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Old 04-03-2011, 11:16 AM
 
352 posts, read 1,784,807 times
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Too all older 70's muscle car era gear heads I need some opinions about installing a catalytic converter onto a magnaflow catback 2.5'' stainless exhaust systems. I have a 72 Monte Carlo and want to reduce the smell of the exhaust onto my clothes. I wanting to drive without having too smell like exhaust fumes and jumping in the shower after driving my vehicle.

My question is do you know of anyone who have a early 70's chevy with cats, if so what brand, style would be a good fit for my car by experience? I looking on autoparts warehouse and they have a variety of universal cats but its hard for me to order one without worrying if it will be a good fit on my vehicle. I have long tube headers where the flange stretches approx. 6'' behind the front wheels. Any suggestions and advice would be helpful.
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Old 04-03-2011, 01:58 PM
 
Location: East of Seattle since 1992, originally from SF Bay Area
28,387 posts, read 50,582,032 times
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Sounds like you have a mixture problem on the carb. Until recently I drove a '72 El Camino 350 4 bl and never had that problem with exhaust smell.
Those good old engines did need a tuneup often to run well, I checked everything at every other oil change, including pulling and cleaning/gapping the plugs.

If you really want to do this you will need to add electronic fuel injection,
oxygen sensors and a computer to monitor and operate them. It's not real practical. Add a cat without the rest and it will overheat, melt and clog up within the first few hours of driving.
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Old 04-03-2011, 02:42 PM
 
Location: U.S.A.
3,306 posts, read 9,009,036 times
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If the fuel is burning properly there is no reason you should reek of exhaust fumes. If its running that dirty you'll just clog up any cat you put on there.
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Old 04-03-2011, 04:41 PM
 
4,248 posts, read 10,228,903 times
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I bet it's running pig rich.
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Old 04-03-2011, 04:55 PM
 
352 posts, read 1,784,807 times
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Quote:
Originally Posted by bisjoe View Post
Sounds like you have a mixture problem on the carb. Until recently I drove a '72 El Camino 350 4 bl and never had that problem with exhaust smell.
mixture problem? I have a 750 holley dp running WOT. Thats the only way the car will stay running. Its a 383 stoker 10:1 comp. with a highrise airgap intake. I recently change the electronic Holley fuel pump at 110 gph at max 9 psi due to it burning out at only after 1.5 years approx 20 hour of running time. I just last weekend swap to a mr. gasket electronic fuel pump at 105 gph at 14 psi. Its made a difference in getting started and better performance. That holley fuel pump wore down my last battery on startups. How about oil? I using 20/50 regular oil. Will using a partial or fully synthetic 20/50 oil make a difference in combustion? Will switching to a thinner grade oil partial or even fully synthetic be wiser? I'm running 160* on the temp meter. I pancake electric fan does the trick. See youtube link of engine.


YouTube - Jeff's 72 Monte Carlo 383 stroker
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Old 04-03-2011, 05:00 PM
 
Location: Vancouver, B.C., Canada
10,715 posts, read 22,325,919 times
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that is alot of carb CFM for a 383 SBC a samller carb and a intake manifold more for low to mid range power would be better unless you run at 6000rpm on a regular basis you don't need such a big carb
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Old 04-03-2011, 05:14 PM
 
Location: Vancouver, B.C., Canada
10,715 posts, read 22,325,919 times
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haha the smell of exhaust fumes reminds me of my 83 bronco with it's 351 windsor that I had installed a manual choke and when pulled all the way out with the choke plate fully shut it would smell pretty bad plus you always had to keep leaning it out it as it warmed up.

bisjoe is right EFI is so much better that carbs really are obsolete

anyways depending on the outside temperature where you live the choke may need adjusting. This will control how the choke will open and close.
Some carbs utilize screws that you can loosen and rotate the choke bi-metal spring. This will change the spring's position and vary the tension increasing and decreasing the operation as needed. Tighten the spring for more choke in cold weather and lessen the tension in warm. Choke adjustment can vary so make sure to lok up the specs.

since the engine is difficult to start when cold, take off the air cleaner and watch your choke in action (get a friend to help for that though). Tap the gas pedal once to the floor before the engine is running (Key on) when cold and see if the choke plate closes. If there are carbon deposits clean as needed and recheck operation. When a choke is operating during warm-up the engine idle is increased, this keeps the engine from stalling at idle, but should decrease as the engine warms up and the choke releases.
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Old 04-03-2011, 06:39 PM
 
352 posts, read 1,784,807 times
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GTOlover the choke is manuel. There's no choke cable install on this car. The only way it will run is WOT without choking. I tried to adjust the choke once closing it a bit at a time after running for awhile in summer temps. The more I adjust the throttle close the car start idling ruff until it chokes. Its a crate motor I bought 9 years ago. I lost all the spec and component sheet.

before I install this carb I had a carter sp 650 cfm and mechanical pump. I couldn't get enough fuel in the carb to keep the engine running smooth at highway speeds. At every toll I stop at the car dies. I had to rev up the engine to get enough fuel in the carb for a launch. Once running it will hold out until the next complete stop. At street level speeds I was ok with no problem.

Last edited by Boo2lowkey; 04-03-2011 at 06:50 PM..
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Old 04-03-2011, 06:48 PM
 
Location: Vancouver, B.C., Canada
10,715 posts, read 22,325,919 times
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Quote:
Originally Posted by Boo2lowkey View Post
GTOlover the choke is manuel. There's no choke cable install on this car. The only way it will run is WOT without choking. I tried to adjust the choke once closing it a bit at a time after running for awhile in summer temps. The more I adjust the throttle close the car start idling ruff until it chokes. Its a crate motor I bought 9 years ago. I lost all the spec and component sheet.
hmm go and add either the manual choke cable or electric choke kit.....However, one simple and inexpensive addition either way is a Moroso 1:1 secondary linkage kit as this is the only place Holley has yet to fix on their own.

When choosing a carb you have to remember that bigger is not always better. Instead I would of stuck with the 600cfm carb and allow a good carb shop to jet and rejet as need be.
here is the part for the electric choke upgrade from holley
http://www.holley.com/45-223.asp

you may also want to get a carb rebuild kit while you are working on it anyways http://www.holley.com/3-1016.asp

Last edited by GTOlover; 04-03-2011 at 06:56 PM..
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Old 04-03-2011, 06:51 PM
 
352 posts, read 1,784,807 times
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GTOlover see my edited post. I planning on getting a electric choke this week.
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