The New Project: Part Deux!

[njsteve]

Fellow member BRUCE from up in Alaska sent me a pair of BE rods for the Formula. Not only did he send me the rods for free, he cut down a tree, carved out a hand-made, secondary metering rod protection box with his chainsaw and then mailed the entire thing to me. [img]<<GRAEMLIN_URL>>/biggthumpup.gif[/img]

Take a look at this contraption!







Man, you guys sure are inventive up there, North of The Great White North. [img]<<GRAEMLIN_URL>>/beers.gif[/img]

[njsteve]

I've been doing a little bit of carb tuning the past few days. I ended up using the same recipe of jets, primary and secondary rods that I used in the 1972 T/A project. This recipe was passed along to me from other far more knowledgable people.

The end result is the following for my original 7042273 carb: 74 jets, 44 primary rods and BE secondary rods. The 1972 7042273 carbs were way too lean from the factory and definitely need more fuel than the emissions lean factory setup, if you want them to run right. A lot of it can also be attributed to the fact that gasoline today has 10% ethanol in it which makes for a leaner, fuel mixture. The Formula is running the stock 068 cam, a four speed, and a 3.42 rear gear which is the same driveline I had in the T/A.

I gotta tell you, the car really comes alive with this setup. When you hit the sweet spot in the power band at around 3,000 rpm, the rear tires break loose in first gear, regardless on how angrily your foot is positioned on the gas pedal. I'll post some video when I can figure out how to drive, shift and film at the same time.

I sent the carb to Cliff's High Performance and he did an awesome job. The carb ran great when tested on the &quot;seat of the pants dyno&quot; in the prior mismatched cam/high compression state but once I did the engine overhaul, I noticed the carb was little lean on the top end for my post engine rebuild combination. (since we didn't know what was inside the engine at the time, he tuned it to what he thought best).

Here are the measurements for the combination of parts I had in my tool box at the time:

Jet/Rod...Cruise area...WOT area......Secondary Rod
71/43 = 2.5070..........3.4283..........CR .0550 S (72 T/A 7042273 stock configuration)
73/42 = 2.7999..........3.6545
73/43 = 2.7332..........3.6545
74/47 = 2.5659..........3.7699
74/44 = 2.7803..........3.7699..........BE .0413 S (72 T/A tuned configuration)
74/43 = 2.8486..........3.7699..........BE .0413 S (Formula tuned configuration)
72/39 = 2.8769..........3.5406..........DA .0443 M (Cliff tuned configuration)

At the moment I have the 43 primary rod in the carb and it's a touch richer than it would be with a 44 rod, since it is a new engine I dont want to lean it out too much. If I do my math correctly, the &quot;tuned&quot; setup listed above is around 10% richer than the stock setup which looks like it somehow offsets the 10% ethanol content.

Once the weather clears I will play some more.

[njsteve]

Spent the day doing my mid-winter, out of hiberaton, engine start up.

It was a nice day so I got the hemi charger up and running for the first time in a year. She started right up, so I took her out for a slow ride on the 40+ year old bias ply tires that the original owner installed back in the day. Sure rides different than the Firebird. :-)

There's nothing like modern radials on a second gen Firebird. They ride soooo nice!

[HemiOrangeTA]

Awesome stuff; very enjoyable to follow. Thanks for the details and pictures/video!!

[njsteve]

I have been hunting down some parts to try to assemble a correct unitized distributor for the car. I recently got one 1973 1112203 off of ebay, a 1974 1112810 from a trade for an old holley carb I wasn't using, and got a rebuilt 1973 1112203 from an auto parts store. I do still need an actual 1972 1112133 in case anyone has a useable core out there.

These contraptions were a standard option on the 455HO Formula and optional on the Trans Am. They were somewhat notorious for glitches, being the first self-contained transistorized ignition developed by Pontiac. In evolutionary terms, if the the later HEI distributor was a modern human, then the Unitized Distributor was a Neanderthal.

The big problem was that the parts were unique and never produced by the aftermarket. The distributor cap, the rotor, the coil, and most of all, the wire set were unique and insanely expensive even back in 1972. The ignition module was housed in the base with wires that connected to the coil pack. The wire set was a molded one piece octopus that required complete replacement as a unit if you burned or broke a single wire. It sold new from the dealer, for several hundred dollars back when a regular points ignition wire set was around $20. So when something happened, the entire distributor was usually tossed and a newer HEI was installed in its place for 1/4 the price.

Here's one assembled:



Here's the three I have now

[njsteve]

The cap is more of a fixture for holding the wire &quot;octopus&quot; and has no internal termainals for the spark plug leads. It has a spring that sits on the top coil terminal and a spring loaded carbon button that is inserted into the center of the bottom of the cap. (the cap on the eft is cracked and missing the carbon button).





The coil pack sits on top of the wire &quot;octopus&quot; and two long screws go through the coil pack, then the wire set and cap and into the distributor base.

[njsteve]

And here is the notorious wire set. The eight spark plug wires are permanently molded into the center ring. If there was a problem with one wire...you had a problem with the whole set and had to replace it as a unit. Big $$$



Here is a chopped up center ring.



There is a way to split the center seam of the molded rubber ring with a razor and insert a regular wire set into the terminals. I will be trying that just to see if it will work. Others have done this with good results in the past.