building an intake manifold, input needed

[torq455]

yeah baby!!! 272!! that's a cool intake but us j-bods can't use them. hood clearance problems.

[FallenZ24]

I think the Trueleo Intake is about the best way to go. It gets rid of the middle and upper intakes and all the air-flow problems. Many of the Fiero guys use them on the 2.8/3.4Ls and love them. The only downside is the $600 pricetag.

Maybe you can get some design "cues" from them and make your own. A bigger cam would deffinately help your situation also, maybe the H-272.

-Joseph

[sharkey]

the lower intake on the mpfi ironhead motors is pretty much the same between fiero, j body and f body. there are some differences in the middle and upper, the j-body one actualy has one bank with 12" runners (from the valve) and one with 19" runners.

with all gen 1 mpfi intakes though, the problem is the tight bend at the top and the port size between the middle and upper. the port size of the head is 2.34 sq/in, were between the middle and upper is 1.42 sq/in, and you have a 135* bend there. this is a huge flow restriction and limits the rpm, however helps the motor make big torque. if i can increase the port size in the middle intake to the same size as the head, it should be able to drasticly increase the rpm range and top end power, it will however sacrifice some bottom end (its a 2.8l, its meant to rev).

the only intake thats "better" is the 3.4l. its a once peice middle/upper and avoids the big 135* (or bigger) bend , but from what i have heard is that it only flows about 10cfm more than the others.

i could use a tbi or carb intake and mod it for mpfi. the problem is, all the carb intakes suck and have very short ports and relitivly small plenum.

as for that camaro intake, it looks cool but realy does nothing but add a big throttle body. it still has the restrictive ports between the 2 intakes and big bend, and small middle runners.

[Superdave]

http://www.trueleo.com/images/fiero_frt_qtr_vac_on_neck2.jpg

http://www.trueleo.com/

nice plenums...


there was a guy a while back that combined a 350TPI plenum and a stock Fbody plenum.. it looked pretty neat too. If i can find the link i'll post it... *edit* found it...

http://www.angelfire.com/crazy3/jimsfirebird/34install.htm

So Sharkey, educate me (and maybe us) on the iron head lower intakes. what's the difference between the early Jbody ones, the fiero ones and the Fbody ones.. anything? any one of them flow better?

Could you pick up a TBI or carb one, get a TB neck that'll bolt to it, make the propper holes for the injectors with a custom fuel rail..


maybe something like this?








good discussion here: http://www.thirdgen.org/techboard/al...t-efi-intakes/

[bszopi]

Well, here is some more info I dug up...

http://www.60degreev6.com/showthread...=plenum+theory

124 posts (some off topic) of some plenum theory discussions we had here about 2-3 years ago.

[treeZ24]

wow guys, way to give good a good informative discussion on building an intake plenum.

http://www.sdsefi.com/techinta.htm

http://forums.hybridz.org/showthread.php?t=100261&highlight=intake+design

i realize thats not exactly what you wanted to see, but its the only link i have on the laptop. the rx7 manifold was for race only, for street use i'd go with longer runners.

i'll put up a couple more later.

http://www.dune-buggy.com/turbo/intake.htm

http://www.physicsforums.com/showthread.php?t=80364

[sharkey]

thanx for the link, some good info to consider.

[bszopi]

I used to have a whole bunch of link from back when I was working on a plenum design for my 3x00. Hopefully someone will be able to chime in, but IIRC, you want to design the plenum volume to be equal to that of the engine volume. And I think that includes the runner volumes as well.

As always, I will post a link to Ben and I's favorite site when it comes to engine theory: http://www.theoldone.com/archive/int...old-design.htm It doesn't really go into too much depth, but gives some things to take into account when designing an intake.

[sharkey]

comp 260h2 and comp magnum 1.6:1 roller tip rockers. and ive tried shifting earlier, as low as 5000rpm. it actualy slowed me down as i drop out of the powerband (starts around 3000rpm) on gearchange.

[1988GTU]

What type of comp cam do you have?

[sharkey]

yea no kinding no love for them. you guys can get off the top end swap thing, im not going to do it, and lets get back on topic of building an intake manifold. you guys seem to be forgetting that the 60* putting down the most power is an ironhead.

[torq455]

shift earlier.

[IsaacHayes]

3400 heads and LIM with a 3500 top hat would accomplish basically what you want to do and possibly make more power with the better heads. Sell the motor and build a 3400/3500 combo to swap in with the blower... Then you'll have PLENTY of power. I know, I know, no love for the iron heads...

[sharkey]

i have thought about tbi, even a carb, howerver neither of those will work well with the ultimate goal of turbocharging it. 3400 heads would be great, the biggest issue is the pistons. i would be needing to pull the motor right apart, and have it rebalanced, and basicly be throwing a good set of $700 forged pistons on the shelf. i may aswell just start over with a 3400, something im not willing to do.

i know the heads flow, the intake doesnt. it just doesnt pull as hard as it can up high, itll go 2.0 60' times, but still only runs 15.5 @ 85mph.

[torq455]

isn't that turbo z24's engine?

lets not forget when you split up the UIM and the LIM, the runners are no longer equal length. you can't keep the LIM and say...put a 3500 kind of UIM on. the engine will vibrate a lot! you could extrude hone it and gain smoother walls and more volume.