Can polution equipment,smog pump,catalytic converters,and all pertinent items be removed instead of replaced on my 1977 L48 or will I be executed by someone in this group the first time I open the hood.Any Ill effects on the motor or will it do better in the performance catagory? Is restoring or replacing those Items a good thing?
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Re: smog pumps, emision stuff,etc.
What's your objective?
If you have your car Flight judged, you'll loose points for missing or improperly configured equipment.
Just removing emission equipment may not result in better performance. You can achieve better performance by remapping the ignition to pre-emission specs without removing any equipment. Disabling the heat stove will reduce inlet air temperature, but could require some carburetor work to get mixture right.
If you car has to be emission tested, any alterations could result in a visual or tailpipe test failure.
If your car doesn't have to be emission tested and you make any alterations, ecoterroists will burn your house down.
Duke -
Re: smog pumps, emision stuff,etc.
Thanks for your response Duke.Being a new Corvette person,I guess "flight judged" is a type of judging.If so,no judging on this car,I only want a good running,good looking car.My days of having cars judged is over.I thought that by removing those few pollution devices the low HP motor would perform better.I'm restoring this car to the nines w/out doing a frame off.I bought it as a beater,which it is.This is my 3rd Corvette but first to restore.The 6 Model T Fords I did in the last 12 yrs.didn't have too many OPTIONS from the factory.The polution pump on this 77 is a whole new thing to me.If someone says its best to leave it on I will,I'm just now learning and this website has been great for the last 2 -3 weeks.I thank all for there responses.Comment
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Re: smog pumps, emision stuff,etc.
If you're not concerned with emission testing or flight judging, the best way to improve performance is backdate everything to '67 300 HP non K-19 spec including the exhaust system and an open element air cleaner. This will probably require richer jetting in the Q-jet, and obviously the HEI will have to be remapped and converted to full time vacuum advance.
If you want to pull the heads, pocket port/port match them. If you want to do the whole engine, select new pistons that yield no more than 9.75 CR and retard an OE replacement cam 4 degrees.
If you want to upgrade to SHP, use the forged replacement pistons dialed into no more than 10.5, and use the SHP cam of your choice.
All of the above is done with OE or OE equivalent replacement parts. No "hot rod" parts are necessary or desireable.
DukeComment
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Re: smog pumps, emision stuff,etc.
Mike, If you take the smog stuff off, dont throw it away as I did. Clean it up and save it. I paid more for the O.E.M. replacement of my 1967 C-2 smog system than the cost of my Corvette in the early 70's. DaleComment
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use early 1970's intake
Use the cast iron early 70's intake without EGR - it's DIRT CHEAP in the junkyard and was factory used on the 255 - 350 HP engines. If you want to save your original carb, get a 1969 or 1970 300 HP carb or rebuilt replacement. Then recurve your distributor and set the timing to the 1969-70 specs and you'll be up and running for just a few $.
MarkComment
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Re: use early 1970's intake
The "conventional wisdom" back in the smog days was that if you removed that ugly A.I.R. pump, all would be well again. Wrong. The A.I.R. pump had nothing to do with the engine running like crap, and didn't reduce or use horsepower. They ran like crap because of carburetor calibration, retarded timing (initial and the centrifugal curve), and "ported vacuum" (or none at all with TCS unless you were in high gear). Dealing with the calibration issues can bring back a lot of performance and improve driveability without digging into the engine or removing a bunch of (rare and valuable) K-19 parts.Comment
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Re: use early 1970's intake
The biggest loss of power on seventies vintage engines was the single bead bed catalyst. According to Dave McLelland's book this added "half an atmosphere" to exhaust back pressure - that's over 7 psi.
My Engine Analyzer computer simulation model of the C2 2.5" exhaust system only creates a little over 3 psi on a massaged 327 SHP engine that produces about 325 net HP at the crankshaft and revs to 7000 versus 10-12 psi on seventies vintage catalyst cars that have much less power. Exhaust flow increases approximately linearly with power, and backpressure increases with the SQUARE of flow.
Improved carburetor and spark advance calibrations can improve driveability and low end torque (or screw them up if you don't know what you're doing), but there's no way to substantially improve upper rev range power unless something is done about the exhaust system, first.
A modern replacement monolithic catalytic converter will help the situation, but a full dual exhaust system must be installed before any internal engine modifications will have much, if any, effect.
DukeComment
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Re: use early 1970's intake
Duke------
...and, unfortunately, it's federal emissions-illegal to install a full dual exhaust on any car originally equipped with a single catalytic converter even if higer emissions performance, monolithic, dual catalytic converters are also installed.
So, if one wants to improve BOTH engine performance AND emissions performance, one can't do it legally.In Appreciation of John HinckleyComment
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Re: use early 1970's intake
One could install a modern small monolithic converter is each pipe, and emissions performance would likely be maintained, however, unless the car goes through some kind of certification program, it would still technically be illegal unless it was recertified.
In California an emission test inspector would have to fail the car on visual inspection because the original single catalyst was changed to a dual catalyst, however, I don't think most inspectors know the catalyst configuration of 30 year old Corvettes, so if the car passed the tailpipe test and the inspector saw two catalysts in the exhaust system it would probably pass.
DukeComment
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