Kind of a long read. This is my daily driver when I'm not installing something on it. Its got a 350 SBC bored 20 over with flattop pistons, timing gears, 275 duration cam (adv), stock "D" 802 heads with cnc alum full rockers, GM HEI with accel coil / control module, weiand stealth intake, holley carb. Trans is a th350 w/ shift kit and redneck 3000 stall conv., rear end is a stock 10 bolt with stud cap and richmond 3:73's with a new eaton posi. The car is lowered ~3 inches, 17 and 18" wheels on it.
I decided to do some upgrades to the engine:
Heads: AFR 195 eliminator 64cc
Exhaust headers: Dynatech 1-3/4" - 1-7/8" stepped, ceramic coated
Intake: Weiand Stealth, port matched to heads
Bottom end: Custom fit crankshaft scraper and rear baffle, ARP stud kit
After seeing an ad for the holley Xefi
systems, I checked out the features on the three systems and decided to get the HPefi
system together with a holley 12-920 pump. Funny thing, that pump says WALBRO on the side with a pn listing it as their 255LPH model.
The install went great but not without a few hiccups along the way. I spent between 4 and 8 hours per day of install. I removed the carburetor and mechanical pump and the old 1/2" aluminum fuel line. The first day was spent installing a 5/16" steel return line and a 3/8" feed line. I couldn't find anywhere to mount the fuel pump below the tank so next best place was beside it, mounted to the floor of the trunk with each fuel filter on each side. (150 micron and 10 micron) I spent part of the next day getting all the fuel line adapters and fittings from the parts store and connecting all the rubber line parts and making flares and installing the TBI.
The 3rd day I started on mounting the ECU and sensors, I tried to find a good place under the dash and a place to cut the 2" hole for the wiring but both proved to be too tight, I suppose there is room under there if some brackets were fabricated, would have made for a more clean looking engine compartment. I mounted the ECU on the pass. side fender, right on top of where the heater hoses clamp. I welded the O2 bung into the passenger side reducer (ok, paid a guy with a dozen donuts to weld if for me hehe, good trade).
I like the mounting into the reducer more than going into the header as the clearance was too tight everywhere on the header plus its a lot easier to remove a reducer, bonus being that I can rotate the reducer to any angle I want, got the O2 sensor at 45 degrees down.
The fourth day I installed the wiring harness and connected the laptop then modified the baseline file, only had to enter in a few simple parameters. The car fired up right away but the idle was surging from 1300 to 500 RPM.
I was messing around with the timing a lot and kind of got it dialed in but the surging was too crazy to get a steady timing indication. Rechecked my install and found out that I forgot to torque the TBI to the intake properly,
I had just hand tightened the nuts earlier because my tools are two miles away in storage and I forgot my small torque wrench that day lol! I fixed that gigantic vacuum leak only to find the engine still surging like crazy at idle. I had a look at the distributor to see wtf was up, checked the vacuum advance, control module, wiring, all was good except for when I checked mechanical advance, the rotor was wobbling off axis about 7 degrees, the mech. advance was fine but the rotor mounting plate was loose/bent. Soooo...
Day five I head back to the parts store, buy a '94 chev 2500 reman. computer controlled HEI distributor, the reman had tighter end play and ventilation screens than the NEW one! Apparently, 0.04 end play is ok now. I bought a MSD blaster 2 coil, MSD coil bracket, MSD rotor cap and MSD rotor, a couple pigtails to wire it up and a 4 pin metripak to link into the holley harness, $385 CAD total, not too bad for a distributor ignition system that is accurate to within a degree from crank to spark. The 1 degree of variation is a whole lot better than the 30-60 degrees my busted distributor was performing. I checked everything in the EFI tuning software, reread the quick start guide which, BTW, was good enough that "I" understood how to do it...in actuality I only needed to change ONE setting in the software to go from electronic HEI to computer HEI. After setting the distributor to what the computer was dialing in, it was all ready to go, or so I thought!
I only got one or two cylinders to fire and very intermittent at best.
Day six to ten was spent playing with cranking timing settings, cranking fuel settings, I think I had over 100 timing / fuel combinations and several battery recharges. After trying all those combinations, I knew the fuel was good, because the injectors were all putting out a perfect cone of fuel down the TB, there was only one thing to adjust on the TB (idle throttle plate angle) and I knew I was getting spark to all spark plugs...I finally checked the plugs MY GOD these were dirtier than a poorly tuned dirt bike.
All brand new plugs which ran less than 20 miles total. All my combination setting and running without bolting down the TBI put a very thick covering of carbon / wet fuel on them that they refused to fire. I regapped them all and cleaned them up with some brake cleaner and a wire brush, stuck em back in, set the EFI tables back to baseline, turned the key and instant startup!
The engine stalled out a few times when I was pushing on the brake, turning headlights on, etc. so I bumped up the idle speed table 200 RPM, it was idling too sporadically anyways. Now cold idling is at ~1100 RPM and warm at ~800. I took her out for a test drive around a few blocks, woke up all the neighbors, some called the cops, it was all great fun. Going off throttle still scares me, the engine drops down immediately to normal idle, never below anymore and never stalling out. Acceleration is very smooth, yet part throttle acceleration is much faster. Full throttle is pretty normal, I just lose all traction like before but it seems more accurate when I lift to regain traction, comes back faster.
This was my first EFI install and quite the experience too. I got so into the more complicated and advanced stuff that I overlooked a couple basic things which is what really made the install go way too long.