Replacing exhaust system

[spoman]

Bit of a story behind this one:

I decided last weekend to check out the exhaust on my 1988 Festiva since it was very loud. I pull it off and find 8 pinholes in the resonator. So I'm thinking I can easily patch this, but they seem too small to make much noise. I look further down the pipe and find a spot where it has almost completely rusted through. I'm thinking, "Okay this is the problem. I'll just patch this and be done with it." However, I decide to check out the rest of the pipe. I found two more places where it was almost completely rusted through and a 1" hole. All of this is even before I get to the muffler, which one of the first things I replaced on the car. So I decide to replace the whole intermediate pipe from the catalytic converter to the muffler. I found one on Amazon for $80 w/ S & H. My Dad also wanted me to get a catalytic converter seeing as the car didn't have one. There's no emission checks here. Well, getting to the point I had to get a new seal and gaskets. The seal I bought (Walker 31360) doesn't fit on the down pipe (the exhaust pipe that connects onto the exhaust manifold), but it's very close. It just needs a few more millimeters. I've never dealt with this kind of seal before. Is it supposed to slip on the flange easily or is it supposed to get compressed onto the flange? It's possible that either the seal is the wrong size or the flange itself is too big.

[drumnerd33]

im not seeing that part number for the gasket... could be wrong gasket, should fit perfect if it was the right one.

[drumnerd33]

Is this the one your needing?

http://www.oreillyauto.com/site/c/detail/FEL0/60286/02412.oap?year=1988&make=Ford&model=Festiva&vi=1128080&ck=Search_exhaust+gasket_02412_1128080_2989&keyword=exhaust+gasket&pt=02412&ppt=C0189

[drumnerd33]

oops i just searched the part number you said.. so you mean the doughnut on the flex fitting... a new one will be tight but should still fit.

[FestYboy]

spoman, if you don't have emissions testing where you are at and your carb system isn't COMPLETELY intact, DO NOT put the cat in.

you'll waste your $$ and quickly kill the cat causing the engine to run like poop.

[spoman]

spoman, if you don't have emissions testing where you are at and your carb system isn't COMPLETELY intact, DO NOT put the cat in.

you'll waste your $$ and quickly kill the cat causing the engine to run like poop.

What do you mean by COMPLETELY intact?

[XFSE71]

If your system is overfueling then the cat may be damaged. The cat may overheat and melt down if the engine is not running in closed loop. closed loop is where the cat takes a breath of air in between gulps of unburned fuel. that is usually no check engine light. no lean rich duty cycle pulse width means cat substrait melt down. a melted down cat will restrict exhaust flow and lose power to the point of no start. You can test it.

[spoman]

If your system is overfueling then the cat may be damaged. The cat may overheat and melt down if the engine is not running in closed loop. closed loop is where the cat takes a breath of air in between gulps of unburned fuel. that is usually no check engine light. no lean rich duty cycle pulse width means cat substrait melt down. a melted down cat will restrict exhaust flow and lose power to the point of no start. You can test it.

So I have to run the carb leaner rather than richer(overfueling)?

[drumnerd33]

A simpler way of putting it... Open loop is a preset air to fuel ratio for starting the car... Once the engine temp sensor is up to temp and tells the computer it is operating at normal temp it switches into closed loop which adjust your ratio by using the sensors. Now if you are stock carb it does have an open loop closed loop if I remember correctly, you don't need to adjust it at all. I agree with leaving the cat off... Of you don't have emissions then don't worry about it.

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[spoman]

Okay well, I'm already getting the cat, so I'm kind of committed here. What do i need to check or do before running the car again?

[FestYboy]

has any of the PAIR system been removed from the intake? essentially, has anything other than the cat been tampered with in the engine bay area. if the air filter housing has been modified in any way or is missing altogether and the tubes from the exhaust manifold to the air cleaner and from the air cleaner to the cat have been tampered with or are missing: DO NOT install the cat.

post pics, that's the easiest way to see if there's something amiss.

[XFSE71]

So I have to run the carb leaner rather than richer(overfueling)?

Running lean will also cause engine damage to your pistons. No you don't want to run lean, and you don't want to run rich. running in closed loop the ECA alternates between rich and lean. So if you run a cat as Ford and the Feds intended the entire engine management system has to be operational. Without a cat you can run rich without a problem. You never want to run lean with or without a cat. You have a FBC (Feed Back Carb) which is capable of the lean/rich duty cycle provided the system is intact and functional. Carbs have a complicated system of vacuum components and hose routing that can be intimidating at best.

[drumnerd33]

When I did my weber swap I disconnected everything including the egr system and I didnt know anything about tuning a carb so I was using the jets that came in the weber... It ran fine but covered the back of the car in black... Lol I ran it that way for at least 5 months then tuned it without an afr gauge and went from 160 mains down to 100 and 110 mains so I was extremely rich and when I pled off my cat... It was just fine. I don't know if rich is bad for the cat or not but it sure didn't hurt mine.. And mine was the original 1988 cat and it was 100% intact and I even turned it in to be recycled and they paid the full price for it because it was perfect. As far as lean yes lean is bad... And over time if you run too lean it will damage your valves, but if your running the feedback carb it's not gonna put you in a lean condition... The fail safe if any of the sensors aren't working is to go into open loop Which will make it rich, so you will lose mpg but not hurt anything... There is tons of people that have no idea about open loo and closed loop and drive with bad o2 sensors or bad temp sensors so they are driving around with the check engine light on and being in closed loop the whole time... Some systems didn't even throw a code to tell you the o2 was misreading and causing a closed loop condition.

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[FestYboy]

^ open loop Drumnerd, a system will default to open loop if something is amiss (bad o2 or ECT sensors)

[MasterTec]

I'm with drummer. I'm running a weber (130/120 jets albeit closer to sea level) as well as the original 1989 cat and have no flow issues whatsoever.

As far as the air injection system goes - well I obviously have the tubes cut and sealed off but even before the swirl valve's diaphragm was blown for God only knows how long and the Cat still survived.

These cats are pretty tough. I'd say that unless you've got a misfiring cylinder you don't have to worry too much about damaging the cat... at least not until at least several months pass.

(for the record I left my EGR, Cat and Evap systems intact)