3500 plenum swap check list.

[farmerz24]

can someone tell me if the throttle cable bracket shown in that above pic is from a 4.3 TB or from the 3100 style? it looks similar to the 3100 but lower down so i think its from the 4.3 . let me know

Chris

[IsaacHayes]

It's from a 4.3l. That's midnightriderz24's picture I photoshoped. He had a 4.3l TB on there. Notice how he doesn't have a powersteering pump on there either!

[IsaacHayes]

Got a few more questions:

1) On using the 3400 TB, IAC passage and the adapter, I can't see how it works on the stock manifold in the first place. Seems the gasket covers up the outlet and would have the same issues as the adapter... Are the 3100 and 3400 TB IAC openeings different? Should I grind a hole on the inside after the butterfly for the iac passage, or make the iac opening no longer seperated from the tb outlet..? What am I missing here?

2) Since the adapter has a larger opening than the TB, should I taper the TB where it mates to the adpater so it doesnt have a ledge there? I know it's going into a larger port, but would that lip cause turbulance and hurt performance?

3) If reusing the stock MAP, how did you mount it? Make your own bracket?

[SappySE107]

You won't be able to use the O ring on the TB side of the adapter because it won't seal around the IAC. The IAC already has a cut out behind the TB to the opening so that shouldn't be an issue at all.

As far as opening up the back, you could but I think a simple rounded edge would accomplish about the same thing.

Make a bracket or let it hang, either way should be just fine as long as you keep it close to the plenum.

[IsaacHayes]

For the life of me, I can not figure out how the IAC passage routes air after it goes through the IAC valve. I can see a bored hole for where it gets air before the butterfly, but then after it needs to go into the plenum, Im at a loss. There is the square IAC hole, but that is seperated from the main TB round passage. I can't see how air gets out of that square hole stock.

I do need to grind somethign on the TB for the adapter right? But I don't see how the IAC works anyways as far as I can tell the stock plenum seals like the adapter will with a gasket..

TIA x2!

[SappySE107]

Ah, i was looking at the 3100 TBs. If its not connected to the main bore on the TB, then yes, you should probably notch a hole to it. Won't hurt anything. Hell, after that if you can weld or fit something in the stock IAC hole location, then you can use the I ring to seal it up instead of a gasket.

[IsaacHayes]

Ok, now were both on the right track. I don't have my 3100 off to look at, so I was just looking at the 3400. I will notch it or plug and put a hole inside. If you read up a few posts I said I thought of that and keeping the o-ring on the adapter. I wonder if JB weld would work good enough?

[SappySE107]

JB weld would work fine for that. Its not a stress item or anything so as long as its clean and you get the back flush, no worries. Just make sure you have a large enough slot cut in there to let the full amount of air past the IAC get to the main bore area. The TBs I have here are notched the full width of that stock hole location you have, maybe 1/8" deep in the back side of the TB. Hope that helps.

[IsaacHayes]

Yes that helps. I guess the TB you sent me has a different setup on the intake manifold(notched opening on the manifold itself)??? Interesting, wonder what car it came off of. It really confused me how the air got out stock!! lol
I think I can do a 1/8" thick slot on the inside tunnel with a dremel.

** I just found out the changes, by looking at pictures of the TB gaskets on oriellyauto.com **.

The old school 3100 52mm TB gaskets cover the square IAC opening, so the IAC opening is notched letting air into the main bore hole.

The 3400/(2000+ 3100) 56mm TB does not have the notch but instead the gasket doesn't cover the whole IAC section, just outlines it. This way the thickness of the gasket allows the air to enter the main bore. I guess they went this way to save one step of machining.

So I guess I don't need that thick of a opening, if the 56mm IAC passage relies on only the thickness of the gasket to let the air by.

Kind of neat to find this out, as if you do a swap to a 56mm TB on any plenum, you will need gaskets for a 56mm TB not 52mm gasket that you bored out.. (unless you cut a space out of it for the IAC passage too).

EDIT: This means you should be able to run a 3400 56m TB gasket with the adapter and not grind on the TB at all.... Not sure why that's on the notes section in the store (grinding). Just need to make sure you use the updated gasket AFAIK....

[IsaacHayes]

One thing occured to me, what about the alternator? I know you loose a bracket with the new style 3400 UIM, but what about the 3500? I see 2 braces on the UIM on my 3100 right now. I'm assuming there won't be any issue, but there just won't be braces used..?

Oh and will a gen2 valve cover bolt up to a gen3 head/LIM? If it does will it clear the metal pipe that goes to the water pump housing/bleeder valve? And will it clear the valve train? Someone suggested using one as they look better (I agree they do).

TIA.

[SappySE107]

Im not aware of it making any difference to the alt. The plenum doesn't support the alternator.

Why would you want to use a gen 2 cover? Gen 3 fits gen 2 so it will work the other way around. However you lose the spot to put oil in, unless you use the vent or pull the cover. Thats pretty lame IMO.

[IsaacHayes]

Well, for a pure asthetics point of view. It looks better than the gen3, more like a traditional v8 cover or something. It's more square. I'm thinking it painted with the top bare polished would look nice. Kind of like the beretta pace car 3.4L motor had done. Taking out the PCV to add oil is no big deal for me. My main concern is if the black coolant pipe that goes to the water pump housing will clear it. Not sure if the gen2 sticks out further than the gen3 or not.

[SappySE107]

Id be more concerned about the rockers clearing as I had a problem with my comp roller tipped 1.52:1 hitting the metal plate in the gen 2 cover. I had to remove it. The 1.6 roller rockers are bigger and higher ratio so you may have issues.

[IsaacHayes]

Ah ok thanks for the heads up. I won't bother then. Maybe at a later time I can play with the looks of the valve cover, but for now I need to just get the 3500 intake on and running. Performance first

[IsaacHayes]

UPDATE: The 3500 plenum is in!! woo hooo! I scored big time! Total cost including shipping: $90.00. What did it come with? Map sensor, IAC valve, EGR, Electronic TB, and the extra vacuum port by the brake booster tube with the fitting I need for my cruise installed!!!!

Yes, that's right, total cost including shipping was $90 and I got parts I can sell off, and the new style MAP sensor so I don't have to worry about mounting mine somewhere with a hose running to the manifold. I'll just put a new wiring connector on my harness. The EGR is the same as the (2001?)+ 3400 motors. It's got a manuf. date of 09/2001 so I know I'll be able to sell that at least.

It was about to fall out of the box and there was tons of bubble wrap on top of the manifold, but nothing below it.. The IAC air tube inlet cracked off, and there is a hairline crack on the TB wiring harness connector, but that's no big deal. BTW I compared the 56mm throttle plate to the 65mm electronic one, and WOW what a huge difference in size. If only the 65mm TB's for our motors weren't so pricey. I can't afford that much on just the TB. And there is no other easy 65mm TB solution that I know of. Oh well, I should still see a big boost going from small port 94 manfiolds to this setup!

Questions for the Guru's:
1) Can the IAC valve be used if the harness is adapted with the right connector?

2) What can I use for a female connector to connect to my stock MAP harness so I don't have to cut my wires? Is there any such thing?
I could just splice the wires and solder in the new style connector with the old one, so swaping manifolds or sensors wouldn't require future soldering/tampering- it would have both style ends on the harness..

3) Where would be a good place to get the connector for the new MAP besides a junkyard? Any cheap place to get GM style connectors? No junkyards close to me have the newer cavilers.

Thanks, and do you think I got a good deal?