gtmotor

Hello forum,

I just picked up an 87 pickup with the 22R in it a few nights ago and it's developed it's first issue. The truck came with a full 2.5" exhaust after the header with no cat. Since I live in an area that requires emissions I decided to have a high flow cat welded in while simultaneously putting a new magnaflow muffler in.

That went in well and the sound was great... very subdued but still a little growly. Last night I was driving home when I thought I heard a metallic "clink" and then what sounded to be a bad exhaust leak. Of course I immediately thought it was the new exhaust components but after a good inspection everything seems to be fine.

It sounds like the exhaust leak is coming from somewhere behind the cylinder head. Maybe those EGR pipes back there? I checked the nuts holding the pipes onto the exhaust manifold/cylinder head and they are all tight.

Maybe the added back pressure from the "new" exhaust blew something off? This engine was just rebuilt 800 miles ago with .040 over pistons and a bunch of other stuff. It doesn't seem down on power now it just has an embarrassing exhaust leak. It's fairly quiet until I stomp on it then it's LOUD.

Any ideas on how to check this? I can't see what's going on behind the cylinder head. I thought about removing the EGR/emissions pipes but I thought I'd check YT first to see if you guys have an easier solution.

Thanks!

abecedarian

There are no exhaust pipes routed behind the engine. EGR gasses pass through the head.
There's just a coolant pipe and pipe for the PAIR system.
You should have a small 'manifold' bolted on top of the main exhaust manifold, no? and it goes to a pipe that wraps around the back of the head and into a valve (the PAIR reed valve), correct? If so, it's meant to supply air to the exhaust manifold, not the other way-round. That may be the cause of your noise.

gtmotor

Cool, I checked the torque on the nuts for the air injection pipe entering the exhaust manifold and they are very tight.

After reading around here I wonder if I blew out the exhaust manifold gasket. The truck just had it's engine rebuilt so I wonder if the PO used the same gasket/nuts to put everything back together. The added back pressure from the new cat may have sped up it's demise.

Is there a way to check for an exhaust leak there? Like some sort of smoke test I can do?

Kiroshu

It may be leaking where the manifold joins the rest of the exhuast. If not replace your meanifold gasket i just did the other day my self. Nothin to it.

sh0kk86

my truck went almost 190k before i had to touch it.

that was about 3kmiles ago when i rebuilt everything minus the block. used fel pro ehaust manifold flange gaskets and thought it was kind of weird that they gave me a cork/paper like gasket, when the stockers were copper.

a couple days ago they already went out, went to napa and got some metallic like ones, hope it will hold up better than the fel pros.

just a possibility

gtmotor

I finally got around to checking all the nuts holding the exhaust together and none of them were really that loose.

However, one was missing where the header connects to the rest of the exhaust. I think this was the "clink" I heard when it fell off. I replaced the nut with a new OEM one and it still sounds terrible. I have a feeling the gasket blew out after that nut was lost. I'll have to replace both gaskets and see if that fixes the issue.