Ok i replaced the exaust head on my engine!! when i start i it was really really loud.. how would you get the exaust head to connect to the y pipe??? It has a ceramic disk but it leaks like all hell! Is thier some sortive pudy or something???

 

DO NOT RUN YOUR CAR ANYMORE!!!!!!!!

THis is how I got th e fires in my engine bay. THey y-pipe isn't sealed to the donut gasket.

Find out which side is leaking, loosen flanges on both sides, seat the flanges better, tighten a little on each side. Enjoy non0exhaust leak again.

 

Don't use the gasket? I don't really get u on what your saying?

 

my y-pipe flange wasn't fully seated/sealed to the exhaust manifold donut gasket, thus letting all that exhaust heat to start melting engine bay internals.

 

It might be a good idea to buy some new donuts. I don't know if you can get the solid metal ones new, but you can buy some that are made of a very short section of exhaust pipe and some soft sealing material in the shape of a donut. If you can get new solid ones, that's best.

The reason I say this is because I was just reinstalling the y-pipe a month or so ago, and while torquing the manifold studs to spec, the donut cracked all to hell.

As Project said, you have to make sure it's seated properly. There's no putty. Just tighten the nuts on the manifold studs slowly and EVENLY checking to make sure the flat face of the donut is flat on the manifold, and the round face looks good and seated in the round flange on the end of the y-pipe.

 

GO TO GM DEALER & get them.
Or find FRAM replacements.
There is a metal ridge, that SEATS in manifold (feel that recessed part in exhaust logs?) & the pipes connect on soft rounded tapered edge.
The ones WITHOUT a metal seating ridge are NO GOOD.
Serious, ONLY the correct ones are to be used.
May need new manifold bolts (metric) right now, too, no biggie a few $ more!
My exhaust doughnuts from Fram cost $9/each.

 

Hey Karl, are your donuts solid or do they have a soft graphite(?) seal? I have one solid one that only mates up with the manifold on its face (it doesn't insert at all) and one soft one that has a short protrusion that inserts into the manifold (with a good deal of coaxing). I also have one more each of the above, both of which are screwed. I haven't found that one seals better than the other, but the one with the protrusion might be a bit more restrictive.

 

My Fram items fits just right (they have the lip you mentioned) & yes, it is a soft material.
No restrictions at all. Yet Tom has set seems like yours & he bore them out (NOT by typing long responese ! & that helped exhaust flow.
Go to GM dealer & ask to see their exhaust doughnut option which should be common on shelf item.

 

I'm not touching my exhaust again until I get those headers from Pacesetter.

 

I am hurrying up as quickly as I can.
Next is fix the heater core, as radiator leak is now solved.
I am anxious to do a road trip to Phoenix.

 

It's too bad I live 2000 miles away, I don't really need my car right now, so I could donate it. BTW, thanks for doing all this for the headers Karl.

 

I've given it a good shot. I'd like to get about 10 - 20 more HP (I'm guessing, if my numbers are reality)
When personal details settle down, I can split.
Once headers made, tho, that part is outta my hands!

 

If you get the cast-iron donut in your hand, look at the sharp ridge in the center. Grind or file that down to create a smooth transition inside the donut. I didn't expect to feel any extra power out of it (figured it was only 1 or 2 HP), but I did... if you've got 'em off, might as well.

 

I'll have to take a look at the busted up donut I have. I don't remember a ridge in the middle. I think it was just that the ID of the donut was smaller than that of the manifold output or y-pipe input.

 

I still have the metal ones from the 2.8. HEavy suckers. The gaskets in the 3.4 manifolds appeared to be the "soft metal" type Karl's talking about.

 

Okay, this donut thing has gone on long enough. According to Advance Auto parts, there are as many as three different part numbers for the donuts, 31550, 85003, and another that I didn't buy. I at first bought an 85003, which is the softer donut with the metal insert that was mentioned above. Then, later, I went and picked up a 31550, which was my mistake and the salesperson's misdirection. I went home and compared the 31550 to the 85003 and the 31550 was way too large and heavy to possibly seat properly in the manifold flange, so I took it back and swapped it for another 85003. When I finally got to replacing the donuts, I got under there and after braking a stud and practically breaking another, lo and behold, the ones that were on the flanges before were the 31550's, and were WAY TOO LARGE to seat properly, which is what was causing my leaks. The part numbers listed above are from Walker parts, and I have witnessed this myself. If you need new donuts, go with the 85003's... they fit into the y-pipe flanges better and are easier aligned due to the metal insert. By the way, I am talking about the 2.8 here.

 

We could have ended this conversation a long time ago if we had some pics of these stupid things.

 

Pics of te stupid things (yes, the nice solid metal ones from the 2.8):

 

Okay, I'll have to swipe a cam from a friend and snap a pic of the two side by side. The ones that Project 2.8 have in the pic are the ones that caused my leak by being way too large. On the other hand, I have one of the smaller ones waiting to be put in (I have to drill and tap a hole for the new stud on the driver's side manifold) that I will take a pic of alongside the others. Oh, and if you notice in the above pic, where exactly do the donut have a place to seal the exhaust? They don't have anything that will sit inside the manifold and allow the gases to pass through the middle of the donut, now do they? That's basically like using a steel plate bolted to the inner hull of a submarine, without any sort of gasket or sealing device- it STILL LEAKS!

 

They seal metal to metal, just like the exhaust manifold to the head. There is no gasket needed for that (until you pull it, because it'll never seal back up like it ws before )

 

First, I'm going to say one thing, if anything on an internal combustion engine could be sealed by metal to metal contact, don't you think that companies like FelPro and Mr. Gasket would cease to exist? Would any of you put your engine together without a head gasket or an oil pan gasket if you could avoid it? I know for a fact that the manifolds are sealed to the heads with a gasket. I've bought one to replace the one I'm going to destroy when I remove the manifold to drill out the stud. The simple fact of the matter is that the oversized donuts DON'T seal properly becuase they DON'T seat like they are supposed to and can be pushed off center or misalign the rest of the exhaust, causing a LEAK, which is what we all are trying our hardest to get rid of!
Oh, and the ones I am talking about are $4 and change from Advance Auto.

 

Well, for the exhaust, I'm pretty sure it's originally just a metal to metal seal. When it's new, it's nice and true and mates up perfectly. And as time goes on they wear together. Also, don't forget that there's a bit of solid crap in your exhaust that also eventually provides some sealing. But you can get aftermarket gaskets for the exhaust, although I've found for manifold to head that metal to metal works better.

 

Okay, I'll take that and raise this whole thing up a notch- While we're talking exhaust, once I get my "new" ECM and get the engine tuned properly, how do I decarbonize the entire engine from the throttle body to the tail pipes? Is it even possible to do rearwards of the manifolds? I really need info on this... my intake is disgusting... almost as much as the tail pipes... yuck!
I have the MFI system and am not spitting out any chunks of carbon out of the tail if anyone is asking, but all the black inside the pipes and intake just isn't right!

 

seafoam. 'nuff said.

What about spitting chunks of carbon out the tailpipe? thems be fighting words

 

Two questions:
1. Will I need to remove my cat conv. to do that? It's relatively brand new- I've only driven the car about twice since I put it on, and what will it do to the rest of my exhaust?
2. Where do I get it?
I was just making sure that you didn't think that I was running overly rich at this point... I'm running just rich enough to carbonize everything but not rich enough to spit out carbon from the tail.

 

1. Disconnect where cat connects to I-pipe.
2. Nappy.

 

Yeah, I think I saw that stuff when I was in there on Monday looking for PB Blaster. BTW, has anyone found that the center bolts on the ex. manifolds are the toughest to remove?
And then what do I do about the piping from the rear of the cat to the back?
Oh, and 2.8, I didn't mean any offense against you with that carbon chunks stuff, I just remembered the problem you had with it and was saying that mine wasn't quite that bad, for now, anyways...

 

Just messing w/ya. AS soon as the TPS ws adjusted, it stopped running rich & shyting all that crap out the pipes. The I -pipe can just hang down, nless you want to secure it to the drive shaft/torque arm.

All exhausut bolts are evil to remove, some more evil than others.

 

My car needs some seafoam too.

 

Secure the I-pipe to the heat shielding for the cat with some wire. There's a little tab on the shield where it bolts to the frame.

When you put the exhaust back together, use anti-seize that's good for high temps. It'll pay off.

 

PB blast is the best spray stuff for bolts but if you are in napa, look for a kind of plain lable can of chain lub, white n green maybe. Its super awesome stuff for losening rusted bolts. Just a dab will do ya.

Matt

 

I aint sure what happened to this center bolt but it seems that it welded itself into place... DOH! I've hit it with the PB four times now and am waiting for the fourth application to sink in... If and when I find the original donuts I took out in the first place, I'll take a pic of them and the new one side by side...

 

Here are the pics:

 

Second, the side view of the newer donut by itself:

 

This is the insert to the newer donut. The wide end is the end that goes inside the manifold:

 

This was supposed to be the first image having the two side by side, with the newer one on the left. This is a shot of the backside of the donuts, in an attempt to show the line on which the y-pipe attaches to on the larger donut:

 

Front view of old donut:

 

Side view of old donut. Notice that it is almost as thick as the entire new donut is with its insert, causing somewhat of a problem on my car:

 

Oops:

 

Just ran into this problem myself. 31550 are too large.

The part number for anyone else having donut gasket problems on at 2.8 V6 use

FELPRO 60538. These have the metal inserts that go into the manifold and also have soft material that the y-pip flange sits on.

This part number is good at advanceauto and autozone.

 

Be careful with those... There was a guy on here who had an engine fire because the pipe wasn't aligned properly and the exhaust gases leaked out against the wire harness...

 

That's the only gaskets that seal my manifolds. The 31550 suck...and I cant find the ones you posted.

 

Ive got 4 of the donuts that ill never use again. Let me know if you want them.

 

Which ones? What donuts do you use? The heavy 31550s? I couldn't get the driver side to seal no matter what I did with the 31550. I don't see how the Felpros would cause a fire if properly installed. I just slipped the insert in the manifold first, then put the donut material on over it.

 

I just have stockers off a 3.1L 2 sets

 

Can you take a picture of them? Curious what the stock donuts look like. Never encountered stock exhaust donuts on the 2.8 or 3.1.

 

Will do. Ill take it here in a hr or so. Ill just edit and add the pic to this post in a few.

 

Hered they be. Same as some of the ones on this thread when it first started 10 years back.

 

heres a lil trick for u guys , when installing the donouts get a bottle of antiseize and coat the donout with it then install it.

the antisieze will smoke a lil bit when u first start it but as it gets hotter it turns into a solid paste sealing everything up nice and tight

 

I see, solid metal. Didn't work for me no matter what I did on the driver side. The Felpro bunch have been good thus far...seals really good.