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hi guys, just thought id show a pic of what im attempting, i had loads of photos but this site dosnt allow there size so ive put a smaller pic of where im at.
the idea is as the roof of the intake sits bellow ridges cast into the uim, and the castings quite thick im simply removing the roof of the runners, i will then mount a new roof on top of those ridges. should increase runner hieght by 5-10mm - the casting thickness is not consistant. seemed quite an easy simple job, i like using the OE intake as well. the increase in runner height should also help the sharp bends. theres also guna be a huge difference in plenum size.
You're going to loose air velocity by enlarging the runners like that, but a larger plenum never hurts. If you can gradually blend the runners back into the stock port size you might be able to pick up a little airflow without hurting velocity.
heres ur best bet
cut the entire middle of the upper out
like this
doing this u can weld back in a square aluminum plate flush with the cast roof of the intake.
this will do 2 things increase plenum volume around 50-65% depending on how far out u cut
and it will also shorten the runners 1-3 inches depnding also on how far u cut
i would extend the cut out to were the start of the radus is this will keep the roof flat and make it eiaser to line up when welding.
also dont clean ur manifold with brake clean, or any other solevents other then paint thiner or mineral spirits,the guy who has to weld it back together wont be cursing u as hes welding it up for ya. glass beading is also something u dont want to do to it before welding
Last edited by project89; Nov 21, 2008 at 12:20 AM.
forgot to mention u will have to weld pieces into the floor as well if u do it this way. they would just be 2 small almost triangles were the openings are were the single runners are
You're going to loose air velocity by enlarging the runners like that, but a larger plenum never hurts. If you can gradually blend the runners back into the stock port size you might be able to pick up a little airflow without hurting velocity.
yeah its real crude now but i will blend everything in, hopefully it will help when i get to swap cams and stuff go for higher rpms. we will see, its all a bit of fun and experimentation. if it dosnt work, it dosnt work. :-)
hi not really, ive got my mates compressor and air tools now, but too loud to use this time of night, need to wait for my next day off, im pretty optimistic though the more i look at it, just started opening a runner 'corner' up. not too sure how far to go with that untill i run into problems stopping vacuum leaks..........
just started opening the bends up, incase anyones interested one side (3 runners ) took me about an hour. this has all prob been done before but ill keep this going just for anyone searching for different ideas and looking at different peoples work.
You can do so much with the stock intake the design stinks, looks good but dont flow worth a darn above 4.5K if really want to wake up the engine - trueleo.com and get one that has been proven to work on the flow and dyno.
truleo is a waste imho, somone here had one and the car made less power on the dyno with it.
ive also seen someone first hand back to back a fiero with a stocker and truleo,car slowed down .3-.4 with the truleo
You can do so much with the stock intake the design stinks, looks good but dont flow worth a darn above 4.5K if really want to wake up the engine - trueleo.com and get one that has been proven to work on the flow and dyno.
Velocity being slowed? Maybe, at the port entry, but the port is getting a longer bellmouth, with the way it's proposed. This will make the flow into the runner smoother and increase the size of the effective plenum. Moving lots of air slower than moving a little bit of air at higher velocity will still move more air. To make more power, you need to get more air and fuel into the cylinders, to do this the port/runner needs to be increased in size, so no matter how you look at it low RPM port velocity will likly be effected in a quest fo more power. Even using switchable runners would have trade-offs.
thanks guys, ive actually found someone who works for a formula 1 team that will weld it all back up for me :-) once ive finished grinding.
im not looking for any mad improvements but i can see it making the car alot more drivable and increasing the rev range.
not sure what else im going to do it, im thinking poss 3.4 17lb injectors and adjustable FPR then itl get a average cam timing chain and bearings.
oh and ill do a little work to the heads as well.
Well you're going to trade off torq for a little more hp higher. These manifolds are not unlike tpi manifolds in that they're designed to deliver torq low in the powerband. Can you make it breathe better higher in the powerband? Yes but how much torq are you going to loose? And can the heads support the flow it'll need higher? Granted we're not talking a drastic change in the powerband, but the heads being limited as they are I'm curious to see just what gains are going to be made.
this sounds like a good project idea. what kind of welds are you gonna use for this? I was thinking of doing something to the middle intake to make it shorter or something would be good but I don't know how to do it. the lower intake is also pretty restrictive but that's more of just making the ports bigger.
yeah the middle intake actually looks like it will flow well, i havnt taken the lower off the car yet. im thinking i might sacrifice another oem manifold to weld up top so it will look stockish ? havnt decided yet though.
the lower is not all that bad, in all honesty the top end of our motors is not that bad.in the next day or 2 ill post a pictures and measurements of some grannational heads stock. u guys are gonan take a look at this stuff and just be liek how the hell can they make that much power out of that junk.
hi p89 thanks for the pic, i did have this idea funily enough. my friend has a 173cui blazer and he bought a 305 tpi to go in it, but run out of space time money the usual, the motors actually palleted up and sitting in a warehouse not to far from me. i will buy another oem intake of ebay to work on so i can try different ideas, since i want this car to be my daily at the mo im not looking for massive high numbers, so im guna keep doing what im doing and see whats happens. The only thing about the above is the runners are still restrictive especially on the bend, but its a good start. im guna buy a ported fiero throttle body i think for this one.
i have a brand new intake im working on,it looks liek the twin tb one i posted in the other thread.its not much to look at now but when i get alil further ill post up some pics.
im just waiting on some material to come in so i can build the plenums
i think that setup would work fairly well on an n/a motor..if don\e right the runner openings could be bellmouthed really well for a nice port entry.and the plenum size should be about right for an n/a engine.not to mention u get the v8 tpi throttle body.
no flow numbers or anything it was just a picture i came across along time ago and saved the picture
had another play today at starting to blend the roofline .... FYI i said earlier it took about an hour to open 3 ports up, it takes much much longer to get them blended in nice ! be prepared for achey hands/arms blah blah lol
works busy over xmas so still havnt done much, itl get there though.
zs&tas
You can C cut that center divider between 4 of the 6 ports. It will allow them 4 cylinders to draw even more air with two ports to draw from. 4 getting more air is better then none.
Francis T.
A stock intake will flow fine if the exhaust and air filter are opened up.
It will pull hard to 6000 and beyond as is. If your falling of at 4500 thats not the intake.
ITB's is not new. It would be easier to use a MAP. Have vacuum lines running to it and the IAC. I think someone here is doing it actually, just not on a 3rd gen
Last edited by firstfirebird; Dec 22, 2008 at 08:25 PM.
ITB's is not new. It would be easier to use a MAP. Have vacuum lines running to it and the IAC. I think someone here is doing it actually, just not on a 3rd gen
I know ITBs are somewhat dated. I've been thinking of a way to make it work for my 2.2 cavalier, but I'm kinda lost because I just dont know what would throw off the sensors and what wouldn't. oh well, its a daily driver I don't need much power from that one.
ITB's is not new. It would be easier to use a MAP. Have vacuum lines running to it and the IAC. I think someone here is doing it actually, just not on a 3rd gen
yeah ive got a pic of one somewhere round here, its a six throttle setup on a 3.4 for a fiero, running the ally heads and lower intake, bet that thing will rev ! something like that i wouldnt bother with the iac.
Yeah its a long termer ! Getting the headers on, got a fiero holley tb coming, and actually get round to routing my cai properly. Sorting chassis rust out then on the rd again !
Eventually light supercharged for a bit while I search for spare heads to work on. In the uk so not easy ! People over asking silly money for our engines.
