LT1inaMGB

I have an LT1 installed in my MGB project car and it has a '94 - '96 Corvette Vortech kit on it. The crank pulley is the 7" double row dampner that came with the kit and the blower pulley is a 3.33". The kit instructions say that the pulley it came with is a 3.12" and that would give 6-8 lbs boost on a stock LT1 engine in a C4.

I had already built my engine to be naturally aspirated before I got the blower kit so it has 11:1 compression due to the quench space being reduced to .040: by milling the block, ported heads, a 230/234 cam with 110 lsa, 1.6 rockers, a 54 mm throttle body, 1 5/8" shorty headers and a 3" very free flowing exhaust.

With the 3.33" blower pulley you would expect the boost to be somewhat less than the stock engine with a 3.12" pulley but it makes 7 lbs by 3800 rpm and 10 lbs by 4500 rpm and it is still climbing. Anybody have any idea why this is happening? I just ordered a 3.6" pulley to see if I can get the boost back to 6-7 lbs at 6000 rpm.

BlowerWorks

Hi MG - got your phone message - call me Monday if you want to discuss. Your boost numbers seem about right. Remember boost pressure is really a back-pressure measurement. For example a restrictive exhaust will result in higher boost pressures yet you are making less power ! It's all about mass airflow (gms/sec) !
When you install the 3.6" I think that will calm you down. Then just use a very conservative spark curve and maybe some water injection. greg

LT1inaMGB

Thanks Greg. I'll probably wait til Tuesday to call and let you enjoy Labor Day.