Stock manifold to long tubes

[LFR]

I am going to get long tube headers but am having trouble. Is the emission control just remove or do I have to cut it and plug stuff or what do I have to do to convert to headers.

 

[smoothandlow84]

I am going to get long tube headers but am having trouble. Is the emission control just remove or do I have to cut it and plug stuff or what do I have to do to convert to headers.

Same question here. I just finished installing long tube headers on my 87 tbi 5.7 liter 350. Now that the headers are installed, i have a backfiring at idle issue. Positive it has to do with the emission contro components. Been working all day trying to trouboeshoot. The last resort would be to tap into the headers and reinstall the emissions similar to what is done with the manifolds. There has to be a better way. I am not concerned with emissions as my truck is exempt since it is considered a restoration and limited use (also insured with Haggerty classic car insurance ).

 

[MadOgre]

What emissions ? The butterfly valve ? The AIR injection ? Cat ? What ?

 

[87ChevyR10]

When I installed my longtube headers, I cut the AIR injection going into the stock manifolds. My truck did not have a catalyst. Additionally, I installed a 4-wire O2 sensor. No after firing or back firing.

My truck: '87 350 with TBI

 

[MadOgre]

I could be wrong but I do not believe the AIR injection has any impact what so ever on engine performance but rather has to do with what comes out the tail pipe for emissions testing.

Basically a way of cheating for GM as your parts per million will obviously drop when you inject clean air into the exhaust.

It was also supposed to help complete the burn cycle after exiting the combustion chamber.

But aside from AIR pumps seizing I don't believe any one could even tell when the system was not working aside from failing emissions testing.

 

[PrairieDrifter]

I could be wrong but I do not believe the AIR injection has any impact what so ever on engine performance but rather has to do with what comes out the tail pipe for emissions testing.

Basically a way of cheating for GM as your parts per million will obviously drop when you inject clean air into the exhaust.

It was also supposed to help complete the burn cycle after exiting the combustion chamber.

But aside from AIR pumps seizing I don't believe any one could even tell when the system was not working aside from failing emissions testing.

Im not sure about older systems but I know in the 90's and early 2000's air injection was used only during startup to prevent the high emissions when the engine is cold and dumping more fuel. Either way air injection is just adding fresh air to the exhaust for emissions and to prolong the cats life, it has no effect on performance whatsoever

 

[MadOgre]

Im not sure about older systems but I know in the 90's and early 2000's air injection was used only during startup to prevent the high emissions when the engine is cold and dumping more fuel. Either way air injection is just adding fresh air to the exhaust for emissions and to prolong the cats life, it has no effect on performance whatsoever

Im not sure if it impacts the O2 sensor on an 87 but yep other wise it does nothing to hurt performance

 

[smoothandlow84]

Update...installed the long tube headers, plumbed them into the dual cats/mufflers and discovered that a combination of a bad plug and a small exhaust leak was the issue. This is the second time I have replaced all the spark plugs with new ones, only to have one not work. I am using autolite spark plugs and yes they were gapped to specs. Funny how such an inexpensive part can frustrate you. While under the hood, I also replaced the cap, rotor, plug wires and some vac lines. I ditched the entire air pump system since the truck is registered as a classic vehicle and is emission exempt. The original o2 sensor was installed on the headers at the collector. The headers didn't come with a bung, so I had to weld one in myself. I can definately tell the difference in throttle response with the headers versus the cast manifolds ( I also shaved about 10 lbs off the weight of the truck swapping out the manifolds for headers...lol).