Custom intake and exhaust manifolds

[ZoskalonMPI]

Alright, everybody has to start somewhere. I plan on doing the, now cliche, DOHC conversion eventually, and to prepare, I want to practice fabbing up some manifolds I have the tools and experienced help at my disposal, and it doesn't look all that hard lol

Ok, so I think I figured out why the MPI batch fired cars run so roughly at idle. The middle cylinders (2 & 3), get more fuel than the outside cylinders (1 & 4). Now, I'm just theorizing, prove me wrong if I am. So I always thought that an injector fires 3 times and that the fuel just sits there until the valve opens on the 4th injection, but I never really thought about it too much. While eating at McDonalds today, thinking about what to do, I realized, that when a valve opens, air from "everywhere" goes towards it. So even though an injector may fire 3 times with "its" valve closed, that fuel travels up through the intake runner and into the one with the open valve. Now the reason for the rough idle, is because the middle cylinders (ignoring the fuel injected from its respectable injector) get fuel from the two neighboring runners and one runner thats two runners down. Are ya following me so far? BUT, the outside cylinders get fuel from just ONE neighboring runner and one that's 2 runners down. Now instead of having two neighboring runners, one of those is replaced with a runner that is THREE runners down. So the outside runners I'm assuming would get less fuel due to the longer distance that the fuel has to travel in order to reach them. Am I right? C'mon! I thought this out pretty well. Or has this been common sense and I'm just barely catching on?

Anyway, I was thinking about getting a plain ol non turbo swirl head off a junkyard, there are millions there, for like $50 and porting it myself. I can follow directions pretty well and hey, I have to start somewhere, somewhere NOT on my good current head . So what do you all have to say or advice about this? How much would it cost to get the head milled a little (0.030 is it?) also. Port and polished head with added compression should boost my power a bit, no?

And now for my MAIN topic in this huge post, I want to start my fabbing career (heh heh) and I was thinking that fabbing up my own intake manifold would not only increase airflow a buttload, but would also provide me with an opportunity to reduce the rough idle. I have my old TBI intake that I could use to save me $20 getting another one off the jy. I'd cut off the runners, port the hell out of it, and weld on some pipe runners that run up and towards the each other. Instead of having the injectors at the base right before the head, I would bunch them all together at the top, kinda like the original TBI set up, but I'd have a MUCH better flowing intake, 4 injectors, and I'd get a 3.3L intake from the jy and use the elbow off it to put on my 52MM throttle body and not have it neck down to the size of a postage stamp like my TI intake does. What do you think of this setup? I have several designs in my head, but I want some input from people who know wtf they're doing . lol. Would there be any consequences in having the injectors much farther from the head? I understand that I'd have to make my own fuel rail(s). But first I want to get the concept straightened out before I get into detail.

I'd also get a TBI exhaust manifold and cut off the flanges and make a header. That should be much much simpler that the intake, and would make my engine smile, right?

How much power gain would I see with the ported head, crazy exhaust, and crazier intake? I don't want to hear "not worth the work/trouble" because it is worth it to learn a new skill and experience :P

P.S. I was also thinking, that if I were to put the injectors on top, outside the runners, I'd be totally unlimited in how many, or how little injectors I could use, as long as I remain above the 1ohm resistance (right?).

[mpgmike]

As for locating the injectors further away from the head, it has advantages and disadvantages. At lower engine speeds, your issue of cross vaporization will only be exagerated. However, at higher speeds, the fuel has more time to vaporize and will make more power (and better BSFC numbers).

Fabbing the intake will be a learning experience, and the quality of your work will have much to do with the power increases. Using a cast iron exhaust manifold for a start may not be such a good idea. Welding to cast iron isn't very easy. It requires pre-heating, nickle welding medium, and post cooling techniques. Even then they are prone to cracking. It might be better to have Jerre Stahl in York PA make you up a header flange you can build from.

As for porting the head, again the quality of your work will make all the difference in the world. Some ported heads actually run WORSE than stockers. Most of the time, there are improvements due to better VE. How much, though, cannot be determined until you're done.

Mike

[tkelly27]

Sounds like a good project. I'd keep the injectors where they are at personally. I think the lean condition is due to the fact that there is a flow disparity from 1 to 4, and not as much dependent on residual fuel in the runners.
http://www.thedodgegarage.com/5digits_air_and_fuel.html
bottom of the page has an interesting discussion.

Is this going to be turbocharged? You're going to need to modify a calibration if it's not.

I'm planning on making a custom sheet metal intake from scratch for my 16v setup with 2 sets of injectors (8 over all) in the runners. One set for alky. I guess that is to say, no matter where you put them you're not technically limited to the amount you can have. Hell, top fuelers have injectors inside the cylinders (I thought they did anyways).

If you take it easy with the head you can get some decent gains. Just don't go wild, and don't leave the die grinder in one spot for to long.

Actually going 16v is not cliche, saying "someday I'll go 16v" is .

[ZoskalonMPI]

I'm not turbocharging it just yet, would have to replace pistons, rods, exhaust valves, etc. But if I'm NOT going turbo, why do I need a calibration? And I realized that it's a little more work than I'd like to spend on making the intake, I think I'd just port match my current one, and port out the throttle elbow to match my 52MM throttle body ha, forgot to do that before I put everything together.

So porting head and intake no real complex biggy, right? Now in terms of the exhaust, I do want to make a header. Does anyone know of a link to somewhere that specificly lays out the entire process of welding the stuff to the cast iron flange? Or can anyone lay it out for me? Are there any very precise machines required, to heat up and cool down or whatever? I mean, a manifold from the yard is $20. Fwdperformance sells the steel flange for $35 but how much would shipping be? And then I'd STILL need the exhaust pipe flange, because they only have the turbo ones. Or would I just not have a flange and just weld/crimp the header to my exhaust pipe? I don't like the idea of not being able to take it out that easily though...

Also, do I NEED a TIG welder? Or can I get away with using a MIG welder?

[tkelly27]

If you're going that route, I'd chop off a T1 log intake (since you can get them for nickels, then use those fuel injector bungs, rail, and flange, weld up the TBI runners and plenum, then put a big TB in place of the TBI. It's really not that hard to fabricate stuff, especially if you have people who know what they are doing around you.

Or are you going with a turbo log intake and the 52mm TB? It's late, "I have no idea what's going on right now..."

Are you going to try and run all 4 injectors with the TBI computer? You may not need a custom cal then... It would be way easy to get the fuel right if you did have one though.

How to make a header? This page shows how to do it for a turbo.
http://www.sdsefi.com/techheader.htm
same concept at the end of the day for a N/A app.

If you've really got people that know what they are doing around you, you can have a gasket, trace it, and cut it out of 3/8 plate steel. I got a 2.5'x1.5' sheet of 3/8's for $8 at a steelyard a while ago. So far I've made a swingvalve flange and a header flange for a SOHC 16v engine and haven't made a dent in my supply.

If you aren't up to that, get the FWDP one, or find a water jet/CNC plasma, laser, etc. place near you. Maybe someone @ your school (or a local college/comm. college... I dunno what or if you are in school or not) would know where you could get a flange cut. May not be cheaper than FWDP though.

I really can't reccomend chopping up the TBI manifold and then re-welding to the cast iron. There are going to be high torsional forces on those joints (due to the long runners I'm guessing you'll be running), as well as huge heat cycling. If you're not good at welding cast iron, I can predict failure. Call me Kreskin...

MIG works, TIG is so much prettier, and easier in my opinion. If you are going MIG, do mild steel. I've never done MIG with SS, but, I wouldn't even want to try it. You pretty much have no choice but TIG when it comes to aluminum.

You're not going to want to use shced. 40 for a N/A manifold like the SDS site. I'd suggest these guys,
http://store.racing-solutions.org/bendkits.html
very reasonably priced! I'll be using them for my tubular turbo header when I build it (with lots of turbo bracing!!)

http://store.summitracing.com/partde...5&autoview=sku
That's the flange most headers use, 3 bolts and the whole thing drops out. Pretty civilized if you ask me. I'd be inclined to save on shipping and get 2 or 3 pairs for my cat and muffler so I could dump them whenever I wanted to.

True TD'er? Can't justify the $5 for a Y pipe?
http://www.turbomustangs.com/smf/ind...ic=65147.0;all
You can either go with 3 of those (1-2-4), or you can use that concept to make a 4-1 setup. Sky is the limit. I'm sure you can figure out a way to not need to buy the cone reducers, or a place to get some super cheap reducers. You can even use the SDS method with the square tube, then beat it into a round shape. Or creative cutting and reshaping of the runner tubes to get them to go into the 2.5" pipe. Or you could break down and add the 4-1 header collector from summit when you order the header flanges.

If you don't take the time to think about what you are doing in the head, it is a big deal. If you take your time, think it out, read what other people have said to do, you can do it. This is a pretty good basic concepts site
http://www.sa-motorsports.com/diyport.aspx
More advanced than that and you're going to have to get into head specific concepts. Even if the guru's give up the goods, doesn't mean you can do it like them, so don't try it on your first go around.

[ZoskalonMPI]

oh man, give me a few days to respond to that, lol, nah. I've been discouraged enough, I'm just going to port everything, save the fabbing for when I have more time and money to pour out. I saved what you said, will help me out a lot later on, thanks.

[ZoskalonMPI]

Alright, I'm still deathly interested in doing this. My brother has access to all the machines and material to make flanges. At work, he could actually design the flange on the computer and have the machine (forgot what its called) cut it out automatically. All this for free, but a lot of work on his part. Would I be able to just take a plate of mild steel, trace the gasket, and use an ordinary drill press to cut the bolt/stud holes out? How precise do I have to be with that? And for the exhaust ports, I can just drill one hole in the middle of the traced port on the plate and then use ordinary porting to open that up to match the gasket, right?

You mentioned to just trace the gasket, but the gasket includes the intake and exhaust manifolds. Would I be better off making the intake and exhaust headers one solid piece? Or would that make it very tight to weld?

I thought about it, and making the intake wouldn't be THAT difficult. Would I just cut the runners off a TBI intake, port it, and weld the pipes to that. Or should I make a flange from the steel? The TBI intake is aluminum, no? So I wouldn't be able to use MIG welding either way on that. And if I make the intake flange, I'd think that I'd need shorter bolts. Where would I get these, or how would I do this?

Since neons are common as hell at the jy, I could get the fuel rail from that engine, cut it up, and reweld it so that the injectors would be right next to each other (maybe in a square shape?). I have spare 19PPH injectors which I'd use, and I could get the 14PPH injectors from the yard for free. So for this, I was thinking, that instead of fabbing up the injector pipe/holes at the top of the intake, I just cut holes out the size of the thickest part of the injector, and weld them there in place. It would save me a lot of work and its not a real pain because those injectors are bountiful so if anything, I'd just cut that part out of my intake and put in a new plate with injectors.

So yeah, that's all I'm gonna put for now. Any input will be appreciated