guitarman376

My car has never had a tachometer, until today. I finished wiring a secondary fuse block underneath the dash, with 12V triggered by ignition. I had the main power feed from the battery fused, and sent into a under dash relay which sends the 12V to the fuse block (only with ignition on). I installed an AutoGage 2302 hooked up to the new fuse block.

My car has a 351w with an original fmx, and in Drive it shifts right about 4200rpm. This sounds and feels right, given that the car has the factory 2bbl intake and manifolds and single exhaust. Waiting to be installed eventually I have an edelbrock rpm intake and summit 600cfm carb, and I am saving for long tubes/exhaust. I figure that would move the power band up to 5000rpms which I understand is totally safe.

I haven't done a highway test yet to see what cruising rpms are at 65-70mph, I have been guessing it will be around 3400rpm.

guitarman376

Well I was way off, turns out my car has 3.0 rear gearing. Only turning 2500rpms at 65-70mph.

Gun Jam

Yeah I run the t5 with the .63:1 OD and in 5th its like 2800RPM at 90 with 3.80 rear end gears

3400RPM is quite a bit to spin on the freeway to keep the vehicle moving at 70. I have found 2500 to be a quite efficient cruise rpm. Sure that depends on cam but anything between 2k and 2800 is probably ideal for 95% of the stuff on this forum.

3400 would be murder on a long trip

Starfury

I cruise at ~3200rpm @ 70 3.25's and a toploader with 24" tires. It's a bit loud and only gets about 14mpg, but it works.

guitarman376

So after my last post I experimented on the freeway a little bit more, and I'm positive I have 2.79 gearing. Around 75mph the engine was turning ~3000rpm. Makes sense how my car has managed ~17mpg freeway IF you can keep your foot out of it.

boogerschnot

You need to install that intake and Carb. You will be instantly happy with the results. It will drive like a different car. I remember when I did mine.. Smiles all around..