Good Morning fellow HybridZ members !
I have been a member here for a little while now and have educated myself with all the astounding contributions from this community. I can't imagine all the work in the detailed threads and builds. Unfortunately I don't have the same skill set or patience for taking pictures or video of all the steps along the way but will still try to contribute. I will warn you I take to long to explain things. Can you tell ?
Picked up a 72 240z with a rebuilt stock L26 running round top SU's about 1-1/2 years ago. Loved the car, always wanted one and it ran ok when warm, terrible when cold. The previous owner looked after the car cosmetically but his mechanical skills were limited so I knew things could be much improved.
I also researched and wanted to do the easy and common driveline swaps so I found an 81 280ZX to harvest the 3.90 R200 and close ratio 5 speed from. The car was original, rusted out and had 54,000 miles. At first, I wasn't going to use the engine as the seller said it had a knock but upon inspection it had thrown one of the lash pads off due to a stuck valve from sitting so long. Anyway, I tore the head off and found perfect cylinder bores, no pitting, ring ridge etc so I figured might as well try using the L28 short block. It was original with it's flat top pistons while the L26 I had was running dished.
I loved the look of the twin SU's but they were going to need work, although they were apparently rebuilt and properly adjusted. Now, right or wrong I didn't want to be dickin around with two carbs so my plans were to replace the intake and carbs with 4 barrel. For me this was best, can be adjusted and maintained easier and I'm a function over form guy.
I researched and decided that the manifold to use was from Arizona Z car. It was dual plenum and would provide more usable torque for the street and would also go with the recommended Holley 390 carb.
A buddy of mine is a very talented, long time drag racer and he offered to work on the intake for me. I didn't really think it would be required for a street car but his theory was that there could be some free horsepower in there and a few extra horsepower is a few extra horsepower. He went about smoothing the ports but did the most work in the plenum. The plenum divider was thinned and much time was spent carving the plenum transition to the runners. Sorry, but these are the only pics I have. Much more work was done and making a thread was never a thought at that point.
Originally I was going to use the L26 so I had decided to rebuilt the 72 E88 head. Whitehead performance did the work and confirmed that I had the early E-88 with the closed chambers. They also confirmed that the original brass seats needed replacing with steel and I decided to replace all valves with the larger size used on the L28 engines. The head needed some aluminum repair but otherwise was in exceptional shape.
I was panicky and conflicted when I decided to use the L28 F54 block as compression might be too high. And after much research and confirmation with whiteheads decided it would be ok. And if it wasn't, I would just use the L26 block.
When I got the head back my buddy again offered his services. He smoothed the ports and bowls and did some other voodoo for another potential horsepower or two. Awesome guy! Also, a mild cam from webcam and new OEM rockers were installed.
Start up and experience with Holley:
Everything went so well. I had expected some issues but the engine roared to life and after a couple mixture and idle setting she was running like a champ. Decided, to take it around the block without the hood on to see how the 5 speed and rear end worked. I was taking it really easy but could tell things were much improved. My drag racing buddy asked what I thought and my response was " I think she really wants to go ".
I was taking it so easy that my busy body neighbor comes over and asks me "what"s the matter with it, it doesn't seem to be running right" Guess he never heard a performance cam before. Anyway, the next day as I was backing out of the driveway the same guys coming over again so I was a little more aggressive and left him standing in a cloud of tire smoke as I'm driving up the road watching from the rearview mirror as the smoke rolls over him . It's one of the funniest things I've ever done and laughed about it for days and the 150 ft black marks are still there. Guess it was running ok after all eh, lol. Timing was set conservatively at 12 degrees idle, 30 degrees full throttle with about another 30 degrees at cruise from vacuum advance due to using the 81 280ZX dizzy and without any pinging.
Anyway, holley was great, no hesitation, instant throttle response, very happy except for the electric choke. It sucked and couldn't be adjusted to my satisfaction so I used that as a HUGE excuse to try an EFI throttle body.
Finally, experience with Fitech EFI 4 barrel:
Overall, everything went very well but there definitely was some issues which had to be resolved. I went with fitech's fuel commander which has a few issues that I wasn't aware of at the time. I sorted them out but there was some head scratching going on.
Venting the FCC center. Fitech says it has to be vented to the tank and can be t'd into a charcoal canister line or any other vent line going to the tank. I t'd into the tank vent which runs to the two way valve which runs to the stock PCV tube coming out of the block. This should be perfect as i'm venting the FCC tank fumes into the same system that vents the gas tank....WRONG!
What I was seeing was occasional A/F ratios which needed huge amounts of trim. The fitech system tunes itself but you can watch it from an included monitor. As an experiment, I installed a clear vent line from the FCC center to a clear apple juice container and took the car for a 30 minute ride. In that time the FCC vent was spewing out enough raw fuel to 3/4 fill the container...WTF supposed to be a vent not a fuel return. What was happening was that fuel was dumping into the gas tank vent line and being sucked directly into the intake manifold through the PCV system causing the crazy fuel trim !
The fix was to vent the FCC into the original fuel return line which runs back to the tank which lets the gas tank vent line function as it should from the rear vapour separator to the pcv system.
Was getting a momentary lean spike with momentary pinging with sudden throttle transitions from cruise or under full throttle while shifting gears and getting on and off the throttle. Never any pinging under full wide open throttle. I tried adjusting accelerator pumps shots thinking it was getting enough but that would not work no matter what I tried.
Next I looked at the distributor function and hooked a mechanical vacuum gauge T'd into the distributor line and compared with what the fitech manifold vacuum was....gotcha, you pesky problem ! Basically no vacuum on the distributor line coming from the throttle body port vacuum circuit. The only time the line saw vacuum was for a split second during sudden throttle transitions as noted above.
The fix would not be quick or easy. You might be thinking just put the distributor on the full manifold vacuum port and I did experiment with several versions of this. Bottom line is my engine idles best without the added vacuum advance and it worked perfect with the carb and so it should work perfect with EFI.
A combination of things were causing the problem,
1. Throttle body is huge and is really meant for larger engines which means you need to almost completely close the throttle blades to get your IAC reading correct. This lowers the blades further from the port vacuum orifice.
2. Throttle blade is very thick compared to the holley which means it has to move farther to uncover the hole.
3. Fitech has the orifice too high. At approx. 6% cruise the hole is too high
I first tried adjusting the secondary blades higher to the hole and closing the primary throttles lower but this resulted with too high an idle while getting IAC adjustment correct.
Basically, I would have to fill the existing orifice and re-drill lower. This took a few attempts as the vaccum circuit is not drilled at 90 degrees but at an angle and had to be drilled from outside in. In the end, this worked along with thinning the throttle blade on the underside to fine tune. Port vacuum works as designed, nothing at idle and full manifold vacuum above idle. Ping on throttle transition is gone. Timing will all be fine tuned in the spring as the cars away for the winter.
Anyway, a lot of work to replace an electric choke !!!!!!!!!!!!!!!!!!
The system works very well, runs perfectly from cold, instant throttle response, excellent power. No dyno's where I live so will take it to the dragstrip this summer to get an idea of the HP.
Sorry, for the messy engine bay, tie wraps etc. Has been a long experiment and the throttle body has been on and off about 30 times.
Tried to insert photos as I went, we shall see if I screwed it up.............sorry for the rambling post.