3400 top end swap questions

[gboogie99]

I just scored a 3400 upper and lower manifold, heads, injectors, fuel rail, and metal valve covers from a chevy venture. Need to know:

1. how to hook up linkage on throttle body. It is on the opposite side from my 3100

2. what size injectors the 3400 from a venture uses

3. where to find the revised manifold gaskets or metal gaskets

4. average gains I can expect

5. is the venture the only 3x00 with metal valve covers, my 3100 sfi doesn't have metal ones

6. should i swap out heads as well or keep what i have and sell the newer ones

7. will i have to get a chip for the swap or will ecm adjust automatically


i know its a lot, but i also know yall have the answers

[gboogie99]

oh yeah, also got upper manifold from a 01 lumina 3100. But I don't know about one thing. Why does the 3400 manifold i got from the venture have the older style egr valve like on my 95 3100, while the 01 lumina manifold had the new sideways type egr valve? just wondering...

[bszopi]

As far as the EGR, the 3400 has had all 3 types of mounting throughout the years.

For the throttle body, you will probably have to use your existing one since it has the integrated MAF, or you'll need to pick up a new MAF and then hope it works with your ECM.

Swap the heads. The 3400s have larger valves.

There is a TSB on the composite valve covers. They have a tendency to crack and therefore leak, so GM went back to metal after a couple years.

As far as the ECM goes, it will adjust somewhat, but will be far from optimal. And with your ECM, good luck finding someone to tune it since its such a unique setup (PROM'd OBD1.5).

I really wouldn't expect too much as far as gains go, unless you get it tuned properly. I'd say maybe 10hp. With tuning, you could see probably at least double that.

[Guest]

Ummm, Brad, what vehicle had the digital EGR and 3400? Last I saw all 3400s were made AFTER '96, (well after '95, but starting in '96 to get technical), by which point the digital EGR was dropped in favour of the Linear and has had two mounting designs for it.

In for pics of this 3100 that has the linkage on the opposite side than the 3400.

'94 and some '95s were the only genIII 660s to use the composite rocker covers, all other genIII 660s have used the aluminium covers.

I'd swap to the 3400 heads as well, due to the larger intake valves. Though this is debatable because the smaller valves of the 3100 will have less shrouding on the outside of the cylinder than the 3400 valves will. But the gain in opening circumfrence will most likely negate this shrouding.

[bszopi]

I was thinking that the first year 3400s had the digital, but I could be wrong. He might be seeing that it mounts horizontally and not vertically, but isn't noticing the different mounting pattern.

This is a bad "pencil" drawing of his TB, but I think you'll be able to see the linkage:

[gboogie99]

about the egr valve, i'll post some pictures up tonight. I thought all 3400 were digital too until I got that bad boy this weekend

venture was made from 1997-2005 and then replaced by the uplander
all had 3400's

[gboogie99]

here are the pics. you can see the different egr mounts in the 1st few pics

[gboogie99]

anybody?

[Guest]

Ahh, I never noticed the linkage location on that TB before for some reason.

Even the electrical layout in that car is going to be quite different, the injector harness connector is at the front of the engine.

If you want to use the 3400 TB, you're going to need to get an L-body cable and L-body TB linkage (if it's different than the TB you have), www.domesticcrew.com, will help you with some ideas.

The EGR situation has been covered numerous times, both here and at DC, there is an article here and is stickied in the FAQ forum at DC, at least for the 2000+ UIM. the '96 to '99 requires an adaptor of some sort, or you can do like I did with my small port hybrid swap and cut off the existing EGR mount and made a new one for the vacuum EGR.

[gboogie99]

but thats what i was wondering about. The egr mount on the original manifold is the same as the 3400. I always thought it was different.

[bszopi]

No, its different. Take the EGR off of your current 3100 and you will see the difference.

[gboogie99]

so i'll still need an adapter ? dang where can i get one for this car?

anybody got the specs on the injectors or know about the revised gaskets for the manifolds?

[AaronGTR]

The EGR mounting on early 3400's was horizontal and it changed to a vertical mounting in 2000.

The early 3400 injectors where 19lb/hr bosch injectors, and those also switched in 2000 to 22lb/hr delphi injectors. If you have the horizontal mount EGR design manifold it's from a '99 and earlier engine, so you'll have the 19lb injectors.

For the gaskets, any place selling them will have the updated versions now. Any dealership, gmpartsdirect.com, etc. There are new cylinder headgaskets, and the lower intake manifold gaskets have some metal disks in them now to keep from over compressing the gaskets. The rest of the gaskets are the same.

All the later 3400's (at least from '99 on) also came with metal valve covers in all cars.

[gboogie99]

So wll the stock throttle body bolt right up? Is there no way to mod the 3400 TB to work with my linkage?

[Superdave]

That TB looks ALOT like a 3800 TB...