Carb/TBI on 3x00

[Canyonero]

Now this was mentioned a while back, and I forget if you guys were joking or serious. I think the conversation was about using a carb w/ aluminum heads. What was suggested was blocking off the usual throttle body opening and mounting the carb/tbi on top of the plentum. Would that really work? I don't know anything about the internal geometry of the 3x00 intake.

Again, I'm asking for Trooper applications. They have a fair amount of vertical clearance, moreso than lateral. It would really ease the swap if a person were able to keep the TBI system. I'm going to do a write-up for the Isuzu community on what I've done with and learned from my Trooper. And I might like to try this on my friend's Trooper.

Would any combination of 3x00 exhaust manifolds, short of custom headers, fit a RWD 4x4 application like this? Again, I don't know anything about them. My Trooper used the same style of manifolds as the stock f-body.

As always, thanks for the insight and advice.

[powerdoctor]

I have always found that a day or two searching junk yards and looking at parts will net some seriously interesting parts.

I would be weary about hooking a carb to the UIM / throttlebody flange.

http://www.kinsler.com/page--Home-Page--13.html

This link is to one of my favorite local shops here in mich.

They made some SICK intakes for the aluminum heads and may have something for you bud : )

[bszopi]

Sure, it would be possible. Maybe not ideal, but it would be possible. People have blocked off the TB opening and welded plates to the top of the plenum before to mount an M90 SC. The only thing I could see as a possible downside is the large volume of the plenum. Looking at a normal carb intake, the volume is mainly only there for a place for the runners to collect/merge. Since the fuel will now be coming from the carb, there will be a chance that the fuel will come out of the mix in the plenum and start to pool inside the plenum space. I'm not saying that it will happen, I'm just saying that there is a possibility.

As far as the exhaust manifolds go, I'd say there is a good chance, but you probably wouldn't know for sure until you tried. You may run into clearance issues around some things (steering possibly?), or it might clear everything just fine. Only thing I see as a potential problem or workaround would be how everything exits. Since the spacing of the exhaust ports is offset, you can't just take 2 fronts (or 2 rears) and make them work the same on both sides. So you'd have to look at how you do the routing of the overall exhaust system, not just the manifolds.

[Canyonero]

Well, something else just hit me. Again, I've seen some discussion here on the subject and I'm not sure if there is a (reasonable) way around it. To keep the wiring simple by retaining the TBI system, this application would need a distributor... which won't clear the 3x00 intake. IS there some way around that?

Maybe this is all just wishful thinking and it should be an all-or-nothing swap. But even w/ multiport and DIS, a vertical throttle body might be more convenient for a Trooper. I really want to get some parts and mock this up.

[geoffinbc]

Yea a plenum below the carb is a bad idea. Unless you have serious airflow you are going to have a lazy intake signal at the base of the carb and it will have horrible drivability. And yes at lower RPM you will get fuel puddling. On a TBI the drivability might not be as bad as a carb but the same problem with fuel puddling will occur.

You might see a drag car with a high rise intake and a plenum but never a street car. There is a reason