MegaSquirting the Crusty Chevy

[SkinnyG]

While I like to think I am very good at tuning a carburetor, and spent quite a bit of time fine-tuning the Rochester in the Crusty Chevy, and while it ~did~ run quite well, the 1970's are over.

My greatest irritant was keeping a screwdriver in the truck so I could tweak the mixtures the teeniest bit every season. Just a little richer, just a little leaner. And every spring, when we were still burning the winter fuel but it was warm enough to vapour-lock, and even with the headers: <i>while driving</i>..... Good times.

So, since I had already collected all the parts I needed, I decided to finally do it. TBI first.



Background on the engine:

10.9:1 compression, fairly lumpy cam with tight lobe centers, loose converter, gears.
Heavily doctored Q-jet, stock HEI.

Day 1

I spend most of Day 1 changing the fuel lines and fuel pumps. The smart way to go about this, is to get 1987 fuel tanks, pickups, and pumps. When I built this truck, I (not thinking all the way through) had bought NOT 1987 tanks (no baffle) to the tune of $100 each when I shortened the truck. This would mean buying two new tanks again ($200) and two EFI fuel pumps ($300).

Instead, I used a low pressure pump I kept for insurance in the boot of The Lethal Locost when the cheap Facet pumps kept failing on me.

The tanks run to the switching valve, the switching valve goes to an AC Delco EP12S mounted at the lowest spot of the frame, which feeds a surge tank I fabricated out of aluminum. The surge tank stores fuel for a late 80's Ford F-150 external pump, which in turn feeds the injectors. The injectors return to the surge tank, and the surge tank returns back to the switching valve and the appropriate tank. The purpose is so you never run the EFI pump dry. Makes perfect sense if you think about it.



Reckneck hackery, no?

I had originally intended to use the factory mechanical pump to feed the surge tank, but the plumbing to make that work seemed a lot more complex.

I picked up a fuel pressure regulator out of China, because it came complete with a gauge for $9, and I just needed the gauge. I will use the regulator on a later incarnation; the TBI unit has its own regulator built in.

I waste-cast an adapter base to fit the Q-jet intake at the foundry at school (I teach highschool metalwork, mechanics and drafting).



I picked up a Holley big bore TBI unit on Ebay, but discovered once I got it that it had 4.3L V6 injectors. I modified a GM injector pod to fit the Holley base (since they aren't really interchangeable), using a 1/4" aluminum spacer I hand made with my wood scroll saw, breaking only two blades. The fuel regulator was modified to be externally adjustable, and the 350 injectors (55gal/hr) were ultrasonically cleaned.



I got the TBI unit mounted with no drama. I had forgotten to tap the back for the brake booster, but that didn't take long to do.

I cut up a (presumably) TBI throttle bracket to fit the TBI where I had it, and still run the TH350. This was actually delightful, because this was the first time I used my sandblasting cabinet in the 13 years I've owned it.

[Malo83]

When can I send my E4ME Qjet for rebuild?

[SkinnyG]

Day 2

I finished up the fuel pumps and stuff on the frame, adding a filter after the EFI pump. Ran the lines up along the firewall, and connected to the pressure gauge and TBI unit. Pressure tested fine with no leaks, and set the regulator to 20psi.

This would have been a WHOLE LOT EASIER if I was willing to cough up the money for new tanks and two pumps. Stupid me.

Today was mostly wiring. The ECU got placed, all the sensors got wired, O2 bung got welded in but it shrank so I had to run into town in the Geriatric Buick to get an 18x1.5 tap. That will get threaded tomorrow, and the wideband will finally be installed.

The relay box is from a Nissan Pickup. It's quite modular, so you can fit resistor packs, or relays, or what-have-you.



The bundled wires near it on the left are all for a heated O2. For now, I want to get it all tuned on the W/B, and then throw in a basic O2 for everyday driving.

I had to get a swivel-able thermostat housing, as the only temperature bung on this older Performer intake is pretty much under the hose itself. The hole is 1/2" NPT, and the sensor is 3/8" NPT. And no, the parts store didn't have that adapter. Instead of wasting more time running around, I bought a 1/2"-1/4" adapter that they did have, as well as a 3/8" pipe tap, and made my own.

I tried to organize wires and make it all pretty like, but dang that's work, and I pretty much need this truck up and running by Tuesday. If it all goes wrong, I can probably still throw the carb back on and drive it.

[D13]

Why not j-yard a complete GM TBI system, 87-91 ish? Unless you have low-cost access of all these mixed make parts, and knowledge of each's range of capability, it would seem a lot easier to buy a beater TBI truck or jyard all the GM sensors and the harness off one, then you would just have to adapt the MS system. If you bought a clapped out 305 truck you would have the 7 pin distributor too, and all you would need is the adapters you have fabbed.

I'm assuming you went MS for the additional tuning capability, since your combo looks to be a little beyond the capability the stock TBI ECM. I think the MS is a big step up over carb, and I know it is much more tune-able than GM stock (particularly with stock PROM).

Not challenging, just curious.

[daddyjeep]

Are you running a factory ECU or did you get one from Megasquirt.

[SkinnyG]

I already had a Megasquirt ECU from another project.

GM TBI ECU needs a VSS, which I don't have. MS doesn't need one. My engine is pretty far from stock. It idles at 8"Hg in gear.

I had previously scrounged ALL the parts, the hard part was plumbing the fuel. The Holley TBI unit came from eBay as I became concerned the stock TBI that I had picked up wasn't going to flow enough air. I'm not afraid of wiring or tuning. Another car of mine is a Lotus Super 7 replica, running a Toyota 4AGE motor, Suzuki GSX/R ITB's, Ford distributorless ignition, Honda Accord injectors, all running off a Megasquirt computer I soldered together from a kit.

[SkinnyG]

Day 3

I'm getting pretty sore folding myself into the engine bay all day.

Today I completed the wiring to the cooling fan (having MegaSquirt switch the fan relay), as well as get the wires ready to do the HEI-8 swap. For initial start, I wanted the old school original HEI in there - a "known good" quantity.

I had nicked an extra snorkel for the air filter, so I took the time to attach it. Looks mean!



I went to re-calibrate the wide-band O2 I nicked from The Lethal Locost, only to discover the sensor itself was dead. I matched the Bosch part number to a 2000-2009 Audi A4. I need to pick up another.

Once all the electrical and everything was done, I fired it up. It coughed, and chugged, and blew enough black smoke to set the smoke detector off in the shop, even with the 18' door open. I opened up the barn fan and turned it on "expel."

Once I got the VE bins sorted, and figured out the Idle Air Stepper Controller, it just ran inconsistent. Tach was everywhere, and none of it made sense. I suspect the VR signal.

As a test, I swapped in the TBI distributor I picked up at the wreckers (looked super good condition), but got less than nothing. No spark. I tested the pickup and module, and determined that the module was likely faulty. I pulled the known good distributor out of The V8 Firefly, and got it to pop once or twice, but only two sparks while cranking and then nothing. Not enough tach signal to the ECU to even keep the fuel pumps running.

So....

Tomorrow I return it back to carb so I can still drive it to work. All the crap will stay in there, just minor re-routing to go back.

I'm pretty pissed off about all this. On the upside - all the really hard work is DONE, and I'll take it on again in the Summer when I have more time.

Grrrr.

[oldpurple]

Well, now I need to make a dual snorkel air cleaner.

[SkinnyG]

I discovered that I didn't understand the various inconsistent and confusing wiring diagrams for the TACH signal.

Once I figured my error, I re-wired the VR, it and tested it still running the Q-jet. Good solid signal! So....

I did it again.

Swapped the Q-Jet out for the TBI, and it fired right up and ran like a charm. A bit rich, though, but ran well.

Tomorrow I'll calibrate and install the new wide-band, and start tuning it.

I'm excited. I am so fraking done with carbs.

[SkinnyG]

Or....

Or maybe Ye Olde Reliable carb ain't so bad.

[KQQL IT]

Best laid plans of mice and men or some such.

[SkinnyG]

Parked to buy a new fuel pump, and battery was dead.

Got a jump, but no tach signal to ECU, no fuel pumps, no spark.

I got frustrated, and decided to go back to carb.

I am suspecting the HEI ground wire lost its connection, which may or may not be the cause. Nevertheless, this truck is my daily, and I can't risk losing reliability or having any down time when I need it for work. I need to "leave the toaster alone" when it's my daily.

So, I've pulled ~everything~ out, and I may or may not deal with it again. Q-jet and HEI are certainly dead-nuts simple and reliable, and this adventure stresses me out.

[SkinnyG]

In other news, to deal with the dead battery issue (and always low voltage reading on the dash), I installed a new 94Amp 12SI alternator for an '84 Camaro 305H.O. (bolts right in). Wow! The voltage gauge never read so high! And wow the truck ran well! And the signal light flash with authority! Impressive.

Dash gauge usually sat at 12-13V at idle, less if anything electrical was on. When the cooling fans were on (30A), the truck struggled to maintain 9-10V on the gauge. Add EFI to that, plus an inverter to run the lappy, then sit in traffic - no wonder the battery died.



For sale: used 10SI alternator from 1977 Chevy C10, low voltage edition.....

[Dead Parrot]

I wonder if some of your mega squirt problems were related to the low volt at idle the 10SI was giving you. I swapped to a 78A 12SI to fix the dimming issue at idle when I was running the AC, wipers, max fan for defrost and lights. From what I have read, a 12SI has about 7amp more at idle then the 10SI and the output comes on quicker as the rpms climb. Didn't need a higher max output for my mostly stock electrical system but the brighter lights during low speed around town driving are nice.

[SkinnyG]

I was also thinking the same thing. But driving around with only the EFI running, it still did the herky-jerky, so I'm not convinced it's 100% the issue, but I would agree it's likely a significant contributing factor.

I looked back at the datalogs from driving with the EFI, and at no point did the RPM signal ever quit, fade, or drop out. So I am more convinced it was a failing fuel pump.

If it wasn't the fuel pump, it's ~possible~ that my bins aren't separated well enough and the O2 sensor is over-reacting. But manually tweaking the VE table wasn't finding a solution either. No matter. I need to make another car my daily so I can spend more time sorting this.

In the mean time, I have more alternator than I've ever had now

[wesmigletz]

Originally Posted by SkinnyG

In the mean time, I have more alternator than I've ever had now

Sorry to hear about your EFI troubles. I'm pretty good with my Q-Jets and Holleys, but have been dragging my feet to install a FI Tech I bought. My truck is a daily driver, too.

With regards to your new alternator, does the factory two-plug connector fit?

Thanks,

Wes

[SkinnyG]

I love EFI, and I've done a couple vehicles before, but this one is repeatedly kicking my ass. FITech is a bolt-on kit, which should work just fine. Mine is a Frankenstein system that is much like running Linux - it works fine, but it's not for everybody. The FITech intrigues me.

If you can tune a carb and a distributor, you can tune EFI. But what's cool is EFI adjusts for altitude, air temp, and engine temp all the time. It's awesome. Your truck will never run consistently better on a carb.

Factory two-wire plug clipped right in, battery cable clamped right on, tabs lined right up with the holes and slots, and the v-groove was in the perfect slot.

The original spacer on the bottom of the factory alternator is supposed to also screw into the case of the alternator, but the threaded boss doesn't line up. Fords used to only use an aluminum spacer and they worked fine, so I didn't worry about it, just bolted it right up.

VERY PLEASED with this alternator so far.

[wesmigletz]

Yeah, I need to quit procrastinating and just get the FI swap done. Rock Auto has the 94 amp alternators with the correct V pulley for $64. I ordered one.

Good luck getting your truck sorted out if you go back to the Megasquirt.

Wes

[SkinnyG]

Thanks. Though I think I need a break from it.

I'm working with the Megasquirt folks to find out why my ECU isn't recognizing the HEI8, but did recognize the HEI4.

I'll need to re-think the fuel system. What I had going was WAY too complex - too many sources for error.

I will try and put off another attempt until summer, or later if I can.

[wesmigletz]

I am leaning toward an OE FI tank with baffles and an in-tank FI fuel pump and a Corvette filter/regulator combo for the 76. An in-tank fuel pump might solve your fuel pump issues.

[SkinnyG]

My fuel pump issues (if, in fact, I am correct that the fuel pump ~is~ an issue), is largely because the fuel pump was purchased from Pick-N-Pull on a 50% off day, and is dubious and unknown history.

Running a low pressure pump to a surge tank to feed a high pressure pump works really well. I've run that on my Super 7 for 8 years. You can run on almost fumes before the high pressure pump begins to starve.

But year, for simplicity - '87 tank, '87 pickup, and in-tank pump would be simple. Not what I did when I bought the tanks three years ago - stupid me.