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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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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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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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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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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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Discussion Starter · #13 ·
And i'm just after seeing the return line from the fuel pump is blanked off just before it goes into the fuel tank.
??
 

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Discussion Starter · #16 ·
I'm sure its not the dip stick as I helped fit the exhaust and it wasn't touched.
 

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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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Discussion Starter · #22 ·
Sorry for only replying now, had to bring the young lad to football.
Its a stick shift, so I think there's no vacuum to the transmission.
But yeah, I see what your saying, to be fair the vacuum pipes cracked could be age related,
but its hard to defend not putting in the fuel regulator, when its so accepted in rebuilds.
The shop that did the work it is a well known engine performance company in Dayton Ohio.

But I have to work with what I've got now, and was just wondering about the fuel lines.
The plumbing is very basic, 2 lines go from the tank to the pump (one is plugged at the tank)
and then one line goes from the pump to carb (with an inline filter).
So still have to figure out whether to use vented or unvented cap?
And I would think the fuel pump return line should be reconnected to the tank,
which would mean the regulator would not need a return line. Does this make sense?

My friends and family say i'm mad, especially as all the parts have to be shipped from USA.
But I lived in the States for 10 years and my happiest memories were when I had a Chevy V8,
and I'm just trying to get that same buzz again, before its too late. I'm 50 now, ouch!
 

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Discussion Starter · #25 ·
what you think is the return line on the tank is actually the vapour line from the tank to a charcoal filter. That charcoal filter should be found beside the radiator. It’s about 6 inches in diameter by 6 inches deep.It acts as your tank vent. It’s hooked up to manifold vacuum port on your carb.
if the line on the tank is capped off you must have a vented cap.
You don’t need a return style regulator.
First you need to check your fuel pressure. If it’s at or below 6 psi you might be okay.
That makes sense. I know where the charcoal filter is and it is not being used.
There have installed an engine and disconnected all the emissions stuff that ruined the horsepower
of these cars. The EGR is gone, the Oxygen sensor is disconnected, and charcoal filter not used.
Seems they put the vented cap to vent the tank and have one line to the pump.
Its a simple fuel to engine setup, to increase the HP, I guess.
I imagine this is what was requested of the rebuild to increase the hp to be the same as the older Trans Am's.
Thanks for that, I understand it a bit better now.
 

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Discussion Starter · #26 ·
Either the line at the tank was for a closed tank vent system that is no longer there or for a regulated fuel pressure return. For sure the original tank vented through a charcoal filter under the hood so I suspect that was a vent line but you really need to get a 1981 service manual so you can trace out what is wreckage you see. If that was a vent line and the source is plugged then unless something else was done to provide a vent the tank is doing without. The simplest is a vented cap whether purchased or a modified original. The other should be a fear looking at the sloppy workmanship you certainly don’t want a fuel tank that can puke in an accident.

Like I said this car has been through a butcher shop, now you need to fix it. By that I don’t mean to return it to original condition but you need to know what was there so you can trace down what needs to be properly terminated if no longer going to be used compared to fixing what needs to be there and making it safe and as orderly as possible.

You need to look at the VIN code and back that into the original configuration of the vehicle.
I suppose it depends on you whether you want to clean the swap up make it look reasonably professional or live with it like it is. Fixing it will take some time and money, this is what project cars are for.

Bogie
Yes Bogie, I can see what your saying, and i'd say your right they changed the car from what it was originally.
And listening to you guys is a great help to me. And i am doing exactly that and trying to tidy it up.
I know that while it has been in Ireland for the last 5 years the guy I bought it from did nothing with it.
Which I think is a sin, if you own a piece of history like this, you have a responsibility to improve it or at least maintain it.
The Chevy V8 I had in the States, I am very proud to say, that I had it for 10 years and it was better when I sold it
than when I bought it, and I sold it for more than I purchased it for, and I did all the work myself.
When the overdrive was jumpy, I went to a Transmission shop and asked them about it, they wanted to replace it,
for $2,000 but I went through the Manual troubleshooting guide and figured it might be the lock-out solenoid.
So I ordered the lock-up solenoid ($50) from the Chevy dealer and I changed it and that fixed it.
And what's more disturbing is I asked the so called transmission expert, could it be the lock-up solenoid!
I'm no mechanic, but it is my ambition try to improve this car, and I really appreciate you guys advice.
So what practical steps do you suggest I take to improve it, as obviously it's not practical to restore to original.
Thanks again
 

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Discussion Starter · #33 ·
Yes, I could find that, and the 350 is a Chevy also, I think.
I was just wondering if the GM42 had any significance, but it doesn't matter.
I took some more pictures, and there is actually 2 hoses connected to charcoal canister,
one goes to side of air filter housing and the other goes into the passenger side of the carb.
And there is a red wire connector just sitting there (on fuel filter in picture),
don't know if that should be plugged in to anything, as nothing obvious.
Also you can see the oxygen sensor in the manifold is not connected to anything (taped off),
but there is something in beside the plugs on the drivers side with a wire attached to it, what is it?
Hope these help give a clearer picture of what's there.

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Discussion Starter · #40 ·
Actually, 1981 was the first year for computer controlled carburetors. I remember it well (worked in dealership).

I'm really doubting this was a completely rebuilt 383 6000 miles ago. What I can't figure is why the intake/exhaust manifold selection on what is claimed to be a fairly expensive build. I'm guessing probably just a novice-swapped-in used 350 and it's tired.

If it wasn't for the 14010207 casting number photo, I would guess this was the original 305 engine with different carb and distributor.
Here are some pages from the 10 page receipt and tech details provided on cam and carb from shop.
I confirmed with the original owner and shop, that they replaced the 305 engine with a 350 bored to 383.

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Discussion Starter · #44 ·
I sent a few pictures of the carb and charcoal cannister, and was hoping for some guidance
on the vacuum hoses as there laid out now.
Basically I'm asking apart from replacing any cracked hoses and caps, is the current vac hose
setup functional. I know it's not the original layout but just want to make nothing major wrong.
I admit I know very little about what vac hoses are needed. Thanks
The 42GM on the block identifies the casting mold used.

Bogie
Cool info, thanks for that
 

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Discussion Starter · #45 ·
I sent a few pictures of the carb and charcoal cannister, and was hoping for some guidance
on the vacuum hoses as there laid out now.
Basically I'm asking apart from replacing any cracked hoses and caps, is the current vac hose
setup functional. I know it's not the original layout but just want to make sure nothing major wrong.
I admit I know very little about what vac hoses are needed. Thanks again
 
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