Ported 3400 UIM vs. Ported 3500 UIM w/ 3400 LIM

[skinrock]

I was discussing some options with Ben regarding going with a 3500 upper on my 3400 Impala. I have stock heads, and that will remain the same for awhile, I don't know if I'll ever change them. Stock cam, too, of course.

I know I want to go with a 65 mm TB, and a ported 3400 lower. The question is, is the 3500 upper worth the extra trouble? I was reading another post about this where he was discussing something similar with you guys, and I noticed it was mentioned that you want to try to avoid differences in sizes, however it also said a 3500 upper would go well with a 3400 lower if they were both ported.

I don't have any real numbers to work with, outside of the charts for a full top end swap, but since I'm not doing heads, I have no idea what to expect with the ported intake manifolds and TB, and whether the 3500 upper is truly beneficial.

I'm just hoping someone has experience with this, and can tell me whether a 3500 upper is really worth it.

[IsaacHayes]

If you port both to the same gasket, you will be fine. The 3500 plenum has more space, no runners, neck that opens in the center, stock 65mm opening, etc etc. It out flows the 3400 once you port it to the gaskets. You can put one on with a little grinding on the neck to clear the FPR and bend the metal line a bit and bolt the fuel rail to the LIM with it moved as far as it can away from where the neck will be. I did that on mine and it all fit fine.

I can't tell you personally cause I upgraded from small port lower intake at the same time. Others have reported power up high as well as power down low.

[FallenZ24]

It's deffinately worth the extra work if you have the opportunity. The 3500 uim flows much more than the 3400 and has extra Plenum volume. Also with a bigger Tb you will gain some throttle response and top-end power.

I think the ported lower and 3500 upper is good for atleast 15hp across the power band. You will deffinatlyfeel the power increase!

I had one on my 3100 and it was a night & day differance.

-Joseph

[skinrock]

Thanks for the input. As long as Ben can grind it for me, everything would be okay...I'd just rather not do that myself. I was hoping the manifolds and tb would be good for 20 hp or so. My ultimate goal is to do 0-60 in under 7 seconds. Doesn't seem like much, but it would be almost 3 seconds off stock.

[SappySE107]

Ive been pretty busy and have only figured out a couple things with the 3500 plenum swap regarding fitment. The DIS coil module doesn't bolt up to the plenum and head studs, but that shouldn't be a problem. Not sure if anyone has made an adapter bracket for this. Same with the cannister purge bracket.

Im going with a stainless steel hex plug for the 3500 MAP location, for those that want to use the original MAP sensor. Finding a good vacuum port with the 90 degree bend and still fitting is not easy. Vacuum line routing is the last obstacle that I am aware of. The neck grinding and fuel rail bias work well. I think those L67 injector brackets with the stock injectors gave it more room but I need to try it again to be sure because my wiring was under the rail initially. I thought it cleared the FPR bracket before but it was skewed real bad for interference at the time.

I have some pics but will take some more and resize to show where I am at with this 3500 upper intake swap. I really want to have the complete kit, or at least visual instructions for everything I can't make perfect right now.

[skinrock]

I'm glad you're willing to work all the issues out. Most places (and I don't mean parts like these necessarily), would just try and sell it to you and say it fits, and make you deal with an imperfect replacement.

[FallenZ24]

Im pretty sure you can use the 3500 map. You just have to get the pigtail and splice it into the existing wiring.

The FPR brakets offered in the store are an alternative to grinding the uim to clear. http://60degreev6.com/store/index.ph...d&productId=61

[Superdave]

Im pretty sure you can use the 3500 map. You just have to get the pigtail and splice it into the existing wiring.

The FPR brakets offered in the store are an alternative to grinding the uim to clear. http://60degreev6.com/store/index.ph...d&productId=61

you can also make a small modification to the FPR and it clears fine.

and yes, the 3500 MAP works great.

[Rhedalert]

I'll 3rd that 3500 MAP sensor. You can also grab it off '98+ 2.2L J-bodies, and newer 3800's also have them. I grabbed a few at the junkyard with the pigtails for all of free. I fabbed a hold down bracket using a small metal clip, bent it to fit. Been great so far for over a year and 30+k miles.

Depending on which 3500 manifold you receive, you may (like in my case) have to drill and tap for the HVAC vacuum fitting (near the alternator) and I also had to bend my power steering pressure line to clear the manifold.

[SappySE107]

I know the 3500 MAP works, but 2 wires are switched right? In order for me to offer that option, I would need to get the sensor and the pigtails and make the adapters. Also, can you take a picture of your vacuum lines? I can drill and tap for a fitting by the PS pump if that makes things easier. 1/8" barbed fittings for the vacuum lines is what I believe they all need.

[IsaacHayes]

As far as the DIS, just bolt up the bracket to the heads like normal. The top bolts don't line up but the DIS plate will rest on the back side of the plenum nice and tight just fine.

The 3500 style MAP is nice to use, keeps it clean. The MAP and pigtail can be found on 98+ J bodies, or on LS1 engines.

Vacuum, just tap the thing by the EGR port with 1/4" NPT and put a barbed fitting on there. Then run a line to the FPR, and to the vacuum ball. (use a T). There sometimes is another vacuum port by the brake booster on the plenum. It is installed on some, and not on others. The rest of my stock vacuum and emission lines hooked up fine.

Ben: The 3500 map wires are the same. They just changed colors. As long as you match it whatever remaining colors you are golden. I think the ABC spots are the same too on the connector. I almost built an adapter but saved my money and just soldered it on. Good idea to tap the port by the brake booster if the plenum does not have it tapped. Mine came tapped with a plug over it. I'm using that one for my cruise, like the factory was hooked up. The other vacuum port I'm runing to a T, to the FPR, and then to the vacuum ball/trans modulate metal line. (that line I re-bent to clear the plenum and look more stock.)

I had pics attached in some thread with all the lines I did I thought somewhere.. My stuff looks like stock unless you know better.

[skinrock]

See my problem is, I have no idea what all these vacuum ports and tapping refers to. I'm a computer geek, I can handle unscrewing things, and plugging in things that have the same shape...but outside of that, lol, not good.

[SappySE107]

Can you get me a picture of your stock upper intake/vacuum setup? The older cars used that vacuum line near the alternator, but all the newer plenums I get have that port plugged off with a vacuum cap. The 98 grand am CCP bracket works great but I don't have a source for those to be able to sell them easily.

[skinrock]

I'll try and ask my coworker to bring his nice camera in. If not, I can try to take some with my iPhone, they should turn out decent, 1600x1200 resolution.

[skinrock]

Ben, my coworker took some really good pictures at lunch time, but they are huge, 25 megs worth of pictures. I'm gonna upload it to my server and give you a download link in a little bit.