1.6 Roller Rockers on 305 TPI

[39PitCrew]

An episode of engine masters proved that 1.5 stamped steel and 1.5 roller rockers had identical numbers, but 1.6 RR improved their test engine by 15hp / 6ftlbs. But their test engine was heavily modded and rev’d up to 7k. I think 1.6 might squeak another 5hp and maybe 5ftlbs. I don’t want to do any restrictors so we’ll see.

Something to consider:
*Where* in the power curve do the 1.6 rockers make a difference?
Where is the peak torque? Remember that HP is a calculated number based on torque and RPM.
So a little more torque at 2000 RPM doesn't really make a big difference in HP; a little more torque at 6500 RPM will bump HP up more.
Your TPI motor runs out of air at 4500-5000 RPM so torque falls off fast and you are forced to shift. However, the 1.6 rocker will let the motor
breathe a little freer at low RPM (so for us math nerds, more area under the curve), likely giving you a little more pull coming out of a corner or
slightly better acceleration for standing and rolling starts.

And if you have to go the restrictor route, talk to the guys who use the exhaust pipe restrictors. My experience dealing with the #39 car
is with the throttle body restrictors we had oil collecting in the throttle body and intake due to the way the air flowed through the restrictor
plate. I don't know if there was some sort of venturi effect or what but we always had oil around the restrictor plate. Sean (#15 Stormtrooper Car)
and David (#39/#88 recently) went to exhaust restrictors and I think the engine behaved more gracefully at mid-high RPM. But as you say,
no restrictor is preferred.

[64GunPilot]

That sounds like good insight. I did feel like everyone was walking away from me coming out of the corners at Cresson but I figured It’s just my driving and lack of car setup. FYSA I don’t have a speedo or a tachometer in the car. Purely shifting on feel and sound.

Just found out a friend of mine at work has some scorpion 1.6 RR on an engine he is swapping out of his street rod. I’m gonna borrow them and take it to the dyno next week. I’ll report back with the numbers.

[39PitCrew]

That sounds like good insight. I did feel like everyone was walking away from me coming out of the corners at Cresson but I figured It’s just my driving and lack of car setup. FYSA I don’t have a speedo or a tachometer in the car. Purely shifting on feel and sound.

I think Sean would agree with me that the issue with the 305 TPI motor is where the torque starts to ramp up
and that the intake manifold/heads basically suffocate the motor at 4500 RPM. The LS motors start making torque
at a lower RPM and then can rev another 1500 RPM over the TPI which completely changes your shift points
particularly during cornering.

Speedo is not a huge deal. But the tach, hope that's on your list to add soon.