I want to swap my 305TBI for a GMPP 350 crate motor with a carb. Can I pass an emissions test (they don't do a visual test but they do put it on a dyno and take it up to 35 mph) My car barely passes emissions tests as it is. I figure a new motor, even if it is carbed, should run better/cleaner than my old 305. I just wanted some opinions. Thanks.

 

You have a better chance in the long run of passing with TBI than carb. You can still pass with carb if it is dialed in right and you use a cat.

 

Can a cat function properly without the use of the air pump?

 

Well it can as long as you are running within 1% of stochiometric combustion. That usually nevers happens though with carb. You can get a cat without AIR. That is the route I would go. However, you cannot beat fuel injection when it comes to emissions. It will save you from future head aches. Cat free is the only way to go carb.

 

So do you recomend a cat or not? You post is a little confusing. But thanks for the reply

 

Use the cat, but get one without AIR. Also get a 3 way cat if you're gonna get one. It has the catalyst rhodium in it as well, which functions to reduce NOx as well.

 

I don't reccomend a cat when you go with carb but since you need it for emissions I would go with a non AIR cat like onebinky mentioned. However, it is hard to find a 3 way cat without AIR. Sorry for the confusion.

 

Eastern converters makes one. I know for sure they have 2.5" and 3", not sure about other sizes. I bought 2 of the 2.5", but unfortunately didn't have room for em.