2.8l with 3400 heads and MPFI swap

[jaons_Wlp]

EDIT: I am now modifying a spare 3400 upper intake to fit a 4.3l TBI on top of it to keep my stock harness and computer. A taller distibutor will clear the #5 runner, I just have to find one that will work.

Plan is to throw on 3400 heads and intakes that i have laying around, T-5 transmission and a astro van AWD transfer case to make it an AWD truck.
my daily driver is a lowered 88 2 door blazer with 4x4, 2.8l and auto transmission. I have reduced the weight of the truck to 2890 lbs with me in it.

The word is that the compression of the 2.8l will rise to 11.1 which would be fine with 93 octane and a proper tune. Will it really only be 11.l or something ridiculous like 14.1 compression? There are head spacers for the 2.8l available that i can coat with copper, would those be reliable to use with head gaskets? what obd 1 computer would be best to use?
This is happening one way or another and will be a cool truck. my other vehichle is a 3400/3500 96 grand am coupe nearly completed.

[Guest]

To make it easy I'd suggest getting a 3.4 from a Camaro, you can then use the 3400 heads or even 3500 heads then. The reason I suggest the 3.4 is is because it's already set up for DIS, with teh crank trigger in the block. To trigger the DIS system using a (RWD) 2.8L block you will need to make an external crank trigger. I made one years ago, back when I was only the 2nd known hybrid, and first turbo hybrid. lol I modeled it after the MSD crank triggers, where the trigger wheel is between the harmonic balancer and the crank pulley.

The SCR will go to 11.5 to 12:1 depending one whether you use RWD or FWD (aluminum head) head gaskets. The FWD head gaskets are a little thicker. Stick with a typical headgasket. Using head spacers is a cheesy way to lower SCR and could actually increase the chance of detonation due to a widened quench distance/height.


On my old Franken60:

[jaons_Wlp]

thank you for the information Raven, the head gasket tip is great. i will use the fwd head gaskets and no head spacers since they effect quench. Im keeping the 2.8l bottom bolted in cause it has only 128k miles and is durable. Ive have enough of bottom end pesky-ness with my other build. Plus it will be something different and cool, not super fast but cool. I was also aiming for better fuel economy which i will get from the better flowing heads and increased compression. The heads are mildly ported with LS blue valve springs, ported 3400 LIM and ported 3500 UIM with lx9 throttle body, Crower stage 3 cam, and Hedman long tube headers modified for the heads. It should easily reach 200 hp and 190 ftlb at the crank. yeah ill work out the crank trigger issue, either make one or buy one if you know of a manufacture? certain 2.8l ECMs only require a crank sensor im guessing?

[Guest]

No 2.8 ECM requires a crank trigger, it's the ignition module that requires the trigger. The ECM gets it's RPM reference (called a "DRP" Distributor Reference Pulse) from the ICM, that is mounted under the coils.

There are crank triggers for FWD swaps on the market. Some people have used these in RWD swaps. Others have cut notches in the crank pulley, but I'm not a fan of that approach.

[jaons_Wlp]

okay thanks, would a distributor extension be possibly? i Would rather have a distributor over DIS if i can help it. From the look of my 3400 block, the cap where a distributor would go, appears to distance the distributor almost enough to have enough room. But i wont know till i try it. also do you know if ill need to keep the 2.8l timing cover and accessory brackets, or use the 3400 setup? there is a video of a 3400 s10 on youtube and it looks like he used all the 2.8l stuff

[Guest]

You need to cut out the #6 runner (originally #1 in the OEM application, but the intake gets turned 180 degrees...) and by the time you get enough clearance and then close it back up the runner is almost completely blocked off, to fit a dizzy. I cut 3400 lower years ago to see just how much it would take. It took more than I thought it would...

I have seen someone make an extension for the dizzy, but it gets quite tall then. It should still fit under the hood of an S10, but the cowl might get the in way. I also explored the idea of retaining a dizzy way back when I did my hybrid swap, even going as far as using the dizzy to hold a custom trigger wheel to trigger the DIS, but decided on the crank trigger set-up I made (as pictured above) in teh end, since the notches would be so small on the dizzy based trigger wheel, I'm not sure it would have worked correctly, since the pattern would also need to be doubled as well.

As far as the front cover stuff goes most people swap to the RWD front cover and accessories, since it makes things easier in most applications, especially where power steering is involved since the intake really needs to be turned around in most RWD applications, which would then have the stock FWD location of the power steering pump interfere with teh throttle body and intake manifold neck along with the T-stat housing turning the lower around as well.

[jaons_Wlp]

thanks for clearing that up for me. since i dont have the resources to make a distributor extension ill have to make a crank trigger work. I work at advanced auto parts so i looked up many late 80's fwd cars using the 3.1l and 2.8l, they appear to have two crank sensors, one in the block and one behind the pulley. Which harness and ecm did you use to only need one crank sensor? the one in the block is for starting the engine and the one behind the pulley takes over when it reaches idle speed

[Guest]

You must be looking at late '90's cars not late '80's cars, no OBD1 60 degree V6 used the 24x trigger behind the balancer. That's a part of the SFI scheme that started in '92 is some 60 degree V6 vehicles and in most by '93, then all 60 degree V6s were SFI in '94. Regardless of whether 24x trigger is used or not, it's not used by the ignition system. The ignition system uses the crank mounted trigger wheel regardless of RPM or operating condition.

The OBD1 ECMS even used on the DIS cars connect just like a dizzy equipped engine would, same 4 wires, same 4 colours, so none of them really use a crank trigger or cam trigger per-se (Excluding the SFI Buick ECMs found mostly on the Turbo Regal and Grand Nationals, along with a select number of FWD cars). However there's an offset in the ECM for the DIS that is required to be set correctly so that timing advance will be correct. Assuming the dizzy calibrations are "0 offset", the DIS applications require an additional 60 degrees of "advance" added to the timing signal to have the spark happen at the correct time, once the timing control is turned over from the ignition module to the ECM, which happens at about 400 RPM, in all of the calibrations I've looked at. That 60 degrees is more coincidence than anything and does not relate to the bank angle of the engine.

So if you use one of the OBD1 ECMs that was originally installed on a 2.8 or 3.1, there's no need to worry about more than one crank trigger and no cam trigger needed.

[jaons_Wlp]

Gotcha, do you know if a 2.8l MPFI ecm from a 3 gen camaro is tunable?
also does anyone know if a high volume oil pump for a 3400 (P/N#134hv) will fit a rwd 2.8l? it looks identical from the picture except the oil pickup tube is larger diameter

[Guest]

Yes, it is tunable, a better option is to get a '7730 from the 3.1 F-body, or Cavalier, Beretta, along with dozens of other cars. If you get it out of a FWD, it'll be set up for DIS already and make starting off that much easier. You also lose the MAF and go to Speed Density when going to the '7730.

The oil pump will fit, but the pick up won't be correct IIRC. I believe the sump is deeper on the S10 oil pan than the FWD oil pans. You can get a later RWD oil pump that will have the larger pick up tube, but be correct for the application.

[Mars]

sorry to thread jack but how do you mate an awd tcase to a t5? Anything special required?


Sent from my iPhone using Tapatalk

[Xnke]

You start with a 4WD T5, and bolt it on. If it's a chevy BW7742 transfer case, it will fit a chevy and some jeep 4WD T5 transmission.

[jaons_Wlp]

i Have an idea that no one else has attempted, im going to take a spare 3400 upper intake and modify it to fit a 4.3l TBI and air cleaner assembly on top of the manifold. It will act like a performance manifold for a carburetor, a High rise and air gap manifold, and it will be ported of course. the original throttle body entrance will be blocked off and a vacuum gauge will go there. The injector rails will still be installed in case i want to go SFI one day. ive been talking to another member and a taller distributor will clear the #5 runner fine, so i can keep a distributor set up and my stock computer and harness. I just have to find the matching distributor. Also i just rebuilt the TBI to new specs and discovered it has a fuel pressure regulator adjustment screw, i can use that to tune the engine. any thoughts on this?

[Guest]

Well, that has been done before and no, a gen3 intake does NOT work the same as a "performance intake", in fact it works terribly from the few that I've seen attempt it with carb.

I don't understand why you'd run TBI, and not just go MPFI. A few wires to swap a fuel pump and you're good to go. The difference between throttle body and MPFI is very little.

Let us know where you find this "tall" dizzy, if they were around, more people have done this by now, or at least used this tall dizzy with the gen3 intake. I'd say just go DIS, you'll never go back to dizzy.


Fuel pressure adjustments does NOT equal "tuning the engine". At best you will get it to EITHER idle or run well at WOT, or some singular state in between, if fuel changes from what the stock ECM is trying to deliver is needed.

[jaons_Wlp]

BECAUSE RACE CAR.

No just kidding, but BECAUSE as i said its my daily driver and i dont have the time for it to be down for weeks. What i proposed is the easy way to get the swap done and running enough to use. If the things were more easy and more information was abundant, perhaps more people would do more with the 2.8l. The engine is not a bad engine, the top end just has to go.
If that is true, then why dont you tell us why it would work terribly? It has got to be better then the shitty intakes on the iron heads, carb or not. Yeah it may not bring as much perfromance as MPFI or SFI but it will work. I said i was installing the 3400 fuel rails and injectors so i can upgrade to MPFI when i have all the bugs figured out. Just a swap of the upper intake and fuel lines will get rid of the TBI. Out of all the GM 6 cylinders produced, im sure there is a distributor that will work. Also im good at figuring out a way to make things work.
It was just general speaking, if there is more air going through the engine at a faster rate it will run lean, so a small bump in fuel pressure will be good enough until MPFI is obtained. Ill prove you wrong and any one else who doubts this.