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Discussion Starter · #1 ·
Hi All,
Please help me with this problem, as i'm really worried about it.
I just got an upgrade exhaust system from the manifold back.
It was a 2" with CAT and crossflow muffler, now its a 2.5" dual muffler with X pipe and no CAT.
I drove the car on a 100 mile journey the next day and noticed the oil on dipstick had dropped 1/2".
I topped it up and did the same journey again, and the same drop on the dipstick occurred.
Also noticed a reduction in power when taking off.

And full confession, I only have the car since February, and when I got it, I changed the oil,
as it was black. But I noticed very soon afterward the oil turned black again.
And the old exhaust always had black deposits on the inside of the tailpipes,
and left black soot stains on the garage floor from the exhaust tailpipes.
But the power was always strong and I never noticed oil being used before.
Any help would be much appreciated.
Thanks,
Jack
 

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Carter Carb eh!
likely flooding a bit. Running rich. Washing oil off the cylinder walls. Rings aren’t sealing. Black oil also from excess fuel.
carter carb known to need no more than 5 psi fuel pressure.
 

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Discussion Starter · #3 ·
Carter Carb eh!
likely flooding a bit. Running rich. Washing oil off the cylinder walls. Rings aren’t sealing. Black oil also from excess fuel.
carter carb known to need no more than 5 psi fuel pressure.
Thanks for your advice. I thought it might be something to do with running rich.
Do you think a regulator with a return to the tank would be best? Any recommended one?
So do you think the newer exhaust with less back pressure is making the problem worse, how?
And why now the reduced power at take off?
Thanks again,
Jack
 

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Regulator choice depends on fuel pump used. Electric pump needs a bypass/return, normal pump doesn’t. No suggestions on a regulator yet.
You might not need one after you tear the motor down for a complete rebuild. If it’s been running rich with fuel wash on the cylinders then your bearings are suspect too.
 

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Discussion Starter · #5 ·
Regulator choice depends on fuel pump used. Electric pump needs a bypass/return, normal pump doesn’t. No suggestions on a regulator yet.
You might not need one after you tear the motor down for a complete rebuild. If it’s been running rich with fuel wash on the cylinders then your bearings are suspect too.
Oh, that's not so good.
How could I check for this damage?
 

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Geranlly no, its possible the carb was rich to begin with but now, the exhaust is requiring a carb calibration change, but in general, it's going to be pretty small change.
 

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Discussion Starter · #8 ·
Geranlly no, its possible the carb was rich to begin with but now, the exhaust is requiring a carb calibration change, but in general, it's going to be pretty small change.
ok thanks for your input.
So as I'm sure you can tell, I'm by no means an expert, so apologies if this is a stupid question.
How likely is it that I'm in real trouble with the engine?
And how do I check it?
Or is it worth fixing the fuel pressure, changing the oil/filter, and seeing if it reduces the oil used?
 

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No stupid questions....I mean at when effort is put in, anyway
I can't see your engine from here so I can't tell you what to think. I'd do some diagnosing and try to figure out where the oil is going and weigh that problem with your abilities for repair and the cost of a replacement. Whats it worth to YOU? I'd start with a leak down test.

Common oil consumption area....
Intake to head interface
Intake bolts at the head
Valve seals
Rocker stud threads
Oil rings
 

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I rather doubt that changing the exhaust system has much if anything to do with oil consumption.

What is needed is a measure of oil consumption between the first oil change and the exhsust up grade.

The fact that the oil change quickly turned black is not necessarily more of a marker than some oils when heated do that. Knowing whose oil and filter is useful info.

Black soot in the exhaust system is typical the drippings is soot in waters of combustion.

It could be carbureting rich which makes this worse and adds to ring and bore wear. This is an old car, some history of mileage on it and of the engine is useful.

The Carter carbuetor does not need much fuel pressure about 5 to 6 psi is all it doesn’t like a hot manifold either it needs about a half inch thick nonmetallic spacer between it and the intake for anything other than an airgap and even then it’s useful.

There are several ways to build a 383 some are a lot better that others without disassembly there isn’t a lot of info to be gleaned from the outside. If you understand what dampers can tel you can determine if the engine was built for external or internal balance which leads to some idea of what’s inside. External damper has a lump on the engine side where internal will be smooth.

Pulling the spark plugs can give info as to whether it’s pulling oil or not. A rule of thumb is sooty and dry is too much fuel, sooty and wet is oil getting in the chamber. There are two sources for the latter one is around the rings the other is past the valve guides.

Look for external leaks especially the corners where the intake manifold meets the head’s and on the backside of the head’s under the valve cover gasket rail and at the oil pressure sender.

Bogie
 

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pressure regulator with return is always good. What is your fuel pressure now. Electric or mechanical fuel pump? I have an Edelbrock carb with an electric pump, and return pressure regulator. Pressure set at 4.5 psi, works like a charm!

Your problem should have nothing to do with the exhaust.
 

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Discussion Starter · #12 ·
Thanks Bogie, to answer some of your questions;
Car Engine replaced
Car had engine replaced with a Chevy 350 rebuilt to 383 in 2000, at 62,400 miles.
It now has 68,400 miles (I have it 8 months and only put 700 miles on it myself).
The EGR valve and emissions stuff was removed at rebuild, and the oxygen sensor is disconnected.
Build sheet;
Keith Black pistons were +.030”, as were the Sealed Power piston rings in +.030”, so the bore on the engine block is 4.030”.
It is customary for us to resurface the block decks, and the block had a new cam bearing set and brass freeze plugs installed.
The new Eagle crank was of course standard rod journals and standard main journals for 350 cid, and had the Clevite (previously Michigan) rod and main bearings installed.
We resized the stock 5.700” connecting rods with new rodbolts and nuts, and used a 400 cid balancer on the engine.
It had a 60# or high-pressure oilpump and new screen; new pushrods and rocker arm kits; a double row, roller timing chain set with steel gears.
It is customary for us to do a valve grind and resurface cut on the cylinder heads, and the invoice shows me the exhaust valves were 1.60” and the intake valves 1.94”; the valve springs were for a street application. The engine was reassembled with a Fel-Pro gasket set.
It looks like the OEM distributor was reworked with a new cap, rotor, ignition coil, module, pickup, vacuum control, and HEI advance curve kit (weight kit), along with Moroso spark plug wires and loom holders.
The Carter carburetor had a fuel line made from #6AN braided hose and an inline fuel filter too, plus an under-the-carb spacer.
At engine reinstallation the following were changed: AC Delco spark plugs; Fram oil filter, air filter, crankcase filter, and PCV valve; Goodyear P/S and alternator belts, lower radiator hose, and 5/8” and ¾” heater hose; it had a new ASC waterpump and Hayden fan clutch; a new radiator and Stant radiator cap and thermostat; and an oil pressure sending unit (for gauge on dash).

Oil
The oil filter recommended on rebuild sheet was Fram PH5, but no Fram in Ireland,
so I used Mahle OC114, which after comparison is a similar deep filter.
Oil used was a generic 10W30, as this was the weight recommended on the rebuild sheet.
As regards oil used before exhaust, the level was always between the dipstick markers,
but some oil could have been used, I can't be sure as didn't record the exact level.
I had only done short runs into town, before exhaust fitted which was 120miles round trip.
And when I checked the oil level the next day, it was down to bottom marker, so I topped it to middle.
I did a similar trip a month later, and again the level was down to the bottom marker.
The oil smells like oil (not gas), and it flows down the dipstick slowly (like oil would).
There is little or no smoke out the exhaust (and certainly no bed smells or buffs of blue smoke).
There is a little wet oil on the driver side valve cover spread bar, just under the oil fill cap.
Opened a plug, broke it as super tight, and it is black crusty around rim of plug, see pics.
The PCV valve is working as rattles when shaken and was replaced at rebuild.

Smell of Gas
Mechanical fuel pump (not electrical) and there is NO fuel pressure regulator on it.
The car is kept in a small garage, and you can smell gas when going into the garage.
The car has always had a smell of petrol (gas), but there are no leaks on the garage floor.
There is no leaks on the intake or fuel lines either.
The exhaust fabricator commented on the smell of gas too, as he was welding.
I put the smell of gas down to the cheap replacement plastic fuel cap on the tank.
It should be a screw type, should it be a vented or non-vented cap??
And does the smell of gas indicate flooded carb?

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That plugs shows 100 percent oil deposits. Oil is being pulled into the chamber from somewhere.
Send a bore scope down the carb to the backs of the intake valves and see what they look like. If they are clean, it's the ring package. If they are also ugly, it's the intake gasket, Intake bolts, valve guide seals, or rocker studs.
 

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Discussion Starter · #18 ·
I didn't pull them all yet.
Here is pics of the carb with the air filter off.
The air filter is dirty and definitely not letting in full air (i didn't change it yet and it looks old).
When I hold a light up to it, very little light can be seen. The paper is grey and there is a smell of oil.
And there is oil on the gasket and some black oily film on the carb wall.
And the hose from the PVC valve where it goes into the carb vacuum area is oily as well, see the pic.
The vacuum hoses and caps are cracked in places.
There was oil on the crankcase breather filter too, a black circle of wet black oil where the pipe opening is.
Could it be possible that restricted air flow, pulled in oil vapor from the PCV valve and from the other side too?
Or am I way off track.
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Discussion Starter · #19 ·
Sorry, I don't have a scope but will try to get one.
I am still confused and would really appreciate any answers to these questions.

What is the smell of gas from?
Should the fuel tank have a vented or unvented fuel cap?
Should the fuel pump return line be reconnected (why would anyone disconnect it)?
Could no fuel regulator cause the oil in the chamber?
Could a very restricted air filter drag the oil vapour into the chamber?
And has the reduced back pressure also made it rich and a little worse?
(I noticed a trend here, where boy racers put on an oversized exhaust system on their
1.6 litre and then the back of their car is black, from black smoke out the pipes)
If I put on a regulator, do i need a return line from it too? (Or no as mechanical pump)

Thanks to all for your help!
 

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Sorry, I don't have a scope but will try to get one.
I am still confused and would really appreciate any answers to these questions.

What is the smell of gas from?
Who knows. Use your nose.
Should the fuel tank have a vented or unvented fuel cap?
Vented if it's not vented somewhere else
Should the fuel pump return line be reconnected (why would anyone disconnect it)?
Depends....need more details.
Could no fuel regulator cause the oil in the chamber?
No
Could a very restricted air filter drag the oil vapour into the chamber?
Yes....
And has the reduced back pressure also made it rich and a little worse?
possible...Not probable you would notice
(I noticed a trend here, where boy racers put on an oversized exhaust system on their
1.6 litre and then the back of their car is black, from black smoke out the pipes)
People are stupid
If I put on a regulator, do i need a return line from it too? (Or no as mechanical pump
Depends on the system. Need more details of how its plumbed. Most likely not

Thanks to all for your help!
 
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