502 Exhaust Manifolds and Risers time
 

It's time for new manifolds and risers on my Cobalt and I'm thinking of going aftermarket. I'm new to the forum so I'm hoping this is in the right section. Does anybody have any experience with this setup?

http://www.cpperformance.com/p-73943...er-system.aspx

Is it as simple as taking the old manifolds and risers off and putting this set of exhaust in it's place? The cost is a bit high but if it means a little more power and a little less emissions stuff, I think I'm interested. Just need to know what the complexity of the install might be.

Any feedback is greatly appreciated. If not this system, any others that are recommended? Seems like I'm looking at $1500 - $2000 to replace the stock with OEM stuff.

I would look at the others ,if u r not going to step up the hp ....hardin /gills,,,seaward stuff. Cp is a good place to get just abt any style // i too looking at another set ....and leaning toward the h.p gill ones from cp

I went with Stainless Marine last year on my 502 and have been very pleased.

Did you use an O2 sensor? I've got 4 O2 sensors with the stupid catalyst system and there is a box that will eliminate the 2 rear ones but it says any aftermarket system I get I need to have the ability to install the front O2 sensors.

If you have catalysis exhaust, I'm not so sure you can go after market, without having something done with the PCM

Right. I found an eliminator system for $400 that plugs into the O2 sensors and lets you remove all the catalyst. But it requires O2 sensor ports on the front side as you have to re-use 2 of the stock O2 sensors for it to work.

So, now I just need to find an exhaust system that fits the 8.2L Mag EC motor that has O2 sensor ports. That is the sticking point.

OK got it, this is the same issue as bypassing the diesel setups. They do make a 3600 set at cpperformance and has the bung installed for the O2 sensor

I would not let the absence of bungs be a major factor. Most risers can be modified to accept O2's. Contact Eddie at Young Performance he does a great job at a fair price and is very reputable (and nice) guy. That's what I did with my S/M setup.

Was he cheaper than sending them to S.M. direct?

He did a lot more to mine than just the bungs so I can't say. I can say either is a good choice for quality.

I have Emi Thunder manifolds and stainless risers. It's a dry joint system. I they came on my boat when I bought the boat. I have been running them 2 yrs now. They seem well made. No issues here.

My main issue is the newer EC motors have the manifold and collector. So, I'm having a hard time finding an aftermarket setup that will fit and bolt up to the existing exhaust elbows. I'm leaning towards just buying an OEM manifold for the side that is cracked and seeing what the insides look like to see if I can get another year out of them.

Has anybody sent their cast manifolds and risers to get acid dipped to clean out the rust / corrosion? If so, who did you use?

Don't see cleaning the inside of the water jackets doing anything other then make it easier to see. If its rusty that's normal and it's not going to hurt anything. If the walls look thin then they are. Salt water manifolds will last about 7 years

Well I spent half the day pulling the port side manifold and exhaust collector off. The good news is the crack in the manifold is on the outside just above where the water comes into the manifold at the bottom. The crack is not through to the inside.

The bad news is one of the water ports on the exhaust collector is clogged completely with rust. So, it looks like I'm replacing the manifold and riser. So now the question is if I can find a decent aftermarket setup for a cheaper price. Seems like $1500 or so for each side and that is just crazy.

What is your serial number?
Is the catalyst still good inside the manifolds?

1A352940

Catalyst seems ok.

Best I'm finding is $1245.42 each side x2 = 2490.84

manifold 8M0045258 amazon $555.43 free ship and comes with manifold gasket
elbow gasket 27-8M2003931 ebay $59.41 +2.94 ship
collector 866391T02 ebay $538.70 + 4.95 ship
collector gasket 27-866390 Perfprotech $83.99 + ship??

The newer style manifolds cost a bit less (not much), but to use them you would also need new catalyst which is another 1100

I was thinking of ditching the catalyst all together and getting one of those cat eliminator systems. How much cheaper was the newer style?

The collector and manifold are one piece and run around 500 each side, so lest say saving 500 each side. The other thing is your current riser/elbow will not work with the new style so that's another 700.

Here is a parts link for BAM, and they show prices but there not the least cost
http://www.mercruiserparts.com/bam/s...1941/16012/160

I would be leaning toward the stainless ones, but even they can rust out given enough time

Well, looks like $2500 or so is the best I can do either way. Thanks for the help.

Do you know if I need the expansion plugs? Doesn't look like they are anything I can get out of the old ones so I was hoping they are already pre-installed.

The core plugs should come preinstalled

Thanks. I'll make a couple calls tomorrow to see if any of the aftermarket companies make a direct bolt up alternative for around the same price. Just doesn't make sense to me to drop $2600 + on the same cast iron crap if I can get something that will hold up longer for about the same price.

I've got a little corrosion on the mating surface where the manifolds mount up to. Can I put / should I put a little high temp RTV sealant on there before putting on my gasket and new manifold?

Also, should I be using anti-seize on the bolts?

Not a fan of RTV on a motor and really not in the exhaust area. I would wire brush and paint, but if they are deep then depending on how deep, suggest using some JB weld high temp and file flat.

Anti-seize would be good IMO

I keep hearing both ways on the RTV. I got everything nice a clean with a wire wheel and brake clean. The pitting is pretty shallow but you can definitely feel it. It's about the length of the exhaust port but only one and at the bottom.

I also heard the high tack copper spray is a good option. I just want to make sure I get a good seal and don't have to worry about this for another 3 or 4 years.

Can you post a pic?

Let me know if these don't show up.

https://photos.google.com/share/AF1Q...pkSGU1OVNqQVdB

https://photos.google.com/share/AF1Q...1xT3pVVVlReEtn

They showed up in the email but not here. Had a look at them and it appears to me that's left over gasket material. Take some 100 or 120 grit sand paper and see if it cleans up.

Photobucket should work
[IMG]http://i609.photobucket.com/albums/t...pskmbv0lc0.jpg[/IMG]

[IMG]http://i609.photobucket.com/albums/t...ps4ypuec0r.jpg[/IMG]

I'll try some sandpaper but I'm fairly certain it is pitting from corrosion. Pictures just don't show it well.

Assuming it is not gasket material, same question as before. Will just the gasket suffice?

The gasket should be able to seal it

So I got the port side all put back together. Hooked up the hose and ran the boat. I loosened up the hose clamps on the down pipe to verify I was seeing water and I can see water coming out the back of the boat.

The exhaust collector is pretty hot to touch but I'm fairly certain it has always been. Is there any way I can verify water is going through the cooling ports? The water I see in the exhaust could be from the bypass that connects directly to the elbow so just want to make sure I'm getting the right amount of water passing through there.

Is there a specific temp I should be trying to make sure the collector is running under? Engine temp never seemed to get high but I'm guessing the exhaust temp sensor just feeds to the computer and would throw an alarm if it got too hot.

I'll tackle the starboard side next weekend.

The exhaust should not get so hot that it will burn your skin when touched. One side will be cooler then the other, that is just how the water flows. I'm going to guess that since your not having trouble with overheating, you probably don't have an issue

Put this on both sides of the gasket and its done. I also put it on the bolt threads . Sort acts like a mild thread locker and anti seize all in one.

https://www.walmart.com/ip/Permatex-...&wl13=&veh=sem

Chris

Got the starboard side all back together and ran her yesterday but just around the canals at idle speed. I'm still worried about the temp. I can lay my hand on the starboard collector and it is cool to the touch. But I can't hold my hand on the port side for more than 1 or 2 seconds if that. It is very hot.

I know the port side is typically warmer than starboard and maybe this is just a matter of I'm only running at idle. Just want to see what you guys think.

I don't see an issue