75 Trans am

75 Trans Am LS2/6spd

I was able to "half" tune this car today.  We were stopped by the rain, so there was no chance to go for any runs.  I will be finishing the tune when the weather clears up.  This car is clean! The owner did an amazing job on it, inside and out.  This is a 1975 Trans Am with a 77 front end.

Specs:

ls2 + .030

Cnc'd ls3 heads

Custom cam 600+" lift more specs later

GM performance single plane intake

850 Speed demon carb. Vac secondaries

MSD 6ls with timing curve 3

Longtube headers

Magnaflow mufflers

Big brakes

6 speed

10 bolt, 3.08gears

The Carburetor

850 Speed demon vac secondary

This is my first hands on, with a Demon.  It is a very high quality carburetor, with very good looks. Read more here about this specific model.  This is a good match for this over all combination. Should make for a smooth tuning process.  It has an electric choke,  4 corner idle and will flow more than enough air. The carb is spec'd for 220-240 duration at .050 which this cam is, and has vacum secondaries.  The main tuning points on this carburetor are the idle mixture screws, power valve, main jets and the secondary springs.  The power valve, jets and secondary spring will be tuned next time.  I will include the afr logs.  Until then.....

My Carburetor

 My carburetor is a 600 double pumper. I modified it for blowthrough and went further by tapping and threading all passages for more fine tuning.

This picture shows my primary metering block. I installed  2, 6/32" brass set screws which I can drill out to any size with micro drill bits. These orifices are fixed from the factory on most standard Holley's. These are the idle feed restrictors. I reduced mine from the factory .031" down to .026" for a nice and lean off idle cruise. The ifr's work with the idle air bleeds to create the idle and off idle air fuel mixture. Bigger= more fuel,smaller= less fuel.

A closer shot.

The above shows me drilling out the factory air bleeds. I drill and tapped for 10/32" brass set screws. I can drill out with micro drill bits for tuning. These mods are rarely needed for a naturally aspirated engine with a properly sized carburetor.

Quickfuel explains the airbleeds operation well. My primary idle air bleeds are .0625 and the high speed airbleeds are .020. The secondary idle airbleeds are .028 and the high speed airbleeds are blocked for now. I am still playing around with the tune.

I have drilled and tapped the power valve channel restrictions for an 8/32" setscrew. The pvcr's give additional fuel flow when the power valve opens.  My idle vacuum is about 13" and  the powervalve I chose, opens at 10.5. A small primary jet helps create a lean cruise but then at w.o.t may be too lean. I am able to use a small primary jet with a larger pvcr. This allows a lean cruise with a properly rich w.o.t.  My primary jet is a 68 with a .070 pvcr. With this combination I have 11.8-12.3 afr wide open throttle on just the primary side, with the secondaries disconnected and wired shut. My cruise afr at 2,000 rpms are 13.5-14.5. Now that I know the primary side of the carb is properly tuned, I can connect the secondaries and continue tuning.

 My project car

1970 Mercury Cougar

I bought it in 1998. This car was originally a 351 Cleveland/ fmx transmission car. It is a base model. For a base model it had lots of good options. Air conditioning, power steering, power disc brakes and a 9 inch rear end. This is a big curvy car that stands out from the rest. I ran the 351c for a couple of years. The camshaft had seized so I rebuilt the engine in high school auto shop. Of course I did it all wrong. Compression was too high, the heads were 4 barrel , the valve springs were shimmed too tight and eventually flattened the camshaft. All this happened after I converted to a t-5 manual which I blew up going into 3rd gear. Something to do with too much power a heavy car and a dumb driver. In my mind the 351c was good for nothing. It was too hard to work on, too heavy and there was more bang for buck to be had else where. Fast forward to now. I did a couple years of research and decided on a single turbocharger. The low and midrange torque was very attractive for my heavy car.

I put 273hp/285tq on a Mustang dyno,  before the turbo. I put down 430hp/488tq on a Dynojet with the turbo. This is a tire frier. I can spin 2nd gear anytime.

Current combination
89 302, stock bottom end unknown miles
Master power t-70 with .68 exhaust housing, running 9 psi
Holley 600 dp E.V. hat
Edelbrock Performer rpm intake with 1" 4 hole spacer (Just installed a Torquer 2)
Steeda no.18 cam .510,.510 220/226 duration 112 lobe sep. With 1.7 rocker arms.
CNC Powerheads E7te 1.90/1.60 valves, ARP headstuds, 9333pt1 felpro headgaskets
Timing locked at 16 deg on 91 octane
Tremec 3550 5 spd
3.25 rear gears

 Since this dyno session I have installed a torquer 2 single plane intake manifold. I am looking for better fuel distribution and maybe shift the power up in the rpm range.  I am currently re tuning the carburetor with my new Innovate LM-2.

Transmission
Tremec 3550 5 spd
Pro 5.0 shifter
Lakewood scatter shield
Hays clutch (Will go Spec 3 later)
Diy cable clutch( will go hydraulic later)
Dark horse performance crossmember ( out of business)

Suspension

I am keeping the shock towers!
Front:
620 springs, kyb shocks, (I want Bilistein shocks later)
Roller spring perches
1" swaybar
I want to do the CPP lower control arms kit
Unisteer manual rack ( I want the power rack)

Rear:
Stiff 5 leaf , leafsprings. I want to stay leaf spings.
I want the Maier panhard rod.

Brakes
Power disc
Front:
70 drum spindles
Mustang Steve brackets
Cobra PBR calipers
13" slotted rotors
Stainless brake hose
Rear:
Drum for now( Will go disc later)

Wheels
I have 17x9 Cobra r wheels.
Fronts: 255/40/17
Rear: 315/35/17 Big factory wheel wells!

I plan on 18x9   275/35/18
              18x12 335/30/18 ( Have to measure carefully)

Fuel system
Factory tank for now( will do a sumped factory later)
3/8" feed
1/2" return
I need to upgrade since that is the outer diameter.
External BBK 255 lph fuel pump
Aeromotive 13204 regulator.

Exhaust
1.5" shorty headers facing forward.
2.5" crossover pipe, merges to a 3" pipe at the turbo.
46mm wastegate with 1.75" pipe plummed into the downpipe.
3" downpipe, split to dual 2.5" tailpipes behind each tire with Full Boar Max flow mufflers.
This car is silent! See my youtube channel.