[caddor38]

Hi folks, another question for the professionals out there and again thanks for your time and efforts!

I am nearing the completion of my 71 Firebird Trans am Conversion. "Still in painter purgatory, but car is ready to go otherwise" . I have question on how high the max RPM setting on my MSD 6al.

Here are the Engine stats: Stroked 455... 4.5", Edlelbrock 87cc heads with the works. Cam is CompCam 308R-10 Solid Cam, .575 lift Int and Ex with Endurex Mechanical Roller lifters, 1.5 Roller Rockers. Please let me know i you need more info.

The Dyno folks took the engine to 5,500 max and HP at 546 and torque was 521.
Max HP was 560@ 5,100 RPM's with Torque at 646 @4,300 RPMS

In regards to setting the Maximum RPM on the MSD I am not quite sure? Any guidance would be appreciated.

[Scott65]

Based only on the power @ rpm numbers, I'd set the rev limiter @6200. Aim to test shift points from about 5600-5900. If it goes faster go up if not don't. If it runs the fastest shifting at 5600, bump the limiter down accordingly.

[caddor38]

Originally Posted by Scott65

Based only on the power @ rpm numbers, I'd set the rev limiter @6200. Aim to test shift points from about 5600-5900. If it goes faster go up if not don't. If it runs the fastest shifting at 5600, bump the limiter down accordingly.

Surprisingly, that is where i set the value initially. Thanks, I appreciate the help and explanation,

[Tom Vaught]

Agree on the 6200 rpm point but most of the MSD rpm chips do not hit the point exactly.
Could be 200 rpm high or 200 rpm low deal on the MSD Chip.

Some experimentation will be required. If a 6000 MSD chip gives you a 6200 actual tach
control rpm then you are good to go. Run the 6000 chip.

Hopefully you have a decent Tach in the vehicle too.

Tom V.

[25stevem]

The big question that can not be answered yet is how fast will the rpms drop down once a shift is made.

That cam is on the small side for a 490 something cid motor as can be seen by how fast the hp noses over just between 5100 and 5500.

Is this a auto trans car and if so what stall speed are you using?

[caddor38]

Originally Posted by 25stevem

The big question that can not be answered yet is how fast will the rpms drop down once a shift is made.

That cam is on the small side for a 490 something cid motor as can be seen by how fast the hp noses over just between 5100 and 5500.

Is this a auto trans car and if so what stall speed are you using?

Yep Automatic Transmission by JW with a 10″ ULTRA-COMP 3200 TORQUE CONVERTER. The Transmission is supposed to handle 850+ HP. My engine builder specked the cam on a streetable car for car shows. This is not the first I heard that the Cam is on the small side. Would you recommend another cam?

[caddor38]

Originally Posted by Tom Vaught

Agree on the 6200 rpm point but most of the MSD rpm chips do not hit the point exactly.
Could be 200 rpm high or 200 rpm low deal on the MSD Chip.

Some experimentation will be required. If a 6000 MSD chip gives you a 6200 actual tach
control rpm then you are good to go. Run the 6000 chip.

Hopefully you have a decent Tach in the vehicle too.

Tom V.

Okay, I will play with 6200 as the starting point

[25stevem]

No, that cam is fine now that I know what your intended use is for the car.
Your posting in the race section so I assumed st
At first with my comment that that’s where the car would be spending must of it time.

[caddor38]

Originally Posted by 25stevem

No, that cam is fine now that I know what your intended use is for the car.
Your posting in the race section so I assumed st
At first with my comment that that’s where the car would be spending must of it time.

Ohhhh, there will be a race from time to time however I will be going to car shows and playing around town.

[25stevem]

Since racing will be only time to time as you say , then stick with what you have now.
With that level of torque production you’ll be spending more time trying to hook up what you have once your at the track if you car is not set up for it already.