Help with 3.4L

[xfactor]

OK so I have an 88 S-10 4X4 that had a Cal emissions 2.8L that spit a crank.
Picked up a 94 camero 3.4L to build. Here is what has been done to motor.
Bored .030 over, Balanced, Hi volume oil pump
This is the ARI cam I used ----
Duration @ .050 - 204in 214ex Duration - 270in 280ex Lift.420in .443ex Lobe Center- 107in 117ex
1.6-1 roller rockers, Molly push rods, Spring, retainer, and keepers from Comp cams on the 94 heads.
Long tube headers with 2.5in magnaflow high flow converter into 2.5in Magnaflow muffler.
Stock 2.8L intake manifold with throttle holes bored out to 1 11/16 and match ported to gasket, 5.7L throttle body with CFM tech adjustable pressure regulator and injector pod spacer. 1 inch "Super Sucker" TB spacer and GM 5325203 45lb injectors @14psi.
I used to build Ford 2.8L motors and they would rev past 6K easy

[34blazer]

Umm...What was the question?

[xfactor]

Sorry - Won't pull past 4500rpm - just flattens out

[caffeine]

Sounds like a 3.4 to me... What valve springs are you using? Stock ones are junk if you wanna rev to 6k

[caffeine]

Also I have no idea how well the TBI intake flows but typically if the heads aren't ported it won't matter. The heads originally came on a 2.8, where they're often considered inadequate, and they were also used unchanged on the 3.4. The result is an engine that doesn't like to rev.

[geoffinbc]

Looks like COMP springs which is good. But the cam is not ideal either for what your trying to do. I have the COMP 252 cam (which has more duration at .050" and more lift) and I have good power to just past 5000RPM. I can take it to 6000 no problem with a bit of a drop in power. Before you rip the cam out you could try to degree it. But ideally you should get a COMP 260 cam. The other thing you should do is put a wideband gauge on that thing and check the A/F ratio at high RPM because I bet its going a bit lean. My trooper drops to about 14.5:1 at 5000RPM which is not ideal for making power. 12.5:1 is usually considered ideal for best power production. I have a spare ECM which I will be getting re flashed with a bit of a different fuel curve to cure the issue.

[34blazer]

get an ALDL cable, and a wideband and start looking at the data

[xfactor]

I'm thinking it's going lean and needs the chip done before i rip into the motor. I bought An ALDL to usb cable and WinALDL to log some data while towing my boat. Also bought blank chips and a burner with the Cats tuning program - I used to crack and hack Dnet cards and boxes - cant be much harder. already tried a JET chip but it was burned for a stock 2.8L so not good enough either. The truck has 4.11s so it shouldn't struggle like it does.

[xfactor]

geoffinbc
I thought about the cam too so added the 1.6 rockers with no improvement.

[geoffinbc]

Win ALDL is not going to help if you are trying to see your Air/Fuel ratio at wide open throttle. Once you get past about 70% throttle you go into fuel enrichment mode and the ECM ignores all O2 data and your long and short term trims will just show 128. Even if it did still read the narrow band sensor would not give you correct readings because it cannot read fuel mixtures as rich as 12.5:1. So my advice, before you burn a ton of chips and change a bunch of hard parts, is to put in a wideband gauge and take a look at things. You will know right away if it is going lean at WOT.

[xfactor]

Just ordered an AFR gauge with wide band O2 sensor from Summit. Also wondering if porting the exhaust side of the iron heads will make much difference.

[Blacktree]

IMO, the first thing to do would be to ditch that TBI intake. To give you a frame of reference, the TBI 2.8 V6 was rated for around 125 HP, whereas the MPFI version was rated for 140 HP. Part of that power increase was the intake, and part was from the bigger valves in the heads. The 3.4 V6 heads will have the bigger valves. But the TBI intake is probably choking it.

The '93-95 F-Body has a nice MPFI intake for the 3.4 V6.

[Guest]

IMO, the first thing to do would be to ditch that TBI intake. To give you a frame of reference, the TBI 2.8 V6 was rated for around 125 HP, whereas the MPFI version was rated for 140 HP. Part of that power increase was the intake, and part was from the bigger valves in the heads. The 3.4 V6 heads will have the bigger valves. But the TBI intake is probably choking it.

The '93-95 F-Body has a nice MPFI intake for the 3.4 V6.

The TBI 2.8L and MPFI 3.4, both being gen1 have the exact same heads, as far as valve sizing and port shape/flow is concerned.

Part of the different rating is not just the different intake manifolds, but the different exhaust systems, different tuning, etc, that SAE ratings require.

[geoffinbc]

Agreed. The TBI intake is not the greatest but it will not choke down a 3.4L if a 4.3L TBI unit is sitting on top. It does have short runners but the SFI intake has huge injector bungs that protrude a lot into the intake ports so it is most likely a wash as to which one flows best. However, the SFI unit surely has better fuel distribution. With that being said I have never had an issue with a TBI intake getting the engine into the 6000RPM range with even a half descent cam. I have even used the stock 3.4L cam with 1.6:1 rockers and Crane Cams Springs up to about 5200 RPM before shifting. It never fell flat on its face like it hit a wall it just kind of tapered off when you got beyond 5000RPM. A COMP 260 really improves performance up top and makes the upper range very usable. I chose the COMP 252 CAM on my 3.2L because I wanted low end torque just off idle and it delivers it very well. I can floor the gas when the engine is bogged right down in the mud or snow and it will pull right out of it no problem.

Heads are identical on 86+ models with iron heads. I don't know where the belief comes from that SFI models were somehow different that TBI models.

[Guest]

I don't know where the belief comes from that SFI models were somehow different that TBI models.

Internet myths based on assumptions that desperately need to be squashed.