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Cat. converter question.

My son and I are finishing up an installation of a 400 sm. block Chevy engine into a '79 El Camino. I just finished installing the aftermarket dual exh. with two cat. converters. 2 1/2 inch pipes. No H pipe, (crossover), and probably won't get one. The fellow who always does all the inspections on our cars said he would pass this non-stock configuration if I had the two converters and welded up a heat stove on the right side header for the early fuel evaporation system, which I've already done. The engine has a mild performance cam and an Edelbrock Performer intake manifold, stock Q-jet that came off the old 305, and tube exh. headers. Now that the converters will only get 4 cylinders worth of flow and heat, and the tube exh. headers will be dissipating more heat than the stock iron exh. manifolds, will there likely be a problem with the car passing the idle emissions test with the sniffer? I know that a cat. converter must get to approx. 600 degrees F. before it will light off, and I'm concerned that it will cool down too much at idle and fail the emissions test for us. Does anybody have any experience with these type of modifications and any advice? Thanks for any help.

Garrett Fulton

Reply to
gfulton
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I did try to do that. But because of the bends to clear the trans. crossmember I couldn't get them much closer than about 2 ft. from the collector. No straight section long enough until that distance. Also had to stagger them as the sides of them would have touched. Anyhow the driver's side is closer to the collector and I'll always make sure he puts the sniffer in that side. Thanks seeray.

Garrett

Reply to
gfulton

when you have the cats welded in, place them as close to the header as possilbe, that will get you your 600 degrees and you should be fine

Reply to
seeray

What you can do is buy one of these inexpenxive temperature sensors, that are hand held, and shots out a infared beam that measures the temperature accurately, then it displays the tempature on the led display. should be able to get one for around $100.00 or less. Look at

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they have lots of them in there. Oh by the way do you have any relatives living in south east Georgia. I had a relative that I remember from when I was small, had the same name as yours. Take care. Robbie. Let me know how you make out with your project. snipped-for-privacy@aol.com

Reply to
Robie

I beleive the requirement for a 79 idle test is 400 ppm in most jurisdictions. Starting in

80 the requirements tighten to 220 ppm. So you may be in luck with the test requirements. If they let you, fast idle the engine at 2500 rpm for a minute just before the test, that may keep the cat lit off during the idle procedure. I've seen it work wonders with pickups with relatively lengthy sections of exhaust pipe before the cat. Also are you using a honeycomb cat or sticking with the old original pea material. Those older "can of peas" cat took quite a while to heat up.
Reply to
joseph cugnini

It's got two new 2 1/2" inlet and outlet honeycomb cat. converters. Good advice on the fast idle and thanks for the specs. on the PPM. There are two long hills right before the place where the inspection guy is located. I was thinking I'd tell my son to lean on it pretty hard going up those hills before he got to the insp. shop to heat up the cat. converters. And, Robie, no I don't believe I've got any kin in Georgia. Most of my branch of the family settled in W. Arkansas.

Garrett Fulton

Reply to
Garrett Fulton

Do you have headers?

If they're mild steel, I hear that ceramic coating goes a long way in keeping cats (and 02's in these newer vehicles) up to temp.

If they're stainless, supposedly they already keep more heat in than coated mild steel.

-marc

Reply to
Marc Westerlind

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