Custom made intake manifold???

[2.8-350TBI]

Hi guys, I was wondering if it would be feasible to build (machine) my own intake manifold. This will go onto a 2nd gen. aluminum head 2.8 I will be swapping into my nissan 720. The custom manifold is to allow for future upgrades, computer, forced induction maybe, and ease of tuning. Any input (negative as well as positive) is greatly appreciated!

[Superdave]

The lower intake is one of the biggest restrictions in the gen2 engine.. but upgrading to a gen3 top end will give you more power overall.


It takes a lot of porting to get the gen2 heads to flow close to what the gen3's do stock.

[2.8-350TBI]

Thanx for the quick reply superdave I forgot to mention the 3rd gen head swap. ...hehehe! Now, I was thinking if it would be worth my time to make an all new one off intake manifold. I would like to run an aftermarket standalone computer on this engine to be able to run some boost. Is there some sort of calculator to figure out suitable runner lengths and plenum volume???

P.S... This engine will be a (turbo) weekend warrior in a 1985 RWD nissan 720 pickup truck.

[1988GTU]

Do a 3500 if you plan to go through all that effort.

[2.8-350TBI]

Plan to keep it a 2.8... 3500 is very appealing, however I absolutely love the 2.8 and want to be one of the few that kicks ass w/ the founding father.

[MidnightriderZ24]

Rule of thumb for manifolds and runners is longer runners= torque. Shorter runners = hp. I agree with dave on the gen3 stuff. Its going into a 710? That's sweet.. I always wanted to put my built engine into an old school 510

[2.8-350TBI]

I would LOVE to see your 3400 in a 510! Theres a local here w/ a vg30det in a 510 running around...

Back on topic, the engine is going to be a 2.8L genII block w/ either 3400 or 3500 heads.

Like this is going to be RWD, I dont want to use the FWD intake mani's, and I like the idea of making my own custom manifold.

What I want to know is how to claculate the runner length and the plenum voulme im going to use. Tha plan is to make power to 7500 rpm. Low-end loss is acceptable, and some mid-range is too. Its not going to be a daily driver.

Thanx for the input guys!

[1988GTU]

Back on topic, the engine is going to be a 2.8L genII block w/ either 3400 or 3500 heads.


Thanx for the input guys!

Cannot do Lx9 heads.

[bszopi]

Most of the links and pics no longer work, but here is a thread from a few years ago when I was working on a custom plenum.

http://60degreev6.com/forum/f96/technical-theory-plenum-design-t26304

[2.8-350TBI]

That was somewhat helpful, but wouldhave been a knockout if the links still worked! Ive been messing around with calculators, and I think my plenum will be 650-750cc's runner length will be 18.5" (From intake valve) , and a 1.5in2 runner area. This is based on a 4500RPM torque peak.

Suggestions?

[bszopi]

I'll dig around my computer to see if I still have the excel spreadsheet I created for runner length.

[IsaacHayes]

Honestly for all the work, using the gen3 stock stuff is easier, works, and makes power. With a turbo you'll put down IMPRESSIVE numbers with a gen3 top end. The FWD intakes can be rotated for RWD config, that is what forced firebird is doing in his TT trans am...

[bszopi]

I will be re-exploring a custom intake manifold for the Mustang...

[IsaacHayes]

Maybe a custom upper, but with the gen3 lower, you really don't need to do anything different. The gen2 lower sucks so bad you'd either end up doing custom or just going to gen3 top end...

[2.8-350TBI]

Thanx for the advice Isaac, and to 1988GTU also.
To make things easier for myself, i'll use 3400 heads and its LIM and im going to fabricate the UIM myself, I like custom parts, and i'll still be able to tune it to what I need it. Plus I can buy a ported 3400 LIM from WOT-tech (like ill really need it). Does anyone know have the runner info (width, length, area) on the 3400 heads and LIM???