IDx

hey.. my friend has a 1st gen.. i dont know too much about 7's but there is a vaccum line that squeaks.. it goes from the block to the intake box.. when tis covered the car idles great, and revs great, but when its not covered the car idles rough.. is this the shutter valve or emissions thing? its one of the 3 holes in next to the carb air thing.. thanks for the help.. should i cover it or what?

inittab

sounds like the shutter valve to me. Blocking off the large hose will disable it and make your car run better. I've done this to mine and a lota guys here have done it as well. Do a search on the forum for "shutter valve" to get better educated on the subject. Good luck!

85RX7GS

iTrader: (1)

This seems to be left out more often than not when tooling with the shutter valve: you have to plug the hose when the engine is shut off.

IDx

ok so what is its purpose? so i can block it off? what do you mean plug the hole when the engine is shut off? thanks for the help

specRX7_22

its purpose is.... when your hard on the gas and let off real quickly to brake or whatever, the shutter valve cuts off fuel to the rear rotor to prevent backfiring. am i wrong?

--eric

85RX7GS

iTrader: (1)

No, you're right. It also makes the rear rotor run lean to be more environmentally friendly. However, left unplugged, it's the leading cause of rear rotor failure.

racermike

Even with plugging the line, you have to check that the butterfly is in, and stays, in the right position.

IDx

we made quick work of it with a bolt and some cement.. we went through the air filter.. so your saying the car will now backfire? (flames? ) we are going to try to switch the secondarys to mechanical tommorow.. how much of a performance gain will you receive by doing this? and what other cheap mods can we do.. thanks for the help

racermike

Not really back fire of course (forward fire) but it will have a greater incidence of occuring, espescially under engine brake.
No greater HP in total, but it will get there quicker!

error402

Just wanted to throw in my comment about performance gains in converting the Nikki carb to mechanical secondaries. Your not going to get any extra HP per say, but you will get a huge difference in response. I would recommend doing it to any Nikki carb. Oh, and make sure you have an extra bread twist tie laying around. I found this to be the easiest to use to tie the secondaries to the primaries. I think Paul Yaw even recommend using one. LOL

-Error402