Header Downpipe problem

[84ZZ4]

All,

Got a problem with my header install. The downpipe is resting on the steering rack heat shield, as seen in the picture below. These are ZZP headers, there have been people that have installed them into H-bodies, but I don't know if anyone has put them in a C-body.

What's causing this? Do the headers just not fit (is an H-body different at the firewall)? Or do I have a bad transmission or engine mount, somewhere?

 

[HotZ28]

Like I previously mentioned, I have installed headers on many different applications. Sometimes, when clearances become a problem, a ball peen hammer comes in handy. There is no other way to alter the original configuration without some modification. BTW, it looks like you have plenty of clearance at the top, so it is possible that your mounts are weak and sinking.

 

[84ZZ4]

I noticed the clearance up top. I wish I'd thought to take pictures before I pulled the factory exhaust, but I know I actually had to lift the exhaust up with a jack before I could change the swaybar (back when I did the suspension upgrade).

Do you happen to know if the factory downpipe is the same size on Ultra and Base model Parks? I can compare where the downpipe is on my '98 with my memory of where things are on the '01 that I'm doing the header swap on. I replaced the mounts on the '98 last year.

I suppose I should also measure where the water pump is relative to the frame rail. I'd assume the NA engines aren't supposed to sit higher in the frame than the supercharged ones? That should tell me if the engine is lower in the car.

 

[HotZ28]

Do you happen to know if the factory downpipe is the same size on Ultra and Base model Parks?

The downpipe has the same part number for both the base & Ultra, so I would assume they are the same size. How much clearance do you have between the heat shield and the rack?

 

[84ZZ4]

It doesn't look like much, I'll take a look tonight.

 

[HotZ28]

The shield looks like it has a sight "V" bend where it is making contact with the collector. You may be able to bend the shield enough at that point to gain the necessary clearance. All you need is about 1/2", just enough to prevent vibration noise.

 

[84ZZ4]

Found the source of the problem. Measuring the front engine lift bracket relative to the top of the radiator support shows my that the front of the engine on my '01 Ultra is about 1/2" higher in the frame than that of my '98 Base.

(It's extremely hard to find anything even remotely flat on these cars, which is why I ended up using that bracket).

I took a wooden board and a jack, and lifted the back half by the transmission pan until the measurement was close to the same. The results are below. I can't see any visible damage to the mounts, but something is causing the engine to not sit right, so I've ordered new mounts for all four corners. If that doesn't solve the issue I may have to pick your brain as to what else it could be.

 

[KShef]

I had S&S headers, now a 3" turbo downpipe that routes to the same area. Mounts should take care of it...mine were/are very close but not resting on the heat shield like pictured.

 

[FFarr]

I had to replace the rear transmission mount on my PAU, mount had broken and was letting the motor tilt aft.
Was making a roaring noise inside the cabin. Was a little pricey, $65. for "Anchor" brand from O'Reilly's

Not listed as a motor mount, listed as transmission mount.

 

[84ZZ4]

Yeah, I got my mounts from RockAuto. $100 for all four, roughly, after shipping. I went with the Anchor solid (instead of the factory hydraulic). The front, rear, and driver's side mounts are all listed as transmission mounts, since that is what they bolt to. Only the passenger's side mount bolts to the engine. The distinction is somewhat arbitrary on a transverse mounted engine, but there you have it.

The reason I measured against my '98 was because I've replaced the front and rear mounts on that car (but not either side mount), so I know they're good.

I priced GM mounts, but even from an online supplier they'd be close to $400 for all 4.

 

[FFarr]

On off topic cars I have taken a floor jack and 2x4, jacked the collector for clearance. Probably wouldn't work with PA soft flexy mounts.

 

[84ZZ4]

Hah, no, all I would probably accomplish is to rip the mount or jam the collector into the tunnel.

 

[84ZZ4]

I do have a bit of good news. The front mount was bad and the rear mount is REALLY bad. So that should solve my clearance issues.

The bad news is... I think I've exhausted my existing repertoire of profanity TRYING and FAILING to get the rear mount out. I'm in the process of developing new profanity.

I think the entire front end is built around that mount. Either that, or the bracket that wraps around the steering rack. I'm not quite certain which.

What a terrible job. The worst part is I can see at least five ways the design could have been changed to make it less horrible.

 

[FFarr]

I do have a bit of good news. The front mount was bad and the rear mount is REALLY bad. So that should solve my clearance issues.

The bad news is... I think I've exhausted my existing repertoire of profanity TRYING and FAILING to get the rear mount out. I'm in the process of developing new profanity.

I think the entire front end is built around that mount. Either that, or the bracket that wraps around the steering rack. I'm not quite certain which.

What a terrible job. The worst part is I can see at least five ways the design could have been changed to make it less horrible.

Mine was a "booger" too. Having done it would make the next one go much faster. Front sway bar is right in the way.

 

[84ZZ4]

It certainly was. I unbolted the endlinks and swung it down, and I was able to "pop" the mount loose somewhat. My problem is that the mount is wedged between the transmission bracket and the subframe rail and won't come out.

Did you have to unbolt the rack from the subframe? I haven't done that yet.

 

[FFarr]

No, did not unbolt the rack from the subframe. Two bolts attaching the rack to the mount I was able to remove/install with a 24" extension and a swivel socket from engine compartment.
I ended up taking the sway bar mounts as well as the end bar links loose, Jack the motor waaay up.
The mount is a light press in the cast housing.

Edit=I removed the bolts from the trans. bracket (Fig.1) so I could move it out of the way.

 

[84ZZ4]

Yeah, my rear mount is a completely different design. It has studs sticking vertically up out of it that are jammed in the bracket.

I can't jack the motor up any higher, as that bracket actually curves under the steering rack. If I unbolted the rack, I could maybe get another 1/8" before the exhaust hits the firewall.

The service manual seems to imply that you are supposed to unbolt the bracket from the engine, but I've no idea how to get at the bolts (they're "on top" of the bracket and can't be easily reached from below).

I suspect my '98 has the same design as your '97, which must be why the shop didn't hate me when I asked them to change it.

 

[FFarr]

Yeah, my rear mount is a completely different design. It has studs sticking vertically up out of it that are jammed in the bracket.

I suspect my '98 has the same design as your '97, which must be why the shop didn't hate me when I asked them to change it.

Yes, very different from a 97.

 

[84ZZ4]

New mounts didn't completely solve the problem, but it did move the header down pipe up enough to pass a couple of sheets of paper in between the pipe and the heat shield. I used a crowbar to add some more clearance to the heat shield. and I think it should be fine now.

Thanks for all of the help!

Also, if anyone needs to change the mount style that I have, you need to unbolt the bracket from the transmission and pull it and the mount out together.