ducting

[jayhawker]

What is the large, approx. 3" diameter, ducting that goes from air box to exhaust manifold? I am guessing it is part of the EGR system... The hose or ducting is ripped and in bad shape, can I just remove it? If so, do I need to block off hole at the manifold? Engine is an 87 4.0 renix

[Keyav8r]

That's the warm air intake duct. There is a flapper valve in the front of the air filter box that is actuated to draw intake air from around the exhaust manifold when temperatures are low or from behind the grill when temperatures are warmer (the normal state for the intake air). You don't have to do anything to the manifold if you remove the hose. Most of them dried up and fell off long ago.

[jayhawker]

Thanks for the reply. Will be taking the rest of ducting off tomorrow. Doing a little research, I noticed the later model's exhaust manifold doesn't have the warm air intake duct. I have either a cracked exhaust manifold or leak at the manifold/head connection as well. Would the later model exhaust manifold be a better design that is less prone to leaking or cracking? What would you recommend, later model stock exhaust manifold or is there a descent header option out there that people use, or just go with a new stock manifold and delete the warm air intake duct? Thanks in advance for any recommendations.

[Kickinmule]

I'm glad you asked about the duct; been going to ask that one and always forgetting it! So delete it is!