porting exhausted mani

[RedGSX21]

I would like to port my exhaust manifold but i dont want to get any cracks in it either. Will porting the manifold cause a higher risk of it cracking later on? I have a 95 gsx. Thanks

 

[groundPork]

Not necessarily. You have to be careful to not remove too much material. That's how cracks start. Stick to blending, and smoothing don't hog out if your not sure. This will actually aleviate stress risers on the walls that could propagate a crack.

 

[kenamond]

Here's what I did with my stock 2G mani: Here is the collector. Here is the #4 runner. I have other pics but haven't uploaded them yet. Just remember to leave that flap in there.

Warning: I haven't put it together yet, so I can't say how well it works or if it will crack, but the 2G mani is less susceptible to fatal cracking than the 1G, though the 2G will normally crack (sample 1 and sample 2 of my mani before porting). I gasket matched a "7cm" gasket (no, it's not 7cm in diameter) and ported/polished my B28 to match. Before. After.

Good luck.

 

[big_eskimo]

That before and after of your Big T28 is a super good port job. And for Kenamond its called an exhaust manifold, not exhausted, it sounds like your mani. needs to take a nap or something the way you said it.

 

[Burnett03]

I would like to port my exhausted manifold but i dont want to get any cracks in it either. Will porting the manifold cause a higher risk of it cracking later on? I have a 95 gsx. Thanks

if done correctly it wont crack..
www.spooled.org/serv.html for cheap good porting

 

[kenamond]

That before and after of your Big T28 is a super good port job. And for Kenamond its called an exhaust manifold, not exhausted, it sounds like your mani. needs to take a nap or something the way you said it.

Thanks! I think it turned out pretty nice. And by the way, RedGSX21 said "exhausted" not me I was looking and was going to edit it, but it wasn't there.

 

[big_eskimo]

Thanks! I think it turned out pretty nice. And by the way, RedGSX21 said "exhausted" not me I was looking and was going to edit it, but it wasn't there.

Oops, I looked at the first post in the reply, if you scroll down it makes the last post first and the first post last, . My bad, but again good job on that piece, looks awesome!

 

[RedGSX21]

yeah had a long day when i posted that. next time i will read over everything. those pictures are awesome. let me know how it goes when it is back on the car. Sounds like if i port it correctly then i should be ok. post those other pics if you can also.

 

[RedGSX21]

Not necessarily. You have to be careful to not remove too much material. That's how cracks start. Stick to blending, and smoothing don't hog out if your not sure. This will actually aleviate stress risers on the walls that could propagate a crack.

Can someone explain how porting will alleviate the stress. Is it just because the air flows more freely or what?

 

[Chaddycakes21]

Yup, its simply that, the hot air can flow more freely.

 

[Talonman92]

What kinda tool do you guys use to do this stuff? Just like an air-dremel thing? or do they make special impact gun\drill attachments?

 

[majik2k5]

Carbide bits. You can buy them here, http://dsm.dejonpowerhouse.com/

They have them listed as aluminum porting cutter, same concept though. Under BOV-MISC-TOOLS at the very bottom.

 

[kenamond]

Okay, this grew to incredible length. Sorry

You CANNOT use a dremel to port much of anything unless you have **days** to futz with it (and dozens of bits). You can polish with a dremel, but you can't take much material off as is required for a port job.

To pull off a large amount of material in a reasonable period of time, you really need a die grinder. If you have a big air compressor, you can use a pneumatic die grinder (like $20-$30 at your local hardware store). If you don't, you can get an electric die grinder for $40-$50 new or less used. I got the Harbor Freight grinder for like $42 or something. Electric grinders seem very rare at your local store, but you can order it online from numerous vendors. Mine was about 14" long whereas pneumatic grinders are more like 6" long. I was a bit suprised when my electric jobbie came in the mail. Still wasn't a problem; just throw the cord over your shoulder with the housing clamped in a vice and grind away steadying with the upper hand and steering with the lower hand.

You also need atleast two carbide "burrs" which are bits for the grinder. Most dremel bits are steel which won't do jack shit to the mani. They must be tungsten carbide. They come in all sorts of shapes and sizes and flute designs. I recommend a double cut carbide cylindrical sphere end burr. The "double cut" part will generate a rougher finish, but it will produce bits of metal much like sand which won't cut you. If you get a single cut burr, you'll get a smoother finish, but you'll also produce 1-2mm shards of steel flying everywhere - much like mini pins (more like sharpened steel hairs) with points on both ends - very nasty and more of a concern to clean up. The cylinder sphere end is just the shape. It's a cylinder with a spherical tip. I also got a single cut flame shape burr which is shaped like a candle flame. This is what made the nasty metal shavings. I recommend around a 1/2" or 5/8" diameter burr. Burrs run about $12-$25 online, but the larger diameter ones are at the more expensive end (do a Google search on "carbide burrs" and you'll soon find out all of the shapes and sizes and single, double, diamond cuts available and know better what I'm talking about). They also come in different shaft lengths so that you can reach farther with them into whatever you're porting. I had 2-1/2" shafts, but that's because that's all they had at my local industrial supply store. After I was done with my porting, I believe that the first one was too dull to keep around for much of anything useful, and the 2nd one was probably half-spent. I firmly believe that they'd last much longer if you stuck to steel (turbine housing) and not cast iron (mani and O2 housing).

The grinder+bur will do all of the major work. The double-cut burrs produce a rougher finish, but you can take care of this in no time with a dremel tool and a "flapwheel" bit. This is like the paddlewheel on an old steam boat, but the paddles are strips of sandpaper. They wear down as you go until you just have the center hub, then you grab another one. I used 3 for the turbine, mani, and O2 housing (including the wastegate and turbine exits). I used 80 grit just because that's all they had at the store. This will knock down all of the bumps and imperfections from the grind in no time with little effort.

Then I finished up by hand sanding using 100 grit (must be aluminum oxide sandpaper), 220, 600 (dark grey paper, not aluminum oxide, but don't know what it is - some wet/dry sandpaper), then wet sanding with the same 600 grit. You can go on to 1200 wetsanding then polishing compound to get literally a mirror finish on your turbine housing, but my hardware store only had up to 600 grit. Looking at the picture of my turbine housing, I figure it's good enough, though

This is all for the turbine housing. Note: I ported my stock T25 turbine housing for practice - to get the feel of the grinder and to get a sense of what metal to take off where.

I had the 7cm gasket from FP for the turbine/mani and used it to scribe a circle on both parts, then worked my way out to the scribe line. Then I would occasionally put the gasket back on to see how close I was getting (when you get close to the scribe line, it starts to hide from you). When I was done, it was damn near flush with the gasket the whole way around.

I also used the grinder to port the mani, but there's something about the cast iron in the mani that makes it slower to grind than the steel in the turbine housing (you could do the turbine inlet grinding in 45 minutes, but the mani took twice as long even though there was less material to grind away). It seemed to partly smear the metal away instead of just cut it away like a mill or lathe would do (that's what it does to the steel). It also dulled my burr pretty quickly. I didn't do anything but use the double-cut cylindrical sphere end bur on the mani - no sandpaper. I did clean out all of the soot from the runners at the heads, but that flapwheel didn't do much at all to the cast iron mani. It knocked down the bumps in the cast finish, but nothing like the turbine inlet.

When you do the runners where they converge in the mani collector, just keep in mind what you think would be a smooth flowing passage. You want smooth curves where exhaust has to go around a bend, and you want the runners to meet such that they are running as parallel as possible to each other. This results in sharp corners where the material separating two runners end - like the flap between the 2+3 and 1+4 runners and the metal where 1+2 and 3+4 come together.

Note about the flap in the mani collector: The 2+3 runners and the 1+4 runners alternate flow while the 1+2 and 3+4 runners overlap, so the flapper keeps the 1+2 and 3+4 gasses from competing when they are combined in the collector. Moral of the story: leave the flap in there! Custom tube manis mated to large turbines will actually keep (in this case) 1+4 in completely separate passages from the 2+3 (even in the turbine housing). The mani will have a "divided" outlet (example from www.turbobygarret.com), and the turbine will have a divided inlet the whole way around the turbine wheel (example from www.turbobygarret.com).

Also, the ridges between 1+4 and between 2+3 divert the gasses toward the turbine inlet, so you want to leave them in there, too (or you'll shoot #1's gasses up #4's runner and vice versa. Same with 2+3. Recall that they are out of phase, so one is dumping exhaust while the other is not).

The stock 2G O2 housing was even tougher than the mani. The grinder was slow to work on it, and the flapwheel dremel bit didn't do much more than clean the soot off.

I set up a "tent" around my workbench with three 8'x10' tarps ($4 each) hung from eye screws in the ceiling just to keep the grinding mess to a local area. I also used the dual 500W halide light tripods baking down on the workspace to get light into the depths of the turbine and mani runners.

You absolutely need a grinding mask (head gear with a huge plastic shield for your whole face) to do this! If you just have safety glasses, just one bur of metal has to bounce off of your eyebrow or cheek and land in your eye to make for a miserable day. You need BOTH glasses and a shield.

Also, search this forum for porting threads and read the one in the Tech Articles section titled, "How to cure boost creep by porting" which has links to great threads on general porting information.

I must admit that I was a bit intimidated going into this project, but once I started each phase, my confidence grew, and I knew what I was doing. I'd do it again in a heartbeat (just have to wait for this turbo to die, then I'll upgrade and do it again )

 

[kenamond]

Can someone explain how porting will alleviate the stress. Is it just because the air flows more freely or what?

I don't want to speak for him, but I think he meant that taking the bumps and imperfections out of the rough, cast finish of the mani will reduce potential "crack starters". Stress concentrators occur where you have sharp changes in the shape of a part, and each bump in the sand cast surface of the mani is such a change in shape. Notch a bar and stretch it apart, and it will fail at the notch. You get the idea.

Complete digression: did you know that they cast metal parts using styrafoam molds (called lost foam casting)? The finish of these parts looks like silver styrafoam. The Garrett center section oil passage of my B28 was foam cast. They pack the foam mold (looks like the part you're casting) in sand and pour the metal in. As the foam evaporates, the violently expanding burning foam gasses hold the sand in place keeping it from caving into the part, and the metal just fills up the space. As long as you can make the part out of styrafoam and fill all the nooks and crannies with sand, you can cast the part (there are exceptions, of course). Many heads and blocks with all of the coolant and oil passageways are cast this way. If you didn't know, now you do

 

[kenamond]

Here are two more pictures of the mani.

Here is a picture of the #1 and #2 runners:

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Here is a picture of the #2 and #3 runners. Notice the crack in the left side of the flap (common, I hear, and it didn't propogate out the top of the mani):

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[Talonman92]

Kenamond, thank you for the VERY informative post. That cover'd just about every question that popped into my head. I do have a rather large air compressor but it seems that if you were grinding for 45 mins, that the compressor being on for the duration would drive me insane. I'm thinking an electrical unit would work well. Once again thanks!

 

[RedGSX21]

kenamond that was a great post man i am learning alot. Thanks for those pictures because in my mind they are what really explain everything the best. Very soon i will take off that mani and port it. Thanks again.