View Full Version : question on intake runner length

07-31-2007, 11:03 PM
I bought a 96 cobra from a guy that was attempting to build it up and Im afraid that he may not have done it right. I took off the plenum a couple of days ago and realized he had cut the runners. they are very short. not sure where you start measuring at but they almost point straight up. they have a slight angle. and the ports are lined up poorly and they were dogsh## welded on. Also he welded a plate in the bottom part covering the lower part but it is not sealed. the car does run but it blows smoke on acceleration and shows both lean codes. as it gets hot smoking isnt as bad but always reapears when you get on it. actually doesnt sound too bad, idle is ok. any ideas on what i should do if i am able to fix this or if I should start over. any advice would be very helpful thanks.
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08-04-2007, 08:49 AM
The runner length would effect how the car accelerates. The 4 Valve works best with long length runners at low RPM range and best at high RPM range with short runners. I have read about the FR500 Intake plenum but that would not do you much help since you have the IMRC's. It may be possible to have a tuner look into it and possibly adjust the lean conditions. The alterations to the runner length may have resulted in more CFM flow and the injectors were not tuned to compensate.....on the flip side, you may have to replacement the plenum (I would look aftermarket first and see if there is a good alternative).