Eliminating the Catalytic Converter

[Bills money pit]

Recently I have read that ZDDP has been reduced or eliminated from most conventional oils. Apparently our older flat tappet engines need the ZDDP to prevent cam lode wear. One downside to adding ZDDP is that it tends to clog the catalytic converter. My question is what would removing the cat and replacing it with a flanged straight pipe do to the ecm system on an 81? I live in Oklahoma and we do not have vehicle inspections. All opinions on this issue are appreciated.

 

[Hib Halverson]

There are many myths about ZDP or the lack thereof in modern engine oils.

For accurate information, see this article here on the CAC:
Corvette Action Center | Tech | Engine Oil Deep Dive - CAC's Comprehensive Look at Engine Oil and Flat-Tappet Camshaft Durability

 

[Bills money pit]

There are many myths about ZDP or the lack thereof in modern engine oils.

For accurate information, see this article here on the CAC:
Corvette Action Center | Tech | Engine Oil Deep Dive - CAC's Comprehensive Look at Engine Oil and Flat-Tappet Camshaft Durability

Thanks Hib, very interesting article. Seems regular oil changes with a good oil is the answer. Also, VR-1 may be a good choice!

 

[Hib Halverson]

Thanks Hib, very interesting article.

I'm glad to be of service.

Seems regular oil changes with a good oil is the answer. Also, VR-1 may be a good choice!

VR-1 is a good choice, especially for a high-performance street driving duty cycle.

For normal street driving, however, the oil that is the best value is Delo 400LE.

 

[SVO]

I'm of the opinion that one should maintain the emission control systems of their vehicles. Not because I'm a tree hugger type, but due to the fact that more & more areas of the country are being forced to comply with Federal air standards. Automotive forums of all types have post where people have modified their cars and then find themselfs having to undergo emission testing that they previously didn't have to comply with.

The issue with ZDP that concerns me is not catalytic converter poisoning but wearing of cam lobes and lifters. I have moved to using Rotella diesel engine oil in my vehicles with "slider" cams. However I understand that diesel engine oils are being reformulated to reduce the ZDP content in them.

 

[Bills money pit]

I'm glad to be of service.

VR-1 is a good choice, especially for a high-performance street driving duty cycle.

For normal street driving, however, the oil that is the best value is Delo 400LE.

Hib, will the delo 400le not kill the catalytic converter?

 

[terry82]

your old cat is not verry good .it can be replaced with a new high flowing cat.but untill you have the money for that ,you can take your old cat off and take a long metal rod and knock all the crap out of it .then put it back on till you have the cash.opening up the cat should not give you a light.

 

[Hib Halverson]

Hib, will the delo 400le not kill the catalytic converter?

It might if you run the cat for 150,000 miles or more. My guess is that you will never accumulate that kind of mileage.

 

[Hib Halverson]

I'm of the opinion that one should maintain the emission control systems of their vehicles. Not because I'm a tree hugger type, but due to the fact that more & more areas of the country are being forced to comply with Federal air standards. Automotive forums of all types have post where people have modified their cars and then find themselfs having to undergo emission testing that they previously didn't have to comply with.

The issue with ZPD that concerns me is not catalytic converter poisoning but wearing of cam lobes and lifters. I have moved to using Rotella diesel engine oil in my vehicles with "slider" cams. However I understand that diesel engine oils are being reformulated to reduce the ZPD content in them.

It's ZDP or ZDDP not "ZPD".

Currently, all diesel engine oils have more than enough ZDP for flat tappet cams in gasoline engines.

Best to use is Chevron Dell 400LE 10W30. Next best is Shell Rotella-T 10W30

 

[Crimson Thunder]

Since you want all opinions, I would ditch the whole exhaust and install a true dual exhaust system and get your 30 HP back the single cat robbed you of.

 

[Rod75]

My question is what would removing the cat and replacing it with a flanged straight pipe do to the ecm system on an 81? I live in Oklahoma and we do not have vehicle inspections. All opinions on this issue are appreciated.

To answer your question: The only part of the C3 (computer command control) system in the exhaust is the oxygen sensor. It's upstream from your cat converter. Replacing/deleting the cat converter will not effect the C3 system.
As preventive maintenance and 'while-your-at-it' suggestion would be to replace the oxygen sensor while you're in there.

GM's catalytic converter design of this era were troublesome as the internals tended to break down and clog up the unit. It's not a bad idea to replace it with something that flows better.

 

[racerone27]

i put dual exhaust from the engine back and did away with the cat. a little more performance and a nice sound. and the new exhaust weighed less than the y-pipe and cat did. steve pastorino

 

[Rod75]

i put dual exhaust from the engine back and did away with the cat. a little more performance and a nice sound. and the new exhaust weighed less than the y-pipe and cat did. steve pastorino

Sounds like a winner Racerone! Another benefit with the cat gone, you may find a cooler temp in the cockpit, as those cat's run hot and hold the heat!
Give it a rap-n-rev and bang a couple gears for me!

 

[racerone27]

i would, rod, if i could. it's an automatic, and i haven't been able to get the carb working just right. i do race oval track modifieds, so, i don't really have to worry about street performance. it's a very nice cruiser. looks like your from mich. maybe i'll see you on woodward or around a2 this summer. i race at owosso and spartan. steve pastorino

 

[Rod75]

i would, rod, if i could. it's an automatic, and i haven't been able to get the carb working just right. i do race oval track modifieds, so, i don't really have to worry about street performance. it's a very nice cruiser. looks like your from mich. maybe i'll see you on woodward or around a2 this summer. i race at owosso and spartan. steve pastorino

I take it your carb is the original. Might be rebuild time? Even if you do rebuild it, they tended to lean the crap out of the mix on those 'electric Q-Jets' as they were the beginning of the 'electronic controlled lean years'. The C3 systems can be problematic for good drivability.

Oval track racing is cool! That's where you get your HP yah-yah's out!

Yeah, Woodward Cruise is my automotive heaven! It's really getting longer every year, starting well into the week before. I've started spending a few odd evenings out there the week before, and I park and watch on the big day, riding the camera mostly.
Don't think I'll have the Vette out there this year. We'll probably take the Impala.
So if you (or anyone on this board) want to meet up out there, I'm game. I always enjoy the comradery! PM me for contact info.