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73-87 Chevy _ GMC Trucks => Engine/Drivetrain => Topic started by: liftedchevys87 on March 24, 2010, 02:31:58 pm
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I bought an 87 Chevy 1/2 ton 350 TBI. I allready took the cats off with intentions of removing the air pump and exhaust manifold and running headers with new pipe and mufflers. Now I found out in Connecticut it has to be 25 years old to avoid emissions testing, so Im debating whether or not to go ahead and run headers with no cats.....I have the fenders off and the bed so Ide like to do all that work now. Just wondering if anyone knows how leniant a shop will be or if they just check the computer for codes....but if they visual inspect for cats or sniff the exhaust, Im in trouble.....So if anyone has experience with Connecticut testing, Ide appreciate a post or email. Thanks
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Where in CT are you from? For your truck it is OBDI so it's a tail pipe test ASM2525. They will check your gas cap, visually inspect for cats and run your truck on the dyno. Go ahead and run your headers but you will need cats. I would suggest fitting your exhaust with test pipes so after the test you can remove the cats. What is done to the engine?
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Im located in Guilford. The engine is stock but Im restoring the truck now (body) and I wanted to run headers and exhaust since the old system is rotted out and I have easy access to everything. If i run headers Ide be eliminating the air pump system too. So If I only need cats on Ill just run the headers/pipes under the bed with cats (i have to weld em back on) and then wait till after emissions to run true duals.
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you could always make fake cats... we do it in utah all the time on old cars. we have california emission laws only stricter exemption age (67 and under only) just cut the cats open, take out everything put a tube in weld it up and your good to go, lol. passes visual inspection, might have to add some alcohol to the fuel and change the timing a little to get it to pass emissions though, not sure.
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If you want a gutted cat you just ram a rod through it and break up all the honeycomb catalyst. Then start the vehicle to blow out the debris (exhaust unhooked from the back of the cat). Much easier than cutting it open and welding in a pipe. Is there an advantage to doing it that way? Not that I ever intend to do that. Vile mentioned the Dyno--I assume that means taking it up to speed with an exhaust analyzer, right? (sorry to hijack)
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The ASM2525 "Acceleration Simulation Mode test” means an emissions test performed at a steady state of twenty-five (25) miles per hour (mph) and which utilizes a dynamometer load set to simulate 25% of the power required to accelerate the particular vehicle being tested at 3.3 mph/second until a speed of 25 mph is attained.
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Thanks for help, does anyone have any experience with running a truck through emissions similar to my situation tho? If I advance the timing and run some chemicals do you think it will pass emissions without any emissions stuff on my truck?
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Why would you want to advance the timing? Tune it up, make sure the timing is set to spec, put a cat on it and you shouldn't have any issues.
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our emissions are really tough here (utah) so you have to do some tricks i think in most other states a tune up and your good, ive never had to change the timing on my cars so i dont know what it does, but i have a few buddys that have had to, i think they retarded it though and had to add chemecals, the truck runs like a paraplegic but passes, then you just change everything back. they also had dummy cats though...
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With the old idle speed tail pipe test it was common to unplug the vacuum advance and leave the vacuum hose off for a cleaner idle test. I would not advance the timing to try and pass emissions.
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Allright thanks for the help, I think Ill just put new oil/plugs, warm it up real good before I have it tested and hope for the best with cats. I was told to advance the timing to burn leaner. Im 16, all though I go to a trade school (auto) and have a fair share of work on cars, I dont have the experience yet for diagnosing/techniques/etc.