I live in CA and have a '77 F150 4X4, 400/C6 that I've had for 3+ years. The truck however, came with a 351M that didn't require a catalytic converter since it complied with Federal emissions standards.

Does anyone know if I have to add the converter, or any other additional smog equipment since I've gone from a 351 to a 400?

I have to get my truck smogged soon and need to know if I have to get any other emissions equipment added on.

 

I dont know much about how strict ca is but can you skip the test if your vehicle originally didnt have smog equipment. If so you can make it look like it didnt come with it. Some of the things I know of are these... Does your fuel guage read "unleaded fuel only" or does it say "fuel" If says unlead nly You need to change it to the regular "fuel" guage, look in junkyards for stuff like this, Since your truck is 77 you might get away with all this stuff because most were not smog equipped. Another thing is, are your gas filler tubes wide open or is there a small hole with a little metal door like the newer cars? Smog equipped vehicles have the unleaded only restricter tubes so you cant put a big nozzle leaded pump in if you put leaded gas in a smog equipped vehicle it damages the catylitic converter. Since a 351 looks exactly like a 400 you can getaway with more. Do you still have the old engine or valve covers? Look for the engine identify sticker on the valve cover closest to brake booster. At the very top you need one that says non catylist. If it doesnt does your old engine say non catylist. These are a few things I know of to do. But if you want to be legal and protect the enviroment Here is what you need... catylitic convertor, pcv system, egr system, all in good working condition. Some vehicles had air pumps and fuel vapor systems and all sorts of other power robbing junk. Now I dont live in a place that needs smog inpections but this is stuff I have heard about. So dont trust me too much.

 

The 400 will pass the "visual" inspection, as it looks identical to the 351M.

As far as cat requirements, the trucks from that era were classified upon their GVW ratings. My '78 (not a CA classified truck) with the 351M, did not have a cat, and was ok'd for the regular leaded (at the time) gas, 'cause it was a 6150 lb. GVW rated truck.

So, you do have some wiggle room, and with the truck being 25 yrs (in a week or so ), you may even be emissions exempt. Time to do a little resasrch!!!!!!

 

i have a 77 F250 with the stock 460. i live in Ca. and last year it passed smog with out any problems, and since then i have gotten it running 10 times better. the only smog stuff it has on it are the egr valve, pcv and i think the evap can. but i am planning on taking all that stuff off when i go to school next fall, ill be in college prolly out of state by then. but anyways, the smog laws for CA are quite weird. so far its a revolving 30 rule, means if your car is 30 years old it doesnt have to pass smog, and it goes by the first time the model hit the showroom floor, so a 77 hit the floor in 76.. so in 2006 we will both be smog exempt. however, they change the amount of emmisions allowed for trucks and cars, depending on weight, and year. my brother has a 72 pontiac that passed pretty easily when it had to, and it has no smog stuff on it. just talk to a mechanic that does the inspection and ask him if it will pass the way it is, if he says no because its a 351, but everything else is fine then take it somewhere else and tell them its a 400 and things should be fine.