I have worked off lots of small problems since I bought the car about a year ago. Now I’m down to a hard one. It burns oil at the rate of 1 quart per 100 miles.

It had a very rich running Holley 750DP so I couldn’t tell if there was blue smoke in the black smoke. Installed an FITech EFI. It works great. No black smoke. I don’t see any blue smoke on startup or most running (with rear view mirror). Occasionally after well warmed up I see a little on decal/accel.

I have read lots of the forum discussions on similar problems and engine characteristics but I am not sure what, if anything, to do. Of course, I want to start with the easiest potential solution – something that doesn’t involve pulling the engine.

The engine runs great. Very strong. No idle or noise issues. I haven’t done a compression test or removed valve covers. Below is what I know based on invoices I got with the car and ProvaMo.

Engine was rebuilt as 393 stroker. Since rebuild, only has about 4,000 miles, but three owners since rebuild before me.
• Invoices show engine rebuilt in 8/2006 by Richards Machine Shop in Euless, Tx and installed by KG Performance in Frisco, Tx.
• 393 stroker kit (vendor?), bored .030 over, valve job and heads install bronze valve guides, 500 series valves, Comp 284HR roller Cam 32-431-8, new roller lifters and push rods, Comp valve springs 924-16, Comp roller rocker arms 1130-16, roller timing set, oil pump.
• Don’t know if valve guide seals were installed. Did find that a distributer with bronze gears had been installed versus what should have been steel. The bronze teeth were worn to a point, not far from failure.
Don’t know what oil was used before I got it. Oil level was low and dark. I have changed twice using a Mobil 1 filter and Valvoline VR1 Racing oil 10W30 weight. The oil took several hundred miles to start darkening after oil change. It has a high-volume pan. I calibrated the dipstick during oil fills to correlate with level in the pan.
There aren’t any leaks. No oil/dirt/residue seen on valve cover breather or PCV. Valve cover hole internal baffles look clean.
Installed mechanical 0-100 psi oil pressure gauge in passenger compartment. Tube comes from rear of engine off tee with electric gauge sending unit. Cold oil pressure is 70/75psi both idle and above. Even after water temp is up to 175 degrees, idle pressure is still near 70psi. When engine is fully warm, idle drops to 30/35psi and quickly increases with rpm to between 65/70psi.
Installed mechanical vacuum gauge in passenger compartment. Vacuum at idle is 10”-12”. Light cruising shows 18”-20” around town and on highway. Moderate demand and acceleration is 15”-17”. Deceleration goes to 20”-23”.
Gas mileage is 10-12 mpg in mixed driving.

SUGGESTIONS FOR PROCEEDING????? I guess one option is to just add a 2 quarts of oil every 200 miles.
Original Post
You can try to isolate it to perhaps one cylinder if you can observe oil deposit on the sparkplug. If it burns oil on all 8 it could be that the valve oil seals have become hard/brittle. But the first thing would be to see if it is an isolated burn.
I’m not a stroker-guy, but I seem to recall George discussing that if things are stroked largely, the oil control (?) ring intrudes into the wrist pin, and this can result in additional oil consumption.

So my suggestion would be to get pictures of the piston (from the engine specs you have) to see if this is potentially a cause that could be investigated.

We in the west have recently had a couple of 'professionally' built stroker Clevelands in POCA member Panteras, that were assembled WRONG. With stroker cranks & rods, if you don't choose your components very carefully, the combination will have the ring package in the piston with the wristpins passing thru the bottom of the oil control ring grooves. So to fix this, a 'bridge' in the kits is inserted at the bottom of each oil ring groove to bridge the wristpin cutout and allow the oil control ring to do its job. The removable bridge-ring is locked in position by various means so it doesn't rotate in the piston like all the other rings, to prevent it from rotating to the wristpin cutout, an end bending down from combustion forces and again wrecking the ring seal. The bent end of one or more bridge rings may also cut a small groove in that cylinder wall. This can scrap a block.

Some kits do not have the bridge ring installed. That means the bottom of the oil control ring assembly does not seal to the piston, nor to the cylinder.

One one of the above engines, two bridge rings WERE installed while 6 were left out. One the other, NO bridge rings were found. It's also conceivable that the bridge-ring anti-rotation system was not installed. So pulling ONE piston & rod may not define the problem. Pull ALL 8 pistons and visually check each assembly for:
-A- a bridge ring
-B- an anti-rotation system for the bridge ring

On both the engines I'm familiar with, they ran well but burned approx. a qt of oil per 100 miles from start up. And no- there's no way to check this except to pull the engine and disassemble, because the problem is buried inside the engine cylinders and is not visible from top or bottom of the short-block.

This may not be your problem, but in any case the engine should be pulled, stripped and visually inspected, then at least ball-honed for a new set of same-size rings, on the same pistons (if they check OK).

It's also possible the rings never seated or that detonation broke one or more rings. This also can scratch the bores. A stroker-Cleveland is a completely redesigned engine and is not simple. Good luck-
I'd look at something simpler LIKE the way that you have the PCV connected.

It is VERY easy to get them to siphon oil out of the valve covers and into the intake manifold.

I went to an oil skimmer.

Recently I noticed a vintage picture of a GT40 that although it had an open breather system, the breather was installed on top of a tank that was being used as an oil skimmer.

I've had the issue on my 68 GT350 and thirty five years ago on a Ford Granada with a 302.

Trust me "Herb", these things suck in oil through the pcv system.

Tie that to a pcv valve that can at best be described as a POS.

I'd look there before I started tearing this thing apart.

I'm not going to argue about strokers having strange ring land locations.

I have a 347, stroked from 302, in my GT350. The ring lands overlap the piston pin.

I do not have anywhere near excessive oil consumption with it.

I don't think that you should automatically assume that is what the problem is.

These strokers have been on the road for easily 10 years now and for the most part are not a problem.

Of course if you want to use it in a taxi cab, it could not be exactly what you want? Wink
Your situation, a quart in 100 miles, is an extreme one.

The list of things that can cause oil burning is lengthy. I agree with Doug to assume its an easy one unless testing proves otherwise.

If this were 40 years ago & the engine was "stock", it would be a no-brainer ... the rod bearings would be shot & throwing excessive oil on the cylinder walls. The second tell-tale of this would be low oil pressure, due to the excessive clearances of the damaged rod bearings. I'd like to mention that your Pantera's rod bearings sound like they are in good shape, and by your description I'd say the engine has tappet bore bushings installed.

My suggestion for proceeding is to have a leak-down test performed, its more informative than a compression test, and it will establish if there is a problem with the rings, or if any particular cylinder stands-out as a problem.

It is true some mechanics like to leave the valve guide seals off, mostly to promote better lubrication of the exhaust guides. The exhaust ports can behave like venturis and suck oil right out of the valve covers and into the exhaust system. This is downstream of the combustion chamber, so the engine can pass a leak-down test, and the plugs can be clean, and this can still cause oil consumption (but technically its not oil burning). If this were the case you should find oil particles on the rear of the car after a drive. Removal of one valve cover and a visual inspection can answer the question of whether or not the seals were installed.

The rest of this is conjecture, just rattling-off possibilities that come to mind, things that other folks haven't already mentioned:
  • The pedestals for half of the rocker arms are located right on top of the intake ports. The casting between the bottom of the threaded rocker arm boss and the intake port is rather thin. When some guys machine & tap the rocker pedestals for adjustable rocker arms, they use a "pointed" tap to re-tap the stud bosses, and that pointed tap pokes holes in the roof of the intake port. That hole will allow the intake system to suck a lot of oil right past the threads of the rocker studs.
  • Installing the second ring upside-down (aka the Napier ring) will cause extreme oil burning.
  • Excessive connecting rod "side clearance" will throw an excessive amount of oil on the cylinder walls. Many mechanics ignore the side clearance spec because they don't understand what it is for. Camshafts and cylinder walls are "splash" lubricated ... the rod side clearance is where that "splash" comes from. It should never exceed 0.020". What this would indicate is that the manufacturer of the stroker crank machined the rod journals too wide.
  • One of the symptoms of an improperly balanced reciprocating assembly is piston ring problems, and of course the usual symptom of a piston ring issue is oil burning.

Good luck, lets hope its something easy to fix, like a pcv valve.
Thanks for all the great input. I'll work on doing the suggested tests and checks. If it looks like the engine has to be torn down, I'll try to wait until snowfall in winter.
A question - to me the oil pressure seems to be very high, especially with 10W30 oil. I've seen some references to a 50 psi relief but mine must be higher. I don't know what oil pump was installed or if the relief was changed. Any thoughts on this?
Originally posted by over50:
... to me the oil pressure seems to be very high, especially with 10W30 oil. I've seen some references to a 50 psi relief but mine must be higher. I don't know what oil pump was installed or if the relief was changed. Any thoughts on this?

if your engine is fitted with an external oil line from the front port near the oil filter to the rear port on top behind the intake, your pressure will read higher than without the external line. also if your gauge sender is connected to the front port near the oil filter you'll be reading direct oil pump pressure rather than from the rear of the engine after all pressure losses

reading direct oil pump pressure turns the gauge into more of an idiot light because you'll never know what the pressure is at the far end of the engine, just that the pump is working or not
This may be helpful? I recently changed inlet manifold and found a few bolts loose and oil laying in the steel valley tray/gasket thing.
There were no paper gaskets just the metal tray which was leaking this had allowed the intake to suck oil and air and also exhaust from the manifold heating. there were no external signs of leakage it turns out I had 3 cylinder that burnt oil and they are now showing signs of the carbon clearing with use. A good day

Originally posted by over50:

... to me the oil pressure seems to be very high, especially with 10W30 oil. I've seen some references to a 50 psi relief but mine must be higher.

The standard oil pressure control spring in the Cleveland is set for 60 psi +/- 10 psi. What this means is that the pressure relief valve is fully closed at 50 psi, and fully open at 70 psi. This is a higher pressure specification than any other Ford V8, indicating the folks at Ford knew they had a lubrication problem.

The 351C is equipped with a hi-volume oil pump from the factory. The oil pump rotor is taller than in any other Ford V8. This is another indication that the folks at Ford knew they had a lubrication problem.

In spite of these measures most Clevelands have a hard time making 50 psi hot oil pressure (measured at 2000 rpm). This is due to leakage via the tappet bores and the over-sized clearances of excessively worn rod bearings. For the last 2 or 3 years of production the hot oil specification was 45 psi at 2000 rpm ... even though the pressure control valve was fully closed at 50 psi! This obviously indicates the folks at Ford knew they had a lubrication problem.

When a high pressure oil pump spring is installed the cold oil pressure usually runs ridiculously high, like 100 psi or more. Enough to burst an oil filter if the owner inadvertently blips the throttle while the engine is heating up. Following is your description from your first post:


Originally posted by over50:

... Installed mechanical 0-100 psi oil pressure gauge in passenger compartment. Tube comes from rear of engine off tee with electric gauge sending unit. Cold oil pressure is 70/75psi both idle and above. Even after water temp is up to 175 degrees, idle pressure is still near 70psi. When engine is fully warm, idle drops to 30/35psi and quickly increases with rpm to between 65/70psi ...

Based upon this description your Pantera's engine appears to have tappet bore bushings installed, as the pressures you described are exactly what I would expect to see with tappet bore bushings, they indicate an engine that has "normal" leakage at the tappet bores and rod bearings that haven't been damaged or excessively worn by the lack of lubrication. The capacity of the oil pump is not being "over-taxed" and the pressure control spring is operating within its intended range.
Agree with my friend George on the oiling issues. I have blown an oil filter clean off the block at high rpms: 50-wt racing oil AND a high pressure spring were the cause. I was NOT the most popular guy at the track that day; clean-up took hours.

Also note that extremely high oil pressures on some 351-Cs with hydraulic lifters can & have caused premature valve float! We had one fully-pro-built Pantera in the area that acted like it had a rev limiter set at 4500 rpms, until the owner, after being nagged by us, installed a brand-new STOCK pump in place of his 'high-pressure' assembly. Immediately, the same engine revved to 7000 with no other changes! Apparently, very high oil pressure overwhelmed the bleeds or check-valves in his lifters..... Such high pressures & flows have also been known to erode main bearings, as well.
It may not be the most likely source but I'm thinking of starting by pulling the intake manifold and resetting it to make sure it is sealed. I think this should be relatively simple but I couldn't find clear instructions on the forum search. I assume there isn't any coolant to deal with and all I have to do is unbolt, remove and replace the manifold.
The manifold is an Edelbrock Performer LB 351 4V, PN 2665. It doesn't appear to have been installed with gaskets. Looks like metal to metal with a little sealant showing where mated to the heads. I don't know if this is good or bad or increases the potential for a leak.
What do you guys think and how should I proceed? I assume this manifold doesn't have an exhaust crossover and thus no valley tray is installed.
It has been a long time since I replaced a manifold but critical points I remember are:

Drain some coolant from the block because there will be coolant right at the top of the heads

Head and block machining over the years can change angles and cause meeting services to not properly meet. Also, a used manifold that has been machined to fit such a situation will not want to fit properly on an original dimensioned block and heads.

Try to lift the manifold firmly straight up. The telltale oil leakage should be apparent if coming from a bad gasket or mating surface.

Throw away what ever end-valley gaskets your manifold gasket kit provides and just use a proper RTV silicone gasket maker. Follow instructions.

Hope this helps.

There is no coolant in a Cleveland intake manifold. A Windsor intake would have coolant running through it.

The Edelbrock does have a exhaust heat cross over cast into it.

I personally don't like the original "turkey tray" gasket. It requires the use of silicone sealant around the ports.

The paper gaskets are a better way to install the manifold with just silicone at the front and rear of the manifold.

Usually if you are going to have an oil leak on the intake manifold it is going to be in the front or rear and at the corners.

I have found oil sitting in the pan of the turkey tray on several occasions in doing Cleveland intakes. Rarely a great quantity. Usually about a tablespoonful or so.

It would be unusual that there is an oil leak into the ports from the valley. The manifolds almost can sit without sealant.

It is MUCH more likely that the oil is being siphoned into the manifold through the PCV system.

It is also possible that the valve guides are worn enough to allow the oil consumption.

If the heads are original and have never been rebuilt, the original oil seals (umbrellas)are probably deteriorated and probably non-existent functionally.

So the oil consumption cause by probability is 1) pcv system 2)valve guides/oil seals 3)oil control rings on the pistons 4) intake manifold abnormality,.

Going from highest probability to lowest.

The biggest caution is that if it is the original valve stem seals have deteriorated. They will crumble, get into the oil pan, either block the screen on the oil pump pick up or worse yet, get into the oil pump, jamb the rotors and damage yhem severely, cause the distributor drive pins to bend or brake or completely destroy the oil pump drive itself.

Also IF the heads have never been rebuilt the original valves tend to break on the stems causing the valve to fall into the cylinder and cause destruction of the pistons, the connecting rods and probably cracking the cylinder walls of the block.
I agree that it is low probability that the intake manifold sealing has anything to do with my oil consumption - but now I am not sure what has been installed on my engine. The Edelbrock LB 351 4V has an exhaust crossover but the gasket they recommend, Fel Pro 1228 doesn't have exhaust crossover passage holes. If the manifold is installed with these gaskets there won't be any exhaust cross over and thus no reason to have a valley tray.
Since I can't see any evidence of gaskets being installed on mine, I don't know if a thin valley tray is installed or not. The exhaust cross over will also be open unless it has been somehow blocked. I may pull it just to find what exists.
Over-50, know that the DeTomaso community has found at least two Edelbrock intakes for 351-Cs that were built wrong for big-port aluminum heads, and WILL suck oil from the valley chamber. This is due to too-thin bottom flanges left around all the intake ports, which sucks gaskets or silicone sealant inside the port bottoms from high manifold vacuum. Edelbrock warranties such manifolds if that's the cause of your oil consumption.
Pull the intake and look. If it appears the bottom of the intake ports are razor-thin instead of having a decent sized bottom flange edge, contact Edelbrock. If you have composite gaskets, the bottoms might be missing or visibly pulled into the ports. It would cost too much to TIG the entire lower port bottoms to widen them, then remachine the sealing surfaces. Just guessing but we suspect these were 2V-intakes that were 'redone' to 4v dimensions, and there just isn't enough metal available to do this. They may have been released in error- likely not very many but as with bad cams, it does happen.

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