Question about Magnaflow High Flow cat on otherwise stock truck

[Supercharged111]

The switch would have been in the late '80s or early '90s. Your Suburban has a honeycomb catalyst. I don't know if early GMT400s had pellets because both my trucks had them cut off by previous owners.

My 88 had the pellet style. All Vortecs had honeycomb, but ike you I don't know where exactly that change occurred.

 

[L31MaxExpress]

The switch would have been in the late '80s or early '90s. Your Suburban has a honeycomb catalyst. I don't know if early GMT400s had pellets because both my trucks had them cut off by previous owners.

Both my 92 and 94 G20 had 3" pellet box cats on the 350 and 305. My 97 Express had dual 3" honeycomb cats and my 99 Tahoe had dual ~2" Honeycomb cats.

 

[Pinger]

When did cats become mandatory in the USA? (Another way of asking when you went to un-leaded fuel).

 

[L31MaxExpress]

When did cats become mandatory in the USA? (Another way of asking when you went to un-leaded fuel).

That varied depending on GVW. My 83 van was born without cats but our 80 C10 had one.

 

[Schurkey]

Catalytic converters were never "mandatory".

Meeting the emissions regulations was mandatory. Cats were just a means to an end.

First use of catalytic converters was '75. My '80 Honda Civic 1300 was born without them--didn't need them to achieve emissions legality. (The '80 Civic 1500 had a converter.)

Middle-'70s Ford products had a catalyst that acted on the exhaust from the right bank of the V-8 engine. Left bank went untreated. I wouldn't have believed it if I hadn't worked on one.

 

[L31MaxExpress]

Catalytic converters were never "mandatory".

Meeting the emissions regulations was mandatory. Cats were just a means to an end.

First use of catalytic converters was '75. My '80 Honda Civic 1300 was born without them--didn't need them to achieve emissions legality. (The '80 Civic 1500 had a converter.)

Middle-'70s Ford products had a catalyst that acted on the exhaust from the right bank of the V-8 engine. Left bank went untreated. I wouldn't have believed it if I hadn't worked on one.

I have seen that Ford configuration as well. What I do not remember is if those Fords had an EFE valve in the opposite manifold that diverted all the exhaust through the cat on cold start and warmup.

 

[Schurkey]

I have seen that Ford configuration as well. What I do not remember is if those Fords had an EFE valve in the opposite manifold that diverted all the exhaust through the cat on cold start and warmup.

Good question. I don't remember either.

 

[Pinger]

Cats in 70s and 80s is way earlier than I expected. Here in UK it was around the early 90s before they appeared to meet emission regs (not mandatory here either - my sloppy writing) which coincided (inevitably and obviously) with the arrival of unleaded fuel.
If cats were in use in the USA as early as the 70s then obviously there was unleaded fuel available. Did its arrival bring about changes to valve seat material/treatment by USA manufacturers?

 

[Schurkey]

Compression ratios were lowered starting in '71 in anticipation of low-octane, low- or no-lead fuel.

Exhaust seats were either hardened inserts (rare) or induction-hardened (common) starting in '71 or '72.

 

[sneakingfart]

I'm glad i started this thread. Very informative.