Ported stock exhaust manifold?

[Stretch]

I just discovered there's a crack in my stock exhaust manifold. I need to replace this. I don't want to buy a long tube header and even a shorty is pushing it's luck to make it into my budget. I will probably replace the stock unit with another (crack-free) stock unit.

Has anyone tried porting a stock unit? Any gains to be found? I know it's different for every car out there, so I figured i'd ask before I buy/try anything.

PATIA!

http://i194.photobucket.com/albums/z95/SlimAndrew/Picture015.jpg

[powder]

I would venture to say it would be a waste of time.

[iceracer]

You could clean up some of the casting flash and maybe match the ports, but as powder said, it probably would be a waste of time.

[MellowedZX2]

Let me just ask, is this a common problem, because two out of two of the stock mani's I have had crakced in the same place on two diff cars.

Joel

[powder]

Let me just ask, is this a common problem, because two out of two of the stock mani's I have had crakced in the same place on two diff cars.

Joel

I cracked 2 on my '03 as well.

I would be willing to guess at the cause too. Did you have your heat shield off?

[DOUGIESTYLE]

Hey that's my original exh. mani.!!

[Stretch]

I cracked 2 on my '03 as well.

I would be willing to guess at the cause too. Did you have your heat shield off?

Okay, I don't know about anyone else, but I find your response bothersome. (not meant in a bad way of course) I've been reading more and more and it appears this isn't totally uncommon to occur.

My car came with only a minor mod (aftermarket stereo installed ..... that's all as far as I can tell so far). The heat shield was only removed because I needed to replace a sensor (don't ask) and that's when I discovered this. I have re-installed it as I wanted it in place.

Why would this be important? I imagine heat dissipation has something to do with it, but I can't imagine why. Radiating heat from the manifold allows it to cool too quickly????? Is the manifold THAT thin?!?!??! More input please.

I'm starting to wonder if I should re-consider a shorty header, especially considering I wanna use my SCT stuff to tune this engine.


LOL @ DOUGIESTYL ..... you want it back?!?!??! It teh suckzorzs!!!1!! hahahaha :?

[potatoman]

get a new one. porting a stock one would be a pain in the anus and not worth it. its cast iron so it would be much harder than the aluminum the head is made of and u would also have trouble getting to most of the mani.

even on the IM if its ported its not really that much of it. just port match to the head and the TB and remove the injector depressions.

after getting the appropriate equipment to do the exhaust mani u would most likely have spent a lot of money for a very disapointing result.

[powder]

Okay, I don't know about anyone else, but I find your response bothersome. (not meant in a bad way of course) I've been reading more and more and it appears this isn't totally uncommon to occur.

My car came with only a minor mod (aftermarket stereo installed ..... that's all as far as I can tell so far). The heat shield was only removed because I needed to replace a sensor (don't ask) and that's when I discovered this. I have re-installed it as I wanted it in place.

Why would this be important? I imagine heat dissipation has something to do with it, but I can't imagine why. Radiating heat from the manifold allows it to cool too quickly????? Is the manifold THAT thin?!?!??! More input please.

I'm starting to wonder if I should re-consider a shorty header, especially considering I wanna use my SCT stuff to tune this engine.


LOL @ DOUGIESTYL ..... you want it back?!?!??! It teh suckzorzs!!!1!! hahahaha :?

My guess is that's the case. W/ the heat shield off it allows the manifold to cool too quick and cracks it. W/ it on it cools slower cuz it traps the heat under neath it.

[capitalcrew]

If you have sct don't bother with another stock manifold.

[Stretch]

If you have sct don't bother with another stock manifold.

Elaborate please?

I have Advantage 2.9 which I just ordered the upgrade package to 3.0 today. I have NO intention of doing other exhaust upgrades and I also have (sniffer) emissions tests to consider.

[99fordzx2]

If your worried about emissons, then get a shorty header with the stock cat. When I installed my header, I found mine to be cracked in the same spot as well just not as bad. It looked like I caught it before it got too bad. Didnt know it was such a common thing. But like the others said, porting a stock mani wouldnt net you much if any gains, as well as the headaches involved with doing this. Also, youd have to worry about a new one cracking again.


-D

[Stretch]

I guess I should'a named this thread "JBA versus Pacesetter shorty". LOL!

Okay, more research to be done.

Thanks all! Appreciated muchly. :winkyface:

[Gregersonke]

Just make sure you get a ceramic coated header. Otherwise, you'll just have too much heat in the engine bay and you'll lose power.

[5spdzx2]

my manifold cracked just like yours did.

Just do what i did and buy the obx header. except, buy the one that doesnt have the 'obx' stamp on it that raises the price up 60 bucks. its the 'cheap' ebay header. but if anyone in there bright mind would read what material each was made of they would see that the obx and the 'cheap' ebay header are the same exact thing. the obx is just the same with there stainless steel name stamped on it with some paperwork, which costs you 60 bucks more...ridiculous.

I bought this 'off brand' header because it was actually cheaper than buying a new manifold. i strongly suggest that you buy this off brand header and just read what its made of (quality stainless steel). this will give you extra power, even paired with a stock exhaust and gain you some mpg. I had a bad o2 sensor and found that my manifold was cracked so i changed both and actually gained an extra 4.5 mpg.

you will get a bit of rasp with this setup but its damn worth the extra mpg and little power. i think the manifold was like 120 shipped on ebay. the header i got was about 110 on ebay...why the hell would i buy the manifold when i could get an obx without the stupid stamp welded on for less?

for everyone else (thinking about getting an OBX):

do not waste your money on the stamp and paperwork that obx gives you with the header. it costs you 60 bucks extra and does absolutely nothing different with performance, quality, and mpg. if your smart you will read the information provided from each and see that they are made from the exact same material. and ill tell you that the welds are perfect. obx buys this header and renames it. that is all.

[Stretch]

From what I can tell so far the OBX and it's knock-off counter-part are only available as long-tube solutions. Am I incorrect? If that is the case I won't be going that route.


Gregersonke - absolutely! I learned that lesson once already.

[Beodude123]

I'm pretty sure porting the stock manifold would be a waste of time. The "runners" are a decent size, and the collector is nice and big too. But the collector placement is so whack, that it robs a lot of power. Even if you enlarged the stock stuff, it wouldn't give you the results you're looking for.

You really need to have some distance on the runners, so that way the exhaust has enough time to propagate down the tubes. There is a lot of theory on runner length, and I won't get on it in here, but it will allow you to have exhaust scavenging. This will actually suck the air from the intake side through the exhaust side during overlap. This allows you to get more air in.

[5spdzx2]

From what I can tell so far the OBX and it's knock-off counter-part are only available as long-tube solutions. Am I incorrect? If that is the case I won't be going that route.


Gregersonke - absolutely! I learned that lesson once already.

dont want to lose the cat?

[zxtwou2]

so wait....you cracked a stock manifold...and want to port another stock manifold to make the walls even thinner? won't that crack even easier?

[Gregersonke]

dont want to lose the cat?

Ceramic coating on the header is important.

[5spdzx2]

Ceramic coating on the header is important.

why? just get stainless theres nothing wrong with it

[MellowedZX2]

to answe your question about my heatsheild, I said I have two manifolds, well one came from a bone stock car with the heatsheild and when I pulled it off it was cracked too, so i think the cooling down too fast theory is plausible, nust not in this case...
And ZXtwou2 is right porting it would only make it thinner.
Thinner metal = weaker metal.

Joel

[2000ZxT]

The problem with the stock manifold is that the exhaust pulses leave the head, smash directly into the front walls of the header and the only thing really directly the travel of flow is coming pulses. Porting the stock header wouldn't do anything for HP I am almost positive. Not to mention the cat is super restrictive and the piping to and from the cat is all over the place with weird bends.

[inis]

my heatshield has been off since the car was new. I've never cracked one, or seen one cracked to be truthful.

You can have mine for 25 + s/h lol

dont need it anymore.

[2000ZxT]

I'm not exactly sure why people take the heat shield off.

When I took mine off I noticed a considerable raise in my coolant temp.....

[ZX2R]

dont want to lose the cat?

He's got a sniffer test coming up.

[mechtech]

You won;t get great gains, but smoothing and polishing will help some.
There really isn't a lot of meat there to modify severely.

[JohnP]

The stock exhaust manifold has a good open design , smooth large bends , the casting has a very smooth surface on the inside . The port size is a lot larger then the head port . The metal gasket is a perfect match to the manifold and larger then the head port . Theres no need to do anything to the manifold . One reason cast iron manifolds crack is from improper torquing of the bolts , by the factory or whoever . Expansion and no room to move , got to crack somewhere . Thermal coat it , it'll work even better.

[Stretch]

Wow, there's some really appreciable feedback here. Thanks everyone.

To answer a couple of questions;

1) i'm not interested in loosing the catalytic converter primarily because of inevitable emissions testing (up here in Canada this is done on a roller with a sniffer running and the car "driving" at 40 kph - once every other year). Secondary reason is that I don't want to spend the extra money on a long tube set up. I've done plenty of playing with cars before and I don't want THIS car to be a headache. I really enjoy the fact that the engine starts to run after 2 cranks when starting. I'm intent (and content) to have a mildly modified, BS-free DD car. I'll put on a few toys, bells and whistles in a while, but practicality, reliability and fuel economy are what I seek now with my "tuning". My SCT PRP and Raptor WILL see plenty of usage on this vehicle, I kid you not. :biggrin:

2) porting doesn't always have to mean that a part is significantly weakened and more prone to failure (read on before you jump to a conclusion here). Many variables at play with this, but this is why I asked this question in the first place. I don't want to take the manifold off to snoop only to be "disappointed". I figured if there might have been some kind of flange or lip within the casting that could have been removed to increase scavenging that would have been easy to do i'd go for it, but such is not the case. At the very least I am thankful to have the great feedback here to tell me not to waste my time.

Thanks everyone! :)

[Stretch]

The stock exhaust manifold has a good open design , smooth large bends , the casting has a very smooth surface on the inside . The port size is a lot larger then the head port . The metal gasket is a perfect match to the manifold and larger then the head port . Theres no need to do anything to the manifold . One reason cast iron manifolds crack is from improper torquing of the bolts , by the factory or whoever . Expansion and no room to move , got to crack somewhere . Thermal coat it , it'll work even better.

Knowing who you are and given your response, i'm inclined to ask .....

I have a "local" resource that I know can produce quality ceramic coatings. I know it's a VERY subjective question to ask, BUT, would it necessarily help prevent future cracking if I were to have a stock manifold ceramic coated????? (honestly, i've NEVER contemplated this scenario with any vehicle before - I feel ackward just asking it)

PATIA John. :)

Honestly, if I can get away with spending less money i'm all for it. An aftermarket header will cost more than what it would cost for me to get this coated, so I feel it's worth asking (especially because this ain't no race car LOL).

[Stretch]

I'm not exactly sure why people take the heat shield off.

When I took mine off I noticed a considerable raise in my coolant temp.....

I'm not sure if you're referring to the temp the EEC see's or the gauge on the dash, but I can understand your scenario if you are referring to the gauge on the dash. I was replacing this same sensor when I discovered this crack, and knowing the sensor is close to the manifold, i'm certain that radiant heat emitting from the manifold would affect the sensor's reading somewhat. Kinda like "fan wash" from a radiator fan blowing hot air on sensors.

Just a thought.

[JohnP]

Most cracking on iron manifolds is from being over torqued when Cold . Final torque should be done when Hot. The stock manifold is very clean inside , no flash or burrs , nothing to remove . Coating won't help with cracking , but it will keep the exhaust gas hotter for a little increase in power .

[Stretch]

Most cracking on iron manifolds is from being over torqued when Cold . Final torque should be done when Hot. The stock manifold is very clean inside , no flash or burrs , nothing to remove .

Got it. Thank you very much, kind sir! :)

[Gregersonke]

Ceramic coating will also keep the heat in the exhaust rather than expending into your engine bay.

[Stretch]

Yup, understood. I thought it might be nice to send my intake manifold for like treatment, but I keep forgetting it's plastic. (sigh) (shrug) Compromise.

[mrwislr]

I saw in this post if your manifold is cracked you can buy a cheap header from ebay to fix it? Is a header and a manifold the same thing?

[Waterboy9000]

im about to replace mine in a week or two. pay shipping and you can have mine