'll never get it apart. Ever. Been there, done that. Oh, a cracked head will often times pressure up the cooling system, so if it keeps forcing coolant out the cap or overflow when running, that's not good. When running, look down the filler hole in the radiator and if you see bubbles, cracked head. Do this starting out COLD!!! DO NOT remove the cap on a hot engine!!!

Don't panic, it's probably something insignificant, or at least I hope so. Good luck!

[GTtim]

Along the lines of an overfilled crankcase, because it is an Avanti a bad fuel pump could cause gas to flow into the crankcase, couldn't it?

Tim K.
'64 R2 GT Hawk

[John Kirchhoff]

Yes, a leaking fuel pump could run gasoline into the crankcase. They usually have a drain hole so if the diaphram does leak, it runs out rather than into the crackcase. But sometimes those holes get plugged up. Like the time I had 20+ quarts of an oil-diesel mixture in a 12 quart crankcase.

[sbca96]

Just to clarify, Avanti, Lark, Hawk or Chevy Corvette, if its got a
mechanical fuel pump it CAN leak fuel into the crankcase through the
diaphram. This is not an Avanti-only problem.

Tom

[GTtim]

I thought that the problem of the crankcase filling up with gasoline was more of a problem with an Avanti because the fuel tank is higher and gravity will bring the gas to the engine. With Larks and Hawks you'd have to have the car parked nose down on a slope, wouldn't you?

Tim K.
'64 R2 GT Hawk

[John Kirchhoff]

Actually a leaking diaphram will leak more so when in use since there's going to be several pounds of pressure on the fuel side looking for a way to get out. When not in use, the static pressure of the fuel alone may not be enough to make it's way through a pin hole, but when under pressure it's a different story. Low oil pressure is a good sign of oil dilution with gasoline. The oil will be thinner than usual and if you smell it, it even has the familiar gasoline scent. On the bright side, if the diaphram is leaking that much, chances are the car won't start or will run very badly because of low fuel pressure. Don't worry, it's something that happens very infrequently. I don't want you having a nervous breakdown from worrying about worst case scenarios.