Hey all, I have a cracked exhaust manifold on the passenger side of my 87 f150 302 5.0L. Obviously this needs to be replaced but I am curious what performance problems could be stemming from this? How hard is this to replace on my own with just basic tools?

 

If your truck is equipped with EGR or o2 sensors after the manifolds air from the crack could give false readings or possibly affect the air/fuel system. Exhaust fumes out the manifold arn't good either.

If you can get at all the bolts easily it will not be too bad of a job. You may have to take off the inner fender liner to gain access to the manifold that way.

 

The manifold on my brother's '84 F150 was cracked. After he took it off it broke into 3 pieces.

You'll probably see some lost performance depending on how back the crack is, but not much. They usually also make a tapping noise.

 

I do hear the tapping noise. Is this a better job for a shop or would it be too expensive? I would hate to break the heads off the bolt or something and be in even worse shape! I've read it's possible to do that then the bolts have to be drilled out. I figured if the shop broke it, that would be their problem and I wouldn't be responsible for any additional cost.

 

Yes, it will be their probablem, but they will tell you the estimate with THE cost of what it WOULD COST to get one drilled out, and if it all goes good they get an extra 100 bucks, but if they do break a head, then they will have to deal with it and still get your 100 extra buck. I got a quote from a shop for 300$$ just to put headers on, no pipes, and i wouldve already bout the headers!! They just take that precaution for the customers.

 

Get smog legal headers instead of replacing with another cast manifold. If you are going to go through the work, you may as well make it perform better than it did to begin with, and prevent it from ever happening again.

Performance wise, it can mess up the fuel air trims, especially at cruise and deceleration, which can cause catalyst damage. The gases leaking from the manifold are rich in carbon monoxide, which is toxic in even small amounts, so repairing should be done for safety reasons. I didn't used to think it was a serious thing to have a manifold leak, till my bro was driving my truck to work each day with a leak. He would be exhausted by the end of the week, and we thought it was because he was working so hard, but he gradually got worse till we figured out it was carbon monoxide poisoning. He had all the symptoms, the headaches, general fatigue, etc. He nearly fell to sleep on multiple occasions, on just a short 20 minute drive.

 

It doesn't do anything noticable to performance especially on a cast iron log manifold. It doesn't have vacuum in the manifold, so the O2 won't be affected.

The noise is what bothers me. I haven't had a problem with fumes on my 96 that has had a blown manifold gasket now for about 5 months. jd

 

Are headers worth the money? I assume I would need short ones because there isn't a lot of room. Since I will have to disconnect the pipes, should I just replace everything (pipes, cat, muffler, etc) at the same time? Any thoughts on the bolt-on vs welded exhaust systems??? Are there sensors that I can screw up if I do this myself? Just looking for some ideas!

 

Just get smog legal shorty headers, I think Summit has some for your vehicle. I think you will gain some performance especially in the top end. I would leave the cats alone unless something is wrong with them. A good performance muffler in the factory pipe size would free up some power and give a throaty tone. I would leave the rest alone unless there is something wrong with it, i.e. cracks, rot, damage.

The bolt on systems are easier to install yourself especially if you do not have any specialized exhaust tools. If you are doing something unusual, you will want use weld in parts, since the pipe will be custom bent. If you do welded in stuff, you may want to put flanges such that factory parts will still bolt up. That makes future replacement or repairs much easier.