Vortec Heads,CPI & OBDII

[sockjock]

Okay I've got a couple questions here...first I am planning to build a motor 4 my 95 blazer and plan on going with the newer vortec heads but I want to machine my CPI intake to bolt up to the new heads. What would be required? Redrill the mount bolt holes? ( I think the CPI intake should make better low end torque and HP compared to the newer intakes) second could I switch to OBDII for better tuneability? What all would I need to do to accomplish this or would I be wasting my time and money? Swapping chips to acheive the right tune sounds more like quess work compared to the OBDII setup. I found a donor vehicle for the parts. It's a 96 Blazer that's totalled in the rear. I'm wanting to boost the HP/Tq as much as possible in the 1800 to 5200 RPM range without spraying it,boosting it or swapping to V8. That's why I considered the newer vortec heads(ported and polished) and the CPI intake along with a 260AHR or 270AHR cam and maybe slightly higher comp ratio along with the OBDII so I can tune it all to work together. Answers,tips, advice?

[rat]

Usualy people re-drill the heads for the cpi intake to fit. Also, you will probably have to add a little bit of height, the '96+ vortec heads have .100" taller ports.

OBDII will not run your cpi injector either. The '96+ stuff has 6 injectors, and they are all high impeadence. The cpi injector is low impeadecne.


So, what i would recomend is that you consider Megasquirt. It is an aftermarket efi controller. It is designed to be tuned. You can make changes in real time while the engine is running, really slick. It also will cost about what a Tuner/Scanner package costs.

You have to come up with a base tune though. So this might scare you off. It isn't necissarialy for a 4.3L. It will run just about anything with the right settings.

You will need to keep your stock computer to run the transmission. The tps would need to be spliced for both units. And i would add a new coolant temp sensor, and iat sensor for megasquirt. You need to run a vac line to megasquirt(it has an internal map sensor). You would also need to decide how you want to run your spark. I would go with ford EDIS. And i would probably keep the stock distributor, so the stock comptuer should still have an rpm signal. And your oil pump has something to turn it. The edis requires a reluctor ring get welded to the crank pulley for a rpm signal.

I answered a very similar question on s10Forum yesterday, if you are the same person let me know, and i will stop.

[1993blazerlt]

why not just keep the stock computer the is plenty of support for the $0D code that you are running, you can change anything that you want on it

[sockjock]

Okay...wow thanx for the info. What do you think of running the CPI intake w/ the newer Vortec heads? Would I make more HP/Tq with it or should I just go with the newer intake also? Also how would I add the height you're talking about? Port the intake .100" or what?

[rat]

Height would have to be added by welding material to the top of the intake, assuming there isn't enough there to begin with.

[sockjock]

So what kind of performance should I expect from the new vortec heads and CPI combo?

I realize both the CPI and MFI are compromises but since no one has fabbed up an affordable TPI or RamJet for our motors what are we supposed to do?

I've looked at the V8 TPI and Ramjet setups and I think the reason GM didn't go that route was because of the added height and the motors not fitting under the stock hood. But it looks like it should be fairly simple for an expert welder to fab up a good TPI setup and way simpler to fab up a RamJet for the 4.3L

[1993blazerlt]

The CPI intake is way taller than a TPI intake, I have a TPI engine in one of my trucks and it is shorter than my CPI, also there was TPI on the 4.3 it was on the turbo charged scylcone it actually used the same throttle body as the V8 TPI

[sockjock]

I could be wrong. I'd like to see the cpi and tpi on a bench in front of me for comparisons. So would the SyTy intake make more power on our motors(minus the turbo) compared to the cpi and mpi intakes? You would have the long runners plus external injectors that could be more easily modded. Am I wrong here too. Or is it all a pipe dream? I really need some good intake suggestions. I don't like(can't afford) the old trial and error method. I prefer going the proven route and use someone else's expertise and experience. ps Thanx for all the helpful info.

[rat]

I doubt the sy/ty manifold would work very well without the turbo. Don't forget you will need a different controls system to run that probably as well.

[sockjock]

So what would make more power across the board(1500 to 5500 RPM) the factory CPI or maybe a edelbrock 2114 converted to MPI ?

[Sparky2263]

With what you are doing, the 2114 would probably yield better results. All the additional fab. the CPI would need would render the difference in favor of the 2114.

[sockjock]

So with 9.5/1 cr.,balanced bottom end, disconnect banlance shaft, port/polished vortec heads, 260AHR or 270AHR cam, edelbrock 2114 conv. to MPI , Hooker longtube headers(fabbed to fit my blazer) I figure I should be in the 300HP range. I would have to use the OBDII setup from the donor vehicle to run the 2114 MPI correct? I don't think OBD1 could run multiple injectors.

[Sparky2263]

I figure I should be in the 300HP range.

The 260 will never get you there. You're gonna want a cam in the 270-280 range to reach those numbers. Head work is gonna be real important also. You'll have to up the exhaust valve size to 1.6 although the 1.94 intake size is fine.

Also, you're gonna hit peak hp between 5200-6000. That's gonna dictate at least a 3000 stall converter. With the 4.3 the 3000 stall will actually stall around 2500 which would be considered minimum with a 270-280 cam.

Personally, I'd build the engine towards the 280 cam. You can zero deck the block to get you around 10-10.5 compression with the stock heads. I'd find a machine shop that has done plenty of performance work on stock heads and has the flow numbers to back 'em up. You'll be stuck running premium fuel, but heck, that's a small price to pay for the results. Compression is the easiest way to reach higher hp numbers. (besides nitrous)

Go that way with it, 300 hp at the crank becomes realistic. Figure 1.2 hp per cu. in. and that comes out to 315 hp not including the overbore.

You are going .060 over to get max cubes aren't you? ;)

All said and done, you'll be running low 13's in the 1/4. Very respectable number for a V6.

[rat]

Or you could use megasquirt.

[sockjock]

Hey thanx for all the tips. I'm surprised that with the ported vortec heads and added compression that a 280 would be necessary to reach 300HP. Yeah I def. plan on an overbore. Can the 4.3 handle .060 over without causing problems? cooling etc. I also plan on using lighter rods. Eagle makes some rods for our motors that are substantially lighter and stronger than stock and priced pretty reasonable. Don't really know what pistons I'll go with yet but I really need to keep compression low enough so I can run on 93 octane as this is still my daily driver. I've always been told that 10/10.5 is too high for pump gas unless you're running aluminum heads.

As far as low 13's go...I can only dream...my 4 dr Blazer is pretty heavy. But we'll see. It would be pretty fun to bust some mustangs with a 4dr family ride and a V6. I think my head would bust.:D

[rat]

I wouldn't recomend the 280hr with fuel injection due to the small lsa. It might be hard to get it to idle. It is certainly possible, but it will take a bit of work.

[Sparky2263]

I've always been told that 10/10.5 is too high for pump gas unless you're running aluminum heads.

As far as low 13's go...I can only dream...my 4 dr Blazer is pretty heavy. But we'll see. It would be pretty fun to bust some mustangs with a 4dr family ride and a V6. I think my head would bust.:D

With aluminum heads you can actually get to 11-1 on pump gas and it doesn't take much tweaking. Shoot for 10-1 or a hair over and you'll be fine. A little tweaking to the spark curve and you'll be in there.

You're right, the 4-door is pretty heavy, but you'll still be solidly in the 13's pushing 300hp or better chp. 275 hp to the ground in my 3050 lb. Blazer ( with me, 3230 lbs.) puts it in the high 12 range with good traction. Very low 13 with poor traction. Figure 25hp less and 500 lbs. more you're still in the 13.7 range.

Rat is right, the 280 will not take a stock idle. Most likely you'll have to program idle speed around 8-900. But, with a quality stall converter, that won't be a problem. Won't jerk and try and stall when you drop it in gear. Sticking with the 270 will probably give up 15-20 hp.