Individual Runner ?'s

[Doubt_Incarnate]

i'm planning to put tegether an individual runner setup for my 3.1, just have a few ?'s. i'm sure are stupid. but thats what ?'s are for.

The base of the project is a '97 3100 topside. heads, etc. i plan on using the 3100 lower intake to mount a custom upper intake that using aluminum tubing will hold a 34mm carb on each end. no the carbs wont be fueled. just acting as TB's. im not skilled enough to make 6 indentical ones.

first ?, how long should the runners be?, i want to keep them longer mostly for the low end, but i think it would look nicer, and fit under a hood also. im counting on the carbs to work as TB's so im still using injectors, no worries about throttle response, or fuel falling out of suspension.

next ?, how is the ecm probably going to respond to this mod? i figured out a way to mount a tps in the throttle linkages. and i was just going to let the iac motor leak some filtered air in the runners past the throttles. but what can i expect to happen first time it starts/tries to start? if it starts at all...

last ?, what kind of tunning would i have to deal with if all else fails? i been lookin at the haltec e6gm but stil think i dont want to pay for one, unless i really have to. i'd rather keep the stock ecm for budget reasons.

[Anonymous]

Not a 3.1, but some other guy's dohc

i dont see any reason why it wouldnt start, but it will need tuning

[Doubt_Incarnate]

that looks cool, im aiming to keep it under the hood, or a cowl.
i want the runners to bring the throttle bodies over the cylinder its feeding, a big crossflow kinda thing. flat as i can make it.

how is he putting those on? looks like he needs a special cast lower intake manifold. or an adapter plate.

[donk_316]

Also in that pic, the injectors are firing about 90 degrees from where they should be. its going to be a tuning nightmare and wont reach its peak performance potential.

[RednBlack]

I do believe that set-up belongs to Aaron.

[Doubt_Incarnate]

i plan on using the original lower intake, so injetors will retain thier stock location. if i do everything right the ecm will just wonder where all the air is coming from. but i plan to make a vaumm "log" for PB, MAP, the IAC vent, and crap that needs vuac to operate, maybe i'll get jucky an djust need to up the injector size, or fuel pressure.

[bszopi]

How are you planning on keeping the stock lower and still keep everything under the hood? I can tell you that it's not going to be very easy, unless you make the flowpath really crappy. I'll show you a reason why...



That is my current project (which I haven't had time to touch since July). I made the bends as short as possible and it's still ~1" to tall to clear the hood. With independent stacks, you'll have to worry about other issues (such as the bell mouths and filtering) that will make fitting it under even a cowl a total nightmare. I'd suggest trying some mockups of different ideas before investing too much into the project.

[Anonymous]

Where is the plenum goin to b on that intkae? Seems to me it won't give many benefits over stock. The runners, if it is how i picture it, will be about the same length and plenum volume, if it is where i think it is, will only be slightyl increased.

and doubt incarnate, tuning it, you said that there will be a carb on each stack, so your gonna use a carb and fuel injection?

[sharkey]

he is going to be running fuel injection, the carbs are going to just be a throttle body.

my biggest worrty would be the iac. you will need to run a log down the center to pick up the vacume, and your best bet would be to have the iac run on one end of that. its going to be hard to keep it all under the hood. what i would recomend is getting an 87 z24 cowl hood and cut the underside of the cowls out. that will give you about another inch to play with

[bszopi]

How can you even think that the runners will be about the same length?!? Stock runners are around 15", whereas those come out to right around 21" total. That would be almost 50% longer runners than stock. As far as the plenum, it will most likely be close to if not slightly larger than stock. It is being designed to bring back some of the low end to the engine, as most available mods for the 3x00s give you a great top end, but really do nothing for the low end. By lengthening the runners and bringing the power curve back down some, the engine should have good power throughout the RPM range. In theory, of course. By going with your idea (no plenum and short runners), you are once again raising the top end performance while killing the low end. Sure, you'll be able to pull like a mad man from 4k+, but the engine is going to suck trying to get up to 3k...

[Anonymous]

Well from the looks of it it looks like the runners would be about the same lenth, assuming the plenum is put right where those runners end. I dont know where you get the extra 6" tho, those are only 2-3" max longer than the stock ones that curl up tot the plenum from the looks of it.

[bszopi]

http://www.60degreev6.com/index.php?name=PNphpBB2&file=viewtopic&t=1676&highlight=plenum+theory

After looking at the numbers again, stock is ~15.75" and I was going for 20". So only an ~4" increase, which still is an increase of 25%.

[Anonymous]

Well your daughter seems to like it, and I cant argue with that!

keep going, it will be interesting to see a dyno afterwards.

[Doubt_Incarnate]

i was going to use 90* bends off the manifold, and bring the carb to sit right over the valve cover. my runners would be like 22-24" long. as far the hood goes, i have the z24 hood and already cut it out underneath, push comes to shove i'll cut the division out and make it one large cowl as opposed to the twins. i've sketched abunch of crap out, to bad i dont have a scanner. originaly wanted to have all throttles inline across, under a scoop that says "SIX PACK" but that make a really crappy setup, to many bends on the front runners.

i suppose 90 degrees is to sharp isnt it? needs to sweep for optimum performance. but then not like the rest of the manifold is designed for optimum performance either. wouldnt it be cool if someone made a base that just completed the heads and covered the valley? just left us the ports and coolant passages to playwith.

the other option i was playing with was just making short stacks and attaching them to the lower intake with a 2" runner, but i dont want the runners that short, and with some cool looking stacks that wouldn't fit. dont want the stuff sticking out of the hood, cuz its offset, look kinda weird, but under a modest cowl would look ok. the old z24's werent exactly racy. so it would be sort of a sleeper.

i appreaciate all the info, im sure it will be usefull. good to see im not the only one trying to go this route.

[Anonymous]

the other option i was playing with was just making short stacks and attaching them to the lower intake with a 2" runner, but i dont want the runners that short, and with some cool looking stacks that wouldn't fit. dont want the stuff sticking out of the hood, cuz its offset, look kinda weird, but under a modest cowl would look ok. the old z24's werent exactly racy. so it would be sort of a sleeper.

The ones on that dohc look great imo, and they are offset. but they are also much closer together than those of the 3.1 lower intake. what about making your own baseplate? you have to have some mechaical inclination if you are going to go this far, a base plate wouldnt be hard at all imo.