LS1-450

iTrader: (33)

Posted here 'cuz there's more chance of finding info. than in external or dyno section since the topic is related to carb intakes.

Looking for info. showing where plenum volume becomes a restriction based on engine air movement. For example: At what point does plenum volume on a Victor Jr. or Victor carb intake become a restriction on stock 346, 383, 427, (no RAM air)? Did RAM air help to reduce the restriction @ speed? How much did a carb spacer help to reduce the restriction...etc?

speedtigger

iTrader: (16)

A lot of us have tried various spacers on our combos. I tried every type 1" spacer in the book and nothing made more power. Some made less. i don't have the hood clearance to run a 2", so I have no data on that.

Hopefully the other guys will chime in on their experience.

dogsballs

Dont believe the ls3 vic jnr is a restriction on 500hp 364 with rectangle heads

1" then 2" didnt make power, but fattened up torque a fraction

WE TODD DID

iTrader: (2)

We played with plenum sizes (mostly with carb pad shape) in last years EMC engine, and the engine liked a small (4150) carb pad entrance over a large entrance to the tune of 40hp. I was using a 2" spacer to adapt the 5" throttle body to the 4150 carb flange entrance. Your restriction is going to be your carb or throttle body. The spacers didn't really do much for us this year since it was efi. I only had a spacer that big so there would be a nice transition from the 5" round hole to the square hole in the manifold. I'm not even sure if that nice transition made a difference to be honest. Now with you having a carb, you have distribution and reversion that you need to worry about, and with that a nice spacer could help.

LivernoisMotorsports

iTrader: (1)

I have played with different spacers and modifying plenum areas on several intakes over the years. Most of the time a power cone spacer is the way to go as they seem to have the best power torque and throttle response gains. More often than not you need more spacer than you thought for max HP. The larger the engine or more RPM it is going to turn it will respond to a very large plenum. Best thing to do is get her on the dyno with some spacers some intake/carb gaskets and do some testing.

LS1-450

iTrader: (33)

Thanks for the replies. Had done a lot of street testing w/ EFI Live when we were EFI, but have only tuned the carb for max timing without knock & A/F ratio.

It's RAM air w/ a hood scoop & dish to keep air from by-passing the carb. W/ EFI I know that MAP was more stable @ WOT w/ RAM air than without. Wonder if RAM air also helps w/ the transition round to square & if any, lack of plenum volume up to 7K?