A few days ago I was in discussion with a reputable engine builder in Illinois RE: a 383 LT1 build. When I expressed my desire to ditch the stock LT1 intake manifold in favor of a carb style single plane intake the tech said to me that I will experience a big decrease in low and midrange torque in going to the single plane.

I thought this was counterintuitive I was lead to believe that the shorter the intake runner the lower the low and midrange torque and the longer the runner are the greater the torque like the famous or infamous Tuned Port Intake on the L98.

He went on to say that though the runners on the LT1 intake are indeed extremely short (3") but the intake has a small plenum volume and this enables the engine to have very port velocities at low and midrange RPM's which aids in cylinder filling at such low RPM's hence the high torque even with short runners

1. Is this true??.

2. What is yours or anybody else who know's experiences with changes in low and midrange torque in switching out the stock LT1 intake for a carb style single plane or anything else(Holley Stealthram, Accel Superram, etc.)????

 

Single plane intakes are popular choice for big cube or top end engines because each port gets equal air flow.Log style plenums with front mounted TB's are know for hi-rev distribution problems resulting in some cyl running rich while other are lean

 

He's talking old school mythology. Swapping intakes will in fact effect your powerband, but thats if you do nothing else to compliment the new component. When it gets right down to it, if you swap to a carb style intake, you can make up whatever loss of torque you experience down low with a simple cam swap. Go with whatever style intake manifold you want to, then get yourself a custom camshaft....

 

Street Lethal,

You are right regarding in fixing any torque loss issues with a custom cam is a maybe a more modern approach to the problem, That what the guys at TPIS suggested to me some time back when I told them about my dissatisfaction about the stock LTx intake manifold's air distribution. But as Vetteoz pointed out that single planes are a popular choice among guys who are building max effort LT1s for reason he pointed out. But I think that being that the runners on carb style single plane sare twice as long as the stock LTx intake that it could be viable option for as guys you are building Hi Performance street LTx's for daily drivers.