69 Camaro TH350 to 4L80E swap - Cam, Converter stall and cruise specs

[mdavidthomas]

I recently purchased my first 1969 Camaro. I have wanted one since I was 15 and now I am 52. The car was built for drag racing and has the following specs:

Motown 400 SBC block with 4.125" bore
Scat 4340 3.75" stroke crank "
Eagle 6.00" H Beam rods
SRP 16cc dished pistons for ~10.25:1 compression ratio
Brodix STS 215 T1 heads with 64cc combustion chamber with 2.08/1.60 valves, mechanical roller springs 1.550" diameter, 255lbs @ 1.9550" installed height, 610lbs open, 0.700" max lift
Comp Cams 252/258 duration @ 0.050", 0.630/0.630" lift, 106 LSA, Billet Steel Mechanical Roller 0.900" base circle cam
Isky Red Zone Mechanical Roller tie bar lifters
Comp Cams Pro Magnum Roller Rockers 1.6 Intakes/1.52 Exhaust
Edelbrock Victor Jr. Single Plane Intake manifold
AED 750 cfm 4150 carb
1.75" long tube headers
PTC 10" Torque converter - not sure on stall speed but guessing 3800-4000 rpm
TH350 Transmission with Full Reverse Valve Body
Moser 12 Bolt Rearend with 3.73 gears
275/40/17 Drag Radials

The car has about ~1000 miles on a 2005 build. Seems to be a strong car but I am looking to do more cruising than drag racing; however, I don't want to give up all the power. I wanted a 4L80E overdrive and maybe a Holley Terminator Max X 4150 Carb style fuel injection unit. Along the way I figured I would route the exhaust out the back instead of the dumps under the car and purchase a hydraulic or mechanical roller from Comp Cams 242/[email protected]" 0.570/0.576" lift, either LSA 110 (Extreme Energy) or 113 (Extreme Fuel Injection) cam and a Edelbrock Performer RPM style intake manifold.

I must state at this point I am totally confused at what to do with regard to the transmission/Stall speed/Cam. The car turns about 3000 rpm at 60 mph in third gear currently and with the addition of an overdrive of 0.75 it will turn ~ 2200rpm. If I change to the Comp Cam 242/248 grind, it states you need a 2800+ stall with it's 2500-6800 operating range. This means the stall speed will be below the overdrive cruising speed at 60 mph of 2200 rpm in overdrive. I could drop to the down to a smaller cam which is a 230/236 duration cam that has an operating range of 2200-5800 which calls for a 2500+ stall speed; however, I think this cam will drop power from ~600 Hp to ~450 HP along with the other changes and I am still over the cruising rpm rating. I know the 4L80E could be programed to hold third gear through a higher RPM and I have read you could lock up the converter immediately in overdrive but I am unsure what to do at this point. I am trying to avoid any bucking or surging while cruising in overdrive. Any suggestion greatly appreciated.




mdavidthomas

[srode]

Pretty car, what color is that?

If it were my car, I would convert it to a manual transmission and keep the power.

[grease]

I have a 69 with 400sbc with the XR282HR cam (it has 230/236 specs you mentioned on the small cam). I run a 2004r trans with 2500 stall lock up converter. 3.73 rear gears and 275/40/18 tires in the rear. I typically keep the car in third gear until I’m at 70 or above. That helps keep things smooth. Trying to run at 60 with the converter locked up is a little lumpy. If I unlock the converter at lower speeds, it works well, I just worry about excessive slipping in the torque converter building up heat. If I had a trans temp gauge, I might not worry as much.

[mdavidthomas]

2002-2004 Corvette Electron Blue

[mdavidthomas]

I have a 69 with 400sbc with the XR282HR cam (it has 230/236 specs you mentioned on the small cam). I run a 2004r trans with 2500 stall lock up converter. 3.73 rear gears and 275/40/18 tires in the rear. I typically keep the car in third gear until I’m at 70 or above. That helps keep things smooth. Trying to run at 60 with the converter locked up is a little lumpy. If I unlock the converter at lower speeds, it works well, I just worry about excessive slipping in the torque converter building up heat. If I had a trans temp gauge, I might not worry as much.

Thanks for the response. I think the 200R4 also has higher overdrive gear than the 4L80E at 0.68 to 0.75. Looks like your rear tire might help you in 3rd gear run a little lower rpm but probably hurts you at overdrive dropping your rpms to 1900 to the 4L80E 2200 rpm. Probably still makes little difference. Any idea what power output your car has using that cam?

Thanks again,

mdavidthomas

[grease]

I haven’t had it dyno’d. It runs really well. It’s 10.5:1 compression, XR282HR with 1.6:1 roller rockers, rpm air gap intake, and 200cc pro topline lightning heads. I would guess it makes 450 at the crank.

[mean buzzen half dozen]

I would install the smaller cam (230/236 duration cam) It will give you more lower end power, ( makes it funner to drive IMO) better squirt off the corners.
The cam in there is a bit over camed with having only 10:1/4 I would also use a 3000 Stall lock-up converter from Circle "D".
Also run a 113 lobe center. This is for a better everyday driver experience & much better mileage, if that is any concern?

Just curious, what is your cranking compression as it is now?

Nice car BTW.