antwaan

So the 2nd time I take the Mustang out of the garage this year it was missfiring badly and after I got it home I noticed coolant on the driver's side and it was in 3 of the 4 spark plug holes on that side. I've been told its my intake manifold by multiple people and I was going to put a new one on and replace the plugs and wires while I'm at it as well as flushing the coolant. I've never gone quite this deep on a repair before but by looking online it seems pretty simple.


I know to stay away from the dormans. I've also looked at putting a PI intake on it (still have npi heads) and even a full PI swap but I can't justify the money for that and I'm hoping to upgrade to a newer Mustang in a year or two. Would that be a good Manifold to get? I'm just looking to get the car in good running shape so I can drive it during the next couple of summers and it was running fine until this.

Also, would I need to replace the fuel injector o rings when get to that part? The guide on American Muscle doesn't mention it but this engine has about 140k on it and I want to make sure the job isn't half assed. Any other tips or things I should replace while I do this?

oh3stang

Here is a great how to, I just did it.

https://mustangforums.com/forum/4-6l...npi-heads.html

antwaan

Thats awesome. I may just do that. It wouldn't cost too much extra for the parts and looks like just requires a few extra minutes of work...

oh3stang

There's another video out there I couldn't find. You actually don't need to put the sealant into the chamber. You can put a nice size dab right at the toe of the boot part of the port under the gasket. I used some bolts and cut off the heads to hold the gaskets in place as I installed the intake to keep everything lined up and unscrewed them once I put in a few of the permanent intake bolts.

MaxxRPM

Installing a PI intake to an NPI motor does add a nice horsepower boost........However, you do run the risk of it leaking coolant (mine always did eventually).
I suggest doing a full PI swap (h,i,c).....But until you get all the pieces together, I would just go to a local junkyard and pull an updated NPI intake off a Crown Vic or Merc......A Dorman NPI intake is just fine. It's their PI intake you'll want to stay away from...........(just my .02).

Ogre

So what's the issue with Dorman PI intakes? I always hear people talk bad about them, but have never seen a post about someone who actually used one...

MaxxRPM

When you set a Dorman PI intake next to the Ford Racing intake, the Dorman's runners and ports are a smaller diameter.

antwaan

Funny story. I got the old intake off and realized it used o-rings and looked the part number up and its a dorman, haha. Its been leaking near the thermostat and cylinder 5. I've got everything off and will be proceding with the PI intake swap this week. I ended up getting most of the parts for the swap for a decent price on Rock Auto and just got a new PI intake from American Muscle.