gutting c-4 catalytic converters.

[Mike M.]

didn't want to risk trashing a LT 5 head due to clogging of the catalytic converters so i've cut the cats in two and removed the catalyst. this leaves a large void( i'd guess about 1000 cc) where the catalyst formely resided. my question is , should i just re-weld the cat can back together or should i insert a piece of 2 1/2" pipe inside the cat halves to reduce possible turbulance. want willy to scream. mikie

[Mike M.]

Re: gutting c-4 catalytic converters.

PS: seem tro ecall the LT 5 headers being stainless when they were introduced in 90. the used LT5 headers i picked up at carlisle hold amagnet and have minor surface rust. suppose they are cheaper grade stainless? need to know type of wire to use in MIG welder when re welding the cat halves. thanks, again, mike

[Clem Z.]

Re: gutting c-4 catalytic converters.

most exhaust systems use 4 series stainless. why not just cut the flanges off of the cats and just weld in a straight section of tubing

[Mike M.]

Re: gutting c-4 catalytic converters.

clem: the LT5 headers are unlike any exh systems i've seen. the 4 tubes leave the head and meet in an irregurly shaped 5" diameter fitting that then grows to 6" in diameter to mate to the cats which are about 6" in diameter. at the end of the cat they reduce to 2 1/2" outlet pipes. wouldn't be a simple matter to weld up a new 2 1/2" outlet pipe to the fitting the 4 header tubes insert into. that would have been the nicest way to deal with the cats, just eliminate them completely from the headers but building fittings to go from the 4 header tubes to the outlet pipe would be a tin bangers nightmare. After cutting them in two and knocking out the catalyst, things have to get better flow wise as the catalyst had to impede flow considerably. mike

[Mike M.]

Re: gutting c-4 catalytic converters.

Mike,
Sounds like you can use the Cat housings as pipe reducers. If so, just weld them back together. I guess they would influence your collector length, so perhaps the straight section can be made as short as possible.
Having spent 35 years as an engineer in the chemical and pharmaceutical industries I have a lot of experience with various types of SS. The exhaust system could easily be 400 series (martensitic), but have also seen magnets stick to 304 (austenitic). This usually occurs after the 304 has been locally heated by cutting or welding (other than TIG welding). By specs, the Fe content of 304 is between 68 and 74%. Heating in the presence of O2 will bring more of the FE to the surface, making the material more magnetic. Grinding and abrasive blasting do the same. That is why in high purity applications (pharmaceutical) we "passivate" SS (usually 304 or 316 low carbon types) after fabrication, to dissolve the Fe brought to the surface, leaving the chromium and nickel which are much more resistant to corrosion. So the magnet test is not always accurate. I can usually tell the difference between the two types by hardness. 400 series is harder than 300. That is why good cutlery is made from 400 series, cheap from low quality stuff from 300 series.
Mike

[Kent K.]

Burn Porshe, burn

mike - if you extend the 6" dia pipes to the rear, you'll either burn up those porshes or give them a garage to drive into thinking they're going into a tunner on the track. personally, i'd turn the 6" pipes out the sides and burn them porshes as they try to pass. hardly likely that'l happen. good luck with the exhaust system. kent #6201

[Mike M.]

Re: gutting c-4 catalytic converters.

Mike:your post quite an education for this ol pharmacist(1970), although i left pharmacy by the road side after med school and derm residency. the prof's in RxY school never discussed the issues you've posted or maybe i slept thru that lecture. thanks again, mike