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Common Sense + Critical Thinking
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the basic parameters of the engine are set: ported heads, upsized stainless valves, mild springs, roller rockers, keeping pressed studs, mild cam.
I assume that you have shopped around for heads as well, there are a bunch of options there as well, even completely upgraded sets of heads can be found for a good deal. You can get aluminum, or stay with cast iron, here is an example: NEW 2 GM CHEVY VORTEC 350 5.7 CYLINDER HEADS

Jegs and Summit racing carry a bunch of options. Some new heads might be cost competitive with rebuilding, just something to keep in mind.
 

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I may still have a spare TBI PCM but you would want to get a chip burned for whatever engine you choose. If your interested I can look in my shop tomorrow. Let me know. I Bored out my TBI and polished it and added police car injectors a riser to raise the height of the injectors and modified the fuel pressure regulator. It sits on an Edelbrock intake manifold and I added a bowl type thing that goes under the air cleaner. I read articles in the past about a dual TBI system and they had many problems with the system. I was not trying to get huge power I just wanted it to be better then stock but I do know there are people that have used the TBI system on 383 stroker engines as well as 400 cubic inch small blocks. Mark
 

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2000 Lifted 4x4 Astro 92 V8-350 Shorty
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My 400 has been sitting on the engine stand for over 20 years.. patiently waiting.
My plan is to put this 400 in my 92.. and move the 350 from my 92 to my 2000.
V8 talk... I'm ALWAYS IN! lol

My 400 small block...
(from my previous van before I supercharged it)
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Discussion Starter · #24 ·
The 0411 PCM was used with a bunch of engines which makes it extremely popular, like a lot of engines/configs, 4.3/5.0/5.7/4.8/5.3/6.0/etc. So you could grab whatever you don't have, like the intake/injectors/wiring harness/PCM etc from the junkyard, for example an 01-03 Express, trucks had them, camaros, vettes had them. That would give you a complete factory proven SCPI/MPFI setup for your engine. Then you can use PCM Hammer and Tunerpro with a cheap adapter to adjust the tuning to your modifications without having to spend a dime on software/vin licensing/etc.
Ah, so it is what I was wondering about--using Gen III management on a Gen I engine. I am curious about this, as the Gen III management seems to be very good. I'll have to learn about how triggering works. I think that the Gen III uses something other than a 60-2 reluctor, and I'm sure that it's something that my L31 doesn't have.
 

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Discussion Starter · #25 ·
I may still have a spare TBI PCM but you would want to get a chip burned for whatever engine you choose. If your interested I can look in my shop tomorrow. Let me know. I Bored out my TBI and polished it and added police car injectors a riser to raise the height of the injectors and modified the fuel pressure regulator. It sits on an Edelbrock intake manifold and I added a bowl type thing that goes under the air cleaner. I read articles in the past about a dual TBI system and they had many problems with the system. I was not trying to get huge power I just wanted it to be better then stock but I do know there are people that have used the TBI system on 383 stroker engines as well as 400 cubic inch small blocks. Mark
Thank you for the offer. I am trying to keep myself from thinking too much about TBI. I know that it is a durable system, but considering what must be done to make it do what I need it to do, it seems that another OE system--a carburetor--would do the job better with less work and with better results.

There was a factory dual system in the "Crossfire" injection of the 1982 and 1984 Corvette, and probably also the Camaro and Firebird of the same year range. I know little about that system, but I believe it was dual 1bbl units. I have seen pictures of dual 2bbl setups that people made. From a fabrication standpoint, I would enjoy building such a creature, but we go back to the fact that this is a family truckster. I can't get too deep into fabrication on this project, and it can't be something that I am forever tinkering with. And it seems to me that dual TBI units would mean dual ECUs, harnesses, and sensor arrays. What could possibly go wrong?!
 

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LOL I totally agree. At one time I had 5 or 6 tbi's and the ecms, But when I moved back to NH I sold most of my overstock. I have stuff in storage in California still but who knows when I can get there again with the resurgence of this covid crap. That is why I said I may have one. Mark P:S. Good luck on your swap.
 

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Discussion Starter · #27 ·
I assume that you have shopped around for heads as well, there are a bunch of options there as well, even completely upgraded sets of heads can be found for a good deal. You can get aluminum, or stay with cast iron, here is an example: NEW 2 GM CHEVY VORTEC 350 5.7 CYLINDER HEADS

Jegs and Summit racing carry a bunch of options. Some new heads might be cost competitive with rebuilding, just something to keep in mind.
We are keeping the factory heads and porting them. For long-term durability on the SBC, my engine builder is recommending keeping factory iron heads. He says that he has seen longevity issues with aftermarket aluminum heads on SBCs. They're fine for weekend cars and toys, but if I need to put up 100K miles free of major services, then we should keep factory iron. That was kind of a bummer for me, because it would be nice to offset some of the V8 weight gain, but I go with his recommendations.

With that being said, the L31 Vortec heads are about the best SBC head GM ever put out. And they respond very well to porting.

If the original heads fail magnaflux, then we might well look at the heads in your link.
 

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Ah, so it is what I was wondering about--using Gen III management on a Gen I engine. I am curious about this, as the Gen III management seems to be very good. I'll have to learn about how triggering works. I think that the Gen III uses something other than a 60-2 reluctor, and I'm sure that it's something that my L31 doesn't have.
They used the 0411 computer on the L31 engine, stock, from the factory. Look at an 01/02 Express with 5.7l, Engine VIN R.
 

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Discussion Starter · #29 ·
They used the 0411 computer on the L31 engine, stock, from the factory. Look at an 01/02 Express with 5.7l, Engine VIN R.
In that case, I am missing something. The factory L31 engine management is CPI, "spider" injection. There is no individual control over the fuel injectors. Injectors are really just nozzles that are being fed by a central unit. Your comment a few comments back mentioned using the 0411 ECU and mentioned an aftermarket intake, which was set up for individually controlled pulsed injectors, if I didn't like the factory intake. So my little brain is thinking of a 0411 ECU that controls CPI, which really boils down to a variation on TBI, being asked to control eight individual injectors, and being plugged into a harness that has wires for eight individual injectors. What am I missing here?
 

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Not all of the spiders are the same. CPI uses only ONE main injector with poppets, SCPI has an individual injector per poppet valve. Have a look here: Astro-Safari-Info - Fuel System
 

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Discussion Starter · #31 ·
Not all of the spiders are the same. CPI uses only ONE main injector with poppets, SCPI has an individual injector per poppet valve. Have a look here: Astro-Safari-Info - Fuel System
OK, that's what I was missing. I didn't know that SCPI and MPFI existed. Thank you for clarifying that.

I wonder why MFPI even existed. At that point, why not go to a fuel rail like everybody else already had?
 

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Because it was a cheap retrofit for the existing SCPI systems poppet valves. It eliminated the poppet valves by using real injectors without having to change anything else, simple/cheap fix.
 

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Discussion Starter · #33 ·
Because it was a cheap retrofit for the existing SCPI systems poppet valves. It eliminated the poppet valves by using real injectors without having to change anything else, simple/cheap fix.
I get that, but GM was already simultaneously doing pulsed LH Motronic type injection on V8, V6, and I4 engines in all of their cars for at least a decade before MFPI. Fitting that injection to their vans and trucks was only a few drill holes on an intake manifold, or a new IM casting, away from being a reality.

Surely smarter people than I crunched the numbers and made the more economical decision. It just doesn't look that way from my armchair.
 

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Yep, a lot of it comes down to cost, if they can save an extra $10 on a billion vehicles, that adds up to a lot of profit ;)

The beauty of the SCPI and MPFI systems is that they can already control individual injectors. Which is what makes the cast marine and Edlebrock v6 intake manifolds great upgrade choices for those that want to use different/external injectors on the v6, mostly for forced induction.

For the v8s you have a lot more options, and will always continue to have more options going forward. I don't see them stopping production of SBC parts any time soon.
Want a stroker kit, v8, plethora of intakes, v8, aftermarket blocks, v8, forged crank, v8, aftermarket/cnc heads, v8, more FI options, v8, want to go distributorless, v8, 400ci, v8, supreme aftermarket support, v8, oh I could go on :)

I guess weight is an issue for some, still waiting to see that math. For me the weight equivalent of an extra passenger in my 4000+lb van is negligible.
Damn you GM, why didn't you make an AstroSS?
 

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In that case, I am missing something. The factory L31 engine management is CPI, "spider" injection. There is no individual control over the fuel injectors. Injectors are really just nozzles that are being fed by a central unit. Your comment a few comments back mentioned using the 0411 ECU and mentioned an aftermarket intake, which was set up for individually controlled pulsed injectors, if I didn't like the factory intake. So my little brain is thinking of a 0411 ECU that controls CPI, which really boils down to a variation on TBI, being asked to control eight individual injectors, and being plugged into a harness that has wires for eight individual injectors. What am I missing here?
this has been a good primer for me......
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I see the Kindle edition is listed on Amazon.

Rod J
 

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Discussion Starter · #37 ·
I guess weight is an issue for some, still waiting to see that math. For me the weight equivalent of an extra passenger in my 4000+lb van is negligible.
Damn you GM, why didn't you make an AstroSS?
That would have made life a bit easier for us, wouldn't it? Same goes for an S-10 SS. I mean, they eventually put a turbo 4.3 in the Syclone that made more power than the V8 at the time, so why not, GM? We could have handled it maturely. We promise.

I don't know the dressed weight difference between an iron 4.3 and an iron 5.7, but I wouldn't think that it would be more than 100lb of added weight. Of course, right around 100% of that added weight is being added to the FRONT of the engine, forward of the front axle line, but it still probably doesn't mean that much. I have thought about moving the 40lb battery to a tidy location in the rear, but I don't want to start playing with weight distribution on a van that isn't going to care--especially if it means losing interior volume in doing it.
 

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2000 Lifted 4x4 Astro 92 V8-350 Shorty
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When I swapped my iron V6 (with iron intake and iron exhaust) with V8 (aluminum intake and headers)... my 92 actually sat higher. I can now slide my jack under it without lifting it a little first.
 

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Discussion Starter · #39 ·
When I swapped my iron V6 (with iron intake and iron exhaust) with V8 (aluminum intake and headers)... my 92 actually sat higher. I can now slide my jack under it without lifting it a little first.
That's a surprise. If it works out for the same for me, I will take it.
 
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