Slowpoke70: Bringing a (beater) 1970 Chevelle into the EFI era

[Slowpoke70]

Hello All,

My name is Enrique, I've owned my 1970 Malibu aka "Slowpoke" for about 10 years now. My family acquired it when I was about 15, and the car was given to me as a graduation gift 3 years later. Initially it was a "Father and Sons" mild restification project, but my dad lost interest in actually working on the car when he hit 55 and my brother is now a busy family man. So I've taken over the project on my own, and it has become a bit of a rolling automotive classroom.

The car turned out to be a bit of a bondo bucket, which became apparent after quite a few runs down Irwindale, Pomona, and Fontana dragstrips - along with a fair bit a of abuse on the street.

Instead of selling it or sending the car off to body shop prison, I've kept it and decided to modify it to my likings while using the car as a "learning lab". I've rebuilt/upgraded the suspension, performed my first engine swap (305 to 355) and later on my first cam/intake/heads swap. Learned to rebuild and mildly modify both Qjets and Holleys. Converted my large cap HEI to external coil with help from Dave Ray. Learned quite a bit about automotive wiring. Swapped a steering box from a Jeep Grand Cherokee. Currently converting the car to Hydraboost and adding Windstar fans controlled by a Volvo fan relay and BMW temp sensor. Next in line is correcting the front suspension geometry with tall ball joints and SPC adjustable uppers (SC&C kit bought lightly used).

A lot of what I do is basically junkyard engineering. I like to take a look at what GM did with the A/G, F, and B-body during the 70's-90's and try to apply what I can to the 1970 A-body platform. I have nothing against using aftermarket upgrades, but I find that many times aftermarket upgrades are just packaged "junkyard engineering" using new replacement parts rather than grungy parts from a donor vehicle. And I'm a DIY kind of guy, I feel like I learn more that way.

In the near future I plan to upgrade to EFI, so I will be here researching and asking questions. I'd like to use as much "junkyard engineering" as feasible to keep costs down and reliability up (using OEM-engineered parts tends to add to reliability many times, in my experience.)

My engine is not a tame stocker. It's a 10:1 355 with Sportsman II heads and a small Isky solid flat tappet (z25), currently fed by a Qjet sitting atop a Holley 300-36 with spread-square adapter. Recently switched from a 3310 Holley to the Qjet quite simply because I wanted to learn how to rebuild a Qjet, and I have to say that even with the dreaded adapter, I like the way the engine runs with the Qjet over the Holley.

Because of the engine/cam, I'm not sure which way to go with the EFI. I'm okay with a cam swap in the future, but I'm not willing to use some tiny near-OEM spec cam. I've had 260 and 268 type cams and I prefer something a bit rowdier, I'm not afraid to deal with the less than optimal street manners.

My ideas so far are:

1) TBI conversion with goodies from Moates and TunerPro. Simplest but future upgrades limited by 454TBI fuel delivery.

2) LT1 intake converted for distributor duty, using TPI harness. Unsure what ECM/PCM/software I would use to run it.

3) LT1 intake and Ford EDIS-8 ignition. Most likely would run this with MSII

[Six_Shooter]

Welcome

I've already replied in your other thread, but I'll reply to a couple points here.

The 454 TBI is not a limit, when you get creative... ;)

A friend of mine has made several 4 bbl TBI throttle bodies, the last one I was involved with and is made up of an oversized 454 TB and a 350 TB. After smoothing and a few other mild modifications, the TB flows over 1100 CFM. It's on an Oldsmobile 455, which IIRC is a 462 now with the overbore, making over 500 HP and 600 ft/lbs. It also has a pretty aggressive cam, I want to say it's a 270 degree or more cam, which yes, meant that I had to get creative with the tune, but he drives it hard and drives it often. I know that the cam was "not to be used with EFI", but it works. I have the idle set a tad high right now at 800 RPM, but it's quite smooth there. At the time I tuned it, I couldn't get the idle lower without getting a lot of raw fuel out of the exhaust. He has since found that there were a couple small mechanical issues that likely caused that and have fixed them. I have not re-tuned idle since then.