Written by: C. Bulloch from his igloo in a frigid Winnipeg
Edited, and added to by: T. Knight

Table Of Contents

1. What does Gen II/Gen III mean?
2. What are the differences between the Gen I/II/III blocks?
3. What is a "hybrid" ?
4. What does "3X00" mean?
5. Why Swap to Gen III engine parts?
6. Where is "X" part located on my new 3X00 engine?
7. What cars came with a Gen III engine from the factory?
8. I want to install a 3100/3400 or a Hybrid What do I need to do?
9. Can I just swap the Gen III heads and reuse my Gen II manifolds?
10. I want to do a swap, but do I really need all that extra stuff you recommend?
11. Why is the power steering pump different?
12. I want to install a Gen III engine in my car. Will it work with my current transmission?
13. Do my old 3.1L/2.8L injectors work with the new 3X00 Fuel Rail?
14. Do I need to use "Custom Pushrods" when using the newer style roller rockers. Why?
15. Should I run my EGR (or other emissions equipment), even if they don't e-test in my area?

When referring to a family of engines produce by GM, similar blocks of different model years are annotated by their"generation". Each significantly improved design of the same engine calls for a new generation. Thus the terms Gen I, Gen II, & Gen III were born.

2) What are the differences between the Gen I/II/III blocks?

3) What is a hybrid?

A hybrid engine, as we refer to it, is taking a 3.1L/2.8L Gen II block and retrofitting on it newer, better flowing Gen III Heads, intake, and exhaust manifolds. Basically its much the same as with small block chevy guys installing late model Vortec heads and performance manifolds onto their small block.

4) What does 3X00 mean?

The 3100 and 3400 engines share so much in common (yet still have differences) that to make things simple when referring to using parts from a 3100 or 3400 we simply simplify the process of typing both out calling it "3X00". The X is a 1 or 4 numerical value for each engine. It's a shorthand way of talking about them. It does *not* mean a hybrid engine as some have thought.

5) Why swap to Gen III engine parts?

They make more power. The Gen3 cylinder heads have flow ratings from GM Performance Parts of:

16.7% more flow on the Intake port of the cylinder head due to revised port design. 31.7% more flow on the Exhaust port of the cylinder head due to better port design and a new revised "D" shaped port

The Gen III Lower and Upper Intake manifolds are also the key to increased performance. There are two sets of different style Lower intake manifolds and corresponding upper Plenums. Both of which flow more air and increase performance compared to the very small diameter and radius runner Gen2 manifolds.

Combine this with Gen III exhaust manifolds, with more potential to flow and you have a good combination to gain a lot of power from your Gen II engine block.

6) Where is "X" part located on my new 3X00 engine?

We created a whole page just to answer this question. If you don't find the part your looking for, ask about it in the forum.

3X00 Part locations

7) What cars came with a Gen III engine from the factory

8) I want to install a complete 3100 or 3400 in my car, Or a hybrid, what do I need to do?

For the 3X00 installation guide, go here. For a Hybrid build guide, go here.

9) I know the heads flow better but I don't want to change anything else. Can I just swap the Gen III heads and reuse my Gen II manifolds?

No, the Gen III heads have very different intake port locations and angles of port entry, they don't line up at all. You cannot "port match" either to make them fit. The exhaust port shape on the Gen II engine is a "Round" exhaust port, the Gen III's use a "D" shaped port where the flat edges of the "D" would hit against the opening of stock Gen II exhaust manifolds. That would create a barrier and cause poor exhaust flow or even exhaust flow reversion (forced to flow back into the head)

10) I want to swap the heads and intakes/or a complete 3400 but I don't want to bother swapping all that other stuff that you recommend.

You have to swap the rest of the components listed in our pages. We get a lot of guys saying they want to reuse their old Power Steering pump. It won't fit, period. All the hoses, pipes, and small "modifications" we have listed are to make the new set of manifolds and heads work in a vehicle that was never designed for these newer components. The newer parts have different styles of pipes, hoses, fittings, and wiring routing or other changes that necessitate the need to use these parts.

11) Why is the power steering pump different?

On the Gen III engines, the lower intake manifold runner #2 sits closer towards the "front" (looking at it transversely) of the engine timing chain cover. The space left between this cover is less than that of the runner to cover size on a Gen II engine. The Power Steering pump has been reduced in width on Both the Pump and the Reservoir to fit. This is why it's very important to get a pump that its complete! You need the pump, pulley, and reservoir all together! The reason our pages describe needing the front engine timing chain cover is because of this:
The cover has the flange for the power steering pump to bolt onto. GM made the bolt holes in a slightly different location and reduced the size of the flange that the P/S pump bolts onto. This flange is now .5 inches thick compared to the thicker flange on the Gen II's at .750 inches thick. The narrow space is needed because pulley has been brought in closer to the pump body which allows for a more compact fitment.

12) I want to install a 3400 or 3100 into my car does this engine bolt up to my old 5spd manual or 3spd automatic transmission?

Yes to both. All GM 60 degree V6 engines, and some 4 cylinders use the same bell housing bolt pattern. These bell housing sizes are sometimes referred to as FWD patterns. The engine that share the same pattern are 2.0L ohv, 2.2L ohv, 2.5L, 2.8L, 3.1L, 3.4L, 3300, 3800. The transmissions that don't work with the Gen III engine are ones that use the different Starter locations: 2.0L OHC (Pontiac engine) 2.3L Quad 4, and 2.4L Twin Cam,

13) Do my old 3.1L/2.8L injectors work with the new 3X00 Fuel Rail? And can I use those?

Yes. The older injectors fit right in with no problems. We recommend using the older Injectors with these setups as with the 2000 and newer injectors you cannot use their new style "Multec2" injectors without a custom tuned chip to allow it to run properly.

14) You list needing to use "Custom Pushrods" when using the newer style roller rockers. Why?

The 96 and newer 3X00 engines all use a Pedestal mounted Roller Fulcrum Rocker arm with a 1.6:1 ratio. These rocker arms are non adjustable and, combined with the Gen III roller lifters, use shorter pushrods than older Gen II non roller lifter engines. When using these rocker arms with the new heads and the old flat tappet cams/lifters the length of the gen III pushrods are too short. The old gen II pushrods are a hair too long to provide proper lifter preload, which is crucial for hydraulic lifters. Without the right preload on the hydraulic lifter plunger you can cause problems. You 'could' possibly get away with using the stock pushrods but we strongly recommend against this. Take the time to measure a set out, or have a shop measure them for you. Places to buy new custom length pushrods are: www.cranecams.com www.pushrods.net

15) Should I run my EGR (or other emissions equipment), even if they don't e-test in my area?

Absolutely. Even if they don't test in your area, your EGR, and other emission equipment will your fuel economy, engine temp, and the environment. Contrary to popular belief your stock catalytic converter doesn't restrict exhaust flow unless it's plugged, which if that's the case, a cheap new hi-flow converter can be gotten off e-bay. The only thing you get from removing your cat is a tinny sounding, rotten egg smelling, exhaust. It should also be noted that if they do test in your area, or you move into an area that tests, it is *impossible* to pass without a cat. Even if you pass visual inspection, your NOx, and HC levels will be through the roof.

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