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To remove converter or not?

Started by CDV13126, August 11, 2015, 07:27:47 PM

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CDV13126

My 1975 CDV has a pellet style converter. I am thinking of draining it so the engine has more power and breathing room. Does anyone here have experience doing this? How difficult is it and is it worth it? Does it actually make a difference for power and stress on the engine?

76eldo

I put a 71-74 exhaust on my 76 Eldorado and it runs much better especially in mid range torque.

I needed a new system anyway.

I'd remove the cat and have a bypass pipe made to go in its place.

Brian
Brian Rachlin
Huntingdon Valley, Pa
I prefer email's not PM's rachlin@comcast.net

1960 62 Series Conv with Factory Tri Power
1970 DeVille Conv
1970 Eldo
1970 Caribu (?) "The Cadmino"
1973 Eldorado Conv Pace Car
1976 Eldorado Conv
1980 Eldorado H & E Conv
1993 Allante with Hardtop (X2)
2008 DTS
2012 CTS Coupe
2017 XT
1956 Thunderbird
1966 Olds Toronado

EAM 17806

Quote from: CDV13126 on August 11, 2015, 07:27:47 PM
My 1975 CDV has a pellet style converter. I am thinking of draining it so the engine has more power and breathing room. Does anyone here have experience doing this? How difficult is it and is it worth it? Does it actually make a difference for power and stress on the engine?
Removing the Cat converter would be a violation of Federal law, wouldn't it?  EAM
Ev Marabian

1976 Cadillac Coupe DeVille, 1989 Chevrolet Caprice Classic, 1990 Pontiac Bonneville and 1996 Buick Skylark

TJ Hopland

Just remember even if there is currently no testing / inspections where you currently register your car its still not legal to remove a cat from a car that left the factory with one plus ya never know what the government folks are going to do next.   

You can get aftermarket cats that flow well for very reasonable prices these days.  I have not looked for a 75-78 E car but I have been surprised a few times how many old cars they still make direct fit cats for. 

If you are trying to get things to flow better getting rid of that manifold thing between the down pipes and cat would have to help.  That thing could not have helped the flow at all.   The curved Y on the earlier cars had to flow better.   If you really trying to get some flow the air cleaner assembly is not exactly a free flowing area either.   
StPaul/Mpls, MN USA

73 Eldo convert w/FiTech EFI
80 Eldo Diesel
90 CDV
And other assorted stuff I keep buying for some reason

76eldo

The feds are too busy looking for terrorists to bother checking our vintage rides for convertors.  Registered as an Antique in PA makes the annual safety and emissions check unnecessary.

I went with a 71-74 style exhaust specifically to get rid of the cast iron box that has both down pipes blowing exhaust into each other and making a hard 90 turn, then going through a 40 year old cat convertor, then through a muffler and resonator.

All i know is my car sounds and runs better and I was able to find NOS parts, except for the muffler and it looks good at the back too.

Brian
Brian Rachlin
Huntingdon Valley, Pa
I prefer email's not PM's rachlin@comcast.net

1960 62 Series Conv with Factory Tri Power
1970 DeVille Conv
1970 Eldo
1970 Caribu (?) "The Cadmino"
1973 Eldorado Conv Pace Car
1976 Eldorado Conv
1980 Eldorado H & E Conv
1993 Allante with Hardtop (X2)
2008 DTS
2012 CTS Coupe
2017 XT
1956 Thunderbird
1966 Olds Toronado

CDV13126


I went with a 71-74 style exhaust specifically to get rid of the cast iron box that has both down pipes blowing exhaust into each other and making a hard 90 turn, then going through a 40 year old cat convertor, then through a muffler and resonator.

All i know is my car sounds and runs better and I was able to find NOS parts, except for the muffler and it looks good at the back too.

Brian,

Can you tell me more about the differences between the 74 and 75 exhaust systems? Specifically what you mean by the cast iron box and down pipes? Where were you able to find an exhaust system NOS?

TJ Hopland

The 71-74 has a a fairly gentle curve from both sides of the engine that make a Y to the intermediate pipe that basically runs down the center of the car.  I'm not an aerodynamic engineer but to me it looks like it would have reasonable flow.    The 75-78 the cat is kinda under the passenger side floor.  Instead of a gentle curves and a Y this system has what looks to be a cast T that is the junction between the down pipes and the cat.   I had one apart and I don't remember the internal volume or passages looking any better from the inside than the outside so it could not have been very good for flow then you hook that to the early cat designs that even when new didn't flow that well it could not have helped things.   

That all being said I was driving my rebuild engine dual exhaust EFI 73 and a all stock down to the cat 75 at the same time and there was not a huge difference in day to day driving performance.  Oddly the 75 got better MPG than the 73 too.    When I got the 75 I had thought the cat was plugged but after I got the carb rebuilt, distributor advance stuff working, and a bunch of vac lines replaced (basically put everything back to stock working order) it started running great.   
StPaul/Mpls, MN USA

73 Eldo convert w/FiTech EFI
80 Eldo Diesel
90 CDV
And other assorted stuff I keep buying for some reason

76eldo

My car is an Eldorado which has a different system than a CDV.

1975 (as far as I know) was the first year for the catalytic convertor and unleaded gas.  There was always AMOCO White Gas, which was unleaded, but 1975 was the year of the CAT and the restricted fill hole in the tank filler, and the smaller sized nozzles at the pump.

On a 76 Eldorado, there are two pipes that come down from the heads and basically face each other.  Then they make a tight 90 degree turn towards the rear of the car in a cast iron "box" that is probably full of rust inside by now.

The 71-74 Eldo system has a more flowing line design as you can see in the illustrations below.

I am sure your 75 CDV does too.

When I removed the front pipes, cast iron fitting, and the CAT it took two people to lift it.  So in addition to removing what I view as a restriction I also took some weight off of the car, not that it will make a difference.

Some people, like my good friend Joe Caristo are appalled by modifications of any sort and would never deviate from the "as delivered" state of the car.  My take is that this is a pretty much invisible change, not like adding duals, and I used a factory designed system, just for a slightly older Eldo.

As far as finding an NOS system, the front pipes and muffler are Walker.  The intermediate pipe and tailpipe with resonator were GM NOS units located on Craig's list.  This was in the making for a few years but when my system was whistling down the road due to holes in the muffler it was time to get this done.

Brian
Brian Rachlin
Huntingdon Valley, Pa
I prefer email's not PM's rachlin@comcast.net

1960 62 Series Conv with Factory Tri Power
1970 DeVille Conv
1970 Eldo
1970 Caribu (?) "The Cadmino"
1973 Eldorado Conv Pace Car
1976 Eldorado Conv
1980 Eldorado H & E Conv
1993 Allante with Hardtop (X2)
2008 DTS
2012 CTS Coupe
2017 XT
1956 Thunderbird
1966 Olds Toronado

TJ Hopland

Brian's reply about his Eldo made me forget that the original question was not about an Eldo.    I don't think the RWD cars had that cast thing like the Eldo's did.   Its been too long since I have been under a RWD 75-76 Cad.  I'm thinking the 77-79 was not too bad of a design, I don't remember it standing out when I had my 78. 
StPaul/Mpls, MN USA

73 Eldo convert w/FiTech EFI
80 Eldo Diesel
90 CDV
And other assorted stuff I keep buying for some reason

76eldo

TJ

No his Coupe would not be like the Eldo.  I was supporting his thought to get rid of the CAT and wanted to explain what I did along those lines.

Brian
Brian Rachlin
Huntingdon Valley, Pa
I prefer email's not PM's rachlin@comcast.net

1960 62 Series Conv with Factory Tri Power
1970 DeVille Conv
1970 Eldo
1970 Caribu (?) "The Cadmino"
1973 Eldorado Conv Pace Car
1976 Eldorado Conv
1980 Eldorado H & E Conv
1993 Allante with Hardtop (X2)
2008 DTS
2012 CTS Coupe
2017 XT
1956 Thunderbird
1966 Olds Toronado

bill06447

If someone wants to keep the cat for a visual authenticity type thing, the innards come out easily when poked and prodded through one end with an iron rod, leaving the shell intact.

Bill

The Tassie Devil(le)

In Australia, it is a well-known fact that the Catalyic Converters are useless after 80,000, as the Cat is degraded that much that more pollutants are being put out than without them.

Not many old cars around here running with Cats.

The older cars without computers run well with "Normal" exhausts.   Especially one that doesn't use an Oxygen Sensor.

Bruce.>:D
'72 Eldorado Convertible (LHD)
'70 Ranchero Squire (RHD)
'74 Chris Craft Gull Wing (SH)
'02 VX Series II Holden Commodore SS Sedan
(Past President Modified Chapter)

Past Cars of significance - to me
1935 Ford 3 Window Coupe
1936 Ford 5 Window Coupe
1937 Chevrolet Sports Coupe
1955 Chevrolet Convertible
1959 Ford Fairlane Ranch Wagon
1960 Cadillac CDV
1972 Cadillac Eldorado Coupe

Smedly

I drained a few of those large cats before etests came to Ontario. there is a round plug on the underside of the cat, if you use a chisel and hammer you can remove the plug then start the car up. This will blow all the pellets out and the just use a frost plug to cap off the hole. It is a 10 minute job.
When a Doctor "saves a Life" it does not necessarily mean that that life will ever be the same as it was, but he still saved it. My 46 may not be as it was but it is still alive.
Sheldon Hay

TJ Hopland

If you look in the service manual for those early years cats they show a service procedure to replace the catalyst.  The 'balls' must have been available as a service part originally.
StPaul/Mpls, MN USA

73 Eldo convert w/FiTech EFI
80 Eldo Diesel
90 CDV
And other assorted stuff I keep buying for some reason

936CD69

Not only were the catalyst pellets replaceable, on a few cars (GM) replacement was part of a 50000 emissions requirement. Most had a flag on the odometer that cover the miles at the specified mileage and said "emission'. The replacement pellet kit had a new plug in the box, and there was a special tool to reinstall the plug. 
Craig Brillhart CLC# 26217
1993 Sedan deVille Spring Edition Carmine Red White Top-SOLD!
1993 Sedan deVille Spring Edition Triple Black
CLCMRC Benefactor #302

CDV13126

So would simply draining the pellets solve the exhaust flow restriction, or is it the whole unit itself that restricts?

The Tassie Devil(le)

Once the pellets are gone, it is just an empty box.

BUT.   What is in each end to stop the pellets from simply getting blown out when the exhaust is flowing through?

Bruce. >:D
'72 Eldorado Convertible (LHD)
'70 Ranchero Squire (RHD)
'74 Chris Craft Gull Wing (SH)
'02 VX Series II Holden Commodore SS Sedan
(Past President Modified Chapter)

Past Cars of significance - to me
1935 Ford 3 Window Coupe
1936 Ford 5 Window Coupe
1937 Chevrolet Sports Coupe
1955 Chevrolet Convertible
1959 Ford Fairlane Ranch Wagon
1960 Cadillac CDV
1972 Cadillac Eldorado Coupe

bcroe

Quote from: 936CD69Most had a flag on the odometer that cover the miles
at the specified mileage and said "emission'.

Yes they did, my 80 diesel had one.  What bothered me was the manual instructions
"Have the DEALER reset the "EMISSIONS" flag.".  All you had to do was reach up
under the dash and pull a little cord.  I threw all that away when I rebuilt the
odometer to an extra digit, currently 314,613 miles.  Bruce Roe

CDV13126

Quote from: The Tassie Devil(le) on August 14, 2015, 08:00:39 PM
Once the pellets are gone, it is just an empty box.

BUT.   What is in each end to stop the pellets from simply getting blown out when the exhaust is flowing through?

Bruce. >:D

Bruce, what do you mean by this? That the pellets would blow through the exhaust into the muffler? Once the plug is out, what is the best way to drain the pellets effectively?

The Tassie Devil(le)

Not knowing exactly how these things are built, the Pellet ones, there has to be some sort of obstruction in the end of the converter to stop the loose pellets from simply blowing out.

With the Ford style, they just use a honeycomb type, and everything holds together in one mass.   These don't have any means of stopping the big block from coming loose.

Bruce. >:D
'72 Eldorado Convertible (LHD)
'70 Ranchero Squire (RHD)
'74 Chris Craft Gull Wing (SH)
'02 VX Series II Holden Commodore SS Sedan
(Past President Modified Chapter)

Past Cars of significance - to me
1935 Ford 3 Window Coupe
1936 Ford 5 Window Coupe
1937 Chevrolet Sports Coupe
1955 Chevrolet Convertible
1959 Ford Fairlane Ranch Wagon
1960 Cadillac CDV
1972 Cadillac Eldorado Coupe