Things That Suck About Installing Headers on an L36 Monte Carlo
#1
08-03-2010, 08:13 AM
Things That Suck About Installing Headers on an L36 Monte Carlo
So I recently installed a set of Speed Daddy (SLP knockoff) headers on my 2003 Monte Carlo SS. These are a direct bolt-on for Grand Prixs. They're stainless steel headers and look great. $205 shipped to my front door from eBay.
They were a B***H to install- because they're tested for fitment on Grand Prixs and not Monte Carlos, and because L36 Monte Carlos have some unique stuff that Grand Prixs don't, these are not a plug and play installation. Plus, it seems like no one out there has installed these on a Monte on their own, so there was no information and I had to figure it out on my own. Main issues were:
-The Monte Carlo radiator cooling fan assembly is too large- front header simply does not fit with the stock cooling fan in place. This requires you to remove the stock cooling fan assembly and replace it with something slimmer- I used two 14" universal slimline electric fans from Advance Auto. I had to cut the stock fan harnesses and splice the new fans in, then mount the fans on the radiator.
(This was a particular pain in the for me, because I tested one of the fans for push/pull configuration and figured the other fan was the same setup- WRONG- after getting everything buttoned up, I found that one of the fans was pushing and one was pulling- grrrrrrrrrrr).
-The Monte Carlo has a power steering line that runs very close to the stock rear exhaust manifold- close enough that the rear header absolutely would not install, since the line was in it's way. I had to remove the power steering line, carefully bend it, and re-install it.
-The location for the front O2 sensor in the SD headers is in a place where there is absolutely no way in hell an O2 sensor would ever fit, unless I clearanced about 4" with a sledge hammer on my firewall. Not going to happen. I had to install the front O2 sensor in the rear location and run a 3" O2 harness extender to meet it. Luckily I'm running catless for now. Not sure what I'm going to do when inspection time comes and I need to slap a cat on it- probably going to stick the O2 sensor in, plug it in, disable it, and run it in closed loop for inspection.
- Transmission filler tube was blocking header crossover pipe from being installed- bent filler tube out of the way. This wasn't bad, just thought I'd mention it.
On top of these fitment issues, I had additional problems:
- All four downpipe studs were rusted/gaulded into place. Spent at least an hour and half just fighting with these bolts to get the old downpipe off. Had to cut the downpipe to catback studs with a dremel and then drill them out- then found that the drill holes I made were too far out on the flange for the new header downpipe flange to fit, and had to re-drill.
- Cylinder 5 primary keeps leaking right where it meets the head. I've really torqued the crap out of it and am hoping it's stopped for now.
- Downpipe to catback flange keeps leaking. I think the cat-back flange is FUBARed now. Not the worst thing in the world, but annoying.
That's about it. It's a bit of a pain to install the rear header- have to remove your intake track/throttle body/tranny tube/wires/fuel lines, ratchet strap the engine all the way forward, and slide the rear header in from the driver side.
Lot's of people complain about crossover pipe flange leaks on these, but (knocks on wood) I've been OK so far.
Just thought I'd share. After performing the install, I really wouldn't recommend installing headers on your L36 Monte unless you've got a serious build going on- they are too much of a pain for a bolt-on car! Not sure if the L67 Montes are similar, but hopefully they're not as bad.
They were a B***H to install- because they're tested for fitment on Grand Prixs and not Monte Carlos, and because L36 Monte Carlos have some unique stuff that Grand Prixs don't, these are not a plug and play installation. Plus, it seems like no one out there has installed these on a Monte on their own, so there was no information and I had to figure it out on my own. Main issues were:
-The Monte Carlo radiator cooling fan assembly is too large- front header simply does not fit with the stock cooling fan in place. This requires you to remove the stock cooling fan assembly and replace it with something slimmer- I used two 14" universal slimline electric fans from Advance Auto. I had to cut the stock fan harnesses and splice the new fans in, then mount the fans on the radiator.
(This was a particular pain in the for me, because I tested one of the fans for push/pull configuration and figured the other fan was the same setup- WRONG- after getting everything buttoned up, I found that one of the fans was pushing and one was pulling- grrrrrrrrrrr).
-The Monte Carlo has a power steering line that runs very close to the stock rear exhaust manifold- close enough that the rear header absolutely would not install, since the line was in it's way. I had to remove the power steering line, carefully bend it, and re-install it.
-The location for the front O2 sensor in the SD headers is in a place where there is absolutely no way in hell an O2 sensor would ever fit, unless I clearanced about 4" with a sledge hammer on my firewall. Not going to happen. I had to install the front O2 sensor in the rear location and run a 3" O2 harness extender to meet it. Luckily I'm running catless for now. Not sure what I'm going to do when inspection time comes and I need to slap a cat on it- probably going to stick the O2 sensor in, plug it in, disable it, and run it in closed loop for inspection.
- Transmission filler tube was blocking header crossover pipe from being installed- bent filler tube out of the way. This wasn't bad, just thought I'd mention it.
On top of these fitment issues, I had additional problems:
- All four downpipe studs were rusted/gaulded into place. Spent at least an hour and half just fighting with these bolts to get the old downpipe off. Had to cut the downpipe to catback studs with a dremel and then drill them out- then found that the drill holes I made were too far out on the flange for the new header downpipe flange to fit, and had to re-drill.
- Cylinder 5 primary keeps leaking right where it meets the head. I've really torqued the crap out of it and am hoping it's stopped for now.
- Downpipe to catback flange keeps leaking. I think the cat-back flange is FUBARed now. Not the worst thing in the world, but annoying.
That's about it. It's a bit of a pain to install the rear header- have to remove your intake track/throttle body/tranny tube/wires/fuel lines, ratchet strap the engine all the way forward, and slide the rear header in from the driver side.
Lot's of people complain about crossover pipe flange leaks on these, but (knocks on wood) I've been OK so far.
Just thought I'd share. After performing the install, I really wouldn't recommend installing headers on your L36 Monte unless you've got a serious build going on- they are too much of a pain for a bolt-on car! Not sure if the L67 Montes are similar, but hopefully they're not as bad.
Last edited by ChibiBlackSheep; 08-04-2010 at 08:57 AM.
#2
08-11-2010, 04:17 PM
Sounds like a lot of fun, especially not clearing the fans.
At least you know you won't have to go through that again.
Couldn't you just get another o2 bung welded onto your downpipe before the cat?
I ended up doing that for a catless downpipe (apparently the '04 doesn't like to run without the rear sensor in) and it cost me all of about $10 (the dp wasn't on the car at that point).
At least you know you won't have to go through that again.
The location for the front O2 sensor in the SD headers is in a place where there is absolutely no way in hell an O2 sensor would ever fit, unless I clearanced about 4" with a sledge hammer on my firewall.
I ended up doing that for a catless downpipe (apparently the '04 doesn't like to run without the rear sensor in) and it cost me all of about $10 (the dp wasn't on the car at that point).
#3
08-11-2010, 04:37 PM
At least you know you won't have to go through that again.
It definitely wasn't something I'm anxious to repeat!
Couldn't you just get another o2 bung welded onto your downpipe before the cat?
#4
08-11-2010, 04:49 PM
A lot of the issues you speak of are issues not just specific to MC's, i.e. firewall clearance w/O2 sensor and trans tube bending.
The fans clearance thing is an MC issue. Never heard of the PS line thing, maybe someone replaced your rack wrong at one point and routed the line incorrectly I don't know.
All header installs are a PITA to get the rear one in right. Some people have gone as far as to drop the rear half of the cradle and finagle(sp?, come to think of it is that actually a word?) them in from the bottom.
The fans clearance thing is an MC issue. Never heard of the PS line thing, maybe someone replaced your rack wrong at one point and routed the line incorrectly I don't know.
All header installs are a PITA to get the rear one in right. Some people have gone as far as to drop the rear half of the cradle and finagle(sp?, come to think of it is that actually a word?) them in from the bottom.
#5
08-11-2010, 05:18 PM
A lot of the issues you speak of are issues not just specific to MC's, i.e. firewall clearance w/O2 sensor and trans tube bending.
The trans tube bending honestly wasn't a big deal- I just thought I'd mention it since I had to do it.
Never heard of the PS line thing, maybe someone replaced your rack wrong at one point and routed the line incorrectly I don't know.
All header installs are a PITA to get the rear one in right. Some people have gone as far as to drop the rear half of the cradle and finagle(sp?, come to think of it is that actually a word?) them in from the bottom.
#6
08-11-2010, 06:29 PM
At least its done now.. Think if you were just starting the job right now?? Sounds like a good job though.
#7
08-11-2010, 06:51 PM
LoLz, this is nothing- at least they physically fit the car. Try putting them on a 5th gen monte instead 
Then you have no choice but to go at it with a sledge and cutoff wheel
Then you have no choice but to go at it with a sledge and cutoff wheel
#8
08-11-2010, 07:46 PM
Try putting them on a 5th gen monte instead
Keep in mind this piece of **** is my daily driver, too- so I had to have it done over the weekend or I'd be bumming rides on Monday. Makes it a bit more dramatic, you know?
