Sniper question regarding acceptable lobe separation LSA 108

[4mulas]

Hello, thinking I want to order a sniper but have been told and have read a little bit on low LSA’s giving grief on, i think, the idle circuit?

im planning on using it on a mopar P5007647 402 crate motor. It‘s a magnum 402 with a roller cam that apparently has an lobe separation angle of 108, motor also uses an m1 intake, which leads to another question.

Does it matter if you put the sniper straight onto the m1 small block intake which I believe is a spread bore style? The MP catalogue for the motor recommended a 4160 style Holley 750 carb (p4349228). The same description for the motor also says the engine is not intended for use with stock tpi injection. Is this because the stock wouldn’t fuel enough or the aggressive cam confuses the EFI?

really hoping @andyf might see this too as he’s had EFI installs with aggressive lsa’s..

 

[JimKueneman]

I know the FITech has that problem but I thought the Sniper did not.. The reason is that the FITech's manifold pressure sensor is only on one side of the plenum and if you don't have a lot of vacuum and running a dual plane intake the pulses cause the sensor to not read a consistent value. A single plane was suppose to help having all 8 cylinders being combined smoothed out the pulses of just seeing 4 cylinders. The Sniper MAP sensor has an internal crossover so it get pressure from both sides regardless of the manifold. Also just a small LSA is not what causes the issue. A nice torque cam with a 108 LSA and short duration will have plenty of vacuum. Adding a long duration cam with 108 LSA is what gives you the vacuum/manifold pressure.

 

[4mulas]

I know the FITech has that problem but I thought the Sniper did not.. The reason is that the FITech's manifold pressure sensor is only on one side of the plenum and if you don't have a lot of vacuum and running a dual plane intake the pulses cause the sensor to not read a consistent value. A single plane was suppose to help having all 8 cylinders being combined smoothed out the pulses of just seeing 4 cylinders. The Sniper MAP sensor has an internal crossover so it get pressure from both sides regardless of the manifold. Also just a small LSA is not what causes the issue. A nice torque cam with a 108 LSA and short duration will have plenty of vacuum. Adding a long duration cam with 108 LSA is what gives you the vacuum/manifold pressure.

thanks for all this!. Apparently the cam specs around 232/235 @50 9or close to that) and
.501 / .515 ish lift

im new to EFI and don’t want to buy a costly $1600 mistake. Yep the $1180 dollar sniper to you is 1600 in canada. Tired of getting hosed!